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TS-2 Mic Preamp Testing

2008-09-05T14:12:23.3270000-05:00

New Preamp Testing

TS-2 Mic Preamp Battery Powered

2008-08-25T12:05:55.9370000-05:00

Start doing prototype of the case... get dimensions of holes and stuff... drill manually, make corrections, keep notes... do some filing to fix the screwups.

Some notes:

The Motherboard, Switchboard and VU meter PCBs... crammed in a 2-inch high, 6" width case. As you can see, it is tight... the switches and capacitors have literally millimeter clearances from hitting the ceiling. The distance between the motherboard and switchboard perfectly aligns with the PCB slot of the case.

Attach the front panel to the PCBs. Check out the input transformer peeking from the side.

Photo of the blue anodized case with the black anodized rack handles temporarily attached.

The switch toggle handles peek out just enough... No accidental flipping of switches. It takes some effort to consciously flip it. Using your thumb and fingernails seems to be the easiest way to toggle it.

The blue anodized finish of the case gives it a weird effect when photographed... kinda like a soft glow coming from the surface of the case.

Forgive the crooked holes for the VU meters, and too large holes for the switches. These were manually drilled.

I'm going to finalize the dimensions, and have a prototype shop do a sample panel for me using CNC.

Hakko 808 Desoldering Gun

2008-08-22T00:54:43.6093750-05:00

So I got a Hakko808 from eBay seller. Shipping was fast, real fast via UPS.
Price is cheap too!

MADE IN JAPAN... not China.

First impressions of the Hakko: It is HUGE! See photo below. Came with extra spare parts, manual, and other goodies for maintenance and cleaning. The manual is well written... no weird Chinese to English fortune cookie translation goofiness!

I was not expecting it to be this big! My rework station also has a desoldering gun but it was small, wimpy, really sucks (in a bad way) and basically useless! A manual desoldering pump is way better than the desoldering tool on my Aoyue rework station.

The Hakko is rated 100Watts, and heats real fast. While huge, it is easy to hold and work with. The bulkiness didn't hamper movement and flexibility.

So I got an old PCB with a bunch of parts and began desoldering resistors, diodes, caps, trimmers and IC socket.

WOW! It is so easy. I dreaded desoldering before but now... it's as easy as soldering.... in reverse! I can suck the solder off an 8-pin IC socket in a few seconds, and the socket just drops off the PCB as soon as the last pin is desoldered.

Clogged holes? Not a problem. Sucks it clean. And note... I'm doing this on a double-sided, plated through-hole PCB. No damage to the PCB pads either. (Note: My Aoyue desoldering gun will suck the copper pad and rip it away from the fiberglass but still leave solder inside the plated through hole. Just total crap.)

All in all... I wish I had bought this Hakko sooner!!!! It is an investment worth buying. Will save you time, and headaches, and not ruin your PCB even when desoldering multi-pin components like IC sockets, trimmers, etc.

TS-2 Mic Preamp Prototype

2008-08-19T00:57:23.1870000-05:00

So hooked up my battery and 2 condenser mics to the pre... turn on power, turn on phantom for both channels, and recorded the VU meter "in action"...

Note: The audio in the video was recorded by the camera.

Youtube video here. (Make sure to watch in high quality mode and view the annotations.)

Enjoy!

SC-1 Preamp mentioned in MIX Magazine... again :)

2008-08-13T01:00:27.1710000-05:00

Ch-Check it out! We're going places. ;D

My SC-1 preamp has been mentioned again in MIX Magazine. Wohoo!

AUGUST 2008 issue

Field Test: Avant Electronics Avantone CK-40 Stereo Mic
http://mixonline.com/gear/reviews/audio_avant_electronics_avantone/

and also back in MAY 2008 issue

Field Test: Peluso 22 47SE Tube Microphone
http://mixonline.com/gear/reviews/audio_peluso_se_tube/

New PSU-4448mk2 Power Supply Kit for Yamaha PM1000 modules (adjustable output voltages)

2008-08-07T13:57:06.2343750-05:00

Newly redesigned, improved, PSU-4448mk2 Kit!

