etheory - a bunch of projects in progress

[Jidis]

I couldn't resist snapping up one of these Texas Instruments PCM4222EVM evaluation boards

I started to grab one of those long long ago when (I think) Jim Williams used to rave about it over at Gearslutz. Almost got it again a couple months ago, but wondered if it was still one of the best options in that range as so much time had past. You sound like it's still up there.

Thanks

 

[etheory]

I'm not aware of any other eval board that provides access to such a high quality ADC.
There quite possibly could be better options out there, but I didn't dedicate enough time to do that much research.
A couple of days of searching gave me this, and I did a bunch of reading and decided it would be a decent enough upgrade to my Fireface 800 converters.
Now that I'm building such incredibly high quality Mics and Preamps/Compressors as DIY, I figured it would be a good idea to at least attempt to match that new sound quality with something that should be able to catch it properly.

 

[etheory]

Woot!
Welcome back..

Why thank you! 

 

[etheory]

Ever since I was a little boy I've wanted to build my own analog synthesizer.
Being completely obsessed with electronic music, I guess it was only a matter of time really.

So. Let's face it. You have to start with the basics.
The bread and butter of synthesis is the VCO.
So, well, this is my first EVER analog VCO (Voltage Controlled Oscillator), built from scratch, and is a more or less perfect replica of an ARP2600 sawtooth-core fully-discrete oscillator with in-built exponential generator.

It even works too! ;D

I'm a very happy chap 8)

The unfilled positions are a discrete op-amp output stage for amplification and re-balancing of the sawtooth output. But I didn't need that for testing, so I'll add that later on.

 

[etheory]

Proof!

Firstly with a lower input control voltage:

 

[etheory]

Now with a higher control voltage resulting in the exponential current sink sucking out more current from the discharge cap, producing a higher frequency! (the waveform is inverted since the ARP2600 additionally has a discrete inverting amplifier/balancer on it's output that I just added to mine):

 

[L´Andratté]

Nice etheory!

I share your passion and once build some pretty similar ones on stripboard and loved running two (or three) in unison, beautifully beating, into a -24db lp, it can´t get fatter.
Would you like to share your layout?

And have you seen this one?
http://groupdiy.com/index.php?topic=54061.0;topicseen

***

 

[Mzaar]

I don't know if you already visited yusynth's website http://yusynth.net/Modular/modular.html but its a must for an analog synthesizer DIYer. Lots of synth module projects (different vco,filters...) with self-etched layout. The webmaster designed the last two arturia's analog synths (great commercial success I've heard) and he's really a nice chap...

 

[etheory]

I don't know if you already visited yusynth's website http://yusynth.net/Modular/modular.html but its a must for an analog synthesizer DIYer. Lots of synth module projects (different vco,filters...) with self-etched layout. The webmaster designed the last two arturia's analog synths (great commercial success I've heard) and he's really a nice chap...

Thanks for the tip Mzaar!

Yes, I'd read every page if his site, and all the other DIY Synth sites on the net, including electro-music forum, Music from Outer Space website, Juergen Haible etc. etc. etc. I'm familiar with it all.
And I could look at other people's layouts and buy kits etc. but I really want my stuff to be completely from scratch. Also I tend to find that the layouts that I do tend to give me better and more consistent results than a lot of layouts I find on the web. Also I tend to incorporate weird and wonderful features into my equipment that's never available on existing material.

In between finishing off these diode comps and amplifiers so far mentioned (which are going well again now), I'll be building a 4 VCO, 2 VCF, 4 VCA analog synthesizer that's partially modular and also includes a special circuit I designed which is a 5 voice super-saw completely implemented in analog using ideas from the saw animator concept, but taking it a lot further.

But as per usual, more on that soon ;-)

cheers,

L

 

[etheory]

And have you seen this one?
http://groupdiy.com/index.php?topic=54061.0;topicseen

That. Is. Gorgeous!
Hadn't seen it before. But thanks for the link. It's.... Inspiring to say the least!

 

[etheory]

Some questions....

I am VERY CLOSE to having my first 4 products ready for wider sale, initially they'll be PCBs for:

1.) EQ Make-up amp - designed to be used as an alternative amplifier to a tube amp in a Pultec - in a class-A solid-state configuration for EQ make-up gain, or any make-up gain really when you might want either DC coupling on the output (PCB supports AC or DC output coupling), or just incredibly awesome sounding make-up gain.
2.) API2510 inspired DOA in standard 2520 footprint
3.) API2520 inspired DOA in standard 2520 footprint (due to the potential similarities with other exiting 2520 adaptations I'm at two minds whether to offer this or not for continued sale - thoughts?)
4.) NTP-M100 inspired DOA in standard 2520 footprint - including original fancy-pants metal can transistors

Due to my rather ridiculously thorough testing processes, I still haven't completely satisfied myself that these are the easiest to construct, most reliable they can possibly be, but I'm awfully close to that realization.

I'll provide as many measurements and data sheets as I can for each of these so you can be sure you'll get the best possible information you can before you begin construction.

