Ry Cooder's Borderline Special

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10thTx
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Re: Ry Cooder's Borderline Special

Post by 10thTx »

Edited and reposted below
Last edited by 10thTx on Tue Mar 19, 2013 11:02 am, edited 1 time in total.
bluesfendermanblues
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Re: Ry Cooder's Borderline Special

Post by bluesfendermanblues »

Great initiative!
Diva or not? - Respect for Mr. D's work....)
groovtubin
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Re: Ry Cooder's Borderline Special

Post by groovtubin »

10thTx wrote:OK, simply for the sake of discussion and offering educated guesses, ......
I 'll offer this idea.

I've attached an editable SCH schematic if someone wants to edit it and offer another idea.

Assume that the schematic is NOT accurate and just a draft idea for discussion purposes only.

I just took one of the 50w Dumblish ideas, changed the values of the LTPI plate resistors and the grid resistors and tacked on a 6G16 Fenderish vibrato with one of the cap values changed.

With respect, 10thtx
in the pic, the pres cap is clearly coming of the TOP of the tail resistor, just in case anyone missed!

respect, jim@Omegaamps
Max
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Re: Ry Cooder's Borderline Special

Post by Max »

10thTx wrote:OK, simply for the sake of discussion and offering educated guesses, ...... I 'll offer this idea.
Tony (talbany) posted: "The amp is a Low plate Classic 50w straight up." http://ampgarage.com/forum/viewtopic.ph ... 815#238815

But AFAIU your schematic it doesn't show a "classic" tone stack: http://ampgarage.com/forum/viewtopic.ph ... highlight=.

Why?

Cheers,

Max
10thTx
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Re: Ry Cooder's Borderline Special

Post by 10thTx »

Edited and reposted
Last edited by 10thTx on Tue Mar 19, 2013 6:45 pm, edited 1 time in total.
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jelle
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Re: Ry Cooder's Borderline Special

Post by jelle »

Max wrote: Why?

Cheers,

Max
The best questions often go unanswered... :lol:

Great initiative, I had not tried to trace this one either. The cathodes for CL and OD should be 1.5K with 4.7uf caps. The caps in the trem appear .05uf, at least to me, based on the size. If I see more, then I will let you know. Jelle
bluesfendermanblues
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Re: Ry Cooder's Borderline Special

Post by bluesfendermanblues »

Updates:

V2b cathode cap should be 1.5k

LFBN on V1b should be not be in a classic circuit - it is belongs to the skyliner

Bright cap should be on a switch
Diva or not? - Respect for Mr. D's work....)
Max
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Re: Ry Cooder's Borderline Special

Post by Max »

bluesfendermanblues wrote:LFBN on V1b should be not be in a classic circuit - it is belongs to the skyliner
AFAIU this layout http://ampgarage.com/forum/download/file.php?id=14346 it shows the circuit of a typical "low plate classic" ODS and shows a LNFB loop at V1b. So why do you think that such a LNFB loop "should not be in a classic circuit" - as you wrote? Or did I misunderstand what you wrote?

Cheers,

Max
10thTx
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Re: Ry Cooder's Borderline Special

Post by 10thTx »

The cathodes for CL and OD should be 1.5K with 4.7uf caps
The layout Max referred to shows 10uf on the clean channel.

It also shows LNFB ..... & from the photobucket pictures, it looks like maybe there is LNFB around V1b on the Borderline Special ?

Maybe the vibrato caps are .047? That might tend to make for a fairly "slow" vibrato vibe, IMO.

V2-b cathode is 1.5k & noted. Just a drawing error, that I'll correct after more input.

With respect, 10thtx
groovtubin
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pres cap

Post by groovtubin »

groovtubin wrote:
10thTx wrote:OK, simply for the sake of discussion and offering educated guesses, ......
I 'll offer this idea.

I've attached an editable SCH schematic if someone wants to edit it and offer another idea.

Assume that the schematic is NOT accurate and just a draft idea for discussion purposes only.

I just took one of the 50w Dumblish ideas, changed the values of the LTPI plate resistors and the grid resistors and tacked on a 6G16 Fenderish vibrato with one of the cap values changed.

