Tube Amp Archive

Define crappy guitar... one that is not set up correctly does not stay in tune and the frets have sharp edges is just as frustrating as a crappy amp and will make anybody give up on the new hobby fast. I would say a $350-400 gently used guitar paired up with a good 500ish combo amp will be night and...

To the attenuator topic: I just got a used THD Hotplate for the JTM45 I built and so far I like it. I'm using its line out into a DAW with free speaker IRs. The THD can be turned down to zero output for silent recording and sounds quite good through the monitors of the speaker. The hotplate also dou...

So Mercury has a 7H 150mA or I can just try the 3H as it can handle 250mA

The layout you posted shows the OT CT AFTER the choke, the Metro Layout shows it BEFORE the choke... I had it set up like the Metro layout shows below from the beginning. So it got a less filtered signal from the PT in the Metro configuration and none of the filtering of the choke and the second cap...

So if we agreed that the ripple voltage is the root cause then there are some additional things to consider: - as Martin pointed out this should be the same for all jtm / bassman style amps and as such widely documented. But it is not the case. So we can conclude that the solution implemented is a g...

Ok, done. I would not call it neat lead dress wise but there is no hum or any other noise which would be lead dress related. I made the mistake to put in a bunch of NOS carbon resistors which added some hiss but my guitar is still more noisy than the amp. Once I put it in its cabinet it won't bother...

Easy. Right now you have the the two leads from the standby switch going to the rectifier cathode (pin 8) and the first cap in the CRC, correct? Disconnect those and put a short lead from the rectifier pin 8 directly to the first cap in the CRC. On the other side of the CRC you should have one of t...

Got it, so there is a fundamental issue with the position of the standby switch as it is implemented on the Fender Bassman layout and the JTM45 layout just copied that mistake same as the Metro Layout. Our modification to make that first cap a part of a CRC filter did not make it worse. The 'essay' ...

Now, regarding to the standby switch. I learned form the posts in this thread that the rectifier only sees the first 32 cap as the resistor decouples the second one the same way the choke used to do. So I would think no need to worry about overloading the rectifier tube... what am I missing?

Done. It worked! No ghost notes everything dimed and neck pickup!!! I added two 470R 5W in parallel between the 32 caps (so a total of 235R resistance). I measured the voltages and it is as follows: CRC filter idea voltages.JPG So the B+ went up from 465V to 480V at the standby switch. I'm not sure ...

So this is how I read your sketch (without moving the standby switch): I need to get this right I don't want to burn down anything LOL

martin manning wrote: ↑Thu Apr 25, 2019 7:30 pm /:^| ...

Sorry man, you are talking to a (not very well) trained monkey LOL I'm a metallurgist by profession and the most complicated guitar electronics stuff I've ever done before is a rewiring of an epiphone LP.
I truly appreciate everybody's efforts to help me solve this thing.

Like this, and yes paralleling two 470’s will be fine. Thanks! The OT (plates) is the one we also called OT CT correct (the brown wire in my amp)? What should be the rating of the 8k2 resistor between the two 16uF capacitor sides? What is the reason you recommend moving the standby switch? Can I ge...

I don't understand the motivation to replace a 110 ohm choke with a 250 ohm resistor. :?: I indicated that I want to get away with one choke for packaging reasons if possible. There is really no good way to place the second choke on the chassis without having to lift the whole circuit board. @Marti...

Tested the mod, ghost notes are back full force!!! Yuck! So OT CT front of the 3H choke is not good. What does this mean? What else can I try before I go back to the no ghost setup?