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Searching for Angela Instruments Schematic for conversion of Dyna ST70 to 6B4G??? Thx!

24.20.221.107
Posted on July 24, 2012 at 08:53:15
SambaMaster
Audiophile

Posts: 65
Location: Tennessee
Joined: August 19, 2005
 In their old printed catalog back in the mid-90s(?) AI published a nifty conversion of the ST 70 to using 6B4G triodes. It was very simple, but I can't find it anywhere and AI is not responding to my inquiry via email.

Anyone happen to have this on file anywhere??? Need it to work on the amp a bit...

Thanks in advance...

mike

 

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RE: Searching for Angela Instruments Schematic for conversion of Dyna ST70 to 6B4G??? Thx!, posted on July 24, 2012 at 09:50:43
Joe Roberts
Manufacturer

Posts: 412
Location: Virginia
Joined: January 25, 2004
 I had it but used it for rolling papers back in Austin.

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Whereof one cannot speak, thereof one must remain silent -- Wittgenstein

Free your mind and your ass will follow -- Parliament/Funkadelic

 

RE: Searching for Angela Instruments Schematic for conversion of Dyna ST70 to 6B4G??? Thx!, posted on July 24, 2012 at 14:28:07
kyle
Audiophile

Posts: 1839
Location: London Ontario
Joined: September 29, 1999
 That's a big spliff Joe!

 

RE: Searching for Angela Instruments Schematic for conversion of Dyna ST70 to 6B4G??? Thx!, posted on July 24, 2012 at 14:55:58
Steve O
Audiophile

Posts: 12360
Location: SE MI
Joined: September 6, 2001
 There was no schematic: only written instructions on how to do the conversion. Is that what you're looking for? Also be aware that the conversion seemed to be geared towards the 6B4Gs that Angela had a for sale at the time. These 6B4s were really repinned 6AV5s and could handle higher voltages than the real thing (he musta bought a few pallet loads at govt auction before he realized that they weren't the real thing). True 6B4s will probably be stressed in the ST70 circuit.

 

RE: Searching for Angela Instruments Schematic for conversion of Dyna ST70 to 6B4G??? Thx!, posted on July 24, 2012 at 15:48:21
Joe Roberts
Manufacturer

Posts: 412
Location: Virginia
Joined: January 25, 2004
 Sambamaster is my neighbor and friend from Austin...he knows I'm lyin'.

In fact, I installed the mod in his amp. No drugs were involved but there might have been some pasta in the deal somewhere.

I have no recollection of the details.


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Whereof one cannot speak, thereof one must remain silent -- Wittgenstein

Free your mind and your ass will follow -- Parliament/Funkadelic

 

RE: Searching for Angela Instruments Schematic for conversion of Dyna ST70 to 6B4G??? Thx!, posted on July 24, 2012 at 20:58:06
Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
Joined: February 9, 2002
 Not what you looking for but years ago I took a pair of dyna 70's and made a pair of mono block 6b4g PP amps.

Removing one OPT on each chassis made room for proper input chokes to knock the B+ down.

Two filament winding and hum pots lowered the hum.

Two 9 pin sockets and I did a modified Williamson front end.

With no feedback they are gainy. :-)

The customer's widow is enjoying them to this day.

If I were to re-do them today I would use a center tapped, phase inverting grid choke and a single driver stage. Something like the Seth.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Searching for Angela Instruments Schematic for conversion of Dyna ST70 to 6B4G??? Thx!, posted on July 25, 2012 at 00:57:44
Joe Roberts
Manufacturer

Posts: 412
Location: Virginia
Joined: January 25, 2004
 >>If I were to re-do them today I would use a center tapped, phase inverting grid choke and a single driver stage. Something like the Seth.

Prototype, in my mind at least, for this topology is some Rock-ola jukebox pentode amps. They used the ct choke inverter but possibly two stages of voltage amplification...I forget.

I discussed this scheme with Mikey L. many years ago. One of the many things I never got around to doing.

I think that the primary of a high impedance output trans would work for the choke, but the MQ unit might very well have better balance and more inductance.

The Peerless A-100 PP 6A5G amp used an S series 10k Peerless OT for a split choke, I built these amps but Mike wound me a nice set of split chokes for the purpose.

But all of this is getting far afield from the Angela 6B4 mod, which was fairly simplistic.




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Whereof one cannot speak, thereof one must remain silent -- Wittgenstein

Free your mind and your ass will follow -- Parliament/Funkadelic

 

Here's a good sounding circuit, posted on July 25, 2012 at 04:37:19
andy evans
Audiophile

Posts: 4378
Joined: October 20, 2000
 My 6B4G PP amp uses 4P1L input and drivers. Absolutely my favourite amp, and 4P1L is a little miracle. Klaus in Russia posted some circuits - see attached link.

I'd take the power supply and filament supply outboard, and the 4P1Ls will need DC filament supplies with heatsinks. But this is an all-DHT design and serious hi-end sound.

andy

 

RE: Searching for Angela Instruments Schematic for conversion of Dyna ST70 to 6B4G??? Thx!, posted on July 25, 2012 at 18:52:13
CharleyW
Audiophile

Posts: 361
Location: Arlington, Texas
Joined: November 21, 2002
 The Sovtek 6B4G's work just fine at ST70 voltages with cathode bias. At least two of us (a guy who goes by Zacster and I) implemented it using the Curcio premium input board. I used a 5R4 "potato masher" rectifier to knock the B+ down a bit.

 

RE: Searching for Angela Instruments Schematic for conversion of Dyna ST70 to 6B4G??? Thx!, posted on July 25, 2012 at 20:29:57
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 Get a hold of "Uncle" Ned Carlson, formerly at Triode Electronics. He has a setup that allows for alternate use of EL34 class tubes and specifically Sovtek 6B4Gs in a Dyna ST70. NOS 6B4Gs will "fry" under the conditions present, but the Saratov made product shares its plate stamping with 300Bs and doesn't "give up the ghost". Don't try to push Sovtek 6B4Gs, or for that matter Sovtek 2A3s, as hard as a 300B is pushed. The Sovtek variants are tougher than their NOS counterparts, but there are definite limits.


Eli D.

 

RE: Here's a good sounding circuit, posted on July 26, 2012 at 20:06:05
mach1
Audiophile

Posts: 399
Location: Brisvegas
Joined: April 24, 2005
 Which version did you build?

 

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