Hey, if it worked for Trainwreck.....
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Tainwreck master volume question
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Well it's just simulations, but...
Using a TW type circuit with a pair of el84's (because that's the circuit I already have constructed) I measured the signal at the power tube grids. The simulation is set up for what would be considered this circuits "sweet spot" by most players.
The top shot is with no master circuit in place. Adding the above master circuit and reducing resistance I started to see signals sharing the same side of 0V (what I'm assuming is "common mode") at about 50k. So the second from top is with the circuit at 40k. Then 20k, 10k and last is 2k. Below that (in red) is the resulting waveform at the amps output.
Last edited by Chuck H; 05-09-2020, 06:54 PM."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz
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"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz
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Originally posted by Helmholtz View PostI agree in principle.
The question remains, how high common mode drive signals could actually be. Are there any measurements?Experience is something you get, just after you really needed it.
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Originally posted by Randall View PostHey, if it worked for Trainwreck.....Last edited by Chuck H; 05-09-2020, 06:57 PM."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz
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Originally posted by nickb View PostFor a 'typical' LTPI with a tail resistor of 22K and with the pot at zero a 1V drive will give you 0.65V on both power tube grids (i.e common mode) and will result in a small output due mainly to mismatching of the power tubes. Seems to remain about the same even when driven hard.- Own Opinions Only -
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"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz
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Originally posted by Chuck H View Post...
{schematic}Experience is something you get, just after you really needed it.
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Originally posted by g1 View PostAll this and still no schematic of the actual master in or out of circuit."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz
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Originally posted by nickb View PostThx. I wanted to check we were on the same page as I wasn't seeing such large currents. To get those numbers I had to drive the PI with 80Vpp. It's VERY interesting. I've avoided this kind of PPIMV but I had never appreciated just how brutal they can be to the power tubes. Almost no power out yet the poor little dears are working their hearts out. I prefer to use a stereo pot."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz
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Originally posted by Chuck H View PostI thought the same thing. At first... Then I considered that the actual AC from the plates is a good bit lower when you take that 0C crossing into account. The actual watts the tubes are making is probably less with the master down, though not a lot. To be honest I'm not sure of this, but it seems that way looking at it. There's definitely some validity in Jon's observation of what's going on and I hadn't considered it before. And even if it's not really threatening the tubes the performance at low volumes looks lousy.
What is concerning about this is that presumably the intention is to allow you to turn the master down and still get decent breakup at bedroom volumes i.e you will still be driving the output tubes hard. OK it's not 100% continuous so they don't melt, but it seems like this MV arrangement is just mean to them and the power supply.
I think the idea should be banned. I didn't like it before now I really hate it.Experience is something you get, just after you really needed it.
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Originally posted by nickb View PostThe truth is quite the opposite. Taking your cct with the master at 2K, the EL84's dissipate a staggering 34W but just 12W with the same drive level with master wide open. The reason being the cathode to plate voltage is large even with high currents with the MV down.
What is concerning about this is that presumably the intention is to allow you to turn the master down and still get decent breakup at bedroom volumes i.e you will still be driving the output tubes hard. OK it's not 100% continuous so they don't melt, but it seems like this MV arrangement is just mean to them and the power supply.
I think the idea should be banned. I didn't like it before now I really hate it.
Sorry Randall. Surely didn't expect this thread to end with "This circuit sucks and shouldn't even be used.""Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz
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