SR45 amplifier

[Paul Joppa]

..., and nobody but Paul J knows exactly what that will look like yet...

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.

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.

[xcortes]

Monoblocks PLEEEEEEEEEASE!

[johnsonad]

Sounds like progress and I'm thankful for that.

[Grainger49]

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]

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

[Jim R.]

Hi Howie,

Ok, I didn't realize you had the pt2s, though I do believe PJ said that the soft-start boards are not suitable for the sr-45s, but I could be wrong about that too. :-)

I'm sure that whatever you build it will turn out really nice.  Even if you don't build an sr-45, the soft-start boards, pt2 and dowdy and exo45xls should make a nice sooped-up paramour II 45, which is what I may do with my other pair of pt2s.  And of course you can add a grid choke to either of these as well. Iron is good :-).

The dowdys are big so you'll probably want to build a somewhat larger chassis -- my plates are 8" x 11.5" OFC copper but I'll be putting the ac inlet and binding posts on the back of the frame instead of on top as is traditional BH style.  These will be a real labor of love for me, as I'm sure they will be for you as well.

-- Jim

[debk]

i ordered iron from Mike today to build a pair of sr-45's

Debra

[Jim R.]

Deb,

What did you order?

-- Jim

[howardnair]

deb -yes, what did you order-i ordered a pair of exo-45 xl in nickel- -i have yet to decide which  chokes i want to use-howie

[braubeat]

Wouldn't the magnequest iron upgrade for the sex amp (BH-1 OT and BH-2 Plate choke) be ideal for the SR-45? IIRC the BH-1 was 4K.

Michael

[debk]

I went for the Paramour upgrade iron BH-5 full Ni and BH-6 plate choke.  Mike said he can get that to me faster. 

see Paul Joppa's post on the similarities of the BH iron to the magnequest iron for the SR-45
http://www.bottlehead.com/smf/index.php/topic,3000.msg36166.html#msg36166

Deb

[Jim R.]

Deb,

If I didn't go with the dowdys, that's the set I would have gone with myself.  With the dowdys in hand and the nickel exo-145s easily available, and the idea to use the tfa-2004s in the upcoming paramount 2a3s, the choice was easy.  Now I have a second pair of dowdys gapped for 60 mA on order to finish the paramounts.
Good luck with the project -- I think you're really going to like these, especially with the solo piano stuff!

-- Jim

[debk]

thanks Jim

It will still be some time before I build them.  Mike said it will take 8 to 12 weeks to get the iron. 

In the mean time I will get the rest of the parts collected

Deb

[xcortes]

I' finished the first amp a couple of days ago and have been troubleshooting it ever since. It works now but the SR voltages are way off. I'm getting B+reg of close to 400v and a 34v bias. I've looked at everything mNy times and can't find the problem. Of course I already tried a different 6cm7 as well as new sets of 316k (2x 158) and 2490k resistors. Any clues as what might be the problem?

Thanks

[debk]

Now that I ordered the iron, now I have to decide what 0.1uf coupling  capacitor to use.
The two I am thinking of are the V-cap CUTF and the Duelund Cast-PIO-Cu.  The V-Cap is about half the price of the Duelund

Anyone have on opinions on which to use?

Thanks
Deb