JTM45 rectifier question

[martin manning]

The voltage changes you are seeing look correct now. You can experiment with lower values for the 1k, e.g cut it in half and see what that sounds like. That’s easily done by paralleling another 1k with it. Lar-Mar ppimv turned up all the way is out of circuit.

[SPeter]

Last night was a 'good guitar tone' night I was able to dial in a good tone and tested the Larmar maxed out. I can stay fairly clean up to four on the dial indeed. I want to do some recording to show you the tone. I think it is great but I want some second opinions on that...

As for the measurements see below. I kept the Metro specs and previous results in the first two table for reference, the last one represents the current state of the amp. Some voltages are still relatively high compared to the Metro values but I guess this is due to the Classictone Transformers vs the Metro spec ones.

voltages as of MAR282019.JPG

Please let me know if you see anything concerning.

Thanks for all your help!

[Roe]

around 210v on v1 is correct for a 45

[Reeltarded]

Excellent! Is there anything in particular that you wish was a little different? Would love to hear it. We like these amps.

[SPeter]

Excellent! Is there anything in particular that you wish was a little different? Would love to hear it. We like these amps.

I wish it had an effects loop but I see that $75 and some soldering can take care of that... I'm referring to the Metro Amp FX loop kit do you think it is a worthy addition? They claim that it does not affect the tone... is that really true?

[Reeltarded]

I am not the guy to like a loop in a low/medium gain amp. I use effects after everything in a load setup. The problem is a reverb gets distorted when you try to drive the amp.

[Roe]

loops don't help with amps like these. before breakup you don't need it. After breakup, it doesn't work too well since the power amp breaks up first. its totally unnecessary

[Reeltarded]

A great thing to do is add a line out on the output and run into effects and other power and cabinets. The other amp and cabinets aren't inexpensive, but the line out costs less than $5 in parts that you might already have laying around.

[martin manning]

around 210v on v1 is correct for a 45

The Metro spec is 180V on V1 plates. It may be worth increasing the 8k2 dropping resistor to say 12k, which should bring the rest of the preamp voltages into line with their recommendations.

[Roe]

the metro has too low voltages. around 400v at 8k is not much at all. originals had 440-450v at 8k or 6k6

[SPeter]

New problem ghosting... it drove me nuts all day I thought it was my guitar but then all three of them are doing it and it is not there on my egnater.

Sweet child of mine lick is horrendous. This is not my clip (I would not want you to die a miserable death listening to my noodling) but my amp does the same thing. It starts at 27 seconds:
https://soundcloud.com/pleximaster/afd-100-no-epa

[SPeter]

So I could get around and record the issue. It is not that pronounced on the recording as I only have a junk microphone but it is still pretty bad:
https://soundcloud.com/user-886567630-6 ... ghostnoise

Clean tones are fine, it seems the harder I hit it the worse it gets. With a soul food pedal it is almost every position is bad on the high strings just cranking the amp it is worse around G and B strings 12th fret

I seprated the power transformer ground from the filter caps but it did not change anything.
Checked all the solders I can see no bad ones.

I excluded the speaker (other amp does not do it with the same speaker) and the guitar (all three guitars do it the same)

Any ideas?

Edit second clip where I hit it with the pedal:
https://soundcloud.com/user-886567630-6 ... hostnoise2

Edit 2
It is only there when the Larmar is above ~80%. This clip shows LARMAR at 30-40% then 50-60%, I can't hear the off key sounds, then I turn the Larmar to 100% (passthrough) and it is there:
https://soundcloud.com/user-886567630-6 ... oiselarmar

[SPeter]

Also jumped the + sides of the 16/16 cap to increase PI filtering to 32uF, did not change anything.

[Roe]

You need to be careful with the grounding to minimize ghosting. Try the larry grounding mentioned on this board and detailed on the metro board. Also, you need good filter caps, esp for the mains and screens. try a 32uf that reads high for the mains. Most originals had 32uf on the mains, although I've seen pics of 40uf on a late 45. Screens could be either 32uf or 20uf. Finally, you need power tubes that are well balanced in terms of transconductance. And the a balanced PI matters if you crank the amp

[martin manning]

The added length of the PPIMV wiring can cause parasitic oscillations. Use of shielded cable or twisting the leads, is necessary. Post photo of your installation.