*New Build Thread* 2nd Gen Hybrid 50w footswitchable FET

[talbany]

Martin
Take a look at the clean master on ODSR #60

Tony

[ER]

That's the same relay set-up that I used on my early style amp with dual masters, lifted directly from the bluesmaster, only I treated the OD master like a normal single master (ignoring relay placement) on a #40 for example with the 180k/1M coming directly off the .01 cap from plate of V2A (second stage of overdrive) with no bright cap. Clean master has a bright cap.

The OD relay bypasses the clean master when engaged, and the OD master switches in and out with the OD stage, works really well for me.

Mine was an HRM but I put my tone stack at the OD entrance like a Hiwatt so theres no cathode/marshall style TS at the back side of the OD.

[martin manning]

Tony, I searched out a thread with some #60 pictures. Has a schematic or layout been drawn for that amp? A significant feature I noticed about this hybrid layout is that the clean master ground is lifted in OD, so it's element resistance is not paralleled with the OD entrance network. All of the other layouts (HRM's) show the clean master grounded directly to the buss, and it looks like the pots on #60 are too.

[talbany]

Yeah but the cl master on 60 is a 2 meg..

T

[amplifiednation]

Where are the #60 shots??

Martin I think the taking the clean master completely out of the circuit when the OD is engaged is to stay true to the 2nd gen schematic, since there is no clean master in those amps (like #40), the resistive element shouldn't be there

[martin manning]

Where are the #60 shots??

https://tubeamparchive.com/viewtopic.ph ... 35&start=0

[ToneMerc]

Where are the #60 shots??

Martin I think the taking the clean master completely out of the circuit when the OD is engaged is to stay true to the 2nd gen schematic, since there is no clean master in those amps (like #40), the resistive element shouldn't be there

Yep, the circuit is then is loaded as intended. Although I have wired it as the single MV as well, it just takes some tweaking to get the right balance.

Enjoy!

TM

[talbany]

Martin I think the taking the clean master completely out of the circuit when the OD is engaged i

Why do you want a master on the clean channel?, Normally it's the OD that is louder and in need of a level control!...I would think if the clean master is switched out and the input vol is cranked when you lift the Cl master and load the OD volume would be pretty loud and harder to balance.... Am I missing something..

Tony

[martin manning]

Martin I think the taking the clean master completely out of the circuit when the OD is engaged is to stay true to the 2nd gen schematic, since there is no clean master in those amps (like #40), the resistive element shouldn't be there

Yes, yes, that's the reason for my original question: did Dumble ever do it this way on non-HRM's or is it somebody else's mod? On the HRM circuits he did not. Either way the signal out of the clean stages is taken directly to the OD entrance, but per all the HRM schematics he left the clean master's element connected from the OD entrance to ground.

[talbany]

I would think if you had the CL master after V1b coupling cap (2 meg would help with loading) like #60 (switched out) but then also have some sort of OD master (after V2b)..Then you would have complete control on both sound pretty good..

In an HRM there is a clean master and the OD level is the master for the OD..
Tony

[amplifiednation]

I would think if you had the CL master after V1b coupling cap (2 meg would help with loading) like #60 (switched out) but then also have some sort of OD master (after V2b)..Then you would have complete control on both sound pretty good..

In an HRM there is a clean master and the OD level is the master for the OD..
Tony

Exactly how I have it wired...i have the OD master still. how would the 2M pot make the circuit different?

[talbany]

I didn't see your layout and thought the OD was a straight 2nd gen..Couple things..If I were to add the OD master I would simply substitute the 1m pot with the 1m feeder resistor..The 180k dumps some low end helping to keep the OD tight..The funky 3 resistor OD entrance is a low gain network so your not going to have to dial back the 1m master very much to get it to balance out..If you want to smooth out the OD tone you could add say a 100-150k resistor in place of the 1m feeder..
The 2m helps with the back to back pot loading!

Tony

[amplifiednation]

I decided I didn't like the dual masters on the 2nd gen...it just didn't seem to be right...the clean was too loud, and I couldn't crank up the OD volume to get the gain I wanted without cranking up the clean...just overall wasn't working the way I liked.

So I decided to go back to the power amp master. I rewired the OD relay like 183, grounded pin 1 of the 1MA master, and wired the wiper of the pot to the pre/power out.

Now I'm back to the state of that pot not doing anything and the amp is making some odd scratching sounds. It's switching channels fine, but the power amp master is useless.

what other changes need to happen? why is this different than the 124/183 scheme??

by the way this amp sounds phenomenal!

[ToneMerc]

I rewired the OD relay like 183, grounded pin 1 of the 1MA master, and wired the wiper of the pot to the pre/power out.

Taylor verify that you do have the OD relay wired for the AGB board and not how's it's depicted in the #183 layout?

Yes, you can wire these just like the later gens. Sounds like you have DC on the Master pot too.

TM

[amplifiednation]

I rewired the OD relay like 183, grounded pin 1 of the 1MA master, and wired the wiper of the pot to the pre/power out.

Taylor verify that you do have the OD relay wired for the AGB board and not how's it's depicted in the #183 layout?

Yes, you can wire these just like the later gens. Sounds like you have DC on the Master pot too.

TM

I used the 183 schematic and not the layout. The connections on the relay made sense to me, although this understanding is very new to me.

How would I have DC on the pot? Leaky cap? Actually I just remembered when I had the amp wired up with the clean master, everything was working fine, but that pot was pretty scratchy then too!!