New 6386 at AES??

[wtmnmf]

I spent a half hour or so talking to the maker of the 670 clone about it and the tubes at AES today. He worked with the tube manufacturer to develop them and then did blind testing of them until they matched the GE tubes. He will not be selling the tubes himself, the tube manufacturer will. He said they will have an ad out in the next month or so. Their primary market is audiophile tubes. I don't think that they have a clue about the demand for these tubes! Price will likely be about 30GBP. Also, I tried to convince the 670 cloner that he could get his part supply quantities way up if he offered us a kit :wink: . He is considering it, but wants to be sure that his product is well received as a quality item and so he is nervous about DIY build quality. The rest of you at AES might swing by the booth and put the DIY bug in his ear. Maybe he will warm to the idea if he talks to a bunch of nice folks. He is a nice guy and fun to talk to.

 

[Matt Ward]

The "nice guy" is Simon Saywood who I know doesn't hang here. He's been working on this for years. I've not heard it yet but am trying to find a way to have a listen and A/B with a genuine article...

 

[CJ]

He had the thing running with music being compressed at the booth.

I really liked what it was doing with the bass.
Sounded like a frickin Beatles album.

He also had a bunch of charts and graphs, freq plots, spectrum analyzers, on his lap top to gander at.

I think he did a great job, as he did not change all that much.

He said the biggest pain was the small choke on the bias supply?
Kept getting hot.
They must have really forced some heavy wire around the core, ala Neve output, where the wire is so stressed that they break sometimes.
Bigger wire means less DCR, and therefor less heat.

 

[Larrchild]

Having built the same circuit using both the original UTC/Triad transformers and Sowters, which indeed sound different, I greatly prefer the Sowters. They are flatter on the HF. A box that lops off the top ocatave is far less useful in a modern environment, regardless of sentimentality.

 

[CJ]

I looked in the back, it was the Sowter group of 670 iron.

Brian mentions instability on the high end of those Chicago outputs.
Maybe that is what was stealing the high end.

 

[Larrchild]

Yeah, I saw that on the fellow's site. Good choice. The Sowter signal outputs are M6 core also, but smaller. Maybe less distributed-c. The A-26 or the Sowter Ni input xfmr didn't change the highs as much as different outputs did.

 

[CJ]

I like that A 26, grain instead of 50/50, so you can really slam it.
(output trans used backwards)

Did I mention that the burn in time for the 6386 was pretty long?

The bias stabilized after many hours, so the new 6386 did not look exactly llike the NOS version, until after burn in, very interesting..
Maybe explains why the user had access to the balance controls.

 

[Larrchild]

CJ, did Brian mean control output or signal output instability? I know the control output circuit has some snubbing.

 

[CJ]

The Chicago PC 150 or whatever it is.

Control output.

I bet itm was the phase angle issue on the tertiary winding getting flipped 180 so that it turned into an oscillator.

 

[Larrchild]

My preamp proved that can be the case. On large peaks it could become a big bistable.
I'm beginning to think a tert-winding should be as large as possible to lower it's ratio and therefore have less parasitic C, etc, while still not loading the main signal.

 

[wtmnmf]

[quote author="Strongroom"]The "nice guy" is Simon Saywood who I know doesn't hang here. He's been working on this for years. I've not heard it yet but am trying to find a way to have a listen and A/B with a genuine article...[/quote]

Ya, that's the guy...

 

[dale116dot7]

[quote author="Larrchild"]CJ, did Brian mean control output or signal output instability? I know the control output circuit has some snubbing.[/quote]

It had some feedback from the output plates back to the front of the amp via an R-C network - that would supply feedback to swamp the phase shift of the tertiary winding. The control amp needs lots of gain and lots of feedback since its load is nonlinear (diodes) and highly capacitive - and the input signal isn't just audio but rather audio with a chunk cut out of the middle. Looks real strange on a 'scope.

New 6386? If the sides are matched, that's a lot better than trying to match eight 6BA6's!

-Dale

 

[CJ]

Sounds like he did a good job on the tubes.
They fiddled with the grid wire spacing til it matched up.

 

[Rob Flinn]

Has anyone discovered who the maker of the new 6386 is ?

 

[CJ]

I do not think it will be a big surprise.
How many tube companies are there out there?

Let's create a list and then eliminate one by one.
I bet we can figure it out.

Obviously, he did not go to Russia and talk with engineers there.
However, Russia might have someone over here as a Tech Consultant.

 

[Nele]

JJ...?

 

[Rob Flinn]

CJ you're more cryptic than a Times crossword !!! :guinness: :guinness:

 

[Larrchild]

A riddle of a core, wrapped in an mystery of wire, covered by a Mu-Metal enigma of a can.

 

[SUPERMAGOO]