freestompboxes.org

here is the link for the power supply: http://www.musikpartner.dk/gemfile.asp? ... supply.pdf. If someone can manage to retrieve it, that would be great!

fulltone272 wrote:here is the link for the power supply: http://www.musikpartner.dk/gemfile.asp? ... supply.pdf. If someone can manage to retrieve it, that would be great!

I can't read it. Is it correct?

Do you think R16= 75k is right?
i simulated this stage and the cathode voltage is at 236v?????
cbriere

help,
- i am trying to build it with 2 x 12ax7 ( i have substituted the tube number pins to fit) , but i have a problem at the last tube stage.
- shouldn't a cap be placed in series with R14?
- still not shure about the value of R16=75K ?

Here is the direct link (bypass ASP) to the PSU section:
http://www.musikpartner.dk/download/Sey ... supply.pdf

It's just two trannys back to back (which I think better suits tube gear then more modern designs)

@cbriere
Why would you build a preamp spec'd for low mu triodes, with 12AX7s to begin with?
But then I'm not sure I would use those values for 6021 either so what the heck, go for it
Where did you get 236v, on V2b pin 5?!
If the schem is correct, maybe V2a is direct coupled to V2b (elivated by the 75k cathode) hence why no coupling cap between the stages?
If that's the case then V2b's cathode should be biased high... but not THAT high

Sorry, have no idea why they choose to design V2b like that, not the purpose and not the implementation.

I mailed Seymour Duncan a while back looking for some suggestions to tighten up the flabby bass.... This was their response:

"I'm not sure I understand exactly what he means by wanting to reduce the "pre-gain bass level". I am going to assume that he wants to reduce bass response early in the signal chain. This often has the side effect of reducing the sensitivity or making the unit feel like it has less gain, but it can also tighten up the distortion.

There are a number of places in the circuit where bottom end can be reduced:
1. C1 is currently .01uF/50V. Changing it to a lower value will reduce bass response in the lead channel only.
2. C3 is currently .0082uF/400V. Changing it to a lower value will reduce bass response in the lead channel only. Be sure to use a capacitor rated for at least 400V.
3. C7 is currently.1uF/400V. Changing it to a lower value will reduce bass response in rhythm channel only. Again, note the 400V rating.
4. C8 is currently .015uF/400V. Changing it to a lower value will reduce bass response in the lead channel only. Note voltage rating.
5. C5 is currently .1uF/250V. This is the first capacitor in the signal chain and is a safety requirement for double insulation rating. Changing it to a lower value will affect both channels. Replace it with a safety agency approved capacitor of the rated voltage in order to retain the double insulated rating.
6. C14 is currently .1uF/400V and is at the end of the signal chain. Changing it will affect both channels. It will tend to have a more subtle effect on the sound but could be useful in cleaning up the bottom end without sacrificing drive to the earlier stages.
All de-soldering so should be done carefully to avoid damage to the PCB and lifting the pads and traces. Of course, modifying the unit voids the warranty, so be careful."

I haven't tried these yet, but it's on my to-do list.