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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 12 Dec 2013, 04:51 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
I'm about to start Matt's 6V6 amp but my own interpretation of his build. I will use his schematic but may vary the components materials but not vary the components values. I intend to use carbon film 1W Rs, cotton coated wire, Russian PIO inter-stage caps, Russian PIO caps in the PS (or part of the PS), resin tube sockets, some very old Australian made black glass 6V6s and old 6SN7 driver tube. I also have some solder from the 80s I will use.

There will be no power tranni but a power filter and a fat choke. To switch it up a little I will be using a SS rectifier bridge and modern electros for filtering. So not all old school. I pick up the last of the parts tomorrow at work and then plan the layout. Re-sprayed Edcor OPTS will be used in UL mode. Images to follow.

Easy to see where the name came from but I will build on this. Stay tuned.

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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PostPosted: 12 Dec 2013, 06:29 
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*GASP!*

At least maybe have back-to-back filament trannies to give some isolation? :eek:

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PostPosted: 12 Dec 2013, 07:37 
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Geek wrote:
*GASP!*

At least maybe have back-to-back filament trannies to give some isolation? :eek:

Strangely I do have a filament tranni with dual windings.

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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PostPosted: 12 Dec 2013, 15:34 
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Location: MB, Canada
mwhouston wrote:
Geek wrote:
*GASP!*

At least maybe have back-to-back filament trannies to give some isolation? :eek:

Strangely I do have a filament tranni with dual windings.


I was wondering.. How dangrerous / feasible would it be to build an entirely transformerless amp.. OTL 6AS7, with mains and filaments direct off of AC :D


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PostPosted: 12 Dec 2013, 16:08 
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Actually when you think about it's probably not that dangerous. 250V is 250V no matter how it is supplied.

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PostPosted: 12 Dec 2013, 17:16 
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mwhouston wrote:
Actually when you think about it's probably not that dangerous. 250V is 250V no matter how it is supplied.

Actually, there is a big difference:
https://en.wikipedia.org/wiki/Isolation_transformer

The keywords here are galvanic isolation.

I can plug in a 250V transformer and grab any one of the HV leads and be just fine. Can you say that for sticking your finger in a wall outlet? ;)

Cheers!

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* Ratings are for transistors - tubes have guidelines*
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PostPosted: 12 Dec 2013, 17:28 
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Geek wrote:
mwhouston wrote:
Actually when you think about it's probably not that dangerous. 250V is 250V no matter how it is supplied.

Actually, there is a big difference:
https://en.wikipedia.org/wiki/Isolation_transformer

The keywords here are galvanic isolation.

I can plug in a 250V transformer and grab any one of the HV leads and be just fine. Can you say that for sticking your finger in a wall outlet? ;)

Cheers!

Geek: I hear you and agree. A tranni does give isolation from the outside world. I should ensure that there are no problems between the GND of the amp and the other system grounds. And even with my DC blocker now in the system all the time.

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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PostPosted: 13 Dec 2013, 03:16 
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Location: Bulgaria - EU
I never will make or buy that amplifier...... :) :eek: :down:

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Projects: OTL 6AS7 Gen, Electric, SEs 2A3 RCA, 300B JJ, 6S4S, 4P1L, EL11 Telefunken, 6AS7 RCA, 6S33S, 6S41S, 6S19P, PP 6005 Gen. Ellectric , headphone ampl. OTL Loftin White 6AS7 RCA....SE E84L& E80CC Siemens&Tel-n.
http://azazello-sound.blogspot.com/


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PostPosted: 13 Dec 2013, 06:39 
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Actually, if you have a hi-pot-tested transformer on the input, use a non-conductive chassis and the OPT will be suitable for the output, it might even get a UL pass ;)

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* Ratings are for transistors - tubes have guidelines*
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PostPosted: 13 Dec 2013, 11:59 
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Location: Arizona, USA
Ugh. I have ranted on this before several times. There is no way I would allow such a thing in the house. A single fault in either the house wiring (I found a reversed hot and neutral just last year and we have been here 30+ years) or in the unit itself can place the full line voltage on the chassis and anything connected to it. I figure that as long as transformers are cheaper than headstones, I believe I'll stick to transformers.

Good listening
Bruce

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