Dynacord Eminant II T - for guitar / bass ?

[walkman]

Hi,

a while back i got an Dynacord Eminant II T , P.A amplifier. It is a hybrid transistor / tube amp. The power section has 2x el34 and 12at7.

It sounds good but very dull , so i though it might be impedance problems in to the mic input or as likely the tubes are old and worn.

the plate voltages are fairly high its supposed to output 80 watts ! , as far as the schematic shows, and i'm not sure how to go about biasing it. That is where exactly to measure the current, and what that should be. I already replaced the 12at7 and that seem to make no difference.

Will modern tubes be suitable replacement for this late 60's amp?

Also , if i wish to use an external preamp , are their any changes that would be suitable to make ?

Is the power section of the amp more suited to say use with an amp modeler as is or , could it be converted to guitar / bass duties , bypassing all the tone controls and preamp

cheers

walkman

see http://www.mif.pg.gda.pl/homepages/t...nac_emin2t.jpg

[Silvertone studio]

In my opinion replacing original tubes is no problem on vintage stuff.. If you manage to get a hold on some unused original tubes, that is off course the best, but the difference is minimal.. Old capacitors (Condensators?) are more likely to cause the problem. I´m not an expert in this field, but I had similar problems with a Fender amp from the 60ies..
Hope you figure it out..

[Albert Kreuzer]

It's all written in the schematic. The power tubes have 10 Ohm current sense resistors (R418/419). The schematic says to bias them at 0.3V across these resistors. That would be 25mA plate current (as specified) plus 5mA screen current.
Most modern tubes will take the voltage as long as you bias them a little on the cold side. I have a bass amp with more than 800 plate Volts and JJ EL34 running for years without problems.
Input impedance is too low for guitar (100k). That will kill your highs. Use a clean boost or a FET follower in front of it. If you want to use an external preamp, you can access the power amp through the tape input on the rear.

[walkman]

Thanks for that ... i haven't looked at that amp for awhile . Its very tight inside the chassis and i didn't want to mess about in there. I will see if its biased ok now.