I am in love, again, i canot help mysef.
This time i want to build an amplifier with the following goals:
-chassis footprint 255x305mm, monoblocks
-use 845, not the boring 300b,Tektronics engineer choice
-i am not going to use big, heavy, ugly and ultrasonic(trouble maker) iso or monolith output transformers
The schematic almost drow itself. Even my mother can understand it( by the way, my mother is an NATO consultant in electronics engineering).
This time i want to build an amplifier with the following goals:
-chassis footprint 255x305mm, monoblocks
-use 845, not the boring 300b,Tektronics engineer choice
-i am not going to use big, heavy, ugly and ultrasonic(trouble maker) iso or monolith output transformers
The schematic almost drow itself. Even my mother can understand it( by the way, my mother is an NATO consultant in electronics engineering).
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Your mother would probably have expected the output transformer to be connected with B+ centre tapped and the 845 anode inputs at either end.
kind egards
Marek
kind egards
Marek
You currently have both 845 anodes at the same potential as each other so they can't push-pull - your output stage is wired parallel single ended.
You look like you are going to great lengths to eliminate capacitors from the signal path and there are only three significant ones left:- two small ones in the AD1 cathodes and one big one in the twin 845 power supply. A parallel single ended 845 output is going make the B+ supply ripple with the whole program material being imprinted over the B+ supply, so ultimately, you'll be listening to a big capacitor charging and discharging. All single ended amplifiers do this by definition, but pretty much no one attributes their perceived variations to sound quality to the bits of the circuit they don't look at.
If the 845s were arranged as a push-pull into a centre tapped output transformer (and you remain class A), then the B+ would be independent of the level of the program material and the B+ power supply capacitor would see little ripple current, because the program material current is just recirculating around the pushing and pulling 845s and output transformer loop. That means you are free to choose a much smaller power supply capacitor, which for those with golden ears, can have more pleasing sonic characteristics. That looks to more closely mesh with your goals.
It seems paradoxical to go to push-pull only to then undo that in the final stage, where it matters most.
kind regards
Marek
You look like you are going to great lengths to eliminate capacitors from the signal path and there are only three significant ones left:- two small ones in the AD1 cathodes and one big one in the twin 845 power supply. A parallel single ended 845 output is going make the B+ supply ripple with the whole program material being imprinted over the B+ supply, so ultimately, you'll be listening to a big capacitor charging and discharging. All single ended amplifiers do this by definition, but pretty much no one attributes their perceived variations to sound quality to the bits of the circuit they don't look at.
If the 845s were arranged as a push-pull into a centre tapped output transformer (and you remain class A), then the B+ would be independent of the level of the program material and the B+ power supply capacitor would see little ripple current, because the program material current is just recirculating around the pushing and pulling 845s and output transformer loop. That means you are free to choose a much smaller power supply capacitor, which for those with golden ears, can have more pleasing sonic characteristics. That looks to more closely mesh with your goals.
It seems paradoxical to go to push-pull only to then undo that in the final stage, where it matters most.
kind regards
Marek
At 4AM, I am not going to analyze all of the circuit.
Some of you do not understand what filenet is trying to do.
But, I find the following:
Single input with a phase splitter
A balanced driver stage to an interstage transformer
A step up from push pull primary to single ended secondary
A parallel single ended 845 stage.
Other than some errors if any, I understand the reason the original poster picked this particular architecture.
It solves the problem of 845 tubes needing very large signal swing to the grid.
By the way, I am a former Tektronix engineer. I designed and built many 300B amplifiers. My friend in Japan built a beautiful pair from my schematics.
But I also used lots of other output tubes . . . 45, 2A3, 6A3, 6L6GC, KT66, KT77, KT88, 5881, 6CK4, 4-65A, and perhaps others too.
I really like the 845 output tube. It is similar to the higher power WE 212E.
I saw and heard a pair of single ended WE212E mono blocks, it flooded the room with light and sound.
A pair of Spica T50 and the WE212E were absolutely amazing! It got me back into building tube amplifiers.
filenet,
Fix any errors, but go with the architecture you picked.
Some of you do not understand what filenet is trying to do.
