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Re: Thanks!!!


 
4/25/2003 2:27 PM
rooster Re: Thanks!!!
Thanks again, Steve!!  
 
I will study this in depth tonight. It looks pretty straightforward, so I'd bet that the OT has quite a bit to do with the sound. From the look of it, if the measurements shown on the schematic are correct, the primary of the OT looks to be about 1K. Looks pretty low for 6V6's, I would've expected 2k-4k. (230 ohms x 4?)  
 
Or am I missing something?  
 
rooster.
 
4/25/2003 7:51 PM
Bruce /Mission Amps
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Yes you ar right, that's a DC resistance of 230 ohms. The primary zed, or impedance, is around 3000 to 4000 ohms.  
 
Bruce
 
 
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4/25/2003 10:38 PM
rooster Thanks, and let's see if this setup sounds good.
Why thank you, Bruce!  
 
It seems to me that a Bandmaster OT running into a 4x8 configuration (4 ohms total) would work fairly well. In fact, since it is set up as a "35W" OT, I could probably run a parallel jack for an extension cabinet. I figure a Bandmaster OT is set up for 4K ohms into 4 ohm output, I could probably run a 2 ohm load into a 2 ohm output with little risk of damage (I think, but maybe not).  
 
SO, I could build a single input version of this amp, using the first 12ax7 for the input stage, driving the tone controls, into the tone recovery, which would be the second half of the first 12ax7.  
 
Then, into the 2nd 12ax7 for the phase inverter(using the 1st half of the tube) and the second half of the tube would be the vibrato (instead of the 6AU6 setup).  
 
Then, a 6SN7 for the driver tube as in the original, and off to the 6V6's, which, according to the schematic, are biased at about 80% through the 12ax7 filaments (I'll be using a 130 ohm resistor instead, I think, that should do the job, what with 19V/150mA and all).  
 
I figure a 275-0-275 PT @ 150mA with a sag resistor of 270 ohms at 10W (to drop 10V or so, I figure around 160mA total idle current draw), and the light filtering the amp has designed into it should provide a very fat soft sound at about 315V plate voltage.  
 
Look OK to you?  
 
rooster.
 
4/26/2003 5:27 AM
rooster Correction!
Make that a drop of about 40V from the sag resistor. I think this may do the job for a good harmonica amp. The voltages at the plates of the preamp tubes are pretty low, so it should have a fairly warm sound.  
 
rooster.  
 
P.S. If this works out, I'll email or snail mail a schematic and layout to Steve, Bruce, or someone. Then it can be posted around here somewhere. If it doesn't, well, oops.
 
4/26/2003 9:43 AM
Sweetfinger Re: Thanks, and let's see if this setup sounds good.
Bill has been pestering me for years to find him a commando. I've offered to build one, but being the nut he is, wants the real deal. Rumor has it that the "sonny JR." amp is a tweaked version of the commando. A fair amount of the mojo from this amp is going to come from the specific speakers (rola?) and the masonite construction of the baffles and cabinet.  
 
Commandos are quite rare. I've only seen one in person and seen only one offered for sale (after the fact on ebay).  
Dumbles appear to be common when compared to commandos.  
 
Holy grail? We already got one..it's..ah,..very nice!
 
4/26/2003 3:46 PM
Steve A.
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Monty Python
Sweetfinger:  
 
Holy grail? We already got one..it's..ah,..very nice!  
 
 
    I highly recommend getting Monty Python and the Holy Grail on DVD since you can switch on the subtitles in English... the "Camelot" song is a real hoot when you can actually understand all of the words. I haven't checked out the newest reissue- the one with the extra 30 seconds of deleted scenes!  
 
    "Life of Brian" was reissued with 45+ minutes of deleted and alternate scenes.  
 
    And then there is the box set of all of the Monty Python tv shows...  
 
Steve Ahola
 
4/26/2003 7:28 PM
neatpete
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MY BRAIN HURTS  
 
ROFL
 
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