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Comments: 9

SC-1 Mic Preamp NOW ON SALE!!!!

After many months of development, testing, troubleshooting, frustration, problems, and accomplishments... the SC-1 mic preamp kit, PSU-1848 power supply kit and power transformer kits are now available for sale!

Click here to ORDER

Photo of a finished SC-1 mic preamp kit! (Note: XLR jacks and wires shown on picture not included in the kit.)

Features:
- Low-Noise, transformerless, High-Quality Mic Preamp
- All solid-state design, using chipsets from THAT Corp and Burr-Brown
- Soft-start, slow ramp-on +48V phantom power
- Crystal clear Red LED indicator for phantom power
- Electronically balanced input and output stages
- 12-position Grayhill gain selector switch
- Gain range from +6 to +72dB, in 6dB increments
- Input RFI protection
- Input clamping protection
- Output surge protection circuit
- Output RFI protection
... read more...

Download PDF file of Assembly Guide/Kit Instructions

Related products like the PSU-1848 Power Supply Kit, Power Transformer Kit, Power Control Kit are also available for sale. Click here.

Thursday, May 22, 2008

New PCB for SC-1 Solo Mic Pre Kit + DC-DC Converter PSU

Thursday, May 22, 2008 11:04:38 PM (Central Daylight Time, UTC-05:00) ( )

So I'm getting ready to send out the new DC-DC prototype... and with the new PCB size, it will fit the smaller case that I wanted to use in the first place.

I created a combined PCB of the SC-1 and this new DC-DC PSU... The whole PCB is sized so it fits perfectly inside the case, and just needs to slide right in. So we'll see how it goes.

I did a little Photoshop trickery to make it look a little realistic... it's not perfect, but good enough.

I'm trying to minimize wiring work, because this is the most tedious of all jobs. So the only wiring work that needs to be done here is for the input and output xlr and the LED power ON indicator.

Alrighty... ordered some 10pcs of prototype PCBs from the factory. Should be here in a week.

These prototype PCBs alone costs $18.60 each. I hope I didn't make a mistake on these board layouts otherwise, that's wasted money.

We'll build 4 prototypes and if they all work, and no bugs... we're going into production very soon... maybe the final production PCB will be ready by end of June. I still need to figure out what to do with the case (finishing)... maybe use a silkscreen to label the front panel. I'll have to outsource that to a factory.

If this gets launched in June, it will also mark the 1st anniversary of FiveFish Studios. We launched the SC-1 kit about the same time last year.

The SC-1 Solo will not be sold as a kit but as a finished product, complete with case, wall wart, etc.

Yes!... it is RED. and it looks great.

So far, this is the biggest sized PCB I've ever ordered. Hope to populate this board and test it ASAP. I can't wait.

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Wednesday, April 02, 2008

SC-1 Solo Preamp (Prototype) powered by 12VDC wall wart (or battery)

Wednesday, April 02, 2008 7:22:20 PM (Central Standard Time, UTC-06:00) ( Power Supply | Project Kits | Recording | SC-1 Preamp Kit )

I'm making CAD measurements of trying to fit an SC-1 preamp plus a Mini-IO module in my extruded aluminum "brick case"... hmmm.. its a tight fit, the TRS jack is almost hitting the top of the case, and the soldered terminals touching the blue trim potentiometer of the SC-1.

I'm concerned about the terminals touching the blue potentiometer. It's plastic so it's non conductive so maybe it's not even an issue. If the case has an extra 0.1" height, it would have been fine. But given this TRS jack is the hi-Z input, I'm afraid it might have side effects.

For sure a VU-meter will fit inside without problems.

Unless I can find a slightly taller case, the SC-1 Solo will probably consist of the SC-1 and a VU meter, plus the PSU board. (at least, for this 1st prototype I'm making.)

My eventual goal is to find a case that will be tall enough to fit an SC-1 plus the IO-module (with input/output transformers)/Mini-IO, and maybe even the VU meter. Now, that would be some hot SC-1 Solo product!

Okay...did the CAD drawings, created the CNC programming then tested it on some .125" scrap aluminum. Looks good.

Loaded the "real" panel and let the program run... X fingers!

Yes... everything fits like a glove! No more manual drilling with a drill press or filing around to make everything fit.

Of course, it takes hours of prep work on the CAD/CAM, testing and final setup... and only about 3 minutes of actual CNC time on the router. Shocked

Shocked

Some photos:

Did the rear panel CAD/CAM/CNC today... I goofed up making measurements on where the DCJack holes should be... so had to do some fudging with a manual file. It's okay... this is just a prototype. But I fixed the CAD drawings to reflect the proper dimensions.

Some photos:

The DC-DC Power Supply installed on the rear panel.

