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Black Lace - 6V6 power amp, direct mains, old school
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Author:  mwhouston [ 12 Dec 2013, 04:51 ]
Post subject:  Black Lace - 6V6 power amp, direct mains, old school

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.

Author:  Geek [ 12 Dec 2013, 06:29 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

*GASP!*

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

Author:  mwhouston [ 12 Dec 2013, 07:37 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

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.

Author:  thehoj [ 12 Dec 2013, 15:34 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

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

Author:  mwhouston [ 12 Dec 2013, 16:08 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

Actually when you think about it's probably not that dangerous. 250V is 250V no matter how it is supplied.

Author:  Geek [ 12 Dec 2013, 17:16 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

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!

Author:  mwhouston [ 12 Dec 2013, 17:28 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

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.

Author:  azazello [ 13 Dec 2013, 03:16 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

I never will make or buy that amplifier...... :) :eek: :down:

Author:  Geek [ 13 Dec 2013, 06:39 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

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 ;)

Author:  gofar99 [ 13 Dec 2013, 11:59 ]
Post subject:  Re: Black Lace - 6V6 power amp, direct mains, old school

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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