Double Shot..my new project, tube preamp..layout & pcb

[stephanovitch]

Congratulation!!!
Your sound is over great!

Try to put transfo inside the same box now.
I don't think that you will have noise induction.

[dschwartz]

the next oine will have the trafo´s inside..it will be a rack mounted preamp..

today i´ll lower the coupling cap to about 2.2nF.. for the high gain channel

[stephanovitch]

Have you try to remove the 5nf cap on plate resistor?

[dschwartz]

yes i did that, also, the first coupling cap is 5.8nF, second 39nF and third 33nF
i lowered the 2,2nF cap in parallel with the 680K resistor before gain pot, for a 1nF..no change..so i´m thinking of putting a 2.2nF (or 3.3nF) alone as a second coupling cap for the high gain channel.. i need just a bit less bass content to clear off mushy distortion on lower strings

[dschwartz]

FYI, i changed the 39nF coupling cap for a 5.8nF and the things cleared up nicely..

[dschwartz]

some new demos, with some value tweaking and changing a crappy EH tube:

Clean-clean
http://diynoise.googlepages.com/cleaner.mp3

clean mid gain:
http://diynoise.googlepages.com/clean_med_gain.mp3

clean top gain:
http://diynoise.googlepages.com/clean_max_gain.mp3

high gain channel-mid gain (marshall style)
http://diynoise.googlepages.com/marshall_gain.mp3

very high gain
http://diynoise.googlepages.com/Veryhighgaion.mp3

all recorded directly to the pc trough my korg ax3000g cab sim (vintage 4x12)

[Karmasound]

Wow


What's the latest scoop on this project?

[Thomeeque]

Missing the 5th stage? well.. it´s a MOSFET BUFFER!!!!!! hehehe...well, if RG sez that they are good..who am i to disagree???

Can somebody please point me to RG's thread/article, where I could read more about using MOSFET BUFFER instead real tube stage? Thanks!

[dschwartz]

here it is:

http://www.geofex.com/Article_Folders/mosfet_folly/mosfetfolly.htm

i am building the rack version right now..still in process

[ambulancevoice]

now thats a true tube pre amp!!!!

[km-r]

this is what im looking for! im waiting for the updated schem... please work on the schem... 

[Rmanen]

So how is the rack version coming along? is it going to be a single rack space?
What VA value did you use for the transformers?

Love the project, btw

[dschwartz]

well, here are 2  pícs of the (unfinished still) enclosure.. 

http://dsmnoisemaker.blogspot.com/2008/01/double-shot-iila-versin-rack.html

the rack is made wth  U shaped 50mm x 25mm aluminum profiles (those used for window making), so the rack is 1.3U or so   

i had troubles with the power supply and the mosfet follower impedance (check some of my last threads), so i ended up using 3 transformers,
- 12V 1A only for heaters and relays
- 12V 500mA coupled with 9V 300mA for B+

and changed the 100k source resistor for the buffer for a 33k...

now how it sounds??

SUPERB!!!!!!!

the clean is pretty sparkly and percusive, not very compressed until some light saturation, some friends told me that sounds pretty much like a  blackface...for my taste, is nothing to throw fireworks, but it was the best i could get with my "easy cheap clean channel" method

The distortion channel is heaven for me, goes from "tube screamer pushed pre" sounds to full metal scooped kick ass bottom end..i´m so proud of the results..really happy...i hope the owner make justice with his playing (i think he plays punk rock  )

[anti-idiot]

just amazing!

esta muy bien la version de rack, se ve que tienes un buen acabado, muy profesional. saludos desde Peru.

[Rmanen]

It looks beautiful, and I'm sure it sounds as good

I'm in the process of thinking up a 1u rack bass pre-amp, and I'm liking your powersupply . The only thing I'm not liking is 3 xformers, so I'll see if I could do it with 2 back to back.

Keep up the good work!

[kurtlives]

OMG what an amazing build!!! COndrads man

Do you have a final PCB layout?

[dschwartz]

Thanks to all for your kind words..

well i don´t have a final PCB, and i think it will never be,  cause i like to tweak the values a lot until i get the sound i like, sometimes that means changing pot values, cap values and resistors..but in this file:

http://diynoise.googlepages.com/double_shot2.rar

i have the latest version of the basic PCB and schems, that will get you on the ballpark..it includes:
- Gain stages PCB: this pcb contains the gain stages and mosfet follower..the output goes to the switching and tonestack (TS)  PCB..
- Tonestack PCB: contains the TS for both channels, a relay switch for the boost, and other for the FX loop. Also the 2nd relay of the channel switching ( the 1st one is on the gain stages PCB)
- Signal schematic
- power supply schematic

BE WARNED that the values on the schem may not match the values on the PCB, i´m kind of lazy and i don´t have time to update all the changes on all the files, specially if i make changes on the physical board a lot. i socket a lot of comnpoinents to tune to taste and use trims for critical resistors..

You MUST understand what´s going on to build this, this is not a "read and build" preamp..it´s a "read, understand, build, debug, tweak and enjoy" kind of thing..

i would be glad if someone builds it...

[dschwartz]

It looks beautiful, and I'm sure it sounds as good

I'm in the process of thinking up a 1u rack bass pre-amp, and I'm liking your powersupply . The only thing I'm not liking is 3 xformers, so I'll see if I could do it with 2 back to back.

Keep up the good work!

my first version had a back to back 1A 12V and 9V 500mA, i used a 7812 for heaters in series with a 7805 for relays...using the 2 regulators in series helped a lot controlling the current load to the xfomers..and got good results..

on the actual version i used 12V relays but i wired them in parallel with the heaters, son the loading was HUGE...
i reccomend the 5V/ 2 regs way (as shown in the schems)

[niopren]

great!!! congrats

te envidio sanamente, algun dia construire el mio   

[petemoore]

  Great to follow along here Dscwartz !
  I've been reading and listening to clips since you started, and noting all the little and big mistakes [er...learning experiences] you've overcome...thank YOU for overcoming them and sharing your experiences in such great detail, and with all the soundclips !
  All your work and diligence and persistance and sticktuitiveness have rewarded you with a fine tube preamp, and us with excellent tutorials on building approaches.
  Tones are super, look is stellar...excellent task management !