Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Twosteps on August 05, 2016, 07:01:09 am
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Hi, everyone. This is pretty much a sequel from this thread
http://el34world.com/Forum/index.php?topic=20640.0 (http://el34world.com/Forum/index.php?topic=20640.0)
About the 5e9a and 5g9 circuit. Thanks to everyone who commented there, was very very helpful.
I've put the choke in and... it works!! Get enough clean power for a 4 piece band before it breaks up and when it does, it still with pretty much the same manner as before. I'm a lot happier :)
Now the tinkering part..
For the tone and the power I could either stop here which is fine or go even further for some more spare power with PRR or BluePlates' plans. I don't mind, I'm now have somewhere to come back to so might as well use this chassis/layout as a bit of a lab rat to kill curiosity.
The factor now is not so much the power or tone. It's the trem. If you come from a 5g9 you'd know what I mean. The 5e9a's trem is very subtle so much that I don't know if it's worth it to buy some vintage switched pot or make a footswitch to turn it off. Is it all down to having a paraphase PI once again for the very reason many people stated there. If you move the trem further from the PI itself it doesn't matter what kind of trem it is, the trem signal will come back to the 2nd half of the PI tube and be amplified? Am I right?
Or is it only the fixed bias one like the 5g9's that won't work? Will the trem circuit from a Silvertone 1482 work? It's cathodyne & cathode bias.
http://el34world.com/charts/Schematics/files/silvertone/silvertone1482.pdf (http://el34world.com/charts/Schematics/files/silvertone/silvertone1482.pdf)
I am trying to either strengthen or replace the trem in my 5e9a.
Thanks again in advance.
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Now the tinkering part..
... The 5e9a's trem is very subtle ... I am trying to either strengthen or replace the trem in my 5e9a.
It shouldn't be subtle. The real Tremolux I owned had very deep, swampy trem.
Compare just the trem oscillator and cathode follower of the 5E9 and 5G9 (http://el34world.com/Forum/index.php?topic=20640.msg217882#msg217882).
Notice there are a couple of differences in the oscillator itself: Plate load is 220kΩ (5E9) vs. 100kΩ (5G9), and cathode resistor is 3.3kΩ (5E9) vs. 1.5kΩ (5G9).
So you might try switching one or both of those resistors to 5G9 values. You could even go as far as using an LED in place of the cathode resistor & bypass cap (Sluckey knows better than me which diodes work well here).
Another spot which could boost trem in the 5E9: There is a 100kΩ resistor bridging 2 lugs of the Depth pot; you could try incrementally lowering this (maybe 56kΩ first, then trying 33kΩ, etc)
The 5E9 point of injection at the paraphrase inverter shared cathode resistor should only require a few volts of trem signal to completely swamp all drive to the output tubes. In other words, a trem signal with peaks about as-big as the idle bias across that resistor. By comparison, the 5G9 needs a trem signal on the order of 28v peak to do the same thing (an order of magnitude greater), because it's overcoming output tube bias instead of preamp tube bias. So there is no way a properly set-up 5E9 should have weaker trem than a 5G9; and therefore it seems a step in the wrong direction to inject trem at the output tube grids if stronger trem is what is desired.
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That seems to be more than enough reasons to stick with this circuit now.
- The confirmation from someone who experienced it first hand plus a very understandable explanation why.
No more asking, As far as I remember the trem I did is quite true to the circuit apart from the speed pot that I use 3mra and just bypass the switch. It's possible that there might some stupid mistakes somewhere. Otherwise I'll experiment with the resistors as you suggested.
Thanks again Mr. BluePlates!! :worthy1:
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Hi, sorry to bring this one back but I have now one last issue to solve and it still... about trem.
Let me start with where I'm at... the amp(from the thread in the above link) is working now, and it was my STUPID MISTAKES!! Yep, confession part here 1. I mistaken depth pot for speed and put the wrong resistor on it - the trem is now not weak anymore 2. Never done an asymetrical PI before I flipped the two sides of the PI tube for convenience this might be why I had problem with the headroom?
Anyway, it's all good now but just one thing - I installed a footswitch an when the trem is on the amp is also get boosted, sounds like it has 10% more gain or something. Is this normal for this circuit, if not where should I check? :w2: :w2: :w2:
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... I installed a footswitch an when the trem is on the amp is also get boosted, sounds like it has 10% more gain or something. Is this normal for this circuit ...
Probably normal. The trem turns the paraphrase inverter more-off to lower volume, but also more-on. And when it's being turned more-on, you'll probably hear that as an increased tendency to distort.
But I never had footswitch with my original Tremolux, so what do I know? At this point, feel free to call me a "more-on"...