Soft start shunt update?

[ssssly]

Any news on when the new soft start shunt board will be available?

[Paul Joppa]

Sorry, the ball is in my court and I haven't done anything on it in the last 2 weeks. It's still high on my priority list; hopefully I'll finalize the experimental PC board design this weekend and get an order in for the experimental parts.

[ssssly]

Any good news to share?

[fvale]

Keep Paul working..... it's a difficult matter!

[Paul Joppa]

Today I received a package from Mouser - we now have the parts in hand for the prototype Paramount application. (We're building two versions for a listening test comparison before committing to a final design.) We'll stuff the boards on Sunday, and burn them in next week.

[RPMac]

Can we pre-order the soft start shunt boards?
I assume they can be adapted for a Paraglow...PG 2.1?

[Paul Joppa]

The design is for Paramount, and assumes you have the Zener string installed - it's not on the board, though new Zeners will be supplied since the voltage is different. For ParaGlow you'd have to figure a way to add that string, which protects the plate load C4S from excess voltages.

Other than that, the modification consists of stripping everything off the driver tube socket and re-wiring it for the 5670 driver and the new board, so it should work with a ParaGlow or even a Paramour II. (Paramour I does not have enough high voltage current capacity, unless you change the 2A3 operating point current - now we're getting complicated!). For ParaGlow I'd have to look at it again to see if the driver plate voltage should be different from Paramount. Given the long history of ParaGlows and Afterglows, it would probably depend on which power transformer you had, for instance.

[ssssly]

Is the Zener string instillation just installing a string of zeners or will this require further more complicated modifications for instal in to a paramour 2 ish circuit?

[ssssly]

How did the prototype work out?

[Paul Joppa]

The Zeners are a string of five zener diodes that protects the C4S plate load at startup, until the hybrid shunt regulator kicks in. In Paramount they are mounted on a separate solder lug terminal strip; in other applications you would have to locate a new strip somewhere nearby.

One of the designs did not work correctly due to excessive leakage from a capacitor; we are experimenting with a different part. The other design appears to work correctly - first test was this morning, as I did all the soldering last night but was pretty tired and that's not the smart time to test a new design! I'm not going to bother listening until I get the Auricaps installed - we are installing identical Auricaps in both pairs of amps so we can make a consistent comparison.

Tentatively we'll do the first serious listening panel on the 20th of March. If the difference is subtle, the amps will probably go into a more extended comparison test at Doc B's place, where he has the Tape Project tapes and decks as source material.

[RPMac]

Paul, I plan to rebuild my Paraglows to a platform with more room to play...so finding room for the Zener string and boards shouldn't be a problem.
How easy will it be to use the boards to try different drivers? As a direct couple amp, this may be too much for my limited knowledge.

You were right about the 6n1p's losing their "shine"...got some new one...brought the sound stage back into the room.

[Grainger49]

Robert,

It has been a while but I bought 10 6N1Ps for $25 delivered a couple of years back.  As cheap as they are and as good as they sound they are still a good deal.

[Doc B.]

We completed the first part of the comparison of two versions of this new update yesterday. We listened at Richard Riley's since my system is set up for multi-amping and we wanted to hear the amps running more or less full range. Richard has completed some really nice sounding speakers using DIY techniques that emulate the superb designs that Alon Wolf of Magico makes - stacked plywood boxes and solid aluminum front baffles. Without a doubt these were making the best sound I have heard at Richard's place yet.

To cut to the chase, we heard differences between the two variations we were trying. Our theories were not unanimous about what was happening and we need to do a little more break in on one pair of amps to eliminate any possible differences due to that. We will continue to evaluate on the system here at Chateau Bottlehead and make a final decision on which circuit version will go into the update kit in the next couple weeks.

[ssssly]

What is the difference between the two?

[ssssly]

How's the comparison coming along?