XLR jacks installed

I do have one concern here and that is... with the XLR jacks so near to the DC-DC PSU, will it affect the preamp's performance? From my limited bench testing, it doesn't seem to be... but the proof is in the pudding... so we'll see how this prototype performs.

I have seen one preamp though (and I'm not naming names) and they have a DC-DC PSU, and a microprocessor, and it's associated crystal clock, and 2 preamps crammed into one small case.

By comparsion, what I have is "roomy" compared to what's inside this other preamp.

And finally... a preview of things to come. Rear View of the SC-1 Solo case.

Arghhh... those XLR bolts are too shiny! Will have to replace them in the final prototype with stainless steel bolts to cut down the bling factor.

I'm also using a flat head stainless steel screws to attach the plate to the main case... but I can't properly chamfer the hole openings because the plate is only .036". If it was thicker, I can get away with it. So the (4) corner screws will have to be replaced with pan head screws (also stainless steel)

All these "minor" fixes will be done as the very last step.

SC-1 Solo Preamp

Features:
- Low-Noise, transformerless, High-Quality Mic Preamp
- All solid-state design, using chipsets from THAT Corp and Burr-Brown
- Soft-start, slow ramp-on +48V phantom power
- Crystal clear Red LED indicator for phantom power
- Electronically balanced input and output stages
- 12-position Grayhill gain selector switch
- Gain range from +6 to +72dB, in 6dB increments
- Input RFI protection
- Input clamping protection
- Output surge protection circuit
- Output RFI protection
- Powered by a linear, regulated 18-0-18 Volts supply, with +48VDC for clean power delivery
- Reduced clicking and popping when changing gains
- High quality Bourns, sealed, conductive plastic potentiometer for volume control
- High quality C&K PCB Mounted switch
- Gold-plated, machined, low-profile IC sockets
- Use of high quality 1% Metal Film resistors, and high-quality ceramic and electrolytic capacitors
- With 5-LED VU Meter
- Neutrik XLR input and output jacks
- Powered by 12VDC wall wart

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Wednesday, March 26, 2008

DC to DC Switching PSU (12Volts to +/- 18V & 48V)

Wednesday, March 26, 2008 6:31:57 AM (Central Standard Time, UTC-06:00) ( DIY | Power Supply | Project Kits )

It's done :) My switching DC-to-DC PSU.

I've been working on this design on and off since October 2007. Several prototypes later, and many $$$, I'm happy with it. All output voltages are regulated and adjustable via multiturn trimmers, +18, -18 and it's a true +48V phantom power... all derived from a single 12Volt input. Outputs are short circuit protected. Just a big spark, but keeps on ticking. Nothing gets blown.

http://farm3.static.flickr.com/2322/2365867488_5f14133bbd.jpg

Powering my preamp and my I/O module (input and output trafo, pad, polarity) with Active DI, via 12V wall wart. No hashing sound, no RF leak, no noise. (Well, okay... when you're at 66-72dB gain... but could be caused by everything not in a metal enclosure.)

http://farm4.static.flickr.com/3068/2352224005_5dc492842c.jpg

Output on all 3 rails are typical like below:

http://farm3.static.flickr.com/2376/2365001131_8b2c1a26ac.jpg

Switching spikes on the DC output of about 0.06Vpeak-to-peak, and interval of 33.333Khz. I can set switching freq. to about 60Khz but the spikes get larger.

So I compromised for smaller spikes at a lower switching frequency... i.e. smaller spike/transients, less RFI energy emitted, less chance that it will interfere with sensitive mic pre circuitry.

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Thursday, March 20, 2008

Mic Preamp SC-1 with Cinemag input/output transformers

Thursday, March 20, 2008 3:54:00 PM (Central Standard Time, UTC-06:00) ( )

Yes!... got some time to do some electronics work today... away from the purchasing role.

Finally built and tested the final, final, FINAL prototype of the IO-module. And it's great.

Man, I love the sound of the Active DI going through the input transformer. Actually, love the sound of anything going through it.

Some pics:

Now, I haven't sent the PCB out for mass production yet, but I have (4) prototype PCBs left. I'm keeping (2) so that leaves (2) extra ones...

I know somebody out there is waiting for this patiently... you're getting these PCBs way in advance of the others.

I'd need to drill some square cutouts first on it... like this

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Tuesday, February 26, 2008

ATI X800XT Fan Upgrade for Mac G5

Wednesday, February 27, 2008 5:47:28 AM (Central Standard Time, UTC-06:00) ( )

So I bought this AT X800XT card... back when it was $499... the first one after a few short months, the fan got noisy and was dying... I sent it back to ATI, then ATI sent back a faulty unit (blocks appearing on the screen), so I had to resend it back again and then I'm good again for a few months.

