Metropoulos Forum

Hi,

I 've finished an amazing amp,
two channel,
the first one is the plexi of the bogner ecstasy and the second is the blue channel.

Its sound incredible but now I want a little more gain in the blue channel.

What can I do?

this is the schematic:

http://milas.spb.ru/~kmg/files/schemati ... Preamp.pdf

I use the structer switch but I need a little more gain without adding any stage more.


Thanks and sorry for my english

The only difference between the schematic with my amp is:

I put two gains, One for plexi and one for blue channel. and are 1Mlog

I delete R19 on the schematic I attached and I get more gain, is it a good way to take a little more gain? thanks!

Perhaps try a bootstrapped cathode follower:

http://www.valvewizard.co.uk/dccf.html
(At the end of the article)

I haven't tried this, but I'm planning a build that will have it. It would affect both channels though.

I try It!!!

It runs, its a low increase of the gain, but I think that it's I need,



If any body know more mods to increase the gain.....


I want to try all mods.


thanks d95err!

the blue channel is ok!

Now I want to make the plexi channel more rocker.

this is the schematic that I made

The gain pot is 1Mlog

subir foto


How I can get more gain to make it more rocker?


One question more, What does the R that I cercled in green (470k to grond before Cf).
In this R is where I conect the return of the channel 2. When I am plaing in plexi channel and I bypass this R I get a little more gain (or volume). When I bypass it when i amb plaing in LEAD channel the sounds cracket, Anyone can explain me this please?

Thanks!

to get more gain: try a 5nf bright cap and a .68uf over the cathode (v2a on plexi). also try to increase the green 470k to at least 1m2

Roe wrote:to get more gain: try a 5nf bright cap and a .68uf over the cathode (v2a on plexi). also try to increase the green 470k to at least 1m2

Since the complaint is not enough gain, I assume the gain knob is already at max, in which case the bigger bright cap won't help. Also, since the cathode follower is now bootstrapped, the preceeding gain stage is already at max gain (close to Mu of tube), so a cathode cap does not help either.

Cutting or increasing the circled 470k resistor will obviously increas gain.

Bypass the 1k .68-2.2u to taste

My power trafo have 350 - 0 - 350 and 325- 0 - 325 V

This are the values and the final schematic:

What do you think about it?



subir imagenes

It seems that your preamp voltages are very low. With 350-0-350 on the PT you should be able to get a lot higher voltages than 200V in the preamp. What is your B+ at the power tubes and phase inverter?

I'm no expert on high gain amps, but from what I hear, high-gain builders prefer something like 300-350V on the preamp tubes.

this are the values with 350-0-350 .

I added a fx loop but I dont draw it, that have 244V .


subefotos

If (and this is just a matter of taste) you want higher preamp voltages, you can try having the supply node for the fx loop in parallell to the rest of the preamp supply rather than in series.

You could also run the last two supply nodes in parallell.

What can I get with higher Voltages in the first and second stage?


Thanks

raza wrote:What can I get with higher Voltages in the first and second stage?
Thanks

Well, as I said I'm not really and expert on this, but the voltages will affect the feel and tone (frequency response, stiffness/loosenes, etc). High-gain often seem to have relatively high preamp voltages. For example, the Soldano SLO has something like 360V on the first stage. The Bogner Shiva schematic I've seen indicates around 250V on the first stage. So your 200V seems unusually low. However, if it sounds good, don't change anything!

To get significant distortion from a "plexi" style channel, you need to turn the master volume to 10, or use a post-PI master volume. If you want more distortion than that, use a booster/OD/dist-pedal.