Now, both rails are adjustable via onboard trimmers for that 100% perfect voltage setting.
Also two on-board LEDs... which you can wire to your front panel to use as a POWER ON indicator.
100% more filtering. More capacitors for ripple filtering.
Standard 0.1" pad spacing so you can use standard 0.1" headers.

More TS-2 Battery Testing

2008-07-31T00:59:37.8590000-05:00

Tested the other channel on the preamp board... oh yeah... it works!

Now, time to do some burn-in testing.

BATTERY TESTING Part Deux...
Hooked up the 2-ch pre to a Tekkeon battery... run some music signal and listened to it on my monitors... everything connected using test clips. What's the current consumption of the preamp? (i.e. with the VU Meters turned off)

* You can see which LED is lit up on the Tekkeon battery which designates the output voltage selected.

TESTING AT 12VDC ... of course no surprise here, it will work

MAX voltage input is 14VDC...

Okay, no surprises there...

Just for kicks... I decided to lower the input voltage to see how it holds up... At what point will the sound disappear and the pre stops working?

Let's try 9Volts... still works.

How about 6Volts... surely it will drop at 6Volts... but nope, it's still working.

This is disappointing... ;D Let's try 4.5Volts input... That should kill it!

Nope... still working...

Okay, the lowest setting on the Tekkeon battery is 3 Volts... let's kill this pre, die die die.

Unfortunately, it's still working. Sound is still coming out of the pre. I've been listening for the past half-hour with the pre running on 3Volts from the battery and no problemo. It's still going.

Nothing feels hot. Not the battery, not the preamp, not the various chips, not the PSU section. Everything is C.o.o.l!

Sooooo, you can say I'm pretty pleased about the results.

PS: Notice my new multimeter? Yep... It's a Fluke, baby ;D

TS-2 Prototype Working!!!

2008-07-28T00:58:31.9530000-05:00

Finally finished one channel and did some testing.... THE MOMENT OF TRUTH is coming! Will it work or not???

Woohoooo!!!!! YES!

At first I wasn't getting any signal and was in a bit of panic... I'm thinking "oh no... what did I do wrong?"

Told myself I need to calm down and re-check everything step by step. Found out I have a loose connection since everything is just temporarily affixed with tape and alligator clips. Secured that connection and now we have continuity.

Device Under Test
Working properly and great.... and powered from a 12VDC power source, wall wart or battery.

Then I heard music... coming from my signal source... YES! It works and passes signal. Sounds good too! Pretty stoked about it. Check the gain settings, it works... check the trim, it works. I tested it with a line level input and an SM57 dynamic mic, and yes, sounds great. I haven't tested it yet with condenser mics since I don't have the switchboard hooked up yet... (the switchboard has the 48V phantom power converter).

After an hour of music listening, hooked it up to my signal gen and oscilloscope to see out how things are.

Check it out... here's the square wave response at 1Khz. Notice how clean and sharp the square wave response is... no ringing, oscillations or instability at either the rising and falling edges!

Square Wave Response 1Khz
Super sharp square wave response. Nice audio quality.

Did some output measurements while we're at it... how high an output can we go before clipping or instability. I'm not expecting it to be high (like +27/28dBu) since we're not using high supply voltages here, just a DC-DC converter PSU... but let's see what can we get...

Not bad.... not bad at all. Some readings....

15Hz @ 32Vpp = +23 dBu
20Hz @ 35.6Vpp = +24dBu
1Khz @ 37.7Vpp = +24.7 dBu
22Khz @ 31.1Vpp = +23dBu
100Khz @ 24.4Vpp = +20dBu
200Khz @ 14.65Vpp = +16.5dBu

Output waveform at 100Khz.