This morning, my 2nd monitor (A Samsung) wouldn't come up. Just black. At first I thought my monitor died... bummer. That got me thinking... maybe I should get another 23" Cinema LCD :) The prices have fallen down to $799. (I got mine back at $1999).

Then just to be sure it's the monitor, I swapped things around... and lo and behold, my Samsung monitor was working!

I opened the G5 case, and see that the video card fan was totally dead... not spinning. NOT GOOD. I don't know how many days I've been running with this fan not spinning.

So today I pulled out the X800XT card and put back in my stock video card (fanless) just so I can continue working. It's a good thing to have spares.

I'm not going to bother sending this back to ATI again. I bought some replacement aftermarket fan and will try to fix this thing instead. Remove the junk ATI fan and use another one instead.

Will update this post as I go....

I just hope the 2nd video port isn't permanently damaged.

I just noticed today that due to the failed fan on my video card, it almost fried the components at the bottom of the PCB. Yes, it smell burnt. I was kinda disappointed when I saw this. I'm thinking maybe my video card is fried (literally).

Remove the old crappy fan from my ATI card. This fan sucks. Do you hear that ATI?????

You can see the old thermal paste sticking on the cpu. So we'll need to clean that out.

And here's the clean chip. I just used an old cotton shirt, and an old toothbrush. Wiped it clean and made it shiny.

I'm using a Zalman VF700-Cu Quiet VGA Cooler fan. It's pretty cheap. $20 I think.

It also comes with some blue small heatsinks for the other chips (RAM?) on the card.

The connector of the Zalman fan isn't compatible with the headers on the video card.

So what do you have to do? Get a cutter, cut the wires on the new fan, cut the wires on the old fan and solder them together a'la Frankenstein. :)

I used some heatshrink tubing to insulate the connection. You can see it in the photo below, along with the new blue heatsinks.

Then... the moment of truth... Put it in my G5 and see if it still works. (Remember, the parts at the bottom of the PCB smells burnt and looks a little crispy.

And the result....... IT STILL WORKS! Now my second monitor works, and not shutting down (turning black). I've got good video on both monitors! :)

So that's done... total time, maybe 30 minutes.

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Saturday, February 02, 2008

DC to DC Switching PSU (12Volts to +/- 18V & 48V)

Saturday, February 02, 2008 10:12:25 PM (Central Standard Time, UTC-06:00) ( Power Supply )

Well, this DCC psu is giving me the headaches. One day, I thought I licked out the problem and it's as quiet as can be... next day, I turn it on, and the fyring noise is back again coming out of the speakers.

I've tested and used my oscilloscope to look for possible problems in the DC-to-DC converter, (though I did found some oscillations that I eventually fixed), there doesn't seem to be any improvement in the crackling sound coming out of my test preamp.

This PSU ripple has never been better, the "frying bacon" sound coming from the inductors is almost negligible, the waveform looks good... but still! There's that crackling sound coming out of the preamp.

In situations like this (i.e. when I become desperate)... I do weird things to my projects. I mean, what more can I lose?

And this time, I decided to remove jumper J1 on the SC-1 preamp, and run using AC coupling. That's strange... the crackling sound STOPPED!

So I went to my shelf, grab a new OPA134 chip, swapped out the old IC2 chip on the pre with the new one, and VOILA! The stupid crackling noise STOPPED! IT's as clean as can be... running on the DC-DC PSU.

I'm going to leave the DC-DC PSU running the whole day, and the preamp... and see if the noise comes back. Otherwise, I think a marginally defective IC2 on the SC-1 PCB was the cause of the noise problem, and not my DC-DC PSU.

I'm happy to report though that using an AC Adapter with my DC-DC PSU powering the preamp and the Mini-IO module, the AC Adapter doesn't even get WARM!

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Sunday, January 20, 2008

IO-Module Prototype #002 Testing

Monday, January 21, 2008 1:01:53 AM (Central Standard Time, UTC-06:00) ( SC-1 Preamp Kit | IO-Module )

Okay, so I got the latest prototype PCB for the IO-Module... time to build prototype #002.

I usually build 2 to 5 prototypes before the kit goes on sale. I want to make sure that it works, that everything works right and performs great, easy to assemble, the parts list correct and all that. It's the DETAILS that matter!

Some pics...

Since the PCBs are prototype, there are no cutouts for the transformers. On the final production PCB, the holes will be cutout by the factory.

So we drill some 3/8" holes on each corner of the square cutout.

And here's a pic of the drilled PCB.

Using a jig saw, we do a rough cut of the square hole... then use a file to smoothen the edges.

Next, we test fit our transformer (Cinemag CMOQ-2S) into the PCB... fits perfectly on the 1st try!

Here's the bottom view.

And a photo showing both the input and output transformers.

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Friday, January 11, 2008

Mini-IO PCBs are here!!!!

