Songwriter Group Build -- Not Gonna Happen

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RJ Guitars
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Songwriter Group Build -- Not Gonna Happen

Post by RJ Guitars »

Out of respect for Hogy and the folks at Komet, I need to withdraw the offer to help folks build one of these amps.
Last edited by RJ Guitars on Sun Dec 28, 2014 2:34 am, edited 5 times in total.
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Blackburn
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Re: Songwriter Group Build -- Not Gonna Happen

Post by Blackburn »

From what Hogy mentioned in a post about Inger, I gathered that the 'Bass Cut' switch may switch out the .0047uf (Classic AC30 'Cut') used for the 'Treble' pot for a larger cap. Not sure which value, but I did try a couple a while back.

I didn't know you were planning on going with both switches.

Edit: RJ, I'm not sure if the bright caps on your layout are correct. I could never figure out why, but I was told more than a couple times that the examination was meticulous and that's what he got. On my schem, they're 200pf and 250pf. I can't see it being much of a difference between the two and in parallel it would be, but they're clearly not wired like that in the pics we've seen. :?
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RJ Guitars
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Re: Songwriter Group Build -- Not Gonna Happen

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guitarsnguns04
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Re: Songwriter Group Build -- Not Gonna Happen

Post by guitarsnguns04 »

The gutshot pic I saw the amp had a NFb. I wonder if the other switch was to turn it on or off....just speculation here. Maybe k decided they liked it in there all the time and deleted the switch on their production model
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BLT
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Re: Songwriter Group Build -- Not Gonna Happen

Post by BLT »

I've also noticed split grid resistors on V1.
BLT
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Blackburn
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Re: Songwriter Group Build -- Not Gonna Happen

Post by Blackburn »

guitarsnguns04 wrote:The gutshot pic I saw the amp had a NFb. I wonder if the other switch was to turn it on or off....just speculation here. Maybe k decided they liked it in there all the time and deleted the switch on their production model
The second switch has been stated as a 'Bass Cut' by Hogy, one of the owners of Komet. NF resistor is 220k and tied to the 16R tap of the OT sec.
BLT wrote:I've also noticed split grid resistors on V1.
V1 is wired in parallel with a 220k plate load resistor. Grid stoppers are each 27k. Cathodes also wired in parallel with a shared 1.5k bias resistor and a 1uf bypass cap.
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Re: Songwriter Group Build -- Not Gonna Happen

Post by guitarsnguns04 »

After some reading it looks like Blackburn is correct. The amp with the octal phase inverter had a bass cut switch and the other with 2- 12ax7's didn't have it.
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RJ Guitars
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SW-30 schematic posted

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M Fowler
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Re: Songwriter Group Build -- Not Gonna Happen

Post by M Fowler »

Hogy made this statement: If you want to experiment with the Bass Cut Switch, look at the JMI AC15 circuit and tweak from there.
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Blackburn
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Re: Songwriter Group Build -- Not Gonna Happen

Post by Blackburn »

RJ, yours looks mostly the same as mine. I don't have the bleeders on my schem, though. Also, reservoir capacitance on mine is a pair of 40uf. Shouldn't be anything to look too deep into. Should turn out to be a good project. :)
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Blackburn
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Re: Songwriter Group Build -- Not Gonna Happen

Post by Blackburn »

M Fowler wrote:Hogy made this statement: If you want to experiment with the Bass Cut Switch, look at the JMI AC15 circuit and tweak from there.
Only thing I could think of was to use the bass amplifier spec'd cap in lieu of the .0047uf. I tried a .1uf and am pretty sure that ain't it. He did say to experiment. These days, I'm mostly just curious and don't really care. FWIW, Hogy also said that Bree sounded better than Inger and that's why they based theirs on that one instead.
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ToneMerc
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Re: Songwriter Group Build -- Not Gonna Happen

Post by ToneMerc »

Blackburn wrote:RJ, yours looks mostly the same as mine. I don't have the bleeders on my schem
RJ added the bleeders

TM
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RJ Guitars
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Re: Songwriter Group Build -- Not Gonna Happen

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ToneMerc
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Re: Songwriter Group Build -- Not Gonna Happen

Post by ToneMerc »

RJ Guitars wrote:
Blackburn wrote: Did everybody catch that little subtle thing on the power supply? They split the rail and V1 actually runs a little higher voltage than V2. Not sure exactly what the strategy is behind that but I just followed the info I had here.
Yeah, I saw that and was trying not to overthink the reason as to why.

TM
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RJ Guitars
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Re: Songwriter Group Build -- Not Gonna Happen

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