This started in the Pass forum, but seems more appropriate here.
My system, maybe the one I'll die with (hope that's a loooong way's off) is about done except for the amp. I've researched, embarrassed to say, almost certainly over 100 hours & narrowed it down to the SS First Watt F4 by "Papa" Nelson Pass, a unique (really) unity-voltage-gain current-source only, 25W stereo/100W balanced mono http://www.firstwatt.com/products/f4.htm more links if interested. My system appears to meet minimum voltage gain requirements.
A respected reviewer & lover of SET 300B loved the F4 alone, but when his SET 300B was inserted between the preamp & the F4 it became possibly the best amplifier ever. (A 20-Ohm resistor is required across the SET outputs for a proper load impedance; the F4 input Z is 48k-Ohm SE/96k-Ohm balanced.) In esence, this strange system may be the perfect "hybrid" amp: an SET driving a unity-gain SS current-source; an SET w/ no current requirements...
Questions for a Stereo SET "interstage coupler" to be inserted between a SS preamp (20 dB gain & 10V RMS maximum output) & the First Watt F4 unity-gain current-source:
What is ideal impedance value for output transformer taps? I assume 600-Ohm beats the normal 8-16-Ohm, thus eliminating the need for the 20-Ohm output resistor.
Your vote for the best output trannies available new? (No used except for compelling reasons.) If your "best" is in the mega-thousand USD range I'll be interested in your other podium choices...
Estimated tranny cost, please specify each or pair; I'm easily confused.
What is the ideal SET for this use?
If needed, what driver tubes?
I'm of course interested in a DIY schematic diagram.
How might one quantify any potential performance advantage of the above custom SET "interstage coupler" vs. a normal SET power amp used in the same way?
Best regards to all.
My system, maybe the one I'll die with (hope that's a loooong way's off) is about done except for the amp. I've researched, embarrassed to say, almost certainly over 100 hours & narrowed it down to the SS First Watt F4 by "Papa" Nelson Pass, a unique (really) unity-voltage-gain current-source only, 25W stereo/100W balanced mono http://www.firstwatt.com/products/f4.htm more links if interested. My system appears to meet minimum voltage gain requirements.
A respected reviewer & lover of SET 300B loved the F4 alone, but when his SET 300B was inserted between the preamp & the F4 it became possibly the best amplifier ever. (A 20-Ohm resistor is required across the SET outputs for a proper load impedance; the F4 input Z is 48k-Ohm SE/96k-Ohm balanced.) In esence, this strange system may be the perfect "hybrid" amp: an SET driving a unity-gain SS current-source; an SET w/ no current requirements...
Questions for a Stereo SET "interstage coupler" to be inserted between a SS preamp (20 dB gain & 10V RMS maximum output) & the First Watt F4 unity-gain current-source:
What is ideal impedance value for output transformer taps? I assume 600-Ohm beats the normal 8-16-Ohm, thus eliminating the need for the 20-Ohm output resistor.
Your vote for the best output trannies available new? (No used except for compelling reasons.) If your "best" is in the mega-thousand USD range I'll be interested in your other podium choices...
Estimated tranny cost, please specify each or pair; I'm easily confused.
What is the ideal SET for this use?
If needed, what driver tubes?
I'm of course interested in a DIY schematic diagram.
How might one quantify any potential performance advantage of the above custom SET "interstage coupler" vs. a normal SET power amp used in the same way?
Best regards to all.
Before going too far, it might be worth noting that this sort of design (a tube gain stage followed by a solid state buffer) is pretty common in the headphone world. So, there's really no reason not to do it with speakers, too.
There are quite a few. Emission Labs makes a few that have a ton of gain and might be worth looking into as they won't need drivers.
If you want to stay with a power amp, the 45 is the gold standard -- 2A3's are nice too. Or, there are lots of preamp tubes: 01A, 26, 1G4, 1H4, 205-D, 50, etc. There are tons, so it is worth a search for DHT preamps, or looking through an old tube manual.
Probably none. Driving speakers is probably easier as the noise floor can be a little higher than with a preamp.
Probably none here, either. But, I do think electra-print should be on your short list of transformers in part because they are very nice, and in part because Jack will wind you anything you want. Other winders I'd consider would be Magnequest, Audio Note, Lundahl, Tango, Tamura, and I'm sure a bunch that I've forgotten. I always buy from Jack anymore.
My sense would be that more components is worse than less, unless they do something specific. I'd drop the solid state pre as it doesn't do anything for you.
see above
can really vary by manufacturer and materials, and the tube you use. A 300B transformer needs to be much larger, and thus costs much more, than an 01A tranny.
See above
If you can keep gain needs low, then a highish gain DHT driving a power tube is probably your best bet. Otherwise, something with low distortion -- 5842, E180F, E810F, 5687, 7119, 6H30, etc. There are lots of options, and it is never an easy decision.
Tubes sound, on average, 2 units better than comparable solid state devices ...
ro9397 said:
There are quite a few. Emission Labs makes a few that have a ton of gain and might be worth looking into as they won't need drivers.
If you want to stay with a power amp, the 45 is the gold standard -- 2A3's are nice too. Or, there are lots of preamp tubes: 01A, 26, 1G4, 1H4, 205-D, 50, etc. There are tons, so it is worth a search for DHT preamps, or looking through an old tube manual.
ro9397 said:
Probably none. Driving speakers is probably easier as the noise floor can be a little higher than with a preamp.
ro9397 said:
Probably none here, either. But, I do think electra-print should be on your short list of transformers in part because they are very nice, and in part because Jack will wind you anything you want. Other winders I'd consider would be Magnequest, Audio Note, Lundahl, Tango, Tamura, and I'm sure a bunch that I've forgotten. I always buy from Jack anymore.
ro9397 said:
My sense would be that more components is worse than less, unless they do something specific. I'd drop the solid state pre as it doesn't do anything for you.
ro9397 said:Your vote for the best output trannies available new? (No used except for compelling reasons.) If your "best" is in the mega-thousand USD range I'll be interested in your other podium choices...
see above
ro9397 said:
can really vary by manufacturer and materials, and the tube you use. A 300B transformer needs to be much larger, and thus costs much more, than an 01A tranny.
ro9397 said:
See above
ro9397 said:
If you can keep gain needs low, then a highish gain DHT driving a power tube is probably your best bet. Otherwise, something with low distortion -- 5842, E180F, E810F, 5687, 7119, 6H30, etc. There are lots of options, and it is never an easy decision.
ro9397 said:
Tubes sound, on average, 2 units better than comparable solid state devices ...
ro9397 said:
100 hours? Novice!
ro9397 said:
10 V RMS is about 28 V peak to peak which may be sufficient depending on your speakers / room / desire for volume. Try it first, before worrying about another amp in between.
If there is not enough volume I would tend towards ditching the SS preamplifier and use a single-ended valve preamplifier with decent gain.
Good luck
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