New Paramour IIs have arrived...

[Jim R.]

Got a little care package from BHQ today with my new powr cord kit, a replacement 9 pin socket and a hole shrinker, and the paramour II manual... and thanks, Eileen for the kisses! :-)

I'll look over the manual tonight and then will get to repairing the broken tube socet tomorrow.

Can' wait to hear both amps together.

-- Jim
.l

[Grainger49]

So, if you have gobs of gain I wrote up Paramour II 12AT7 to 76 driver conversion instructions.  I did it for the Paramours I have (last of the originals) and Doc sent me the Paramour II manual so I could write up the same conversion for it.  It has been confirmed by a couple of Bottleheads who have followed my directions.

It looks cool having two Coke bottle tubes on top, not that it matters to you, and it sounds very good.

[Jim R.]

Grainger,

I probably won't change the driver tube until I do the SR-45 conversion, and then it will probably be a 6dn7, and if possible, maybe a 9-pin to octal adaptor for the original 6cm7 (as long as it will be plug and play with no bias or CCS adjustments needed.)

I think I have the one bad amp somewhat jury rigged and should hopefully be able to test it today.  I'm supposed to be getting my new power cables today, and then I can put the system backtogether and give it a spin, and with my new setup, I can swap power amps in a matter of minutes.

-- Jim

[Jim R.]

Well, my kludge to fix the tube pin on the driver tube socket worked -- for about 5 minutes.  Enough to hear what I was looking for.

I've been running my office system with 4 amps in rotation the past couple of weeks and after all is said and done, both my EL84 Carina and the Paramour IIs have come out on top, so the
Fi monos and the Ampino will be on the block.  Nothing wron with them and they are both great amps in their categories, but the rina and the Paramours just sound better in this room with the speakers I have.

Tomorrow I'll have to get serious and fix the bad tube socket on the one paramour once and forall.

PJ, you did a remarkable job on this amp, especially considering what it sold for!  Color me impressed.

-- Jim

[Jim R.]

Ok, I think I have made a decision and have decided to upgrade the paramours with the stock opts from the paramounts, once I convert those ver to d2a3s with the soft start boards.  The problem is that I don't know what the inductanceof the stock paramount opts are, and I'd like to try to pick the right plate choke for the job.

What I would have available are the stock PCs from the s.e.x., paramours, and paramounts and/or maybe the stock PCs from the stereomour -- depending on which amps I put the bcp-15 (50 mA version) in.

It looks like with a padding resistor in the paramount psu, and the soft-start boards, I will be able to use the bcp-15s in the paramounts, so the original paramount PCs are, I'm guessing, the best match for the paramount OPTs in the paramours.

Am I missing anything with this scenario?  I just figure I can turn over the paramours with better iron and then anybody who needs some original specos can have the ones out of the paramour and/or s.e.x. mps.

-- Jim

[Paul Joppa]

OK, we may need to archive this somehow. I can't believe that it's never been compiled before!

Paramount stock plate choke: 24H, 70mA, 330 ohms
Magnequest PC-7 27H, 70mA, 430 ohms

Paramour II (obsolete) stock plate choke: 10H, ca. 60mA as plate choke, 270 ohms
Magnequest BH-6: 40H, 50mA, 540 ohms

Stereomour stock plate choke: 20H, 50mA, 590 ohms (black wire tap)

SEX stock plate choke:30H, 35mA, 750 ohms
Magnequest BH-2: 50H, 40mA, 540 ohms

(Not yet released) SEX-2011 stock plate choke: 40H, 35mA, 830 ohms (red wire tap)


(The parafeed capacitor is estimated from the choke inductance, not the output transformer inductance which is generally so much higher as to have little effect.)

[Jim R.]

Thanks, Paul.  Very useful information to have.

-- Jim

[Jim R.]

Decided to hold on to these after all, but will build them as basic 45s and then maybe later think about upgrading to SR-45s.  I will be ordering an exo-45 and bpc-15 40 mA, and will take it from there.  Yes, will have to rework the operating point, but that's fine.

-- Jim

[Grainger49]

I'm curious, does the X_l of the choke equal the X_c of the parafeed cap giving a complementary complex impedance?

I will have to store the choke data somewhere.

  .  .  .    (The parafeed capacitor is estimated from the choke inductance, not the output transformer inductance which is generally so much higher as to have little effect.)

[Paul Joppa]

I'm curious, does the X_l of the choke equal the X_c of the parafeed cap giving a complementary complex impedance?

I will have to store the choke data somewhere.

  .  .  .    (The parafeed capacitor is estimated from the choke inductance, not the output transformer inductance which is generally so much higher as to have little effect.)

That's part of the story.  :^)  The complementary impedance can only happen at one frequency, and that frequency is not arbitrary.

The first thing I did was to simplify everything to just the source and load resistances, the plate choke inductance, and the parafeed capacitor. The main assumption is that the output transformer inductance is high enough that it appears as a resistance when loaded by the speaker which itself is assumed to have a constant resistance with no reactance. These assumptions make it clear that the results are a starting point, not the final word!

Then I non-dimensionalized the mathematics - normalizing all reactances to the load resistance and the frequency at which the normalized inductive reactance is unity (X_L/R = 1). The capacitive reactance is similarly normalized. Then I ran some simulations, looking at the load on the tube as well as the frequency response. That's because if the load on the tube gets much lower than the normal design value, the tube will distort even if the transformer does not. The best compromise in my judgement occurs when X_C/R = 0.5, which after undoing the normalization means C = 2*L/(R squared). That's my starting point value though I may adjust it for various practical reasons in specific designs.

[Grainger49]

Thanks for walking me through the math.  It has been several decades since I have done any of this.