Tube Amp Archive

A single shared resistor supplying the screen grids seems to have been a preferred arrangement for Phillips-Mullard with the EL34, see ‘operating characteristics’ p3 and 4 of https://tubedata.altanatubes.com.br/sheets/010/e/EL34.pdf Selmers tended to follow that https://el34world.com/charts/Schemat...

Thanks for all the responses! I will take a look at the schematics provided above. As mentioned above, only the 120W version of the amp has screen resistors. The output tube board is underneath the power supply board, and unfortunately they are layered upon each other so close that there is not even...

Hi! I have a Peavey Triumph 60 which is designed without screen resistors in its 2 x 6L6GC push/pull output section. I'm considering adding screen resistors, but it is not easy to find space for them in this amp, due to the way the output tube PCB is placed underneath another PCB, with little space ...

Oops, I should have caught that one...

Thanks, you have probably saved me from a couple of hours searching for a non-existent defect!

Hi! I think I'm having a problem with an Electroharmonix 12AT7 LTP PI on a homebrew amp. The voltage difference between grids and cathode is very large, around 20V. Still, the amp works fine at low volumes. I havent turned it up. I'm using the circuit (and notation) here: http://www.freewebs.com/val...

I wanted to mention one thing on this topic (sorry if it was covered, the previous posts confused me a bit): Did you consider putting in some sort of built-in (switchable) speaker emulator? That could be cool. Perhaps your customer will postprocess the signal either by using software speaker impulse...

I would say that you do need the 1Mohm resistor. Otherwise the open cap end will reach a high voltage no matter how good it is (unless the "leakage resistance" of your cap is infinity, which is impossible) Also, the answer would otherwise depend on the input impedance of your voltage meter. Say your...

Could you recommend a good tutorial or book that speaks of the tweaks and or amp design optimization as it relates to different type of speakers? For example: a 12 inch Alnico works best with this amp layout or Altechs work great around this type of design. Something that can help me to realize the...

Thanks. Sure seems like theres a lot more hi attenuation that that with 220k, but i guess calculators don't lie. The calculator doesn't lie, but thereare a few caveats. First of all, the proper resistance value to use in the calculator should include the output resistance of the preceeding part of ...

Go here: http://www.muzique.com/schem/filter.htm Input resistance 220000 ohm Capacitance: 0.00015 uF Gives a low pass corner frequency of around 5000Hz. It simply calculates the corner frequency using the formula f = 1/(2*pi*R*C) The capacitance 150pF is an estimate I've seen for the total capacitan...

Thanks guys! I'm going to stick with type B unless I have a good reason to change it. It is more compatible with the way I wanted to implement switching at the end of the preamp. Q1: Type B in theory would impart a larger signal to the PI because Type A attenuates the signal w/ the 1M resistors prio...

Hi guys, I have a question on Hiwatt PI circuits. I'm in the process of modifying a Ceriatone "Hey What 103" (a Hiwatt "clone") into a full-fledged dual-channel preamp. Instead of combining the channels after the first tube, they are combined closer to the PI (I also added a preamp tube). I'm not ex...

Nope. It does not pop. Thanks xtian, that's very helpful! My amp has a cathode follower in front of the PI stage. I'm going to switch between two separate preamp channels. This means that it might be worth a try to keep the CF common to both channels, and have the switch just in front of it. I theo...

Do you find that the rhythm/lead switch is noisy or not? I mean, do you hear a noise from the speaker when flipping the switch?

I'm thinking about a similar feature in one of my amps, hence my interest.

Thanks!

How about these:

Rocktron:
http://www.rocktron.com/products/speake ... ocitys112/

Somebody discussing a Mesa Boogie wedge cabinet (with pics):
http://forum.grailtone.com/viewtopic.php?f=9&t=40041