But, I find the following:
Single input with a phase splitter
A balanced driver stage to an interstage transformer
A step up from push pull primary to single ended secondary
A parallel single ended 845 stage.
Other than some errors if any, I understand the reason the original poster picked this particular architecture.
It solves the problem of 845 tubes needing very large signal swing to the grid.
By the way, I am a former Tektronix engineer. I designed and built many 300B amplifiers. My friend in Japan built a beautiful pair from my schematics.
But I also used lots of other output tubes . . . 45, 2A3, 6A3, 6L6GC, KT66, KT77, KT88, 5881, 6CK4, 4-65A, and perhaps others too.
I really like the 845 output tube. It is similar to the higher power WE 212E.
I saw and heard a pair of single ended WE212E mono blocks, it flooded the room with light and sound.
A pair of Spica T50 and the WE212E were absolutely amazing! It got me back into building tube amplifiers.
filenet,
Fix any errors, but go with the architecture you picked.
Hmmm....
The 80-100W high impedance (14-19k Raa) PP transformer will be big ... very big, ultra heavy, and this monster isn't pretty (cover helps a little), but exactly not ultrasonic. 🙂
Really?
I think most people will have understood paralleling the output tubes would have been for for current.
I think most people will have understood the choice of phase splitter, step up and push pull were for voltage.
It's not like anyone has misread the schematic.
He obviously just wants to double the power he got from the same 8010/ad1/845 thread a year ago and is shoehorning it into iron supplied by Lundhal.
kind regards
Marek
I want the output stage to be single ended and i want to solve the problems that come with this:
-increased output resistance
-limited upper bandwidth
-and not the last, hum from AC heating
That s why i am choosing PSE
Even with lots of silicon it will weight big, without silicon it will be an monster.
Big value capacitors and regulators after, i am expecting to solve the ripple problem, even a 5k6 output transformer will help reflecting a smaller ripple on output.
Yes, ultrasonic is not the most fortunate term, i mean, lets say above 60khz upper -3db limit
Love your work 50AE!
Single input with a phase splitter-correct
A balanced driver stage to an interstage transformer-correct
A step up from push pull primary to single ended secondary-its an step down, i am looking only for maximum 13W that the output transformer can give
A parallel single ended 845 stage-correct
Very impressing builds, that makes me the bad guy?
filenet,
I should have looked up the Lundahl 1671.
I assumed that all windings have the same turns. In that assumed case . . .
1V plate 1 to primary 1
1V plate 2 to primary 2
These do not add signal voltage, they are essentially in parallel.
1V secondary 1 in series with 1V secondary 2: 2V to grid 1
1V secondary 3 in series with 1V secondary 4: 2V to grid 2
That explains why I thought you were using the interstage as a voltage step up.
I apologize for not looking the 1671 specifications.
I see you are using the interstage as a 2 to 1 + 1 transformer. Repeat for the other half of the windings.
1:1, no voltage step up.
I should have looked up the Lundahl 1671.
I assumed that all windings have the same turns. In that assumed case . . .
1V plate 1 to primary 1
1V plate 2 to primary 2
These do not add signal voltage, they are essentially in parallel.
1V secondary 1 in series with 1V secondary 2: 2V to grid 1
1V secondary 3 in series with 1V secondary 4: 2V to grid 2
That explains why I thought you were using the interstage as a voltage step up.
I apologize for not looking the 1671 specifications.
I see you are using the interstage as a 2 to 1 + 1 transformer. Repeat for the other half of the windings.
1:1, no voltage step up.
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excellent ++++ 🙂
But the schematics and "conception" is for my opinion totaly wrong.
You will "kill" very rare AD1 in phase splitter and also very rare 8010
.
The right aproach is to use one AD1 moderate Io for driver and probably You can drive 845 even in parallel. AD1 has lower Ri and good current output. 845 have also lower Ri, in parallel will be 2 x lower so the OT will be easy to mount.
Ad if You lower the power range the Rare and expensive tubes will last much longer
in the same time You will spare pairs to repalce after 6-8 Years... Maybe more...
845 are obtainable with new production...
.
cheers