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Old 27th March 2009, 04:22 AM   #1
mosfets is offline mosfets  Canada
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Cool FRANK"S 6SN7 preamp/linestage

Not 100 percent this is still the defined component value set?
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Old 27th March 2009, 04:31 AM   #2
mosfets is offline mosfets  Canada
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Default PCB?

A PCB for Frank's preamp? Oh my, why would you when point to point wiring is so easy? I'da know, cause this is easier for me?

Your thoughts on this would be grand. Could have errors as I have not spent much time on it. I have new amps, speakers and now to round out the project I added a DIY pre. All projects in the oven cooking in the kitchen. The speakers and amp are ready for assembly and I'm concurrently working on them.

Cheerio!
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Old 27th March 2009, 04:45 AM   #3
mosfets is offline mosfets  Canada
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Default Power?

I found this schematic(Aburquerque Power supply) searching through DIY(and Frank's pre) too.

I have not yet done a PCB for PWR but I think I could muster one in a jiffy. Oh no! Solid state PWR! Why? Hey guys I'm hard core on sound but there has to be a limit. My ears have limitations. I hop yee-all understand. I know it is not everybody's cup of tea when it comes to DIY valves.



Aburquerque Power:
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Old 27th March 2009, 04:56 PM   #4
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Default SUGGESTION

If you already have this 6SN7s at hand and are willing to make it, just take a quick look at the RPA preamp on my webpage www.tubeaudio.8m.com

The line stage of the RPA uses ECC82, but since the sub is the same, you can copy all values and make it with the 6SN7.

It will sound way, way, better. Maybe you should first try the original schematic posted, and than change to the suggested RPA line stage, just to understand why I wrote the above.

For the power supply, try to stay unregulated, with chokes and eventually a tube rectifier (like 5Y3).

Regards,
Alex
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Old 27th March 2009, 05:33 PM   #5
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3 caps, ouch! Any reason why you don't like Franks's DC coupled version?
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Old 27th March 2009, 06:30 PM   #6
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Quote:
Originally posted by leadbelly
3 caps, ouch! Any reason why you don't like Franks's DC coupled version?
Alex is talking about the line stage part of the preamp (which is also DC coupled). I only see one cap at the output... just substitute a 6SN7 for the 12AU7.


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Old 27th March 2009, 06:37 PM   #7
athos56 is offline athos56  United States
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Alex's line stage looks like a CCD line stage I was going to do. If you look at the TCJ article here and here you might find further explanation.
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Old 27th March 2009, 06:48 PM   #8
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Quote:
Originally posted by korneluk
Alex is talking about the line stage part of the preamp (which is also DC coupled). I only see one cap at the output... just substitute a 6SN7 for the 12AU7.
I wasn't responding to Alex, I was responding to mosfets. There are 3 caps in the version of Frank's preamp that he wants to build. IMHO Frank's DC coupled version is a better choice.
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Old 27th March 2009, 08:45 PM   #9
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Default CCDGC

Yes, I use those or a similar type of gain stages troughout my preamp designs, since I like them very much.

Broskie gave it a name - CCDGC. At the time internet in Serbia was a very disputable affair Anyway, this is not about "who did it first" but about the fact that the topology is one of the very best.

Regarding the PCB, I was surprised to find out that a lot of those who have made the line section of the RPA preamp have used my PCB design, care of a good friend - Elvis (his site is nowhere to be found, he seems to have vanished from internet tube life) to whom I sent the design files.

When it comes to the other "similar" schematics, yes I do not like the superfluous caps (I cannot see a valid purpose for the one before the grid of the first triode). And, what I actually do not like is that the first triode draws too little current, while the second actually drives too much current (yes, there is such a thing as too much current, even for cathode followers).

Well, if you want to have the first one draw more, and the second one draw less, in the end there is no reason why should they not drive the same current (in counterphase, thus "constant current draw"). Eventually I stumbled upon the Broskie line stage and adopted his "additional" resistor on the cathode follower as a good idea. Else, I would have ommitted it just like in the gain blocks of the phono stage...

Anyway, the RPA actually has a 5670 implementation of this stage, and over the years several different versions were implemented with various tubes by various people, every time with good results.
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Old 27th March 2009, 09:16 PM   #10
athos56 is offline athos56  United States
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Yeah, I'm more interested in things that work vs. who did what when or who calls it what...

I have some #56 triodes sitting around, I was planning on putting one together after I got the parts I needed.
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