psychodave":5gerjaat said:Interesting take on it. Like a mix of other modders into one.
FourT6and2":2blfbfh2 said:
glpg80":i0afi9bb said:What makes this different than a normal Jose? What changes did you decide to make?
NewReligion":i0afi9bb said:Sounds great FourT6and2. I count 14 different value and or addition/subtractions to my circuit take. Of course they all add up.
What are you using for Iron?
David...♫
FourT6and2":3ac5uolq said:glpg80":3ac5uolq said:What makes this different than a normal Jose? What changes did you decide to make?
The clearest way to describe the differences is to read the schematic and compare to any others you find.
NewReligion":3ac5uolq said:Sounds great FourT6and2. I count 14 different value and or addition/subtractions to my circuit take. Of course they all add up.
What are you using for Iron?
David...♫
PT: Merren 1202-55
OT: Merren 784-139
Choke: Metro 352-114
fusedbrain":2q9x88u0 said:I see where you are using a 330pf snubber cap on the 100k plate resistor a la Friedman etc..vs a cap to ground as seen in the Ceriatone Chuppa / Yeti and some Fortin schemes. Just curious about your thoughts on the 2 options and if you tried both methods in this amp?
Amp sounds great by the way
Nice job!
Edit: just noticed the 1n cap to ground over the 68k.
Still interested on your take on plate snubbers....thanks!
FourT6and2":1o361m9g said:fusedbrain":1o361m9g said:I see where you are using a 330pf snubber cap on the 100k plate resistor a la Friedman etc..vs a cap to ground as seen in the Ceriatone Chuppa / Yeti and some Fortin schemes. Just curious about your thoughts on the 2 options and if you tried both methods in this amp?
Amp sounds great by the way
Nice job!
Edit: just noticed the 1n cap to ground over the 68k.
Still interested on your take on plate snubbers....thanks!
I've tried caps in lots of places to kill highs: plate bypass, after a coupling cap to ground, from grid to ground before the grid stopper, from grid to ground before the stopper (which would be the same as from gain wiper to ground), bypassing that 68K "feel" resistor, bypassing the NFB resistor, etc.
They all have slightly different results. Just depends on your tastes and the specific amp. Gotta try them all on your specific amp/build and see what sounds the best. That's why I just use a decade box that clips in and I can cycle different cap values until I find one I like.
fusedbrain":3e00wcp7 said:Interestingly, the scheme is labeled as a Fortin Cali, but it's very close to a Ceriatone Chuppa
fusedbrain":1uf1u8z2 said:FourT6and2":1uf1u8z2 said:fusedbrain":1uf1u8z2 said:I see where you are using a 330pf snubber cap on the 100k plate resistor a la Friedman etc..vs a cap to ground as seen in the Ceriatone Chuppa / Yeti and some Fortin schemes. Just curious about your thoughts on the 2 options and if you tried both methods in this amp?
Amp sounds great by the way
Nice job!
Edit: just noticed the 1n cap to ground over the 68k.
Still interested on your take on plate snubbers....thanks!
I've tried caps in lots of places to kill highs: plate bypass, after a coupling cap to ground, from grid to ground before the grid stopper, from grid to ground before the stopper (which would be the same as from gain wiper to ground), bypassing that 68K "feel" resistor, bypassing the NFB resistor, etc.
They all have slightly different results. Just depends on your tastes and the specific amp. Gotta try them all on your specific amp/build and see what sounds the best. That's why I just use a decade box that clips in and I can cycle different cap values until I find one I like.
Yeah, lots of different Jose schemes out there and lots of things to experiment with for sure.
I'm working on modding a 1987xl re-issue into one of these Jose type amps right now, so that's why I asked.
I'm retro-fitting the original Marshall ST1 PCB, so I'm using SBE 225P caps throughout as they fit into the board. Just that fact alone will have a big effect on what value components I end up with and where they go.
