PS idea
So how about this idea?
Use SS rectifier for the A,C, and D PS nodes.
A = 325 V
C = 276 V
D = 238 V
For the B and E nodes use a separate winding and a weak tube rectifier, maybe a 6AL5?
Use 200 V for both these nodes, looking for the voltage to sag significantly when the screens suck more current than the 6AL5 can easily supply.
This would have the screens and the input tube sagging and compressing under heavy load.
And the output tubes plates and V2 and V3 on a stiff supply to maintain a certain level and response to output the sagging/compression of the screens and V1.
Does that sound like something that might work and produce that cool guitar tube amp sound?
So how about this idea?
Use SS rectifier for the A,C, and D PS nodes.
A = 325 V
C = 276 V
D = 238 V
For the B and E nodes use a separate winding and a weak tube rectifier, maybe a 6AL5?
Use 200 V for both these nodes, looking for the voltage to sag significantly when the screens suck more current than the 6AL5 can easily supply.
This would have the screens and the input tube sagging and compressing under heavy load.
And the output tubes plates and V2 and V3 on a stiff supply to maintain a certain level and response to output the sagging/compression of the screens and V1.
Does that sound like something that might work and produce that cool guitar tube amp sound?
PT specs
This is a pic. of the PT I planned on using.
It is the PT I used on the 6V6 Plexi's I am making.
It comes out of the HP gear I got the premium EL86s out of.
I used the 440 V .22mA tap with 3/16 output and 4 CT Gnd with SS rectification to get 325 VDC on my 1st 6V6 Plexi.
I haven't finished the Quad 6V6 yet, but PSU indicated I will get like 318 VDC with 4 6V6s increased current draw.
I expect this PT to give me around 325 VDC with the EL86s on the same tap.
So I still have 2 364V CT windings with excess current capacity available.
FW rectification with 2 6AL5s might give me the voltage and current I need for the screens and V1.
I also tapped the 3/16 winding for my - bias on the 1st Plexi.
This one works great, sounds fantastic, and the PT runs cold as ice.
On the Quad I'm using an individual bias board from China to be able to bias all 4 output tubes independently. I'm also trying to use primary tap 6/7 for the <65 VAC my bias board needs on it's input. It has 120VAC on it in my 1st build. I think I need to supply like 25-30 VAC to my Chinese board for the correct bias range for my 4 6V6s.
I haven't tried it to see if that is all going to work yet.
If I can get PS and Output circuits I think will work for the EL86s I might return to tapping the HV winding for my - bias voltage. I think I might like to have individual bias adjustments on this too. I guess that will depend how the individual adjustment setup works on the Quad.
This is a pic. of the PT I planned on using.
It is the PT I used on the 6V6 Plexi's I am making.
It comes out of the HP gear I got the premium EL86s out of.
I used the 440 V .22mA tap with 3/16 output and 4 CT Gnd with SS rectification to get 325 VDC on my 1st 6V6 Plexi.
I haven't finished the Quad 6V6 yet, but PSU indicated I will get like 318 VDC with 4 6V6s increased current draw.
I expect this PT to give me around 325 VDC with the EL86s on the same tap.
So I still have 2 364V CT windings with excess current capacity available.
FW rectification with 2 6AL5s might give me the voltage and current I need for the screens and V1.
I also tapped the 3/16 winding for my - bias on the 1st Plexi.
This one works great, sounds fantastic, and the PT runs cold as ice.
On the Quad I'm using an individual bias board from China to be able to bias all 4 output tubes independently. I'm also trying to use primary tap 6/7 for the <65 VAC my bias board needs on it's input. It has 120VAC on it in my 1st build. I think I need to supply like 25-30 VAC to my Chinese board for the correct bias range for my 4 6V6s.
I haven't tried it to see if that is all going to work yet.
If I can get PS and Output circuits I think will work for the EL86s I might return to tapping the HV winding for my - bias voltage. I think I might like to have individual bias adjustments on this too. I guess that will depend how the individual adjustment setup works on the Quad.
Attachments
Have been holding back making my *CW5 amp, might be time to move it up a notch on the pecking order of projects. Just which OT to use? Have a 1760H Hammond 6.6k:16/8/4 ohm transformer, made as a replacement for the BF Deluxe. Or I have a 6.6k transformer out of a Wurlitzer organ that ran 7868 output tubes. Or do a 6L6GB amp with that one? Really wanted to use a switching PS for this amp though. With a lightweight speaker be real easy to haul around.
If with the Hammond OT, when you connect a 16 ohm speaker to the 16 ohm tap you get a reflected plate load of 6.6K.
Then if you hook up an 8 ohm speaker to the 16 ohm tap you will have a 3.3K plate load, which is just about right.
Darn, well that works then.
Thought about it and the Wurlitzer wouldn't have multiple taps. Just looked, nope. Then that one will be destined for 6L6's.OT
I checked my stock of OTs last night. I've got one that came from a Hammond organ H-100 that had 2 PP 7591s. It has multiple taps, but from finding it's Z I should be able to run it at 3100 ohms plate load. That works for the little EL86s, and it looks to be high enough wattage that unless I start ramping up insane voltage levels for the EL86, like George (Tubelab), it should have no problem handling the output.
That means I've got a PT, OT, and all the tubes needed to do an EL86 Marshal Plexi derivative.
But only being a repair tech and not a competent designer yet, I still need some guidance on building a circuit that won't destroy my parts and just needs to be tweaked to suit my tastes.
Anyone have any feedback for me on my idea to use a second HV supply and a pair of 6AL5s as Full Wave rectifiers for my screens and V1?
I checked my stock of OTs last night. I've got one that came from a Hammond organ H-100 that had 2 PP 7591s. It has multiple taps, but from finding it's Z I should be able to run it at 3100 ohms plate load. That works for the little EL86s, and it looks to be high enough wattage that unless I start ramping up insane voltage levels for the EL86, like George (Tubelab), it should have no problem handling the output.
That means I've got a PT, OT, and all the tubes needed to do an EL86 Marshal Plexi derivative.
But only being a repair tech and not a competent designer yet, I still need some guidance on building a circuit that won't destroy my parts and just needs to be tweaked to suit my tastes.
Anyone have any feedback for me on my idea to use a second HV supply and a pair of 6AL5s as Full Wave rectifiers for my screens and V1?
Unless I am wrong about the Marshall's I thought they were more beefy in the PS area and they were more stiffer than Fender's 57 Bassman, capacitors and choke twice the Bassman value. The later Marshall's even had stiffer supplies. No Tweeds these. I would probably use a VVR for the screens, a Mosfet, zener, dial in the voltage drop with a pot and then a couple of resistor.
non common tubes
I did pull out a couple of Mullard 6J6s and 4 good 6AV6s not Mullards.
I was leaning towards only using the non common EL86s with always available 12AX7s just in case.
What do you think, just go with the already proven posted schematic with the all non common tubes used?
Or try to figure my own Plexi design out with only the EL86s as uncommon tubes used?
I did pull out a couple of Mullard 6J6s and 4 good 6AV6s not Mullards.
I was leaning towards only using the non common EL86s with always available 12AX7s just in case.
What do you think, just go with the already proven posted schematic with the all non common tubes used?
Or try to figure my own Plexi design out with only the EL86s as uncommon tubes used?
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