SR45 amplifier
- Thread starter debk
- Start date
johnsonad
New member
xcortes said:
I'm in two of those reckless groups and intend to be in the third once released
. It sounds like the Dac is coming together and the SR45 isn't far from some of our minds. PB you are wetting our appetite for possibly another SR amp in the future? Maybe something with higher output? 
I'm not so sure about higher powered shunt regulated amplifiers. There are a whole ton of variables that get a little nutty when you try to move to a ~400V regulated supply that is capable of ~100mA.
We have a nice amount of data on running the 45 shunt regulated, we have little to none on much else.
We have a nice amount of data on running the 45 shunt regulated, we have little to none on much else.
I was thinking that a high voltage b+ and three od3s in series could work. Since I use a power plant I have zero variations in power supply and that reduces the design problems and the need to leave headroom for high or low b+. That could give me a direct coupled sr 2a3 (not active loades, of course). Or a lower voltage b+ and a cap coupled sr 2a3.
To a reasonable degree, it's the pass element in the regulator that demands the most attention. The TL431 is specified to be able to sink 100mA, and when you power on such an amplifier, the directly heated output tube is going to start drawing current before the indirectly heated regulator tube allows the TL431 to do much of anything (thankfully). This, of course, presumes that you aren't powering on the amp with no 300B in it (this is something we had to deal with for the BeePre).
The 0D3 stack will produce the voltage you desire, but the performance isn't sufficient for a power amp (in my opinion).
The 0D3 stack will produce the voltage you desire, but the performance isn't sufficient for a power amp (in my opinion).
howardnair
New member
ok -so one can order the tfa-2004 and the bcp-15--or the bh-5 and bh-6-would there be a preference-like deb i am putting parts together--thanks howie
howardnair
New member
mmmm---so somewhat non commital-but we are getting somewhere-the exo 45/46-is for a 45 tube-the 2004 is not necessarily so---
now maybe i should ask mike for a exo-45-in nickel with 8/16 ohm taps--and go with the dowdy chokes--wellll!!!!
now maybe i should ask mike for a exo-45-in nickel with 8/16 ohm taps--and go with the dowdy chokes--wellll!!!!
howardnair
New member
reply to aaron johnson-do you happen to know if the exo-45's that mike has in stock are nickel or pinstripe?
howardnair
New member
Aaron-thanks--i just emailed mike for the EXO-45 XL and will see what happens-i asked about chokes on hand also-bcp-15 or the dowdy chokes-next to order will be everything else-from the power supply choke- power caps to tube sockets and everything in between-while i am here the SR-45 power supply shows a 10h chokebut does not show how much resistance-anyone know what i will need there-as for the cathode bypass cap-how low can i go there if i use a polyprophylene film-i may use them in the power supply also-thanks howie
Hi Howie,
Do you have the paramour II's -- that is the amp that the sr-45 is built on, so I'd also guess that the ps choke would be the triad c7x at 270 ohms. I don't know the value of the cathode bypass cap, and I also don't know what board was used for the shunt reg board/c4s either and if that is still available or not. The amp also requires the pt2 power transformer. Of course I'm talking about the existing SR-45 here, not the new one that will be forthcoming, and I'm not sure which one you're talkiing about. If the latter, it is probably best to wait on the plate choke as this is going to be a critical part of the overall system voltage calculations.
But back to the original sr-45, BH is not releasing the schematics for this anymore, and it may be difficult to get another run of the pt2 power transformers as we just did one last summer. So, in short, a lot to juggle here and it would be premature to jump the gun on too many parts at this point.
A note about the dowdy as it applies to the original sr-45 -- Mike gapped mine for 60 mA instead of the usual 40 mA, which gives an inductance of 80 H vs. 125 H for the original. Mike also expllained that this actually provides better ac and dc balance in the choke specs, and results in a complex impedance that is more favorable for a opt with a 5k load -- such as the exo 4x models. Whether or not this choke, in either form, would be suitable for the new sr-45 is still a big unknown, so I'd wait until the design is out first.
I have the old version and will be using the dowdy gapped for 60 mA in conjunction with the EXo-145 in nickel -- a version of the exo-45 xl with an even larger stack and with the secondaries wound with litz wire, also somewhat more expensive than the standard nickel 45 xls.
So, if at this point you don't have the paramour IIs and instructions and parts for the sr-45 conversion, you'll have to wait for the new design, and nobody but Paul J knows exactly what that will look like yet.
Hope this helps,
Jim
Do you have the paramour II's -- that is the amp that the sr-45 is built on, so I'd also guess that the ps choke would be the triad c7x at 270 ohms. I don't know the value of the cathode bypass cap, and I also don't know what board was used for the shunt reg board/c4s either and if that is still available or not. The amp also requires the pt2 power transformer. Of course I'm talking about the existing SR-45 here, not the new one that will be forthcoming, and I'm not sure which one you're talkiing about. If the latter, it is probably best to wait on the plate choke as this is going to be a critical part of the overall system voltage calculations.
But back to the original sr-45, BH is not releasing the schematics for this anymore, and it may be difficult to get another run of the pt2 power transformers as we just did one last summer. So, in short, a lot to juggle here and it would be premature to jump the gun on too many parts at this point.
A note about the dowdy as it applies to the original sr-45 -- Mike gapped mine for 60 mA instead of the usual 40 mA, which gives an inductance of 80 H vs. 125 H for the original. Mike also expllained that this actually provides better ac and dc balance in the choke specs, and results in a complex impedance that is more favorable for a opt with a 5k load -- such as the exo 4x models. Whether or not this choke, in either form, would be suitable for the new sr-45 is still a big unknown, so I'd wait until the design is out first.
I have the old version and will be using the dowdy gapped for 60 mA in conjunction with the EXo-145 in nickel -- a version of the exo-45 xl with an even larger stack and with the secondaries wound with litz wire, also somewhat more expensive than the standard nickel 45 xls.
So, if at this point you don't have the paramour IIs and instructions and parts for the sr-45 conversion, you'll have to wait for the new design, and nobody but Paul J knows exactly what that will look like yet.
Hope this helps,
Jim
Paul Joppa
Moderator
Haha! No, there are a lot of things I haven't settled yet, so I certainly don't know what it will look like. We made some helpful decisions last week, and I'm working hard to make sense of them in a concrete circuit.Jim R. said:
I do expect the design to center around the PC-3 and OT-2, same as in Stereomour. I'm playing with various ways to keep it flexible in terms of the kind of changes Bottleheads like to try, but I can't say yet what variations will be practical. Actually, I haven't even totally decided between a stereo vs. monoblocks implementation.
Grainger49
New member
The 2A3 version of the Paramour II uses a 100uF cathode bypass cap. So does the 45 version of the Paramour II, non SR-45.
howardnair
New member
jim -i bought the PT-2's in the group buy--and the soft start boards from BH-i have had the schematic for well over a year--so-hopefully sooner than later i will build these -i am planning a wood chassis-but this time i am going to use a metal under- chassis or sub-chassis- i wander through the hardwood stacks at the lumberyard looking for a few pieces of wood that light my fancy-after these are built i will buy a eros phone stage--and then think about tape deck upgrades-i have a akai deck but i keep looking at the technics and otari's on epay--grainger thanks for the answer-100uf it is
howie
howie
