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 Post subject: Re: 6EM7 power amp
PostPosted: 18 Nov 2013, 07:22 
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Golly just won another 10 X 6EM7 tubes. All Samsung tubes. Any one for a good PP schematic for these babies???

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 Post subject: Re: 6EM7 power amp
PostPosted: 18 Nov 2013, 18:06 
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Joined: 08 Aug 2009, 03:11
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Location: Chilliwack, BC
Congrats! :D

I did a PP guitar amp with these, didn't sound too hot on OD. Can't remember the load I used, but was getting about 8 watts outta it, clean.

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 Post subject: Re: 6EM7 power amp
PostPosted: 18 Nov 2013, 18:39 
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Geek wrote:
Congrats! :D

I did a PP guitar amp with these, didn't sound too hot on OD. Can't remember the load I used, but was getting about 8 watts outta it, clean.

You don't know where I can get a parallel 6EM7 schematic from do you? My mate Don wants some of my tubes but would like to build a parallel version. Maybe if we ask Matt nicely he may knock-up a parallel version for use.

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 Post subject: Re: 6EM7 power amp
PostPosted: 18 Nov 2013, 23:17 
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Parallel class-A is easy... Power and current is doubled, anode load is halved.

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 Post subject: Re: 6EM7 power amp
PostPosted: 18 Nov 2013, 23:26 
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Geek wrote:
Parallel class-A is easy... Power and current is doubled, anode load is halved.
I would like to see the driver triodes design: totempole, two stage??

So instead of a 5K OPT you use a 2.5K OPT? What of Rk?

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 Post subject: Re: 6EM7 power amp
PostPosted: 19 Nov 2013, 01:53 
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mwhouston wrote:
Geek wrote:
Parallel class-A is easy... Power and current is doubled, anode load is halved.
I would like to see the driver triodes design: totempole, two stage??

So instead of a 5K OPT you use a 2.5K OPT? What of Rk?

2.5K, yup!

Rk would be divided by two, so just parallel in another resistor.

Driving voltage remains the same. You can use the same driver circuit.

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* Ratings are for transistors - tubes have guidelines*
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 Post subject: Re: 6EM7 power amp
PostPosted: 19 Nov 2013, 02:29 
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Geek wrote:
mwhouston wrote:
Geek wrote:
Parallel class-A is easy... Power and current is doubled, anode load is halved.
I would like to see the driver triodes design: totempole, two stage??

So instead of a 5K OPT you use a 2.5K OPT? What of Rk?

2.5K, yup!

Rk would be divided by two, so just parallel in another resistor.

Driving voltage remains the same. You can use the same driver circuit.

But now I have two driver tubes. Am I missing something? Thanks for the info so far.

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 Post subject: Re: 6EM7 power amp
PostPosted: 19 Nov 2013, 07:28 
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Just parallel them, too :D

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 Post subject: Re: 6EM7 power amp
PostPosted: 21 Nov 2013, 18:21 
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When building Abstinence I want to use some different inter-stage caps.

I ordered these: 8x 0.033uF 500V AUDIO teflon capacitors K72P-6. They didn't come in time so I installed orange drops. I like the sound of the amp so much I decided to change nothing. Now the Teflon caps have arrive and just looking at them I know I must use them. I will remove the orange drops and replace with these beautiful Russian teflons. They feel heavy and the outer metal has a satin feel about it. I have some five-nines silver wire I will use to hook them up. Also when the 4uf PIO Russian caps arrive I'll put them in too and the Sophia Electric rec tube.
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 Post subject: Re: 6EM7 power amp
PostPosted: 23 Nov 2013, 20:18 
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My 4uf 400V Russian PIO caps arrived today (on Sunday, since when?). Tomorrow I will replace the 22uf first cap in the PS of Abstinence with the 4uf caps, add some small resistors to the plates of the rec tube, replace the orange drops with the Russian Teflon 0.033uf signal caps and replace the 5Y3 with the gorgeous looking Sophia Princess mesh plate rec tube.

Abstinence is about to take on a whole personality.

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