Hi,
I am building a stand alone power amp for experimentation.
The current components being used are Komet style transformers with choke, full bridge rectifier, 5881 power tubes using a Dumble inspired PI circuit.
My plan is to marry this generic power amp with a variety of stand alone preamps everything from high gain to clean and everything in between.
Do you have any recommendations on a stand alone power amp that would be suitable for such an application?
Happy New Year!
Regards,
Decko
Power amp build on the bench
Moderators: pompeiisneaks, Colossal
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Power amp build on the bench
There are many, what is your main playing style?
Changes in the output tube type, the way they are biased,the PI and if the power supply has a choke or not, and the plate voltage used will be the main factor in playing and tonal differences!
Changes in the output tube type, the way they are biased,the PI and if the power supply has a choke or not, and the plate voltage used will be the main factor in playing and tonal differences!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Leo_Gnardo
- Posts: 2585
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- Location: Dogpatch-on-Hudson
Re: Power amp build on the bench
I'd just copy a mid 60's Fender output section from inverter/driver on out. They're simple and sound good, even for hi fi. Select the power you need, 15 or 40 or 80 watts, appropriate iron and output tubes, then it's drill baby drill. View any '64 Fender schematic for Deluxe, Bandmaster, or Twin, there you are.
Add an input triode for some gain, as you'll need a couple volts of signal at the inverter input to drive the amp to - and beyond - clip. Wouldn't be a bad idea to follow the gain stage with a volume control, then you can maximise your signal to noise ratio, also see how your preamps act when they're dialed wide open with MV down for overdrive tones. Heck you could even put in a PPIMV if you like. With both, you can decide which MV you like and employ that on your final build.
Add an input triode for some gain, as you'll need a couple volts of signal at the inverter input to drive the amp to - and beyond - clip. Wouldn't be a bad idea to follow the gain stage with a volume control, then you can maximise your signal to noise ratio, also see how your preamps act when they're dialed wide open with MV down for overdrive tones. Heck you could even put in a PPIMV if you like. With both, you can decide which MV you like and employ that on your final build.
down technical blind alleys . . .
Sunn Sceptre
I've finished this and it sounds great. Perhaps I've got a problem related to either over driven input or supply caps undersized. But I'm leaning towards an over driven input when the FB circuit is cut out. I've been told the input may have to be cut back to reduce clipping, but that is at near full volume
I use this with an Amp Emulator and they all sound great through it. The Iron is from two different amps.
https://tubeamparchive.com/viewtopic.ph ... sc&start=0
The final schematic is towards the end of page 1 and drawn on graph paper as I haven't had the time to learn another software program yet. I have built the Fender LTP and they sound very nice also and work well with a variety of amp tones.
silverfox.
I use this with an Amp Emulator and they all sound great through it. The Iron is from two different amps.
https://tubeamparchive.com/viewtopic.ph ... sc&start=0
The final schematic is towards the end of page 1 and drawn on graph paper as I haven't had the time to learn another software program yet. I have built the Fender LTP and they sound very nice also and work well with a variety of amp tones.
silverfox.
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Power amp build on the bench
If you go and look at the spec's for that 5881 tube you can see how much PI drive signal it takes to output a given amount of rms output, above that the output stage will start to clip as more signal is appled and the power supply starts to dip!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
When I do Actually Check?
Is that a signal I can put on the scope at the Grid of the power tube and measure peak to peak? I haven't done a thing yet with the New Year and all and it works good enough to play... I have read somewhere on the Internet: You can't measure some of the signal in the phase inverter since the signal is so weak. But then it should be something in the 30 volt range if I can measure it. I think.. I'll look up the value in the tube data sheet.Stevem wrote:If you go and look at the spec's for that 5881 tube you can see how much PI drive signal it takes to output a given amount of rms output, above that the output stage will start to clip as more signal is appled and the power supply starts to dip!
silverfox.
Re: Power amp build on the bench
Think of it this way:
not even need for a datasheet which shows a generic or average value:
a) the power tube is held at idle (no signal) at bias voltage.
Say, -52 or -38V or whatever.
b) it reaches maximum current conduction with grids at 0V
3) so peak signal voltage is bias voltage.
Easy, huh?
4) so RMS drive voltage is 0.707 * Peak voltage.
not even need for a datasheet which shows a generic or average value:
a) the power tube is held at idle (no signal) at bias voltage.
Say, -52 or -38V or whatever.
b) it reaches maximum current conduction with grids at 0V
3) so peak signal voltage is bias voltage.
Easy, huh?
4) so RMS drive voltage is 0.707 * Peak voltage.