Problem with tremolo..

mdancakster

Member
Messages
6
Hello there,
I have a problem with tremolo in my Tremolux. The pulses are really strongly audible (ticking) if the tremolo is engaged/on (even if there´s no signal from the guitar) and I don´t know what´s going on. It´s the tweed 5e9A schematics but I finally changed the paraphase PI for that of tweed deluxe 5e3 because of better overall sound (as in EC Tremolux circuit – cathodyne PI); if the circuit was the original one (5e9A) everything with the tremolo was OK. After changing the PI scheme the problem with tremolo occurred. All the measured voltages values in tremolo are + or - 20% of the original 5e9A schematics. I´ve already tried to change the tremolo valve for another three but nothing changed). Any suggestions? Many thanks. Regards, Martin.

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Messages
6,708
I have no firm idea....

( I edited this post and left only the pertinent statement remaining. I misread and misinterpreted what was going on there.)
 
Last edited:

Jeff Gehring

Gold Supporting Member
Messages
7,520
You mentioned you changed the PI configuration -- how much did you do besides that? The 5E9 has the tremolo signal doing high level modulation of the power tubes' bias. The EC thingie has much reduced amplitude LFO applied to that new gain stage's cathode, like a Vibro Champ.
 

pdf64

Member
Messages
9,016
I finally changed the paraphase PI for that of tweed deluxe 5e3 because of better overall sound
Are you sure that the amp was working properly when configured as a 5E9A? What aspect of the sound is better with a cathodyne, compared to the paraphase?

The 5E9A circuit will inherently have way better rejection of the trem modulation signal, as it is mixed as a common mode signal to a balanced system (hence it will cancel out), whereas the Eric Tremolux mixes the modulation signal in a single ended system, with no cancellation effect.
 

HotBluePlates

Member
Messages
14,197
... The pulses are really strongly audible ... 5e9A ... but I finally changed the paraphase PI for that of tweed deluxe 5e3 ... After changing the PI scheme the problem with tremolo occurred. ...

Sounds like you're hearing pulsing background noise. That's 100% normal in a VibroChamp/EC Tremolux style circuit. As @pdf64 says, the 5E9A Tremolux cancels the pulsing noise because of where it is injected in the paraphase inverter.

... Any suggestions? ...

Personally, I'd go back to the 5E9 circuit. The biggest amp mistake I ever made was selling an original '55 Tremolux.

If you absolutely don't want the paraphase inverter, move the trem injection point to the output tube grids, like a 5F11 Vibrolux. If you do that, you might want to keep the cathode follower buffer, but the cathode resistances will need to be re-jiggered (they cut a lot of trem signal as they're drawn in the EC Tremolux schematic, and wiggling the output tube bias will require much less attenuation of that trem signal). Short of that, you might want to reduce the 470kΩ oscillator plate load back to the 220kΩ found in your original Tremolux circuit.
 

JJman

Member
Messages
994
As mentioned, we don't know if you changed only the PI or also the trem to the EC scheme. The 5E9-A trem modulates the cathode of the PI so changing (only) the PI to cathodine is likely not kosher. You would now be modulating the thing that modulates only one of the output tubes.
 

pdf64

Member
Messages
9,016
The 5E9A has a trem depth control, whereas the Eric Tremolux doesn't; there are so many queries that are unresolved by your description of what's been done, it would be way better to sketch a schematic of the amp as it is and upload it to imgur etc, and provide a link.
 




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