What's the Next Step?

Build the 2nd channel on the TS-2 preamp board, then test together the Motherboard and Switchboard...
Metalwork/CNC for the case, verify measurements and hole locations

So far, I'm pretty pleased with how everything is working out, from concept and design on paper, to CAD, to a working prototype.

TS-2 Mic Preamp - Testing & Working!

2008-07-27T22:24:50.7500000-05:00

Finally finished one channel and did some testing.... THE MOMENT OF TRUTH is coming! Will it work or not???

Woohoooo!!!!! YES!

At first I wasn't getting any signal and was in a bit of panic... I'm thinking "oh no... what did I do wrong?"

Told myself I need to calm down and re-check everything step by step. Found out I have a loose connection since everything is just temporarily affixed with tape and alligator clips. Secured that connection and now we have continuity.

Device Under Test

Then I heard music... coming from my signal source... YES! It works and passes signal. Sounds good too! Pretty stoked about it. Check the gain settings, it works... check the trim, it works. I tested it with a line level input and an SM57 dynamic mic, and yes, sounds great. I haven't tested it yet with condenser mics since I don't have the switchboard hooked up yet... (the switchboard has the 48V phantom power converter).

After an hour of music listening, hooked it up to my signal gen and oscilloscope to see out how things are.

Check it out... here's the square wave response at 1Khz. Notice how clean and sharp the square wave response is... no ringing, oscillations or instability at either the rising and falling edges!

Square Wave Response 1Khz

Did some output measurements while we're at it... how high an output can we go before clipping or instability. I'm not expecting it to be high (like +27/28dBu) since we're not using high supply voltages here, just a DC-DC converter PSU... but let's see what can we get...

Not bad.... not bad at all. Some readings....

15Hz @ 32Vpp = +23 dBu
20Hz @ 35.6Vpp = +24dBu
1Khz @ 37.7Vpp = +24.7 dBu
22Khz @ 31.1Vpp = +23dBu
100Khz @ 24.4Vpp = +20dBu
200Khz @ 14.65Vpp = +16.5dBu

Output waveform at 100Khz.

What's the Next Step?

Build the 2nd channel on the TS-2 preamp board, then test together the Motherboard and Switchboard...
Metalwork/CNC for the case, verify measurements and hole locations

So far, I'm pretty pleased with how everything is working out, from concept and design on paper, to CAD, to a working prototype.

TS-2 Mic Preamp - Motherboard

2008-07-26T22:24:01.8900000-05:00

Anyways... finally got some time tonight to do some work on the motherboard.

First, populated the PSU section to see if it works... yup, A.O.K. (had to jumper the switch temporarily since the motherboard isn't hooked to the switchboard.)

So far so good, the switchboard, 48V section, and now the DC-DC section are all working fine.

Work done so far... all resistors, zeners and diodes stuffed.

Tomorrow after church service, I'll solder the caps, IC sockets, pots and switches and XLRs, then start testing.

TS-2 Mic Preamp - Switchboard Prototype

2008-07-26T22:23:06.6560000-05:00

Built the TS-2 switchboard PCB, tested the 48V phantom power section and it works A.O.K!

LEDs will be mounted under the board.

I can already see a few minor changes to the board design... need to push the switches a bit more forward, maybe by 0.1"

The height clearance is perfect... about 1mm for the caps and about 2mm for the switches between these parts and the celing height of the case. Real tight...

Again, here's the initial design that existed only on the computer.

And here it is, in real life (with a few minor changes as you can see.)

Now, off to build the main motherboard.

TS-2 Mic Preamp Prototype PCBs

2008-07-23T22:21:03.7960000-05:00

UPDATED:

New prototype boards came in today... wohoo!

Let's do some test fittings...

The (2) VU Meters

and oh yeah.... 2 input transformers.

This is the switchboard...

A preview of things to come...

Next step: Build a prototype using these new boards and see if it works.