Stalker thank you for that little program, it seems quite handy and could be a major time savor! I'm already pretty comfortable performing calculations associated with ohms law (voltage dividers, voltage drop, power dissipation, current and the likes) by hand. So should I treat the resistors as a string of resistors in series all having an equal current passing through them connected to ground at the end, declare the voltages I want at each node in between each resistor and do some algebra with ohms law and the likes/pick some arbitrary values to determine the values of each resistor?
Thanks again!
Thanks again!
okay small update, i think I'm just going to build the power supply in this schematic:
http://www.muzique.com/news/images/Epi1.gif
If the amp its powering hasn't blown up yet than mine shouldn't!
ill be using the hammond 269 ax
http://www.muzique.com/news/images/Epi1.gif
If the amp its powering hasn't blown up yet than mine shouldn't!
ill be using the hammond 269 ax
First resistor (3 to 5W): "sees" all the current
2nd( 1-2W): only passes screen and preamp currents
3rd(1/2-1W): only preamp current.
And so on. Follow the current.
2nd( 1-2W): only passes screen and preamp currents
3rd(1/2-1W): only preamp current.
And so on. Follow the current.
I need to revive this thread! I'm working on a similar idea (SE el84 & 6V6) though driving each of the tubes with a separate volume and tone control. I'm building it more for curiosities sake and I can post the schematic if anyone is interested.
I happened upon this thread and noticed that it ended before we got to see the finished product from youngb4.
How did it turn out?
I happened upon this thread and noticed that it ended before we got to see the finished product from youngb4.
How did it turn out?
Old guitar amp thread revived so I will move it to Instruments & Amps per forum policy.Hi,
I'm thinking about a lower power version of the Mesa Simulclass with EL84 and 6V6.
How can I choose the impedance of the transformer when different tubes share the same primary?
Thanks in advance
I'm thinking about a lower power version of the Mesa Simulclass with EL84 and 6V6.
How can I choose the impedance of the transformer when different tubes share the same primary?
Thanks in advance
Thanks Bill,
yes I know that separate winding would be the easiest solution, but I would like to know how can I calculate it when different tubes are on the same primary. If the tubes are the same it's easy, you divide the needed impedance and multiply the needed current by the number of paralleled tubes, but when tubes are different?
yes I know that separate winding would be the easiest solution, but I would like to know how can I calculate it when different tubes are on the same primary. If the tubes are the same it's easy, you divide the needed impedance and multiply the needed current by the number of paralleled tubes, but when tubes are different?
Thank you nicoch58. Yes, safety rules would be use the highest and divide by the number of valves in parallel. But then how would the two loadlines will look like?
load line is by bias.... as b+ and reflex impedence from speakers are fix
set each tube at is best ...
set each tube at is best ...
You need different windings,period.
You also need different bias and different signal drive, note DC attenuators on a pair tubes.
"Different" repeated 3 times means you CAN NOT just put them in parallel.
You also need different bias and different signal drive, note DC attenuators on a pair tubes.
"Different" repeated 3 times means you CAN NOT just put them in parallel.
Hi, the schematic in post 107 shows one winding with separate taps, not separate windings. So I am not sure who is speaking to what, i.e. proven design vs personal experience; is everyone on same page.
If you wanted the BEST design with the MOST power output, you would not be fooling with mixed teams of donkeys and dogs.
Anyway "tubes is tubes". For the same supply voltage and safe dissipation, any post-1939 power tube "wants" about the same impedance.
Mesa surely came up with their odd-couple team parameters by throwing darts and testing. I suspect the different impedance is more about the "expected sound" of the two types than any theoretical optimization.
Ah. Some are pentode and some are wired triode. The triode won't make as much power as the pentode and the best fit may be about 1.5X the load impedance. We could plot lines but what would we learn? (I can't hear nothing holding a plot to my ear.) And deal-killer: the selection of dual-Z trannies is about zero. I would hang it all on a 6.6k winding and let the triode mode be low power.
Anyway "tubes is tubes". For the same supply voltage and safe dissipation, any post-1939 power tube "wants" about the same impedance.
Mesa surely came up with their odd-couple team parameters by throwing darts and testing. I suspect the different impedance is more about the "expected sound" of the two types than any theoretical optimization.
Ah. Some are pentode and some are wired triode. The triode won't make as much power as the pentode and the best fit may be about 1.5X the load impedance. We could plot lines but what would we learn? (I can't hear nothing holding a plot to my ear.) And deal-killer: the selection of dual-Z trannies is about zero. I would hang it all on a 6.6k winding and let the triode mode be low power.
There's a common "fix" for a Fender, saw it in an guitar amp book, I forget which, that is PPPUL, to fix the "dryness" by just triode strapping 2 of the output tubes, 1 on each side. No other changes required.
In fixed bias the different signal and different bias can be easily fixed by adding a voltage divider with one side grounded for the EL84: with two resistors we lower the signal and increase the grid reference voltage.
Having 12 and 14 W of max plate dissipation their loadlines won’t be that much different either. I would consider 5 kOhm Raa and 350 Vdc for both.
I can consider 23%UL and no nfb to make the curves even more easy to be fitted by the load.
Will it be that wrong?
Having 12 and 14 W of max plate dissipation their loadlines won’t be that much different either. I would consider 5 kOhm Raa and 350 Vdc for both.
I can consider 23%UL and no nfb to make the curves even more easy to be fitted by the load.
Will it be that wrong?
Of the schematic in post #107 you could say that it's scores "3 x different" because:
1) The four tubes don't share the same winding completely (because of the use of the taps),
2) They are biased differently (because of the voltage dividers on the two triode connected tubes), and
3) They get different signal drive (because of the voltage dividers on the two triode connected tubes).
For some combinations of tubes it's apparantly possible though to score "0 x different". On page 40 of this 1953 issue of Radio & Television News there's a description of such an amplifier ("extended class a" with a pair of 807's running in triode mode + a pair of 807's running in pentode mode): https://worldradiohistory.com/Archive-Radio-News/50s/Radio-News-1953-09.pdf
at the end, the output transformer doesn’t know if I have connected one tube with the same characteristics of the other two tubes, or two sligthly different tubes.
So that “equivalent” tube couldn’t be connected? God, why?
Correct me, but the “equivalent” tube has the curves that are the sum of the currents of the two different tubes at same voltages (g1, g2 and a).
Easy if the tubes are the same, not so much if they are different.
But it certainly can be done.
I would like to know how.
So that “equivalent” tube couldn’t be connected? God, why?
Correct me, but the “equivalent” tube has the curves that are the sum of the currents of the two different tubes at same voltages (g1, g2 and a).
Easy if the tubes are the same, not so much if they are different.
But it certainly can be done.
I would like to know how.