The diyAudio.com preamp project!

[dorkus]

hi everyone,

ok so maybe this is the dumbest idea ever, but...

for the last several months i've been trying to figure out how to build my own preamp. i think there are a lot of nice commercial power amps out there but a good preamp is hard to come by for some reason. i've thrown some questions out there and have gotten great ideas from everyone. however every time i check out the forums, i see even more great information out there. basically what it comes down to is there are a lot of smart people here who know a hell of a lot more than i do about circuit design. soooo...

let's make the official diyAudio.com preamp!

i want to collect everyone's latest and greatest ideas on everything - circuit topologies, parts selection, power supply design, chassis fabrication, whatever - and distill everything into what will hopefully be a very cool and very nice-sounding preamp. kind of like those engineering projects we all (or at least some of us) did back in school, it will be a group effort. like any good project though, we will need some requirements. here is where i'd like to start:

- must be solid state
- must be DC coupled (no single-ended circuits i guess sorry )
- HF response at least -3dB @100kHz
- ideally implemented with all or mostly SMT devices
- each channel will be a separate module
- must have a digitally-controlled attenuator with at least 1dB resolution over a 70dB range
- a microprocessor control unit will handle all control functions

these requirements may sound a little quirky to some of you but the point of it is to make a very modern, fully customizable unit that will work as a flexible but sonically-transparent control center for multichannel formats (e.g. SACD).

we can collect ideas on this thread, and i will put up a website dedicated to the development of the preamp where we can store data, pictures, schematics, etc. i will also do the prototyping, and if we get to the point where we can start building i will get PCBs printed etc. and pick up the tab when necessary. if enough people are interested i can even build extra modules for other people to play with and send it to them (in that case donations would be appreciated to offset the cost). basically i will do most of the legwork, i just want you guys to throw all your best ideas out there!

if any of you elders out there think this whole thing is just silly, please feel free to flame me and and i will stop the thread and go crawl back into my parts bin...

what do y'all think?

cheers,
marc

[HarryHaller]

Knock yourself out! We're all ears..... Requirements this exact is what consultants get paid for. Try John Curl.

H.H.

[jleaman]

I would like to be apart of this i have lots of ideas ill post some in a day or soo.

[HarryHaller]

Do you apart or a part of? Knock yourself out too. May you two could knock heads together....

H.H. (Hard Headed)

[Joe Berry]

. . . but why the requirement for SMT? Wouldn't a through-hole approach be more DIY-friendly?

[HarryHaller]

Once again.....

[HarryHaller]

I can hardly wait. Mark Twain once said that a camel is a horse designed by a commitee. How many humps in the frequency response?

[Ren Hoek]

Yes, I want to apart, far apart.

Ren

[dorkus]

harry: you spend a lot of time on these threads. do you sit there and neurotically refresh your diyaudio.com window every minute or two like me?

anyway, two votes of confidence is good enough for me! i'm sure this thread will get long and messy eventually (or at least hopefully it will) but the web site i'll put up will help us distill the signal from the noise, so to speak.

joe: i want this to be a thoroughly modern design, so i think SMT is the way to go. traditional through-hole is more DIY friendly i guess but after asking a few people, SMT does not seem so hard to work with (at least building is not - disassembling is a different matter). it also has a lot of benefits: the absolute shortest signal paths, minimal parasitics, better thermal coupling, etc.

steve: i have not heard the pass labs stuff but there is no doubt in my mind that it sounds as glorious as people say it does. but if i'm not mistaken, don't all single-ended circuits require capacitor coupling? while AC-coupled circuits can sound excellent, again i am aiming for the absolutely most modern approach possible and i'd like to avoid capacitors in the signal path. it is just the design philosophy i would like to take, and not a put-down of the more old-fashioned approaches which can and do sound excellent. if we can do single-ended w/o the capacitor, then great!

harry (again): that's a great quote, and unfortunately i'm sure it will apply to this thread. but hopefully we can keep the tone of discussion constructive at all times and make some headway with the design.

ren: sorry you don't like my idea. is it just the idea of a group project, or maybe my requirements that bother you? just curious...

keep in mind that if we have a lot of conflicting ideas as to what will work best, we don't have to offend/favor anyone by choosing one over the other. i will just build them all! then i can listen and measure to see how they perform. it may not sound practical but it will be the most constructive.

cheers,
marc

[Apogee]

Marc -

I deleted my earlier post because I wasn't certain if the Pass Stuff was actually DC coupled... I was going to check...

Regardless, I've heard quite a few preamps and to my ears the Pass stuff is damn near the best if not the best I've heard...

No, I don't work for Nelson and have no vested interest...

Find a local dealer, bring the best front end you know of (borrow from friends etc..) and put it up against the current X stuff. You will be very surprised!!! It will set your target reference...

Another angle would be to find a local Adcom dealer and audition the GFP-750 (also Nelson's design). Very simple circuit and very good sound... It is my understanding the it's cross between the Zen and the Aleph circuits both of which are available...

Just a few reference ideas...

BTW - I'm not against DC coupled or any other criteria; it's just that I've heard DC coupled preamps that can't hold a candle to the above...

I'm sure the tube guys will love this post...but if you want tube warmth with SS slam then go listen to the above...

Steve