Teh Snorkler

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Ben Waylin

Ben Waylin

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What makes this pre-amp circuit tick ?

Can this JCM800 amp mod be considered the genesis of all Bogner's designs ?
 
I actually don’t know a lot about it. There are schematics out there I believe. Plate driven tone stack 4 stages is what I recall.
 
RedPlated said:
I actually don’t know a lot about it. There are schematics out there I believe. Plate driven tone stack 4 stages is what I recall.
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Right. Bogner built it as a pre-amp mod into a combo amp for Ron Champagne.

Legend has it there were 2 others made, around that same time time period.

It was put in as a small, blue circuit board with two 12AX7's on it.

xovqvPA.jpg
 
I was reading the info about it in that link and what really caught me was when he said " it doesn't have that horrifying "modern" sound" lol.
 
ccn said:
I was reading the info about it in that link and what really caught me was when he said " it doesn't have that horrifying "modern" sound" lol.
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I'm thinking that goes along with some of the other Bogner discussions here, of late..

Where folks are seeking "older" Bogner designs for the very same reason.

I'm actually hoping to hear from @Fusionbear on this one, because I'm trying to learn something about it - being a novice at amp modding.
 
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"The plate driven EQ allows the controls to be more effective; variable loading on the gain stage produces a larger range of variation as the controls are manipulated. Whether someone likes this or a CF better is a matter of preference.

The Cathode follower was part of a feedback controlled stage to drive the EQ in the 5E6-A Bassman. The loop provided a virtual earth mixing function, and the output impedance of the stage would be reduced and drive the EQ more easily. A CF follower was the easiest way to drive the loop and consequently more accurate when driven by a low impedance.

This gain stage configuration changed when the 5F6 eliminated the loop and had the PA feedback bootstrapped to the EQ which lessen the load on the CF. The 5F6-A eliminated the PA feedback connection.

Marshall and Traynor copied the 5F6-A Bassman and perpetuated the CF in their designs. Some view the CF as an essential part of the Marshall, or Bassman tonal signature. Others regard the CF as a vestigial tube stage of an earlier circuit."

-- renshen1957
 
The Rhythm sound on Facelift was a boosted Blackface Bassman; Butler Tube Driver. Out of R Champagnes mouth; here on the forum. Snorkeler was leads n cleans.
Through 70s greenbacks.
No need to blow 6K on a Bogner modded Marshall.
 
Racerxrated said:
The Rhythm sound on Facelift was a boosted Blackface Bassman; Butler Tube Driver. Out of R Champagnes mouth; here on the forum. Snorkeler was leads n cleans.
Through 70s greenbacks.
No need to blow 6K on a Bogner modded Marshall.
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Yeah. Dirt was 3~4 amps blended, also.

I wouldn't even consider buying one of those insanely-priced modded amps. :ROFLMAO:

I'm building the circuit into a pre-amp that I can run as a boost into my JCM800. Looks like it might cost me about $85 in parts. :cool:
 
PLX said:
I'm thinking that goes along with some of the other Bogner discussions here, of late..

Where folks are seeking "older" Bogner designs for the very same reason.

I'm actually hoping to hear from @Fusionbear on this one, because I'm trying to learn something about it - being a novice at amp modding.
Click to expand...

Bogner amps I'm not too familiar with. They just never did anything for me. I do respect his "mad professor" skills though. But, it's really just a matter of preference. The circuits are not hard, there isn't any magic going on. It's just different combinations of plate resistors, cathode resistors and caps, and coupling caps. Find a combo that works and play....
 
Fusionbear said:
Bogner amps I'm not too familiar with. They just never did anything for me. I do respect his "mad professor" skills though. But, it's really just a matter of preference. The circuits are not hard, there isn't any magic going on. It's just different combinations of plate resistors, cathode resistors and caps, and coupling caps. Find a combo that works and play....
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I managed to sketch the mod schematic from the hi-res photos of the "blue board".

I guess the thing that might make it different is the plate driven tone stack.. which I've seen almost everyone who does this mod seems to implement a little differently.

J0aTQbS.jpg
 
Chubbs said:
https://www.scribd.com/document/416098004/Bogner-Snorkler-Mod-Draft1
Found this online. While I’m not autistic enough to confirm the values they do look close to the ones in the above photos. Kinda hard to figure out what’s going on outside of the way the tone stack is configured. Perhaps a bunch of low end pre tone stack that gets shaved out by the slope and re-flavored middle and bass caps?
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Yeah, that one pretty much agrees with what you see on the blue circuit boards.

The photos tell you what type of capacitors Reinhold used in each place in the circuit, not just the component values.
 
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Fusionbear said:
Looks similar to the TUT high gain mod that you also see almost verbatim in the Rocca's
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I have TUT vol 2, but I don't find that circuit in there.

I'm building it as a pre-amp inside an old amp chassis, rather than modding my JCM800.

Looking forward to hearing what this circuit sounds like !
 
glip22 said:
I also belive there are major tone stack changes. David Hopins knows the answers
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I have 5 schematics at this point, including the ones from the snocone forum, and there are a few variations in how the tone stack is implemented.
 
PLX said:
I have TUT vol 2, but I don't find that circuit in there.

I'm building it as a pre-amp inside an old amp chassis, rather than modding my JCM800.

Looking forward to hearing what this circuit sounds like !
Click to expand...
See TUT4
 
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