Hi guys
I’ve read just about all the posts on 845s here (and at AA). I’m interested in doing an 845 SE power amp, and just now have some funds and time. I'm after designs not too complex or too expensive.
I was going to say a two stage amp is preferable, but a three stage with not too much complexity is fine. I will probably use a TVC, but can add a good preamp if I need more gain.
I’m a way off being able to design a circuit, and with three kids and other audio projects too, I won’t have time for a lot of tweaking ..
I’d like to go for a 45 into an 845 parafeed. Who has a circuit for such an amp?
If using an IT, I’d lean towards not too much up or down; but I prefer to build cap-coupled first and maybe try IT later.
Thanks
I’ve read just about all the posts on 845s here (and at AA). I’m interested in doing an 845 SE power amp, and just now have some funds and time. I'm after designs not too complex or too expensive.
I was going to say a two stage amp is preferable, but a three stage with not too much complexity is fine. I will probably use a TVC, but can add a good preamp if I need more gain.
I’m a way off being able to design a circuit, and with three kids and other audio projects too, I won’t have time for a lot of tweaking ..
I’d like to go for a 45 into an 845 parafeed. Who has a circuit for such an amp?
If using an IT, I’d lean towards not too much up or down; but I prefer to build cap-coupled first and maybe try IT later.
Thanks
just an idea that works fine
tubelabs 45 into 845
Not a parafeed amp but you can mod the power stage. 845 needs a couple of stages to be driven properly.
Ciao
tubelabs 45 into 845
Not a parafeed amp but you can mod the power stage. 845 needs a couple of stages to be driven properly.
Ciao
Parafeed 845 into 845
Check out this amp out. Even though it is not a 45 into 845, you may get some ideas or mod it to use the 45.
http://www.cognitivevent.com/av_monstro.html
Check out this amp out. Even though it is not a 45 into 845, you may get some ideas or mod it to use the 45.
http://www.cognitivevent.com/av_monstro.html
Gluca
I was for a while very keen on tubelabs’s approach, but I think the PCBs are not available yet, and I’m now likely to go P2P with an exact circuit.
quinnling
il Monstro (282 pounds) is the maybe the King Kong of 845s . . alas adaptations are beyond me at this stage.
I will look further for a circuit that I’m after, or closer to it.
Thanks
Richard
I was for a while very keen on tubelabs’s approach, but I think the PCBs are not available yet, and I’m now likely to go P2P with an exact circuit.
quinnling
il Monstro (282 pounds) is the maybe the King Kong of 845s . . alas adaptations are beyond me at this stage.
I will look further for a circuit that I’m after, or closer to it.
Thanks
Richard
www.tubelab.com/845SE.htm
On further thought, I like the idea
IMO not attractive as laid out & shown (but easily changed). Apart from the extra power (which may or not be a benefit, depending on your speakers, dB needed), George’s claim:
‘the A2 amp does a much better job of recreating highly dynamic music which contains a lot of transients. Snare drums, rim shots, the sound of a cello being smacked sharply with the bow.”
Should really suit my primary musical taste (rock).
But "no free lunch" . . if dynamic music sounds better, I wonder what disadvantages might or do accrue??
Cheers
On further thought, I like the idea
IMO not attractive as laid out & shown (but easily changed). Apart from the extra power (which may or not be a benefit, depending on your speakers, dB needed), George’s claim:
‘the A2 amp does a much better job of recreating highly dynamic music which contains a lot of transients. Snare drums, rim shots, the sound of a cello being smacked sharply with the bow.”
Should really suit my primary musical taste (rock).
But "no free lunch" . . if dynamic music sounds better, I wonder what disadvantages might or do accrue??
Cheers
Gluca - your thoughts?
I am considering a small “reverse experiment” on tubelabs’s amp:
Have the two MOSFET stages switchable in or out, preferably seperately, to compare the sound (see if they sound preferable in or out) and have control over output for different speakers (and probably tone).
The two MOSFET stages (to my reading) join the existing circuit at seven points. So a switch that moves the MOSFETs in or out would need to join to all seven points - would this work?
Are switchable stages feasible?
Cheers
I am considering a small “reverse experiment” on tubelabs’s amp:
Have the two MOSFET stages switchable in or out, preferably seperately, to compare the sound (see if they sound preferable in or out) and have control over output for different speakers (and probably tone).
The two MOSFET stages (to my reading) join the existing circuit at seven points. So a switch that moves the MOSFETs in or out would need to join to all seven points - would this work?
Are switchable stages feasible?
Cheers
GAH!? I dont know. I dont like the idea of having switches hanging around in a 1KVish amp. Maybe George (tubelab) can pop in and say more.
Usually I build two different amps (left+right) and listen to them at the same time without switches. At the end I choose the one I like more (actually my left ch is always different from my right ch ... I keep on modding them -LOL-)
Ciao
Usually I build two different amps (left+right) and listen to them at the same time without switches. At the end I choose the one I like more (actually my left ch is always different from my right ch ... I keep on modding them -LOL-)
Ciao
Yes, I intend to build two different amps (left & right) and listen to them at the same time,
one a tubelabs 45 into 845, and
one a “conventional” cap coupled 45 – 845, likely a 6P5GT input, 45 driver 845 v3.jpg here: http://world.std.com/~doyle/
Both with a good 10 K OPT (that I have) and 1000V B+.
