Soft start shunt update?

[Doc B.]

The amps that were not broken in came off the oscillator yesterday so things should now be even between the two. Eileen is having a minor/medium difficulty medical procedure done today so I will probably not be able to do any eval for a day or two.

[Rick58]

Oooohhhhh ... good thoughts, prayers, etc. are headed your way! Hopefully everything is (gonna be) OK. Take care of her - the eval can wait a few days!  Best wishes,  - Rick.

[Doc B.]

Thanks Rick. She came through the procedure in great shape and we should be back in full swing in a few days.

[Rick58]

Be sure and give her a (gentle) hug from all us Bottleheads!  Glad to hear everything's A-OK. Now rest up a few days - both of you! 

[Air]

I, like all subjects of the "Queen" are concerned when she is ill or incapacitated. Give her our very best wishes for a speedy recovery. -Chuck

[ssssly]

Hope the queen is feeling better.

[ssssly]

So how are these suckers sounding?

[Doc B.]

A week ago we ran the amps in for several days with a sweep generator. We just cleaned and overhauled the system yesterday to make sure everything was at 100%. This morning we compared the two setups. In the initial comparison a few weeks ago I heard differences in the midrange and the bass and they were identically good on the top end.. So today we rigged my active crossover system setup with the amps playing midwoofers. Even after the break-in I heard the same differences I heard initially, even when trying of a few different types of 5670s we ran. So I think we are a step closer to getting this done.

[ssssly]

Do they both sound good just in different ways or is one substantially better than the other?

Would large modifications be needed to integrate this into a SR-45 circuit?

[Caucasian Blackplate]

The SR45 is not directly coupled, so adding this type of soft start seems needless..

[Paul Joppa]

Once we get the Paramount version out there, I'll take a look at the SR45 - since I want to at least build one. I have a modified design to try out, with DC filaments. I'll also look at other applications. The plan is still to replace all the C4S boards with this new version, eventually. This may take a long time, but it is in the plan.

[ssssly]

Paul:

Per your here I was waiting on these boards for my rebuild/upgrade

"The PT-2 can support a shunt reg driver, copied from the Paramount - anyone who wants to do this should probably wait for the new Paramount driver board with time delay and other goodies; the upgrade kit will be available - might as well convert to the 5670 driver at the same time."

Planned configuration was PT-2, TFA-2004 Nickel, BCP-15 plate chokes and EXO-003. CLCRC full wave schottky rectified power supply with the signal circuit alla the upgrade iron variation with the plate voltage reduced to 275 and current increased to 55mA (also per your suggestion). After reading several posts about the great sonic improvement I also was planning on incorporating the shunt board you have been working on.

Would you suggest this new board for my application or the original SR45 shunt configuration?

[Paul Joppa]

There does seem to be some confusion here.

The PT-2 can deliver 60mA of DC high-voltage current. If you stay with the 50mA 2A3 current used in the Paramour, there is 10mA left, which is enough for a twin-triode shunt regulated driver - we'll have the new board set up for the 5670 in the Paramount so that's a good choice, but others can work.

If you raise the 2A3 current to 55mA, which is more optimal for the 3K impedance, then you have only 5mA left and can't shunt regulate the driver. Also, the BCP-15 cannot support more than 50mA of plate current. So I'd stick with the 50mA/300v of the original Paramour; the increased inductance of the BCP-15 goes a long way to make up for the slightly off-optimum operating point.

The SR45 replaced the 2A3 with a 45, cutting the output power in half. The 45 operates at 250v and needs only 36mA, so there is enough current left over (just barely) to shunt-regulate the entire amp, not just the driver stage. We produced a very limited run of semi-kits a couple years ago for this - semi-kit meaning that there was almost no manual and not much developmental testing. It was intended for advanced experimenters. We never saw enough potential sales to justify the full development effort, but we liked the sound so much we wanted to make something available to at least a few.

I posted a few minutes ago in the other thread, sorry for the confusion and I hope this note helps make sense of my other one!

[AudioDave]

Sorry for being so impatient but I was wondering what the status is on the soft start shut upgrade for the Paramounts?
Thanks!
Dave

[Paul Joppa]

The circuit is done. It's just a matter of getting a batch of parts in and writing the manual. Probably won't happen until the Stereomour manual is done, but the "final proof-of-concept" prototypes tested OK this week so that shouldn't take more than a couple-three weeks - assuming Doc B can get downstairs pretty soon!

I'm fairly sure the initial product will be the Paramount replacement board, including conversion to a 5670/2C51/396A driver tube. I haven't talked to Doc B about the detailed process, but I'd expect the Paramount to be revised accordingly - the main issue is revising the manual, which is WAY more work than you might think.