SR45 amplifier
- Thread starter debk
- Start date
Paul Joppa
Moderator
IIRC, the Dowdy choke is quite large and unlikely to fit on the Paramour II chassis.
To clarify, increasing the already high) OPT inductance has little effect. Bigger is always better for the plate choke.
Note that you would probably want a larger parafeed cap; I get 28uF (14 to 56uF range).
To clarify, increasing the already high) OPT inductance has little effect. Bigger is always better for the plate choke.
Note that you would probably want a larger parafeed cap; I get 28uF (14 to 56uF range).
Just to keep the discussion flowing, I also have a tl-404 looking for a home. I have been wanting to mate it with a 71-a tube with battery powered filaments(as the tube was originally designed for). I bet this sr-45 circuit would be killer for this application. It might even be possible to do shunt regulation and ccs on the power tube with the more modest voltage and current requirements of the 71-a. What does everybody think? Crazy?
Michael
Michael
Paul Joppa
Moderator
With 380-400v available, I see no reason you couldn't do a shunt regulated, C4S loaded, direct coupled 71A amp. You'd want to trim the driver bias to get the voltages right, and re-adjust every so often - but if a half watt is enough for you and you're comfortable with battery filaments then you're already crazy enough that this will be no bother! What do you see for a driver? 01A perhaps?
Paul Joppa
Moderator
PT-2 has more magnetic headroom, but the voltages etc. are significantly different. I'd need at least a conceptual design and voltage budget to comment further.xcortes said:
Paul Joppa
Moderator
Thanks, Deb - I had a great trip.
I can't seem to locate the SR45 conversion page - does anyone have the link at hand?
Meanwhile I'll mark up my schematic to show terminal labels and parts as used on the current (v4.4) board. I assume the original web page had a schematic? Hopefully that will be enough information to revive the design. The new boards are available as the "soft-start" kit for Paramount, including a trimpot for setting the driver bias precisely; you get a new driver socket (useful) and a 5670 tube (less useful).
It appears that the clip-on heat sink will work as long as your power line voltage is not much above 120v. This was always a marginal aspect of the original SR45 design.
By the way, the original used the 6CM7. The 6CS7 is very similar, but looks a bit more linear in the published curves. IIRC the pinout is a bit different, but just mention it in case someone wants to experiment.
I can't seem to locate the SR45 conversion page - does anyone have the link at hand?
Meanwhile I'll mark up my schematic to show terminal labels and parts as used on the current (v4.4) board. I assume the original web page had a schematic? Hopefully that will be enough information to revive the design. The new boards are available as the "soft-start" kit for Paramount, including a trimpot for setting the driver bias precisely; you get a new driver socket (useful) and a 5670 tube (less useful).
It appears that the clip-on heat sink will work as long as your power line voltage is not much above 120v. This was always a marginal aspect of the original SR45 design.
By the way, the original used the 6CM7. The 6CS7 is very similar, but looks a bit more linear in the published curves. IIRC the pinout is a bit different, but just mention it in case someone wants to experiment.
The instructions and schematic were never published but were supplied with the original kit instead. I have my own copy that could send to you Paul or to anyone BH authorizes me to do so.
Saludos
ps. Paul: I have a Board Meeting and Quarterly Earnings release coming next week so I really shouldn't be thinking about the 71As project. BUT so far what I have in mind is 01Aa driving 71As. Battery heated filaments. Independent PS for driver and power tubes with RS080 and exo-01 on the 01A and pgp 8.1s and (maybe Dowdys) on the 71A tube's one. DC, SR and C4S loaded each. I triamp but for this iteration I will only build two pairs because I wan't to try to direct couple the Ionovac tweeters (another project). I already have the two pair of TL404s, and most of the ps iron for both sets. I'll try to post a first attempt of a schematic next week. You mentioned "crazy enough", right? Let's set a new world record for Dunken factor.
Saludos
ps. Paul: I have a Board Meeting and Quarterly Earnings release coming next week so I really shouldn't be thinking about the 71As project. BUT so far what I have in mind is 01Aa driving 71As. Battery heated filaments. Independent PS for driver and power tubes with RS080 and exo-01 on the 01A and pgp 8.1s and (maybe Dowdys) on the 71A tube's one. DC, SR and C4S loaded each. I triamp but for this iteration I will only build two pairs because I wan't to try to direct couple the Ionovac tweeters (another project). I already have the two pair of TL404s, and most of the ps iron for both sets. I'll try to post a first attempt of a schematic next week. You mentioned "crazy enough", right? Let's set a new world record for Dunken factor.
Paul Joppa
Moderator
Thanks, Deb. Turns out, I had downloaded it a while back but failed to file it where I could find it! That manual has the schematic which I propose to modify. (Actually it is a later version than what I have in my files - I'll check but I think I just added the RC stability network to the shunt reg part.) Notice that it's version 3.5 - there was actually quite a lot of development before the kit was offered!
I made up a few sets of custom boards for this circuit a while back. They mount just above the power transformer, hold a large heatsink, and free up lots of space around the heatsinks.
I don't have a ton of documentation on these, but the connections are not too complicated.
I don't have a ton of documentation on these, but the connections are not too complicated.
2wo
New member
That is the one I was thinking of. I have always been a little worried about the small heat sink on mine. This also looks easier to implement then the original PCB. Granted it was not the original purpose but it is a bit of a Kluge with all the jumpers.
Would you consider having a few more made, or make the file available?...John
Would you consider having a few more made, or make the file available?...John
I will talk to Doc/PJ on Monday about this. Last time I made a few, he and PJ gave me their blessings, I'd just want to double check that this is still OK.
Paul Joppa
Moderator
I guess I have to say this, lest the thread get out of hand.
I have NOT placed this design, or the circuit diagram, in the public domain. When it was a semi-kit, I got some recompense from the sales. And, as I said early in this thread, I am working on a second-generation version from which I expect to get some income if it does become a kit.
I don't have a problem with a few enthusiastic Bottleheads making versions for themselves, especially if it involves purchase of PT-2s and/or C4S boards, both of which produce some income for me. It does become a problem for me if I lose ownership of the design. It's more a legal issue than a financial one - my monetary compensation is small, but it does validate ownership of the design.
Intellectual property is a very tough issue, which we as a society are barely starting to deal with in an age where copying and disseminating have become so much easier. I'm sure the whole concept will see huge changes over the next couple centuries. Meanwhile we muddle through as best we can.
I have NOT placed this design, or the circuit diagram, in the public domain. When it was a semi-kit, I got some recompense from the sales. And, as I said early in this thread, I am working on a second-generation version from which I expect to get some income if it does become a kit.
I don't have a problem with a few enthusiastic Bottleheads making versions for themselves, especially if it involves purchase of PT-2s and/or C4S boards, both of which produce some income for me. It does become a problem for me if I lose ownership of the design. It's more a legal issue than a financial one - my monetary compensation is small, but it does validate ownership of the design.
Intellectual property is a very tough issue, which we as a society are barely starting to deal with in an age where copying and disseminating have become so much easier. I'm sure the whole concept will see huge changes over the next couple centuries. Meanwhile we muddle through as best we can.
