Has anyone built a good sounding 845 SET Amp?...
Does anyone have a schematic and photos of a good 845 SET Amp?...
I've built a 6N1P/KT88, and 6SN7/300B SET Amps, and I'd like to move up the ladder for the next project into ultimate Triode territory and 1kV land. I recently bought a nice PP KT88 Amp, but even in Triode mode, it doesn't produce true Triode sonics. I plan on using quality parts, Lundahl transformers and Juipiter Cu Coupling caps, etc. A 6SN7, 300B, 845 project would be ideal, but if someone has a good proven design I'd love to see it.
My speakers are also DIY:
1. SBA 6.5" D'Appolito with Be tweeter. 91dB/W
2. Scan-Speak Ophelia: MMT 7" Revelators with 714000 Be tweeter. 89dB/W
Thanks
Does anyone have a schematic and photos of a good 845 SET Amp?...
I've built a 6N1P/KT88, and 6SN7/300B SET Amps, and I'd like to move up the ladder for the next project into ultimate Triode territory and 1kV land. I recently bought a nice PP KT88 Amp, but even in Triode mode, it doesn't produce true Triode sonics. I plan on using quality parts, Lundahl transformers and Juipiter Cu Coupling caps, etc. A 6SN7, 300B, 845 project would be ideal, but if someone has a good proven design I'd love to see it.
My speakers are also DIY:
1. SBA 6.5" D'Appolito with Be tweeter. 91dB/W
2. Scan-Speak Ophelia: MMT 7" Revelators with 714000 Be tweeter. 89dB/W
Thanks
Take your 300b amp and stick a 845 in after the 300b. 300bs are pretty common driver tubes for the 845.
Build an outboard PSU to give the 845 the stupid high voltage it needs, slap some different output transformers on the thing and boom, done and done.
Honestly though, I would not go with 845 tubes. The amps that I have heard that use them all sound kinda high strung and a bit harsh. Plus, the 845 uses seriously high voltage, puts out a lot of heat, and puts out way more power than you need.
I would consider something like a 300b push pull amp to get some more power while still keeping things a bit safer and more practical than the 845.
Build an outboard PSU to give the 845 the stupid high voltage it needs, slap some different output transformers on the thing and boom, done and done.
Honestly though, I would not go with 845 tubes. The amps that I have heard that use them all sound kinda high strung and a bit harsh. Plus, the 845 uses seriously high voltage, puts out a lot of heat, and puts out way more power than you need.
I would consider something like a 300b push pull amp to get some more power while still keeping things a bit safer and more practical than the 845.
With my best intentions I'd like to say it, but if someone wants to build an amplifier with a tube of this high weight category, one should be able to engineer his own schematics a long time ago.
So my advice to you is - take a few steps back and reopen the dusty books.
A tube is only a fraction to the whole contribution to the sound signature of the amplifier and to the measured specs.
Let's not draw conclusions about a car just by looking at the rims.
But the fact the 845 is a high power tube, uses a kV supply and outputs roughly 110W of heat is an issue, yes. I'd call that the winter season amplifier
So my advice to you is - take a few steps back and reopen the dusty books.
A tube is only a fraction to the whole contribution to the sound signature of the amplifier and to the measured specs.
Let's not draw conclusions about a car just by looking at the rims.
But the fact the 845 is a high power tube, uses a kV supply and outputs roughly 110W of heat is an issue, yes. I'd call that the winter season amplifier
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Ten years ago, I probably would've had a little forum temper tantrum about this and spent way more time than I should trying to argue against this point, but you're completely correct!
I currently have a pair of Shuguang 845's that I took in trade that needed new power transformers (shocking right? ha ha). I got them up and running, and they are absolutely miserable to listen to compared to a low voltage 845 project I have running that puts out a lot less power. They are the third set of 845 amps that I've built/fixed in recent years that all exhibit that same unpleasantness that none of my other DHT SET amps seem to, but I can't correlate this to anything I've measured. The thought crossed my mind that it might be the output transformers, but they are 5K units that make damn near 35H, and I even temporarily soldered them into my lower voltage project and it still retained the same characteristic.
You can get 20W out of a 300B if you're willing to flog the tube a little bit. Just do that!
Bad idea. More likely just a waste of money. 845 tubes and similar are demanding.
No and no. It calls for a properly designed supply.
Honestly the 845 is not a tube for people that think making an amp is like LEGO bricks. Bad results are not surprinsing at all if this is the approach....
On top of this there are a lot of 845 chinese tubes around that aren't good a all. It's definitely not something for someone on budget and/or cannot design an amp.
Thanks everyone for the candid responses. I didn't know that the 845 tube designs were that finicky and inconsistent with tube supplies. It's just that PP KT88 amp is not providing the harmonics, spatiality, and holography that I'm seeking even with tube substitution.
Any ideas for a good SET design that can provide 20W?...
Any ideas for a good SET design that can provide 20W?...
to drive 845 @1kv 75ma, you need approx 110vrms (a1)
which 300b se should be capable.
you may start wire 300b opt as choke, feeding signal to 845 grid.
nice thing here is to use old amp, as a booster.
2nd thing, replace 300b opt with hi-current interstage tx (http://www.lundahl.se/wp-content/uploads/datasheets/1677.pdf)
for 845 tube, LL1691 is designed , has bigger power headroom
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I have seen a couple amps that use a 300b to drive 845s in parallel. I don't think it would be too much of an issue to have a 300b driving a single tube.
You can make a high quality outboard PSU. Furthermore I would argue that having an outboard PSU would actually be better because then you can focus on designing it for the soul purpose of powering the 845 tube. You wouldn't need any crazy rc circuits to bring the voltage down for the rest of the tubes. Tons of high quality amps have two separate power supply circuits, so I don't see what the issue is.
This looks interesting. It's a design by Rikard Berglund. It uses inexpensive tubes. I have not heard it. I am too afraid to build anything with more than 450vdc.
Try A Screen Driven Driver Stage Article By Rikard Berglund From Sound Practices Issue 8, Winter 1994/1995
Try A Screen Driven Driver Stage Article By Rikard Berglund From Sound Practices Issue 8, Winter 1994/1995
Danfrank is correct.
I built a boat anchor last year using the GM70 which is easier to drive than the 845.
Tried RC, LC and IT, the IT was the best out of all of these methods.
Consider the GM70, you can build a nice amp with 1000v supply, I’m getting about 25 Watts in A1 and 50w in A2
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