Topic: Greetings... my new mic preamp.

[su6oxone]

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

Truly impressive.  Wish it were going to be portable size, I would be all over it then.  Looks great though!

[rowjimmy]

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

Truly impressive.  Wish it were going to be portable size, I would be all over it then.  Looks great though!

It is going to be portable sized... per the rest of this thread.

[su6oxone]

It is going to be portable sized... per the rest of this thread.

Okay, thanks for the info.  I only read on the first page that it wasn't going to be very portable sized but haven't yet looked through the other 16 pages.  Anyway, if it's going to be portable sized, then I really need to have one of these. 

[deadheaded]

i have no need for a preamp, i have a schoeps vms 5u, but this is the best thread i've read.  i have followed this from day 1.  it's been fun to follow the progress of this taperssection preamp.
+t fishfivediy
best of luck and welcome aboard.
ed

[fivefishdiy]

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. 

[fivefishdiy]

Got pulled to steak grilling duties and making home made creme brulee's  

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.

[Phiegze]

You have a waiting list going?
  

[fivefishdiy]

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. 

[rowjimmy]

Very cool stuff.
A lot of the technical details are lost on me (though I'm learning more every day) but I've really been enjoying this thread.

[fivefishdiy]

Well... a bit of bad news. 

This project was going smoother than normal, that it's very unusual. I was expecting problems and now I got it.

The VU meter boards are 0.2" too tall! They will need to be redesigned, and remanufactured and reduced in size to less than 1" height.  Also, since they will always be vertically mounted, I don't need the jumpers and headers for configuring the change of direction movement of the LEDs. That should reduce cost too.

While fiddling with the board with power applied (i know, it's stupid), my metal XLR jack flopped over the board and caused some shorting. Now the on-board PSU is dead. And I don't have any replacement parts. That was my last part! Arrrgghh... Parts are on order but will probably not arrive until later this week, or early next. So my planned burn-in testing won't happen. 

But here it is... the finished TS-2 preamp motherboard. From design to working prototype in 3 weeks.




So when you buy this pre, not only are you getting a high quality sound, but rest assured, you're also getting high quality components, parts, and build assembly inside the case. Even the stuff that people normally don't see, are important to me. "Simplicity Counts...Details Matter." If you open the case, I don't want to be embarrassed by what you'll find. 

That's all for now... 

[intpseeker]

+T!

I know less than nothing about electronics, but this thread, the jpg's and your explanations have been instructive and entertaining at the same time. It's great to be able to watch something taken from an idea to a reality. Thanks!

[anechoic]

looks very nice...can't wait to see it go to market
keep up the great work!!!

[illconditioned]

Very nice.  I would certainly trust gear made by you, all that testing is excellent.

By the way, are you using THAT chips as line drivers for the output?

  RIchard

[fivefishdiy]

Very nice.  I would certainly trust gear made by you, all that testing is excellent.
By the way, are you using THAT chips as line drivers for the output?

Thanks! 

Yes, those are THAT chips for the line output driver. These will drive 600-ohm loads without breaking a sweat.




UPDATE:
Here's the VU meter board (Rev1.1) mounted on the TS-2 motherboard.



As I said earlier, it was 0.2" too tall.  So I had to do some relayout and bring it down to 1" height.... it's getting smaller and smaller, see photos below.


This means more $$$ expenses to remanufacture the new Rev1.2 boards. Bummer...

But no big deal, I can reuse the Rev1.1 boards and they'll be perfect for use with 1u rack cases.

If you're interested in VU meters for your audio projects, I also sell them as kits... $19 ea.
Let me know if you want the VU-1 or the VU-1B style.
- 5-LED VU
- wide supply range.. 4V to 24V. (on-board voltage regulation to +18V)
- You can change LED direction via jumper wires to allow for horizontal or vertical mounting.
- on-board trimmer for calibration
Watch a video of it in action.
http://www.fivefishstudios.com/video/VUMeter.mp4

Note:
The 5th LED on the VU meter lights up at +17dBu... but the pre can do at least +23dBu output (from 15Hz to 22Khz) before clipping... so you have a good 6dB buffer before actual clipping. That should be plenty enough margin for normal use.  (At 100Khz, output before clipping goes down to +20dBu... still good 3dB margin... but who can hear 100Khz anyway? )

[jerryfreak]

i dont want to jump the gun, but when do you think you will have pricing figured out?