Saturday, January 12, 2008 5:31:36 AM (Central Standard Time, UTC-06:00) ( )

This MINI-IO is very fun and easy to assemble. Within a few minutes, you could have a completely assembled kit.

To re-iterate... this kit gives you POLARITY CONTROL, -20dB PAD, and MIC/INST select switch, plus an onboard ACTIVE DI with fully, electronically balanced outputs.

It is a stripped-down version of the IO-MODULE. The only difference being the IO-MODULE has provisions for input and output transformers.

The MINI-IO is meant to be used in conjunction with a preamp module. It works with the SC-1 preamp kit, or any preamp you're working on where you wish to add the above controls and features.

Power Supply Requirements are +18/-18, +48V for phantom power.

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Wednesday, January 02, 2008

Wednesday, January 02, 2008 10:22:35 PM (Central Standard Time, UTC-06:00) ( )

I finished assembling my CNC. (Got it from eBay)... Using Mach3 software... It's a complicated piece of software but I think I'm getting the hang of it. I'll probably buy it after I play with it some more.

Tested the CNC doing some movements and "pretending" to cut/route something... I need to buy a router to install to it so it can do some real cutting.

Some photos:

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Friday, December 28, 2007

SC-1 Preamp + IO-Module

Friday, December 28, 2007 10:21:06 PM (Central Standard Time, UTC-06:00) ( )

Took some photos today.

Did some more tweaking on the IO-module PCB design... getting ready to pull the trigger for another prototype PCB run.

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Sunday, December 23, 2007

Oscilloscope photos and audio samples ... DCC-1848

Sunday, December 23, 2007 10:19:52 PM (Central Standard Time, UTC-06:00) ( )

Using the DCC-1848 prototype PSU, loaded with my SC-1 preamp, the IO-module and the VU meter board.

0.2V/DIV

0.1V/DIV... you can see some noise/spikes occuring at regular intervals.

Not bad...

And audio samples.
The Setup:
My SC-1 preamp... with an IO-module and VU Meter board. Everything powered by my proto DC-DC Switching PSU... (12Volts input to +/-18, +48V). Preamp outputs going to a patchbay, then going to a MOTU 828mk2 input. Recorded using Digital Performer. MP3 set at 256Kbit sample rate. Preamp, IO-module, VU meter board and PSU unracked, no case, no shielding, no grounding... just PCBs sitting on my workbench.

First sample:... preamp gain set to 54dB, *unterminated XLR inputs*, max volume
http://www.fivefishstudios.com/audio/DCDC54dB0R.mp3

Second sample... preamp same 54dB gain as above, but XLR inputs terminated with 150R resistor.
http://www.fivefishstudios.com/audio/DCDC54dB150R.mp3

Third sample.... preamp gain set to 72dB, *unterminated XLR inputs*, max volume
http://www.fivefishstudios.com/audio/DCDC72dB0R.mp3

Last sample... preamp gain at 72dB, 150R terminated XLR inputs, max volume
http://www.fivefishstudios.com/audio/DCDC72dB150R.mp3

OK! I think I found the problem and managed to reduce the spikes in the DC INVERTING section. I don't know if the pictures make it obvious but it's a definite improvement.

EARLIER

FIXED? Definitely better... reduced noise and pikes.

I think I'm ready to do a revision 2 of the DC-DC Converter PCB, so I don't have components hanging on the top and bottom of the board (was trying out different things). I think the rest of the problem is now caused by the PCB layout.

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Saturday, December 22, 2007

IO-mod + VU meter ... mated together

Saturday, December 22, 2007 10:18:37 PM (Central Standard Time, UTC-06:00) ( )

The image “http://farm3.static.flickr.com/2354/2128942629_08c0dca3b6_o.jpg” cannot be displayed, because it contains errors.

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Thursday, December 20, 2007

DCC-1848 Prototype Testing... SUCCESS!!!!!!!!

Thursday, December 20, 2007 10:16:23 PM (Central Standard Time, UTC-06:00) ( )

Woohoo! Success. My DCC-1848 PSU is working. DC-to-DC Power Conversion from a single 9V battery (or wall wart).

Okay, what happened? Yesterday, I was moaning that everything was a disaster...

First of all, don't work on your building your prototypes at 1:00 in the morning.

My Mistakes:

1. The biggest mistake of all... I sent the wrong PCB gerber files to the PCB fab house. So I got the wrong PCB back. The hole spacing, and layout are wrong, so components are inserted crooked. This made working on the prototype PCB harder.

2. I have a silkscreen mistake on the PCB. During the building of the prototype, I followed the silkscreen on the PCB... instead of my schematic. Result? I inserted the wrong value of capacitor on the (-) Inverting section. But still... this should have not prevented the circuit from working.

3. And the real cause of the problem.... <drum roll>.... I inserted a diode backwards. Stooopid mistake. My silkscreen shows the correct orientation but I didn't noticed it, and I inserted the diode backwards.

