I am thinking about modding my IV to IIC+ specifications. Bright cap, two fat caps, and a lower pass cap. Anyone else try this? Crunchier and more aggressive, more lowend balls and thickness, and take out a little more fizz on top. But with pentode. I am not looking forward to peering inside the super-crammed-in-guts chassis.
Mod a MkIV to IIC+?
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dodger916
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I like your initiative! But, you might wind up with something that doesn't sound like either. It might also be hard to sell. Then again, you might wind up a unique kick-*** amp!!
C+'s are going relatively cheap these days.
C+'s are going relatively cheap these days.
Well, I took a gander and , heh heh, maybe some year, but not today. Too chickenshit to unsolder one trillion wires to get at the pcb. I don't like tack soldering either, not even for this. It's the long and arduous process of making a wiring diagram, triple checking it, and the de/soldering that I'm not looking forward to. One of the cool things about doing your own mods is you can always go back, but I don't want to go in the first place. Not yet anyways.
Restless Rocks
Well-known member
A very wise decision. The IVa lead circuit is already extremely close to the original C+ wiring. The only mod I've done to a Mark IV that I felt really useful was to convert the Mid/Harmonics switch to the older mark "pull Deep" wiring.
Boogiebabies
Well-known member
Restless Rocks said:
That makes it a totally different amp. I love it too.
straitouttahell
Well-known member
Restless Rocks said:
PLEASE, tell me how to do that!
Boogiebabies
Well-known member
The Mid Gain cap is 2.2uf and the R2 cap is 15uf. In the C+, the pull deep is a 15uf. Get it?
straitouttahell
Well-known member
Boogiebabies said:
Not really, think I have to take a look at the schematics.
By the way, how is this mod supposed to work? Is it supposed to add or subtract meat to the overall tone?
Boogiebabies said:
Ah, I now see how they are a very similar circuit, and I missed how the 15u is only for R2, but the mid gain stuff is a whole stage sooner than in the IIC+ and III, which both place the pull deep after the verb and loop in a buffer stage. In the IV, that 15u cap is already there, making the pull deep "always on". Doesn't it make the gain flubby if you do up the mid gain cap? Or since it's late in the circuit of the amp, does it sound just like only a bass boost? When I flick the switch, it seems to affect gain too.
Boogiebabies
Well-known member
Don't look at the C+ schematic, look at the circuit. In the C+ circuit it goes on V2 pin 3.
V2 pin 8 has a 1K resistor only.
V2 pin 8 has a 1K resistor only.
straitouttahell
Well-known member
Boogiebabies said:Don't look at the C+ schematic, look at the circuit. In the C+ circuit it goes on V2 pin 3.
V2 pin 8 has a 1K resistor only.
I'm more confused than ever :?:
I'm not familiar with tube technology...
Boogiebabies
Well-known member
straitouttahell said:Boogiebabies said:Don't look at the C+ schematic, look at the circuit. In the C+ circuit it goes on V2 pin 3.
V2 pin 8 has a 1K resistor only.
I'm more confused than ever :?:
I'm not familiar with tube technology...
The V2 on the C+ schematic is backwards.
straitouttahell
Well-known member
OK, OK, I'll keep it as it is :lol:
