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Old 25th October 2010, 08:32 PM   #21
athos56 is offline athos56  United States
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Default How about...

Making the input a 6SL7 LTP, to a 6SN7 CF Driver, to the 6V6 with 12v battery fixed bias and the screens to the UL taps. Wouldn't be that much more in terms of complexity... (And maybe some Shade...)


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Old 25th October 2010, 08:34 PM   #22
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Originally Posted by lawbadman View Post
I did actually consider that amp but I got scared when I saw it needs a -160Vdc. That means I would need an extra high voltage trafo, and im trying to keep costs down.

Do a search for the 6GK5/6V6 music machine. It's the updated version, and only needs -66V for the CCS. I've built the 6GK5/EL34 version, and it's the nicest sounding amp in the collection so far.

The -66VDC is supplied by a tiny 44V toroid.

6v6 music machine build help!

Last edited by boywonder; 25th October 2010 at 08:46 PM.
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Old 25th October 2010, 08:51 PM   #23
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Originally Posted by lawbadman View Post
I did actually consider that amp but I got scared when I saw it needs a -160Vdc. That means I would need an extra high voltage trafo, and im trying to keep costs down.
In the overall costs of implimenting the music machine (as it should be done), an additional small trafo is negligible. It doesn't need to be a high power piece of iron since its only setting up a voltage for the first stage - some 15ma if I recall correctly.

Poinz does some very convoluted connections to make a couple of common PTX's work, but the required combinations can be acheived in a number of ways.
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Old 25th October 2010, 09:30 PM   #24
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Originally Posted by stalker View Post
Where did you read it? I have serious doubts about that.
Gernsback Library Inc.
april 1956
Crowhurst and Cooper
"High Fidelity Circuit Design"
chapter 6
Drivers and Inverters

I'm not arguing against, I actually like the Mag style, and I believe it sounds very good, even with theoric weaknesses..
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Last edited by Mosquito; 25th October 2010 at 09:38 PM.
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Old 25th October 2010, 09:43 PM   #25
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Originally Posted by athos56 View Post
Making the input a 6SL7 LTP, to a 6SN7 CF Driver, to the 6V6 with 12v battery fixed bias and the screens to the UL taps. Wouldn't be that much more in terms of complexity... (And maybe some Shade...)


Athos
So, completely redesign it then? Sounds like a complex response to a simple problem - the 6V6 doesn't need huge voltage at G1 to drive it, just an appropriate driver/splitter. Why throw another pair of tubes at the issue? Ditch the SL7 and go SN7 voltage amp to SN7 concertina splitter. Job done.
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Old 25th October 2010, 09:47 PM   #26
athos56 is offline athos56  United States
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Quote:
Originally Posted by aardvarkash10 View Post
So, completely redesign it then? Sounds like a complex response to a simple problem - the 6V6 doesn't need huge voltage at G1 to drive it, just an appropriate driver/splitter. Why throw another pair of tubes at the issue? Ditch the SL7 and go SN7 voltage amp to SN7 concertina splitter. Job done.
Sorry, half snark, should have left it alone

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Old 25th October 2010, 10:32 PM   #27
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ayieeee, we are all guilty at some stage! :-)
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Old 26th October 2010, 12:45 AM   #28
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May I immodestly intrude?

Check "El Cheapo" out. The 12AT7 has a higher gm than either the 6SL7 or the 6SN7. High gm and low RP make for better performance in a driver.

For all practical purposes, the 'AQ5 shown in the schematic is a 6V6 in a 7 pin mini package. Zero parts value changes are needed to build with 6V6s.

Triode wired "finals" yield approx. 6 WPC. If the O/P tubes are set up in ultralinear mode, about 12 WPC are available.
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Old 26th October 2010, 03:00 AM   #29
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Thanks for the suggestion Eli.
What are the voltages (or range of voltages) for B+, B2+ and B-?
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Old 26th October 2010, 07:50 AM   #30
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Tube rolling might improve it and I don't know way the first cap after rectifier is so high! I think it should be 30.
I've seen that a lot with these old designs. They were trying to build it on the cheap, and resistors are a good deal cheaper than ripple chokes, but half as effective for ripple attenuation. They abused the hollow state diodes with over sized reservoir capacitors. They were counting on an atechnological public to be unaware that having to constantly replace the 5Y3s wasn't normal. It didn't hardly matter when you could go to any grocery store, pharmacy, radio/TV repair shop and get replacements for a $1.50 (or whatever they cost).

Of course, a big reservoir capacitor like that is going to bust the specs for Isurge. That should be less than half that size. 34uF behind a 5U4GB comes to something like 815mA of Isurge, and that one is rated for a max of 1.0A of Isurge.

You need to get that capacitor down in size, and use an LRC ripple filter. If you want to keep it cheap, then consider an active decoupler after the reservoir capacitor.
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