As soon as I noticed that problem, desoldered the diode, and used a brand new diode to put into the location, and VOILA!!! IT WORKS!!!! SUCCESS!!!!

Some pics...

Here, you can see +18Volts output from a single 9V battery.

And now... the problem section... the -18V Inverting section. But as you can see, it's now working! Smile

Smile

And the biggest question of all... can it do 48Volts for phantom powering?
Sure can! Check it out... +48V output from a 9V battery source.

Just for kicks... let's see what's the highest voltage we can achieve...

NOTE: The PSU is regulated and adjustable. So just because I'm calling it a DCC-1848, it doesn't mean it can't go higher than 18V, or 48V.

And here's a picture of my ugly prototype power supply...

This shows the +48V section that I'm scrapping. Instead, I'll use the same design I used for the +18V section for the +48V section.

It's an ugly piece of work... BUT IT WORKS!!! This is so cool.

BTW, I checked the PSU DC output on my oscilloscope... it's clean. I thought my oscilloscope was not working, but there was very very very tiny ripple, no oscillations, or any nasties.

Of course, the real test is .... when connected to my SC-1 preamp, how does it sound? i.e. will I hear any whining, nasty, artifacts leaking into the preamp?

That's the next phase of my testing.

For now, I'm really pleased with the outcome of this testing.

Okay, did more testing...

The above voltage readings were UNLOADED. So what happens when it's loaded?

I tested the DCC-1848 PSU prototype loaded with (1) channel of SC-1 Mic Pre and (1) IO-module.

My goal here is to keep the output voltages at +18, -18 even with a running load.

It seems that a 12VDC input is the ideal input voltage for the DCC-1848. (which is what the original intent was anyway... powered by a car battery or wall wart)

When the input voltage drops below 9.8Volts, we get +18.2, and -17.8VDC outputs. Weird. And get this... the PSU PCB emits a high pitch sound (later on this...)

I set the gain of the SC-1 preamp all the way to the max... +72dB, max volume, and listened at the output on my KRK monitor. Wow! You wouldn't believe it... It's just hiss, only hiss, no RF junk, no nasty interference that you would expect from a switching PSU, just plain hiss. In fact... and I hate to say this... the output IS cleaner than a linear power supply powered by the AC mains! I can't believe my ears. Totally *unexpected*! I would expect that switching PSU to emit more junk and be more noisier than my linear PSU. But I'm very surprised.

BUT...

Of course, there is a big BUT...

Right now, I am having this high-pitch vibration coming from the PSU PCB.... no, the noise is not coming from the preamp, nor is the noise travelling from the PSU to the preamp... The high-pitch sound is coming from the PCB itself!!!

I narrowed the source of this high-pitch sound down to the Inverting Section. And further narrowed it down to the Trimmer and IC sockets. It seems the mechanical contraptions inside that trimmer is vibrating at a high pitch that you could hear it. When I touch the trimmer, the pitch changes and if I squeeze the legs of the IC in the IC socket, the sound disappears or lessens.

Also, I could hear what I thought was an AM radio... coming from the Trimmer! kinda like a "crystal radio" From some listening, I found out it's WSM radio station. We live only a few miles away from it.

This WSM tower is gigantic-enormous. See this writeup.
http://www.oldradio.com/archives/stations/ccs/wsmtwr.htm

The question is... will other people hear this weird high-pitch sound coming from the PSU PCB? Or is it just me, since I'm pretty close to this AM tower?

Anyways... I'm also thinking of maybe replacing that trimmer in the Inverting section with a different kind of trimmer... and see if the sound/vibration goes away.

Another thing is maybe I shouldn't use IC sockets and just solder the IC directly to the PCB. This will remove any vibration (within the IC socket contacts) that can be amplified.

Well... so far, right now I'm looking at this with a magnifying glass, scrutinizing it and I'll try to solve any anomaly, issue, noise, design problem before I call it a final version.

In summary...

** the noise performance of the switching DC-DC psu is excellent. No penalties, nor does it affect the performance of the SC-1 preamp.

** a 12VDC input seems to be the ideal/sweet spot. This won't be a problem since 12VDC wall warts are easy to find.

** Need to find a fix for the high-pitch vibration coming from the PSU PCB.

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Saturday, December 01, 2007

IO-Module Prototype... Success!

Saturday, December 01, 2007 10:12:25 PM (Central Standard Time, UTC-06:00) ( )

The IO-Module PCB's are here!!!!!

One step closer to bringing some iron flavoring to our SC-1 preamps... and about 2 steps closer to having an API-type preamp offering in the future!

As you can see, the square hole for the output transformer is not cutout because this is just a prototype order. So I'll have to cut it out manually. When I place my production run order, it will be cutout at the factory.