I was thinking of having a switch on the tubelab design, but you are right a switch on a 1 KV amp would require great care.
Cheers
one a tubelabs 45 into 845, and
one a “conventional” cap coupled 45 – 845, likely a 6P5GT input, 45 driver 845 v3.jpg here: http://world.std.com/~doyle/
Both with a good 10 K OPT (that I have) and 1000V B+.
I was thinking of having a switch on the tubelab design, but you are right a switch on a 1 KV amp would require great care.
Cheers
I finally have a few minutes (too many people hanging around my office at work to be on the forums)....
Yes, I built a breadboard version of my 845SE, but I was nowhere near it when the power was on. 1100 volts generally will not give you a second chance, and death is rather irreversible.....
I tend to set up the whole circuit, then listen and measure, then move on to the next circuit. This makes A-B comparisons hard. My workbench, and the Tubelab 3 breadboard does not have the space to accomodate two 845 sized channels simultaneously.
For simpler amps, I do build two (usually identical) channels and try any experiments on one of the channels. Use a switch (suitably grounded) that allows switching the two speakers. Differences become obvious when they swap sides. Sometimes it helps to use a mono input signal. This is absolutely the way to audition different OPT's, the "reference" transformer in one channel, and the "test" transformer in the other channel.
I have not had the time to tinker with my 845 amp in a while, but I did discover that the power supply is very important to the sound in this amp. This is true for all SE amps, but this one is seems to be more critical (or my last two power supplies were just lousy).
THoughts
I'll try to send you the schematic, but the basic rundown on the 45-845 IT parafeed amps I have (www.electronluv.com for pics/info) :
input transformer (600:15k I think) -> 45 (dc filaments, B+ somewhere like 200v) -> 1:1 5k IT (I forget if this is parafeed or not - could be either really), 845 output (900v b+) -> parafeed output trans/plate choke. Dual power supplies for the 2 tubes. AC or DC fils on the 845.
What transformers do you have already? The key in doing 45-845 in a 2-stage setup is getting enough gain, hence the need for a step-up input transformer.
-Ed
I'll try to send you the schematic, but the basic rundown on the 45-845 IT parafeed amps I have (www.electronluv.com for pics/info) :
input transformer (600:15k I think) -> 45 (dc filaments, B+ somewhere like 200v) -> 1:1 5k IT (I forget if this is parafeed or not - could be either really), 845 output (900v b+) -> parafeed output trans/plate choke. Dual power supplies for the 2 tubes. AC or DC fils on the 845.
What transformers do you have already? The key in doing 45-845 in a 2-stage setup is getting enough gain, hence the need for a step-up input transformer.
-Ed
Hi Ed
While I like the idea of just two stages, Gordon Rankin suggests that step-up transformers tend to compress the sound.
That of course would be in lieu of whatever negatives an extra stage would introduce.
What do you think of that line?
Do you recall how many mA on the B+? And does the schematic include the PS?
Cheers
While I like the idea of just two stages, Gordon Rankin suggests that step-up transformers tend to compress the sound.
That of course would be in lieu of whatever negatives an extra stage would introduce.
What do you think of that line?
Do you recall how many mA on the B+? And does the schematic include the PS?
Cheers
further info
Gordon has strong opinions about things, to say the least. ;-) he thinks that about all IT's or stepup trannies, I believe. My ears disagree with that presumption of his. But he is a smart guy, I tap him for advice on occasion too. he knows his stuff but take it with a grain of salt. still working on finding the schematic.
I'd take a good step-up (esp. @ the input) over a 3rd stage of amplification. The 2-stage will be quieter, all else being equal.
-Ed
Gordon has strong opinions about things, to say the least. ;-) he thinks that about all IT's or stepup trannies, I believe. My ears disagree with that presumption of his. But he is a smart guy, I tap him for advice on occasion too. he knows his stuff but take it with a grain of salt. still working on finding the schematic.
I'd take a good step-up (esp. @ the input) over a 3rd stage of amplification. The 2-stage will be quieter, all else being equal.
-Ed
> Gordon . . thinks that about all ITs or stepup trannies, I believe.
I saw at the AA a while back, that’s one of his “top 10 peeves”
> I'd take a good step-up (esp. @ the input) over a 3rd stage of amplification.
Yes, I’m thinking eg ElectraPrint, James, Silk
(Doesn’t have to be parafeed) Does anyone have a 2-stage (ideally) 45 stepup 845 SE circuit?
Cheers
I saw at the AA a while back, that’s one of his “top 10 peeves”
> I'd take a good step-up (esp. @ the input) over a 3rd stage of amplification.
Yes, I’m thinking eg ElectraPrint, James, Silk
(Doesn’t have to be parafeed) Does anyone have a 2-stage (ideally) 45 stepup 845 SE circuit?
Cheers
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