Codename Gigantamour

[ssssly]

My Paramour I to Paramour II.5 rebuild has now been renamed the Gigantamour. Due to the enormous chassis that will be required for my SR-45ish Paramour rebuild my friend Daisekei renamed the beast. In order to fit all the oil filled caps, extra iron, and allow for veritcal routing to keep wire lengths to an absolute minimum while isolating power and signal paths from one another, the chassis will begin with a 8x13x4 3/4"x3/8" thick aluminum C channel. This will then be attached to a 10x15x9"ish base.

Working on final layout this weekend and the height may grow another few inches. And as of the moment planning on polishing and then stripe brushing the aluminum and wrapping the bases in vintage fender yellow striped tweed. Still have to pick some handles, as they will way about 25lbs each.  

The ever changing plan, as of now, is a 6cm7 SR-45 signal circuit with a Schottkey rectified CLCRC power supply. Shinkoh Tantalum resistors for high voltage paths and Vishay Nakeds for low voltage paths. Diversitech motor runs for the first two PS caps and an Obbligato for the last. Rest of the caps, minus the shunt regulator, are Russian PIO. Have both an enormous Russian PIO and an Obbligato oiler to try out for the Parafeed coupling cap.

Iron is Bottlehead PT2, Magnaquest TFA-2004 Nickel stripe, BCP-15, and EXO-003.

Hoping to have it done by the beginning of July. Wish me luck.

 

[ssssly]

Power supply question,

After reading the Hammond 155j thread I have been wondering if I could eliminate the other resistor in the power supply for the following

CLCLC filter:
    C1: Diversitech 50uf
    L1: Hammond 155j
    C2: Diversitech 50uf
    L2: MQ BCP-15
    C3: Obbligato 100uf PSU cap

Will this work into a 6cm7 SR-45 circuit?

 

[Paul Birkeland]

The current rating on the 155J is not sufficient for the SR-45 circuit.  Look for chokes rated for 80ma.

 

[lth1]

I am also in the process of converting one pair of Paramour I's to shunt regulated 45's.  Hardware is similiar; TFA-2004, BCP-15, PS-2, and CX-7 choke. 

My question is concerning the 3000:8 ohm impedance ratio of the TFA-2004, would it be better to use a 5000:8 OPT in the SR-45, and, what would this do sound wise?

Cordially,
Lee Hankins

 

[Paul Birkeland]

The circuit is specifically designed for the TFA-2004.  Going up in transformer impedance will lower the power output a bit, and may improve damping.  I believe, however, that using the BCP-15 with a 3k transformer should give better bass than going to a 5k transformer. 

Did you have a different 5k transformer in mind to use?

 

[Paul Joppa]

The SR45 as we've done it runs a power supply current of 60mADC, so that is the minimum current rating for the power supply choke. The Hammond 1255J is rated 30mADC I believe, and the Magnequest BCP-15 is rated 50mADC, so neither one is acceptable in the power supply.

As I have posted before, the operating point of the 45 in this circuit is optimized for the 3000 ohm load. This is a perfectly good operating point for the 45, and sounds very good. Other operating points are possible, but would require adjustment of the plate voltage and current to optimally match the impedance, and this would require re-design of the shunt regulator as well.

Incidentally, for anyone else thinking of it, the old Hammond power transformer is not up to the task - you need the PT-2 that was standard on the Paramour II.

Also incidentally, I am not entirely happy with this design - we put it together to try out the concept, and it does indeed sound extremely good, but I'd prefer to set it up with a few changes. Some are for better reliability, and others are for better performance; DC power to the filament is an example. I have a design in mind and will be making a prototype when I get some time to spend on it. This new design will most likely use a 3K or 4K transformer impedance.

 

[ssssly]

What are the specs for the CX-7 or the stock plate chokes from a SEX?

 

[ducati guy]

My power supply for the SR-45 that I built was a pseudo-choke input using a small first cap to boost the voltage to 372V. I used a Paramount power transformer (don't know the designation) to a full wave Schottky rectifier. CLC filter (0.68mF - 20H (Lundahl 1673, 100 mA) - 200 uF. Got an output voltage of 372V to the shunt regulator with about 45 mV ripple,  I think. Very low ripple after the shunt regulator, so I'm not sure you need the extra filter stage.