I still have a few things to work out, but hopefully I can come up with something that sounds halfway decent.
I started with this concept, and tweaked from there. There are a few issues with this scheme, but it seemed like a cool place to start.
Interestingly, the scheme is labeled as a Fortin Cali, but it's very close to a Ceriatone Chuppa
It sounds good, but the schematic I posted in the OP is where I ended up after building a bunch of Jose variants.
I tune to my ear and check voltages but every amp is a bit unique due to OT's etc...
NewReligion":ts5r3327 said:There are so many variations on this circuit. On this R11 (Drop R) looks a bit stiff but may suit this variant well
Also the 820 cathodes are interesting. I never tried a jose with all three cathodes at that value.
FourT6and2":df7toilk said:NewReligion":df7toilk said:There are so many variations on this circuit. On this R11 (Drop R) looks a bit stiff but may suit this variant well
I think you mean soft? 22K dropper will make the amp much looser and more gainy. But... it depends on what the starting voltage is. Maybe that particular amp had a really high B+. That's why you can't just use any old schematic verbatim. There are lots of components in an amp that must be tuned specifically for that amp. Like the B+ dropper. If the B+ is like 500V, then maybe a 22K dropper makes sense. But if the amp has a 425v B+, the a 22K dropper is going to equal mush city.
Also the 820 cathodes are interesting. I never tried a jose with all three cathodes at that value.
That's what's in the Ceriatone Chupacabra.
Yup, classic example of fitting the mods to the amp at hand. I'm dealing with this now in my amp.I think you mean soft? 22K dropper will make the amp much looser and more gainy. But... it depends on what the starting voltage is. Maybe that particular amp had a really high B+. That's why you can't just use any old schematic verbatim. There are lots of components in an amp that must be tuned specifically for that amp. Like the B+ dropper. If the B+ is like 500V, then maybe a 22K dropper makes sense. But if the amp has a 425v B+, the a 22K dropper is going to equal mush city.
fusedbrain":3puka4k3 said:Yup, classic example of fitting the mods to the amp at hand. I'm dealing with this now in my amp.I think you mean soft? 22K dropper will make the amp much looser and more gainy. But... it depends on what the starting voltage is. Maybe that particular amp had a really high B+. That's why you can't just use any old schematic verbatim. There are lots of components in an amp that must be tuned specifically for that amp. Like the B+ dropper. If the B+ is like 500V, then maybe a 22K dropper makes sense. But if the amp has a 425v B+, the a 22K dropper is going to equal mush city.
For example, in a stock 1987xl,the first droppers after the choke are 2 x 10k's in series, but my PT is only putting out 460v B+.
After subbing in a 330k plate load resistor on the first triode, the plate voltage there is only 105v .
That ain't gonna work for what I'm after from this amp, that's for sure!
Yeah, great idea. I'd love to do that, but where the hell do you get a 5watt pot??FourT6and2":2dsjge2l said:fusedbrain":2dsjge2l said:Yup, classic example of fitting the mods to the amp at hand. I'm dealing with this now in my amp.I think you mean soft? 22K dropper will make the amp much looser and more gainy. But... it depends on what the starting voltage is. Maybe that particular amp had a really high B+. That's why you can't just use any old schematic verbatim. There are lots of components in an amp that must be tuned specifically for that amp. Like the B+ dropper. If the B+ is like 500V, then maybe a 22K dropper makes sense. But if the amp has a 425v B+, the a 22K dropper is going to equal mush city.
For example, in a stock 1987xl,the first droppers after the choke are 2 x 10k's in series, but my PT is only putting out 460v B+.
After subbing in a 330k plate load resistor on the first triode, the plate voltage there is only 105v .
That ain't gonna work for what I'm after from this amp, that's for sure!
You can probably go down to 10K on that dropper then. I have a 5-watt, 50K pot that I clip in for the B+ dropping resistor and tune the amp with that. Then solder in the final value.