Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Paramount => Topic started by: xcortes on October 19, 2009, 12:30:17 PM

Title: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: xcortes on October 19, 2009, 12:30:17 PM: nt
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Paul Joppa on October 19, 2009, 05:17:03 PM: I doubt it.

We did a prototype, but it turned out to be pretty difficult. There are heat and reliability issues, specifically with the current source that supplies the shunt regulator. It has to dissipate nearly twice as much power as can be easily handled by a TO-220 device. Whether we go to a larger TO-3 or use two or more TO-220 or TO-126 devices, or use a tube, it will take some engineering design and experimenting time to come up with a stable, reliable design that can be built as a kit.

What makes sense to me right now is fully shunt regulated 45 amps. Once the Stereomour is out and I have a bit of time, I plan to pursue that as the first step. So far, Doc B is not very excited about such a product, but as a designer I am so I'll probably continue to work on it. I want a pair for my own system, for one thing!

Remember, shunt regulation is very inefficient The regulator will usually dissipate at least as much power as the output tube, without contributing any audio power itself. And SETs are already quite inefficient.
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Jim R. on October 20, 2009, 05:43:22 AM: Paul,

I could get excited about an SR 45 amp too, so if you come up with a good solution, I'd be glad to give it a try.

-- Jim
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: tsingle999 on October 26, 2009, 08:05:34 AM: I am excited about the stereomour as a SR45 product! I am currently addicted to the SR45 Paramour II. Taran
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: fvale on October 26, 2009, 01:11:34 PM: I'm also addicted to the SR45 Paramour and I'd really like one day to see a fully SR2A3 amp from BH!
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: 2wo on October 29, 2009, 06:40:25 PM: I too, would like to see a SR-2A3. I have been thinking about what it would take to ramp up the 45 regulator. I was thinking of paralleled FETs or IXYS1045
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Bas Horneman on October 30, 2009, 12:18:54 AM: Quote
Till the Dowdy Lama showed up with his mighty GM70 (we are not worthy
Could you tell me more about the GM70?

Kind regards,
Bas
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Len on October 30, 2009, 11:12:36 AM: Quote from: Bas Horneman on October 30, 2009, 12:18:54 AM
Could you tell me more about the GM70?

Kind regards,
Bas

Amazing sound, when built by Jim. You need about a kilovolt for the HT, and the equivalent of an arc welder for the filaments. These amps normally weigh in at 80-100 lbs.

I've been collecting parts for one for years. It's up in the 211 amp category, IMO.
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Bas Horneman on October 30, 2009, 11:20:58 AM: Quote
I've been collecting parts for one for years.
Same here. Couple of months ago I bought the filament transformers....and this week some custom made teflon based sockets from ebay. Got parafeed transformers from MQ years ago.
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Len on October 30, 2009, 11:38:51 AM: Quote from: Bas Horneman on October 30, 2009, 11:20:58 AM
Same here. Couple of months ago I bought the filament transformers....and this week some custom made teflon based sockets from ebay. Got parafeed transformers from MQ years ago.

Mine will probably be push-pull. Only because I have a nice pair of Jantzen electrostatic hybrid speakers here collecting dust, and they need at least 20 watts to come alive. 2a3's don't even trigger the circuit for the electrostatics sometimes.
Title: Re: GM70
Post by: 2wo on October 30, 2009, 06:45:00 PM: Hi Bas,

Have a look at this thread...John

http://www.audiophiletalk.com/cgi-bin/yabb2/YaBB.pl?num=1241360431

Better info here

http://www.audiophiletalk.com/cgi-bin/yabb2/YaBB.pl?num=1241385501
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Bas Horneman on November 02, 2009, 12:21:09 AM: Thanks 2wo!

Wish Dowdy Lama would put up a schematic. :)
[EDIT] Oeps never mind. Found a description in one of the thread you posted. Essentially it is an 826 LC coupled to the GM70.

Kind regards,
Bas
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Len on November 02, 2009, 01:30:15 AM: Quote from: Bas Horneman on November 02, 2009, 12:21:09 AM
Wish Dowdy Lama would put up a schematic. :)

Hi Bas,

I've read posts from Jim that hint at why he doesn't post schematics any more. It seems that when he did, some people would just throw the parts together and complain that it didn't sound good, etc. He believes in best practices for everything he builds, and it's not just the parts that make his designs work. It's one thing to build something sloppily at 400V, another at over a KV.
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Jim R. on November 02, 2009, 01:40:27 AM: Actually, the B+ on this amp is only about 740 volts. Not child's play, but better than >1kv. And the amp weighs a mere 300 pounds.
Title: Re: Can we expect a fully shunt 2a3 conversion kit soon? -nt-
Post by: Len on November 02, 2009, 04:35:29 AM: Quote from: jrebman on November 02, 2009, 01:40:27 AM
Actually, the B+ on this amp is only about 740 volts. Not child's play, but better than >1kv. And the amp weighs a mere 300 pounds.

I haven't looked at them lately, but I seem to remember that the lower voltage GM70 designs use more current than the "corona" versions.

And don't forget, 300 lbs is a mere 150 lbs per channel. Almost as portable as the Quickie :-)