So it's time to test this baby!

And this is a preview of what it will look like.

I can't wait to build this board and test it.

Just imagine your SC-1 preamp mated to this IO board....

- Input Transformer
- Output Transformer
- Hi-Z Input with ACTIVE DI... converted to balanced out, then routed to the input transformer.
- Pad Switch -20dB
- Polarity Switch
- Mic/Instrument Switch

Got some work done on the IO-module today...

I stuffed it with components, and just use jumpers (temporarily) to wire the output trafo.

Then I connected it to my SC-1 preamp and then listened to the sound.... arrrgghhh... something is not right. It sounds horrible. Weak. No bass. Instead of amplifying the sound it seems to be making it weak.

What's wrong? I tested every part of this IO-module on a breadboard so I know it should work.

I reviewed the datasheets for the input trafo and my PCB design. They're all correct.

Then, on a last ditch effort, I tried bypassing the output transformer and WHAM!!!! Loud sound filled the room!!!!

Hmmm.... why would it sound great with the output trafo bypass, and not when it's in the circuit... so I untaped all the jumper wires, and on one of the wiring, I have an open circuit. I grabbed a long nose pliers and made sure the wires are twisted tight and making good contact.

Test again, and whooppeeeee! It works.

Really, really really sounds great. If the stock SC-1 sounds great, this is even better. I can't describe it but it's just beefy while still being musical and all the high frequencies still being there. Beefy without being muddy.

I listened to the sound and compared between the output trafo bypassed and not... and frankly, I can't hear much difference. It's wired right now as 1+1:1+1. So basically 1:1.

The output trafo doesn't really add much to the flavoring. But it does contribute to signal isolation due to the transformer properties.

The input trafo adds about +18dB gain. And not only that... most of the flavor seems to come from the input trafo itself. So if you're looking to save some money, you can skip the output trafo but I would 100% recommend that you use the input transformer. It's where the flavor is!

... but come on... if you're going to spend money on the input trafo, might as well buy the output trafo! Otherwise... what's the point? The point of the IO-module is to add the input and output transformers.

Well.. okay, there's the active DI circuit that's part of it.

Then I have a -20db pad switch.

The output trafo can be wired as 1:2 if you want an additional 6db gain.

So let's see... 72db gain of the pre, +18dB of the input trafo, and possible +6db from the output trafo...hmmmm... 96dB gain total???? Shocked

Shocked

(PS: I haven't tested the DI input yet... I need to hookup a guitar here )

Photos:

From left to right...

POLARITY --- -20dB PAD ---- MIC/DI INPUT ----- HI-Z GUITAR INPUT

I'm going to order some more switches and do a second prototype using a different input transformer.

But I think I can honestly say the IO-Module is a success! Really sounds great!!!!

UPDATE: Just a correction. I removed a resistor during my testing (when I was troubleshooting) and when I added it back, the input trafo does not add +18dB gain. So we're cool. still +6 to +72dB gain from the preamp.

The output trafo, though, can be wired as 1:1 or 1:2 and if wired 1:2, will give you an additional FREE +6dB gain.

PS2: Also tested the DI input with an electric guitar. I can't play squat but yeah, it works... sounds good too. The output of the Active DI is routed also to the input trafo.

You know what's going to be next, right?

So if we get a breadboard, and put some discrete opamp module (I have some Forsell JT-992 and some Melcor) and just add a few resistors and capacitors and hook it up to this IO-module... why... we basically have an API-type preamp!

So in summary....

SC-1 preamp kit + IO-module = RNP/DAV/API hybrid preamp.

Discrete opamp + IO-module = API-type preamp.

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Thursday, November 29, 2007

DCC-1848 Prototype Part 2

Thursday, November 29, 2007 10:10:46 PM (Central Standard Time, UTC-06:00) ( )

I sent out this PCB for prototyping.

If this design does not work, I have another solution I can try out.

But I'm hoping it will work... I think it will... otherwise, this will put a kink on my future plans.

Also, I'm still waiting for my IO-module PCB... it's supposed to be a 5 day turnaround time, it's now 2 weeks! I may have to find a new PCB fab house for prototypes.

Also need to start creating a prototype PCB design for my 5-LED Vu meter.
http://fivefishstudios.com/forum/viewtopic.php?t=170

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Sunday, November 25, 2007

Sunday, November 25, 2007 10:09:34 PM (Central Standard Time, UTC-06:00) ( )

I've been playing around with some comparator chips, trying to create a working LED VU meter. This is my 2nd attempt. My first attempt was frustrating so I abandoned it.

This time, I played around with values of the capacitors and resistors so the response/speed of the LEDs are to my liking, and added current limiting resistors so the load to the PSU is very light. (Note: Red LEDs are the most "green" LEDs, consuming as little as 5mA of power.) I also learned a few tricks that I think if I have applied it to my 1st attempt, it might have been a success.

