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Total Posts: 87
This Year: 24
This Month: 0
This Week: 0
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, 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

5-LED VU Meter

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

Test Jig

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

IO-Module

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

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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Monday, November 05, 2007

CNC Machine

Monday, November 05, 2007 9:58:39 PM (Central Standard Time, UTC-06:00) ( )

Bought a custom CNC machine. I'll try and see if I can use this to machine the rear and front panels of the SC-1 rack case.

Probably for the rear panel, it won't be a problem since we're just drilling holes in the back. The front panel may be a challenge requiring high tolerances, and don't know if this "cheap" CNC machine has tight tolerances to engrave letters and numbers.

Hmmmm... I forgot, the front panel is also anodized... so probably, I'll just use the CNC machine for machining the rear panels and have the professionals do the front panels.

This got me thinking... if this works out just fine, I'll be able to do custom machining of front panels for other kinds of cases to put the SC-1 in. Maybe even offer it as an additional service.... but that's thinking ahead too far.

Right now, my goal is to find a faster way to manufacture the rear panels for the cases. That should save me time waiting for cases from the factory.

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