SR45 amplifier

[debk]

One last suggestion.  Try a well broken in KK Teflon cap as a cathode bypass, bypass.  Still just use jumpers.  I have done this in my Paramours and my Ack! dAck!.  Those stayed in.

What value do you suggest?   I have KK teflons in 0.47uf
Today I put in a 1uf Mundorf silver/oil cap as a bypass.  I keep putting it in a and out of the circuit.  Not a huge difference, but it sounds a little smoother with it in.

Thanks
Deb

[Grainger49]

Deb,

The 0.47uF KK Teflon is big enough.  I would get by with 0.1uF or 0.22uF.

How many hours does the KK Teflon have on it?  If less than 100 it would sound bad by itself.  If less than 400 it isn't completely broken in.

[debk]

The KK teflons have about 300 hours on them.

I will get some 0.22uf  and try them.  They are big suckers, not easy to fit in with everything else I haev in there


Deb

[Paul Joppa]

...
So PJ, a similar line of thought and a question. I plan on using a pair of 300b amps for 80Hz and up (drivers have little below 70 Hz). 5k OPT primary, 1500 Ohm cathode resistor, 80 H plate choke. Can I get away without a bypass capacitor and have quality bass that low?

"get away with"? sure. But that's quantity bass!

"quality bass"? there is no substitute for trying it and listening.

Seriously - I can't see a predicted level difference that would matter, but there will be phase differences and other more subtle effects (i.e. those that are hard to measure but easy to hear - there are uncountably many of those!).

[najo49]

I go to this thread from time to time. Is there any hope of a regulated power supply for the parmour anytime soon.

[Paul Birkeland]

I go to this thread from time to time. Is there any hope of a regulated power supply for the parmour anytime soon.

Which Paramour?
Which power supply?

[Doc B.]

Paramour is a legacy product. We will not be releasing any more upgrades for it.

[najo49]

Paul, The paramour 2 and I would like to have main power supply regulated. Or, is it possible to put the soft start paramount kit on the 12at7? I suspect this would be major work. But I was wondering. But Doc I was reading in this thread the possibility of a board being avail. on a limited basis w/0 a manual,or am I mistaken.Jann

[Paul Birkeland]

The paramour 2 and I would like to have main power supply regulated. Or, is it possible to put the soft start paramount kit on the 12at7?

Why? and why?

The soft-start is technology implemented to stabilize direct coupling, which the Paramour does not employ.

Main power supply regulation and 2A3 operation is not possible on the PT-2.

While you "could" install the soft-start upgrade into the Paramour II, there are no instructions for this, and any installation errors will be your sole responsibility to troubleshoot. 

[Paul Joppa]

@najo49 -

What we have been using for regulated high-voltage power is a shunt regulation scheme. This requires both more voltage and more current from the power supply, as well as adding the regulator circuit. That's the reason why the old SR45 uses a 45 - the tube itself needs less voltage and less current than a 2A3, thus the Paramour power supply could power a shunt-regulated 45. It also explains why you can't easily convert a 2A3 amp to regulated operation.

Because I am not happy with the design of the original SR45, I have asked Doc B to not sell anymore of the boards. Instead (as described in various places in this long, rambling thread!) I am working on an SR45 design done right. When we have a working prototype, I'll start a new thread.

The Paramour II, however, does have enough power supply headroom to run a shunt-regulated driver stage (with unregulated output stage). The easiest way to do this is to use the Paramount soft-start upgrade kit. There are no explicit instructions available, but the conversion is similar to that for the Paramount. You must use the (included) 5670 tube instead of the 12AT7.

[caffeinator]

If you just want a kind of dumb soft-start, it might be possible to implement using an Inrush Current Limiter in the incoming mains power.  Note that this will somewhat slowly ramp all power, filaments and B+ alike - not sure that's what you're after.

See the linked datasheet for more info.  I've used the CL-90 variety in kits for small push-pull tube amps, typically in the return leg from power trans primary to neutral (w/ hot switched upstream of power trans primary).

http://www.mouser.com/ds/2/168/920-325D-LR-245176.pdf

[xcortes]

I use cl 90 in all of my amps.

Right now I'm building a pair of Paramours and I'll be using the driver boards from my Paramounts that were replaced by the soft start ones.

Someday I hope Paul's new sr45 are released ad kits and I will build three pairs.

[caffeinator]

Well, if I'm doing something that Xavier is doing..well..I'll keep doing it.

Garcon!  CL-90's, all the way around!

[howardnair]

output  transformer question-i am finally getting around to building the SR45-i am laying out on posterboard my wiring diagram-this concerns the MQ exo45 output transformers-there are 4 wires 2 on either side-i pair is red and blue and the other pair  is black and clear--the red and blue read .436k-and the black and clear read 1 ohm-so the red and blue go to my outputs -i will guess that red is positive -how may i ck this to be sure--and on the black and clear wires one wire goes to the plate via the coupling cap the other to the junction of the hum pot, cathode bypass cap and cathode resistor-does it matter which wire goes where?

thanks howie

[johnsonad]

Usually with Mike's iron, red and blue are your primaries. The black and clear will be your output side.