SR45 amplifier

[2wo]

Congratulations on your 40th, have fun on your vacation...John

[debk]

Paul,
Happy anniversary have a great trip!

Debra

[tsingle999]

Enjoy your trip! 40 years is a long time! You guys deserve it!
My grandparents made it to 69 years. People would ask my grandmother had she ever thought about divorce. She always said no never but there were plenty of times i wanted to kill him;)

[johnsonad]

Happy anniversary Paul! Have a safe trip!

[Jim R.]

In the existing design, what would be the ramifications of changing from a plate choke of about 360 ohms (what I understand is what the bpc 15 is) to something a bit higher, say 50 ohms more -- DCR is what I'm talking about here.

Any places to make other adjustments? OPT will be 5k.

Just about done with planning the sr-45 rebuild and will layout and start machining the top plates this week.

-- Jim

[2wo]

Hi Jim, The increased DCR will drop a few more volts across it. So the voltage at the plate of the 45 will be 10-20V less...John

[Jim R.]

John,

Thanks -- with my higher line voltage I'll probably not have to do anything to compensate then.

-- Jim

[debk]

Just finished one SR45 amp so far.  It is a very nice sounding amp!
Now to start on the second one

Deb

[johnsonad]

Congrats Deb!  Keep us posted!

[Jim R.]

Hi Deb,

Glad to hear that this is under way.  Any details to share? Have you considered using the 6dn7 as a driverr tube? Pobably too late now. What are you using for iron? Purple, I assume :-)

-- Jim

[debk]

I built the amp from the schematic of the SR45 and referred to the Paramour II manual for some of the construction.
Iron is:
Magnequest BCP-15 40ma/50H
Magnequest BH-5 Nickel outputs
Magnequest Grid choke
Triad C-7X Power supply Choke

Coupling capacitor:
V-cap CUTF 0.1uf
Parafeed Capacitor:
Clarity Cap MR 10uf

EML mesh plate 45 tube

I built it on a Paramount chassis panel

I have only listened to the amp in my lab, I will put them into my regular system when I finish the second amp.  I have been very impressed with the sound so far.  It made the old Klipsch Heresey I have in my lab sound very smooth, nicer than any other amp I have tried them with.

When they are both built and broken in a bit I will post my impressions

Deb

[Jim R.]

Hi deb,

That should be a really nice setup with the Orcas and or your fe-206 speakers.

I too just can't get past how beguiling these amps sound, even with OS american 45s -- I'm getting very impatient waiting for   my 98 db speakers to arrive and I've decided to put off any new amp construction until I've got the sr-45s tuned /voiced to the new speakers, using the existing chasis as a test bed for those experiments. I also have a backlog of other projects to keep me busy through the cold weather months, and by then I should have a very good idea and detailed plan for rebuilding the sr-45s in a new chassis with a slightly modified layout. These are some seriously good amps even if PJ doesn't seem totally happy with the design.

If you want a couple of nice heat sinks for the sr/c4s board, PM me and I'll send you a couple.

-- Jim

[debk]

Thanks Jim!

I too think they will sound great with the Orca's
Like you I have way too many projects, maybe I will have time to finish them this winter.
I also have too many amps, ok that is a good thing 

I will PM you about the heat sinks, the ones included with the SR45 kit get quite warm.

I never thought this thread would get this big when I started it, it has over 17,000 views now!

Deb

[debk]

The SR45 amps are done!!  They sound great, probably the best sounding amp I have built to date.  Not as forceful as the 2a3 Paramount, but more detailed and refined.  Very, Very smooth sounding amp, a great match with the Orca's!  They will only sound better as the components break in.  Grainger, I know I should have burnt in the V-cap CUTF :-(

I have some film capacitors on order I want to replace the 47uF elecrtrolytics with.



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Deb

[2wo]

Hi Deb,
looks nice, did you find a spot for the grid choke? You are using the same iron complement as my current amp, no V-cap though .
  I don't remember if you had a chance to hear it at the Bottleneck meet a a few years ago...John