With respect, 10thtx
in the pic, the pres cap is clearly coming of the TOP of the tail resistor, just in case anyone missed!

respect, jim@Omegaamps
Here`s pres cap, shouldn`t be too hard at fig out, that`s def a huge factor in tone of this amp, can ya draw it up 10thx?

jim
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talbany
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Re: Ry Cooder's Borderline Special

Post by talbany »

The layout for the low plate classic was taken from the layout of 124 which was origionally a low plate classic before the upgrade to Skyline EQ..

At the time this was all we knew about the low plate classic amp?

After the Boarderline pics were graciously given to us by Gil clearly shows this amp to be a LOW PLATE CLASSIC! w/trem added :D It would also make some sense that he used 4.7 uf on the cathodes since this was a 50w amp!!.. :shock:

I also went back and checked a few other shots I had of the Carlos Rios (Now owned by Ben Harper) which is also a Low plate Classic 100w and this amp too has 4.7uf on V1 a&b cathodes

Conclusion..Since 124 was updated to Skyliner specs perhaps the bypass caps were also changed to suit some customers needs (using 10uf)instead of the normal 4.7uf CL1 If this is the case we should rethink the layout for the low plate classic
I cannot tell from the shots Gil provided that 124 had these 10uf caps and I assume IC-racer who origionally did the boards for the layout I used on 124 and the low plate classic got the info from the hand drawn pics from Billy provided with the pics Gil posted from 124..

If others have more images from an actual (non updated) low plate classic (100w) and can confirm these amps did indeed come stock with 4.7uf caps we should consider updating the low plate classic layout to 4.7 on CL 1
BTW..The layouts are there to provide some historical data taken from actual Dumble amps..You can most certainly use either 10uf or 5uf on your personal builds with good results!!

Thanks

Tony
Last edited by talbany on Tue Mar 19, 2013 6:52 pm, edited 3 times in total.
" The psychics on my bench is the same as Dumble'"
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mhartman
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Re: Ry Cooder's Borderline Special

Post by mhartman »

Greg D. Clark posted this incomplete Visio layout of the Borderline Special before all of his drama went down. I'm not all that interested in this amp, but perhaps someone who is wants to take this and finish it off.
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10thTx
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Re: Ry Cooder's Borderline Special

Post by 10thTx »

OK, I have made some edits.

Changed clean cathode caps back to 4.7uf
Corrected V2b cathode resistor
Eliminated previously drawn PAB & put switch on volume bright cap
(however, I am not sure the rock/jazz is drawn correctly?)

..... and redrew the presence cap attached to the tail resistor. However, I am having trouble evisioning that making any difference in the tone? And that seems to be inconsistent with other Dumblish build schematics.

With respect, 10thtx
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groovtubin
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Re: Ry Cooder's Borderline Special

Post by groovtubin »

10thTx wrote:OK, I have made some edits.

Changed clean cathode caps back to 4.7uf
Corrected V2b cathode resistor
Eliminated previously drawn PAB & put switch on volume bright cap
(however, I am not sure the rock/jazz is drawn correctly?)

..... and redrew the presence cap attached to the tail resistor. However, I am having trouble evisioning that making any difference in the tone? And that seems to be inconsistent with other Dumblish build schematics.

With respect, 10thtx
Have a HARD time blvg it wouldn`t make a difference, you think he screwed up on purpose?

respect, jim
vibratoking
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Re: Ry Cooder's Borderline Special

Post by vibratoking »

..... and redrew the presence cap attached to the tail resistor. However, I am having trouble evisioning that making any difference in the tone? And that seems to be inconsistent with other Dumblish build schematics.
Doesn't it look exactly like 183 and 102? That's my recollection of those circuits. I don't think we have to rely on whether HAD made a mistake or not. Can't we reason it out on our own? You can see that as the 2.2k pot approaches a short, more highs are shunted to ground. In fact, at very high frequencies, that cap approaches a short circuit. I do agree that the presence circuit doesn't make massive differences, but it is audible to my ears...and that's saying something.
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