I am intending on offering each in 3 configurations:

1.) Just the PCB
2.) PCB + FULL Parts kit
3.) Fully assembled (significantly more expensive, but guaranteed to be tested and also you will receive a calibration sheet to verify it's quality and operation in the state it was before it's shipped - also I'm a habitually clean and fastidious builder, so your product will be as flawless as you could ever find in terms of construction quality).

Next would be the compressors (U274 clone, original etheory jfet comp design and potentially a U373 clone), but I'm holding off due to their significantly higher complexity, both for my own organization (start small, grow slowly) and to ensure builders get those with the lessons learned from these simpler ones.

Also I would like to know how that all sounds to everyone? Does that sound good?

Also I have the following options I was wondering if people could tell me whether they are interested in:

• Gold or standard finish for PCBs (my preference is gold, but some people don't think it's the best finish to work with).
• Black/Red/Blue/Yellow/White/Standard Green finish (I prefer black or white pcbs purely cause they look really really cool - but it might be a per-project choice - is there an overwhelming preference from anyone here?
• Printed vs digitally supplied instructions (I prefer digitally supplied via a link, to conserve those trees!)

It's unlikely that the first test round will include versions with parts kits, since I'll need to ramp up my stock to allow that to happen smoothly and do a few more negotiations with my suppliers, but, it's all looking pretty good so far.

Any thoughts on these options, and preferences, I'd love to know.

THANKS ALL!

 

[ramshackles]

• Gold or standard finish for PCBs (my preference is gold, but some people don't think it's the best finish to work with).
• Black/Red/Blue/Yellow/White/Standard Green finish (I prefer black or white pcbs purely cause they look really really cool - but it might be a per-project choice - is there an overwhelming preference from anyone here?
• Printed vs digitally supplied instructions (I prefer digitally supplied via a link, to conserve those trees!)

You might want to think about these in terms of cost. Both a gold finish and a non-green solder mask will bump up the cost and if you are doing small runs, this can be fairly significant. They won't make any difference to the audio quality...so maybe tee up what the extra cost per board would be and decide if you can either accept a lower profit (if you are selling for profit) or if your potential customer will be happy to pay that cost.

Plus: Digitally supplied instructions! of course....

 

[etheory]

After what has felt like an eternity my Vishay Sprague Axial Electrolytic output caps and Cornell Dubilier Metallized Film input caps are here!
Time to finish these prototypes and do my final sets of tests before I pass them on to you guys!

Very excited 8)

 

[etheory]

You might want to think about these in terms of cost.

I tend not to worry about cost if the device is meant to be used for a quality application but I understand that not everyone wants the same thing.
I love using the best parts I can afford at the time, even if it includes saving up for a bit, but yes, I guess when you are marketing to a wider audience you need to cater for different needs to your own.

Both a gold finish and a non-green solder mask will bump up the cost and if you are doing small runs, this can be fairly significant.

I understand that, which is another reason for asking whether people have particular preferences. If it was me it would all be black, ENIG-gold finish with thick copper tracks for hard-wearing resistance for people who might be a little heavy handed. Yes, definitely costs more, but not a great deal more. But thanks for the feedback, I'll definitely consider it.

They won't make any difference to the audio quality...so maybe tee up what the extra cost per board would be and decide if you can either accept a lower profit (if you are selling for profit) or if your potential customer will be happy to pay that cost.

All good points and along the lines of what I was thinking. Harder/thicker copper tracks I think are good for experimenters who might want to swap out a few parts, so that's definitely something I am keeping in mind.

Plus: Digitally supplied instructions! of course....

.pdf's linked to from the receipt/link would be cool I think.

-- P.S. What spacing is optimal for the M3 screw holes? I've simply been working on a 1mm grid, placing the screw holes towards the periphery of the PCB. But I know certain cases have pre-drilled matix-holed panels. Is there some consistent hole spacing anyone can recommend to be "the most compatible I can be" for more standard cases?

THANKS!

 

[Dylan W]

What are the advantages/potential uses of a 2510? They have much weaker driving capability than a 2520, right? But I can't imagine they're that much more economical to build.

 

[etheory]

My 2510 is not the standard one.
It's been pimped a little bit.
It's less parts, so every slightly cheaper, and Bruno2000 did some tests for me in his studio and found that the 2510 variant I came up with had less noise and distortion than a 2520 and ran a lot cooler whilst driving a similar load.

Hence it's good as the first stage of a two stage amplifier, since it introduces less noise, and doesn't have quite the same drive capability.

However the e2510 can directly drive a transformer without even breaking a sweat and has output protection so should be nearly unbreakable in comparison to the original.

 

[etheory]

Here is a set of pics of the make up gain amp prototype now with the correct capacitors.
Looks pretty good to me!

Vishay Sprague 516D series axial caps on the output and for filtering and Cornell Dubilier 150D series Metallized Polyester caps for the input and LPF rolloff, and what have to be the best looking heatsinks I've ever laid eyes on! Excited much....

Measurements soon....

 

[michal_k]

looks, great! what are the board dimensions?

 

[etheory]

5.58cm on the short side and 13.34cm on the other.

As you can see there is room to shrink the area around the capacitors to be a bit smaller than that so I suspect a few less cm on the long side when I'm done.

 

[mig27]

Just wondering if the e274 is still happening?
Still in love with your sound samples..