The VU meter is composed of (5) LEDS, with dB range from -13 dB to +17dB. The 3rd LED (i.e. the middle LED) is the 0dB mark.

The current for the LEDs is regulated, so the LEDs light up with the same intensity, regardless of the PSU voltage fed to it... which can be anywhere from 3+V to 16V. The max voltage rating of the chip is 18V, and I just connected it directly to the PSU-1848 and so far, it's working fine.

I added a trimmer to help you calibrate the 0dB mark of the LED VU meter.

I've tested the VU meter connected to the PSU-1848 and SC-1 and happy to say... no change in sound characteristic of the SC-1 even though I didn't use a buffer.

I tried connecting the VU meter input to the HOT (Pin2) of the XLR output, and at the INSERT jacks of the PCB, and either one works just fine. The sound of the SC-1 isn't affected. So that's good.

UPDATE: You can buy this VU Meter Kit by going to www.fivefishstudios.com

Now the big question now is... where can I use this? There is no more space on the PCB of the IO-module to add this LED VU meter.

I'm thinking, maybe, use this LED VU meter on the upcoming "API" type module preamp. .... there'll be plenty of space on the motherboard PCB, since the rest of the stuff will be located on the external IO-module PCB.

So that's the plan... Check this out.

See... they have a 7-LED VU meter. I'll have a 5-LED VU meter on the new preamp.

I finished designing the PCB for the VU Meter.

Total square area: 3 sq. in. (1" x 3")

Now, I'm thinking should I even do a PCB prototype for this, or just go ahead and order 100 production run PCBs? I think the cost will end up being the same. Hmmmm... do I have enough confidence on this layout? Are there silly mistakes I've made?

The VU Meter board is working sweet!

I'll post a short video clip of it in action.

I was feeling brave on this one... I didn't do any prototype PCB design on this one.. I ordered production quantities immediately. Tested one of the PCBs, stuffed it with components and it works.

The VU meter is cool in the sense that you can use the board either horizontally or vertically. Just adjust the on-board jumpers on which direction you want the LED lights to go... left to right, or bottom to up.

From a design that exists only in my computer...

to a working product!

Been playing also the whole afternoon and tonight with my DCC PSU board. Happy to say, no components are overheating (or even getting warm) even after hours of operation!

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Saturday, November 24, 2007

DCC-1848 Prototype

Saturday, November 24, 2007 10:08:04 PM (Central Standard Time, UTC-06:00) ( )

While waiting for the IO-module PCB to arrive, I'm starting to design the PCB for my new PSU.

It's a DC-to-DC converter, that will allow powering of the SC-1, or for that matter, any project requiring +/-18 and +48VDC from a 12VDC or 12VAC source.

So my goal is to be able to power the SC-1 using wallwarts or batteries in the future.

The battery option will be useful for tapers and other field recordists.

Here's the preliminary PCB component layout.

The PCB measures 2" x 3.25" only.

Done... just need to do some component size checking, and then I'll send it out for prototype manufacturing.

To fit in a 1u rack, the heatsink must be 1" high.

I don't know if this thing will work, I have not breadboarded this... so I'm doing straight into a PCB. With switching PSU being sensitive to PCB layout, I'm not 100% sure if I did everything right.

I'll need to re-read the datasheets and look for PCB design guidelines and fix anything that needs fixing before sending this off.

Fixed size of capacitors.

New PCB size... 2" x 3.375"

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Saturday, November 17, 2007

Saturday, November 17, 2007 10:05:20 PM (Central Standard Time, UTC-06:00) ( )

I need a way to rapidly test newly assembled boards without soldering any wires on the connection pads.

So I made this test jig. I just plop in the newly assembled SC-1 board, hook up XLR connections, and apply power. If successful, release the board, pack and ship it out.

The breadboard area is for future use... i.e. creating INSERT modules.

This test jig can also be used to test newly assembled PSU boards.

The pogo pins I bought from eBay. These are spring loaded contacts with very fine and very sharp tips. They make contact into the PCB under test, and apply pressure to it for a good, reliable connection.

The yellow PCB holder keeps the PCB under test secure.

Yeah... I'm gearing up for some major assembly work so I can start selling ready-made preamp units in a rack case.

I tested the "Test jig" today using a newly assembled SC-1 kit.

The jig works great. I was able to test the SC-1 preamp without soldering any wires to the PCB, and still having a good, reliable contact on both the power pins, input and output XLR jacks. Pretty pleased with it.

I think I just need to add some "guide posts" so the PCB under test do not sway side-to-side too much even if I'm flicking the selector switches or phantom power switches.

