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Vacuum Tube OTL power amp!!
Vacuum Tube OTL power amp!!
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Old 20th November 2011, 04:57 PM   #421
M Gregg is offline M Gregg  England
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OK I have only listened for a short time..

I can tell exactly what it is....when the ct was disconnected there was a frequency shift from bass to treble..ie bass was light by comparison

Now there has been another shift...treble is less..bass is grainy maybe more but possibly moved lower down the scale

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M. Gregg
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Old 20th November 2011, 05:56 PM   #422
Alastair E is offline Alastair E  Wales
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Here you go, Some simple PSU layouts with descriptions....


http://www.audiodesignguide.com/my/ocl.jpg
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Old 20th November 2011, 06:05 PM   #423
M Gregg is offline M Gregg  England
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Alastair,

I have fitted 300 Ohm and it sounds great hum is very very low in the speakers..
I would go so far to say I cannot hear anything in the one speaker
(I do mean can't tell its on, thought the speaker cable was disconnected)I guess with a bit of juggling of the 6633C's I could get it lower on the other side...

So I think this is the value I will stick with plus the unequal resistors..

To me the difference is chaulk and cheese..

Thanks for the links..for me the 1K in the PSU is now 300 Ohms..


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M. Gregg

Last edited by M Gregg; 20th November 2011 at 06:11 PM.
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Old 20th November 2011, 06:13 PM   #424
Alastair E is offline Alastair E  Wales
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Did you try the old transformer as choke ploy...?
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Old 20th November 2011, 06:20 PM   #425
Dimitris AR is online now Dimitris AR  Greece
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Quote:
Originally Posted by M Gregg View Post
Alastair..
Just thinking out loud here..

While after 4hrs listening to the OTL with Deadmau5 (for want of a better name)

deadmau5 "16th hour" - YouTube
Got to test the bass haven't you..

Shakes my laptop across the table.. and hammers the Alpairs into submission
Very deep bass....anyway..yes there are fuses and bypass caps just not on this pic...
Some discussion going on....
Sounds great!!







Regards
M. Gregg
It is better to connect the center tap of the trafo right to the capacitors without the 1K resistor , and use a protection circuit for the loudspeakers to prevent any DC voltage that can destroy them .
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Old 20th November 2011, 06:29 PM   #426
M Gregg is offline M Gregg  England
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Quote:
Originally Posted by Alastair E View Post
Did you try the old transformer as choke ploy...?
Not yet work getting in the way...I will keep trying different things..and post what I find..

There is no question that with the resistors as they are the sound stage is way better...it closed in with the Ct direct connection..why I don't know at the moment...

There must be a reason for this I will try a few things..see what happens..

I have thought about a crowbar circuit that just plugs across the speaker..small module..

Also looking at the cheep choke idea...or electronic choke....so much to try..lol


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M. Gregg
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Old 20th November 2011, 09:20 PM   #427
Dimitris AR is online now Dimitris AR  Greece
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Gregg , you can play with the value of R16 470K , decrease it .
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Old 21st November 2011, 07:59 AM   #428
M Gregg is offline M Gregg  England
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Gregg , you can play with the value of R16 470K , decrease it .
Dimitris,

What value are you thinking of reducing to and why?

I would like to hear what your thoughts are on this topic
Title: Avoiding unpleasant overdrive tones

Its at the bottom of This link:
http://www.freewebs.com/valvewizard/cathodyne.html



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M. Gregg
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Old 21st November 2011, 09:58 AM   #429
donerlank is offline donerlank  South Africa
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Originally Posted by Matthewong View Post
Hi, would like to ask whether the vacuum tube OTL power amp worth to build? How is the sound performance if compare to normal output transformer type?? Does anyone has any good schematic diagram for OTL power amp, can share out, thinking to try to make one.
If u haven't found the OTL amp on this thread that is to your liking and if youre hell bent on a 6AS7G OTL you'll find it on t he Bonavolta home page then click on Audio & Electronics page, click on amps go down a long list of all sorts of amps, click on 6AS7 PP & OTL then click on 6AS7GA OTL there u will find a scheme by Bruce Rosenblitt Glass Audio 1990 (yikes, its 21 years old! Don't led Leadbelly see this! Or were in for a Spanking!) Personally, I did not like what I saw. Too many tubes to get down to 8 Ohm. No less than 8 tubes per channel. Personally I would try Alistair-E's project.
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Old 21st November 2011, 10:51 AM   #430
Alastair E is offline Alastair E  Wales
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Quote:
Originally Posted by donerlank View Post
If u haven't found the OTL amp on this thread that is to your liking and if youre hell bent on a 6AS7G OTL you'll find it on t he Bonavolta home page then click on Audio & Electronics page, click on amps go down a long list of all sorts of amps, click on 6AS7 PP & OTL then click on 6AS7GA OTL there u will find a scheme by Bruce Rosenblitt Glass Audio 1990 (yikes, its 21 years old! Don't led Leadbelly see this! Or were in for a Spanking!) Personally, I did not like what I saw. Too many tubes to get down to 8 Ohm. No less than 8 tubes per channel. Personally I would try Alistair-E's project.

No reason why you shouldnt use 6AS7G/6H13C or any of its varients in this circuit...
You'll prob have to play around with the cathode-resistors to get the bias you want but I see no reason why they wouldnt perform when set up...

I'm currently running some 6C41C which has a similar ratings of two sections of 6AS7G wired in parallel....

The 470K is there for a reason--As described in that article. At normal signal levels, it has no effect on sound, as the PI has a very high input impedance, Its only when the PI gets to the point of clip of the PI that it comes into effect....
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