Metropoulos Forum

Hi, After read this forum for long time I decide to post in it with a problem....

First of all I am from Barcelona ( Catalonia)
I am guitar player for 20 years and also I like electronics
ups and sorry for my English.


I have already finish a new amp, Its a 2 channel plexi. The first channel is simple plexi, where I can get cleans and amazings crunchs. the 2nd channels is a cascade mod (Aldrich).

The problem that I'vent volume enough. To here a good clean, I need to put the gain at 9 o clock, the volume channel at 3 o clock, and the PPIMV from 2 to end depends of the loud I want.
When I put END! I think that I don't have loud enough. If I compare, I ve about the same LOUD that a other amp Single ended 6l6 about 15 W
What can I do? What is brong?
Here the schematic of preamp ( the 2nd chanels is the first that i tried that after I change for aldrich mod), Power supply and power amp.

What voltages are you getting at the poweramp and phase inverter?

The preamp voltages look a bit wierd, is it drawn correctly? Is the first preamp stage really supplied by B+2 (same as the power tube screens)? I was expecting B+5 here (and lower voltage than the previous B+ nodes).

Another minor wierd thing is how the presence control is wired (drawn correctly?). As drawn, negative feedback will be removed completely when presence is turned down. Should not affect the overall volume much though.

Finally, when comparing with the 15W SE amp, did you use the same speaker for both amps?

Yes, I put B+2 in V1 to test about headroom, but now is with B5 the preamp. I didnt hear any chanche in the volume when I change it.


Here the power amp Voltages:

subefotos

the only diferencebetween the schematic and real power amp is that I put 2 control of bias to put unmatched tubes and in the PPMV pin 3 of each part I conect ¡ his bias.


The presence run good, I see many amps that draw this schematic for example:
http://lidbjork.se/amps/Mark_Huss_Plexi6V6c.gif


And Always I use the same cabinet 2x12 vintage 30 8ohms. and I have more or less the same loud that the 15W SE amp

Have you checked the 470 ohm resistor between the two 1megs in the PI? Using a 470k by accident will result in low volume from a new build.

Yes, Is a 470 ohms, Its correct!

Its a big shit!

Testing the amp the Gain Channel dont have this problem becouse the signal pas for 5 stages and in the clean/plexi pass for 3.

How can amplificate more the signal in the clean channel? I need to put other stage? I want more volume no more gain.

Have you tried temporarily bypassing your pre PI MV? Having a pre and post PI MV can rob you of a lot of volume.

This is the real preamp that I have in this moment:

subir imagen

I've the posibiti to ad other preamp tube and half of it to " clean chanel" and the other half to SEND fx, I am using a Fxloop with only one stage, in the return ( the fx have a bypass switch)

Can I add other stage in the "clean/plex" without adding gain? only up the volume signal?

Ok Iam going to try it in 5 minuts!

neikeel:


YES!!!!!!!!!!!!!!!


What can I do to have a good Master volume?what is better a pre PI or Post?

why I lost the volume with the PPIMV?????