Some photos:

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Friday, November 16, 2007

IO-Module Rev 1.2

Friday, November 16, 2007 10:14:11 PM (Central Standard Time, UTC-06:00) ( )

Caught a stupid mistake... the DPDT push button switches were too far out. So I pushed it back in... not too bad, there's plenty of space on the board so it was not a major re-layout.

I also sent the PCB out for prototype manufacturing. So now... we wait.

When I get the (5) prototype boards back, I'll try (2) different input trafos on it. And may also try different output trafos.

I try to make is possible that every square area of the PCB is covered in ground plane. It helps reduce noise. Either there is ground plane covering on the top, or bottom, or both. The ground kinda acts like a shield.

There is one thing bugging me on this design and that is the 2 pcb traces crossing the circular transformer on the top copper layer. I tried to find some other routes, but it's either I'll have to increase the width of the PCB, or reduce the trace width... both of which I dont want to do. I guess I can also run it around the board, but these traces are carrying low level mic signals, I don't want it winding around the board. so off straight they went... passing and crossing under the future location of the input transformer. We'll see how it goes.

Because this board can be used for other preamp modules coming out in the future, I made the output trafo flexible in its wiring. There are solder pads on the PCB so you have the option of wiring it 1:1, 1:2, 1+1:1+1... whatever. Or you can even use a chassis mount trafo, and just run flying wires to the board.

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Tuesday, November 13, 2007

Tuesday, November 13, 2007 10:02:21 PM (Central Standard Time, UTC-06:00) ( )

I'm done deigning the PCB for the IO-module!

Optimized paths and simplified routes, move components around for simpler routing, made sure ground fill is covering as much of the PCB... had to nudge paths a mil here and there.

Design Rule Check and Error Check reports 0 errors, 0 warnings in the PCB design. That's always a nice thing to see Smile

Smile

I just now need to clean up the text and part#s so they don't overlap and are easily readable on the PCB silkscreen.

I designed a logo for FiveFishStudios. My goal is a simple design that can be etched/milled/CNC'd easily. (looking forward to getting my own CNC machine to do custom cases in-house)

Here's a photo of the new logo. It's a fish, and a sine wave. And the fish is made from normal and inverted sine wave... kinda like a balanced line.. opposite polarity on each line. The fish eyes remind me of solder pads on PCBs.

BYW, this is just Rev1.00... prototype.

I'm still deciding about that output transformer that can be made switchable in/out by simple switches (instead of jumpers).

That "little" feature will add (2) relays, another switch, and on-board regulators to bring down the 18Volts supply to 12V (or 5V) to power the (2) relays... and also increase power draw on the PSU. And I'm thinking if all that is worth it for something that may or may not get used a lot in the field by majority of people.

As I said, this is only Rev1.00 PCB... using relays will definitely shorten the signal path around the PCB... which is always a good thing. I am concerned about the signal path travelling from the XLR jack to the IO-module, before reaching the SC-1.

But then again... that same signal just came from 50ft or 100ft of mic cable from the source, so maybe a few inches of extra travel (via the IO-module) is not really a big concern.

The schematic for the IO-module is done... I forgot I had this finished, but haven't tested a few sections of it in real life... well, tonight I got to test the output trafo with the SC-1... and tested it also with both the input and output trafo... MAN!!! IT sounds really great! I dig it.

Anyways, I've finally decided on the input and output trafos.... THIS IO-MODULE WILL BE AWESOME!!!! REALLY!

I've designed this IO-MODULE so it can be used for a future FiveFish preamp model... i.e. re-use the IO-MODULE with a different main preamp board... voila... a new preamp model/design. i.e. It will be modular in approach.

So guys... WATCH OUT FOR A FUTURE PREAMP PRODUCT FROM FIVEFISH!... more likely will happen after the IO-MODULE gets out the door and is in production.

Finished. But I don't want to send it out yet for PCB prototype manufacturing. I want to wait until the output trafo I ordered gets here so I can test fit it on the PCB printout.

So far, everything looks good. Size is 4.5" x 3.5". All switches and DI jacks are PCB mounted... both input and output transformers are also PCB mounted.

I'm using Molex connectors for the Power connection, and for hookups to the SC-1 board. There is also an extra power connection so you can wire the SC-1 board to the IO-module instead of running power lines all the way to the PSU.

So it will be PSU ----> IO-Module -----> SC-1

The two switches are the polarity invert switch, and the mic/instrument select switch.

The 1/4" jack is for guitars/bass, Hi-Z instruments. Yes.. it's a built-in DI circuit! And not just any DI... the output of the DI circuit goes to a balanced converter, then to the input transformer... to give it that additional flavor! I mean, it's an expensive trafo... why not use it! It's probably overkill. But I think it will sound nice. I've breadboarded it and I like the sound. Very quiet too.

I added a -20dB PAD... reduce width to 3.00" and extended length.

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