 

[ducati guy]

Sorry. Just remembered - power transformer was center tapped Magnequest PGP 8.1, not the Paramount transformer.

 

[ssssly]

Would like to have less than 30mv to the regulator which should be feasible.

 

[Grainger49]

  .  .  .    Incidentally, for anyone else thinking of it, the old Hammond power transformer is not up to the task - you need the PT-2 that was standard on the Paramour II.  .  .  .    

Paul, I am not familiar with the changes of the Paramours.  Did the Paramour 1 have more than one transformer?  The one I have, very, very late Paramour 1, had a transformer that looks similar to the Bottlehead designed transformers but smaller.  Is this the old Hammond power transformer you refer to?

 

[ssssly]

The Hammonds have wire leads coming out of them. The PT-2 has solder points on it. Don't know if there was anything between the Hammond and the PT-2 though.

 

[Paul Joppa]

The C7-X is 10 henries, 270 ohms DCR, and rated 90mADC. Originally a Triad design, made in Mexico by Magnetek to the old design using perfect layer winding with kraft paper between the layers. This construction makes for better sound as a plate choke, in my opinion. It was replaced with a Hammond-manufactured choke to the same specs but using a bobbin and as far as I know not using layer insulation; there was no advance notice and the item is still sold under the original part number.

There have been only two Paramour power transformers. Prior to the Paramour there were three power transformers used for the earlier products (original SEX, Afterglow/Paraglow, B-glow/ParaBee, and various custom eXcites). The first was a cheap surplus item from Antique with a copper band, second was made by deYoung, very pretty looking with the copper band and many many leads, and the Magnequest PGP8.1 (and a few 230v version PGP8.2) with solder tabs.

All the above is to the best of my memory, which may of course be fallible. Hope that helps!

 

[Grainger49]

Thanks, mine is definitely the Bottlehead transformer with lugs, no wires.  Having just come in out of the yard, it is 85 here today, I didn't walk down the hall to turn them belly up, I opened a picture of mine.

Cool!  I have a Magnequest power transformers, plate chokes and output transformers on my Paramours.  I know you, Paul, were around when I ordered one of the last few remaining Paramour kits.  This was just before the Paramour II release.

 

[Paul Joppa]

Just a note, the PT-2 is a Bottlehead design custom made for us. I specified it pretty carefully but did not design it. It's not a Magnequest product. The PGP8.x is the only Magnequest power transformer we've used, and it puts out more voltage than the 2A3 can handle - except in direct coupled mode, as in the Paramount or the older Afterglow/ParaGlow.

Yes, I do remember you getting one of the last Paramour I's! I'd forgotten that we replaced the Hammond with the PT-2 before we moved to the Paramour II. IIRC you have the BCP-15 and TFA-2004Jr, which were the baseline for the BH-5 and BH-6 which had not yet been released.

 

[Grainger49]

Ok!  You are right except (I think) the output is a TFA-2004 (Sr.).  The laminations are just under 2" thick (I just measured them).  I fell in the crack between the time that the Paramour upgrade iron was available and the Paramour II iron was available.

 

[ssssly]

So the C7-X will work then. Was hoping on something with a bit more inductance though.

How about the SEX plate chokes?

 

[Paul Joppa]

ssssly, the SEX plate choke is 35mADC. Maybe the Paramount plate choke or the BH-7 which can both take 70mADC and run 20-25 henries IIRC.

Grainger I'd forgotten you had the Seniors. No way you can do better for that amp; effortless bass due to conservative magnetic operation, the best midrange in the business (IMHO) and sweet highs.

 

[ssssly]

So after looking at the SR45 schematic again, it has the BCP-15 as the plate choke.

Since I also have a pair of EXO-003s, which are listed at 60mA, they will now be used for the choke in the power supply.

Starting to think this was my original plan and somehow things got switched around in my jumbled brain.