I am currently building up a single ended EL34 amp, and I am soooooo ******** bored waiting for the transformers to com ein that it has developed into quite a project.
Originally I was going for minimalism, with a small CLCRC oil cap supply, but I got bored and wired up a mosfet regulator... then I added some other bells and whistles... and NOW I have an Amperex EF184 just BEGGING to be hooked up as a CCS.
So my question is, has anyone done it and what would the caveats be? I have done pentode CCS in preamp sections, but always with triodes. What should I be mindful of if I convert this thing to parafeed and load up the plate of the EL34 with the EF184?
Thanx.
Originally I was going for minimalism, with a small CLCRC oil cap supply, but I got bored and wired up a mosfet regulator... then I added some other bells and whistles... and NOW I have an Amperex EF184 just BEGGING to be hooked up as a CCS.
So my question is, has anyone done it and what would the caveats be? I have done pentode CCS in preamp sections, but always with triodes. What should I be mindful of if I convert this thing to parafeed and load up the plate of the EL34 with the EF184?
Thanx.
You can't use a CCS with pentode - they will both fight each other and the tube won't bias up properly.
If you wire the pentode in triode mode it's fine.
regards
If you wire the pentode in triode mode it's fine.
regards
CRUD! That's right... i remember now why I have not done it.
OK, how about a solid state gyrator circuit loading the plate of the EL34?
OK, how about a solid state gyrator circuit loading the plate of the EL34?
Why are you fixed on using the EL34 as a pentode. Do you really need the extra watts. It will sound better in triode mode.
I have built a SEPP amp using 807's as the output tubes. The CCS load is made from a TT21(KT88 with top cap). I tried one of Gary Pimms Pentode CCS's but the voltage across the TT21 collapsed. I had voltage to spare so I dropped about a 100V between the CCS and the 807 in order to stiffen the CCS. I took the output from the top of the 807 rsather than the MU stage option.I sent it through a 1000V 4uf Paper in Oil cap and it drives a 6V mains torodial (about 120VA). Sounds really sweet and a very simple circuit overall.
This configuration hums very little with only minimal power supply filtering.
Shoog
I have built a SEPP amp using 807's as the output tubes. The CCS load is made from a TT21(KT88 with top cap). I tried one of Gary Pimms Pentode CCS's but the voltage across the TT21 collapsed. I had voltage to spare so I dropped about a 100V between the CCS and the 807 in order to stiffen the CCS. I took the output from the top of the 807 rsather than the MU stage option.I sent it through a 1000V 4uf Paper in Oil cap and it drives a 6V mains torodial (about 120VA). Sounds really sweet and a very simple circuit overall.
This configuration hums very little with only minimal power supply filtering.
Shoog
Shoog said:
Yeah, I am pretty set on pentide... that was the whole point of the thing actually, to try out a SE pentode amp. I wired up a gyrator circuit last night out of a mosfet, a cap and a resistor. I'm going to give it a try when my parts come in unless anyone has a warning for me against the idea. I have never uilt one before, so I'll have to see what happens. Worst case scenerio=blown mosfet, and then i am only out about $1.
I suspect hes not planning to use this amp for hifi, he might not object to a little distortion. I wouldnt be surprised if its way overdriven to boot.
Tweeker said:
I suspect hes not planning to use this amp for hifi, he might not object to a little distortion. I wouldnt be surprised if its way overdriven to boot.
DANG! Did the hair and guitar give it away? THAT'S IT, I'm changing my avatar to a Westinghouse 300b! They are sexier than I am anyway.
But honestly, in terms of output stages, your average instrument amps and hi-fi amps are not too dissimilar in general design terms: parafeed is parafeed, SRPP is SRPP, AB1 is AB1. They just vary in freq response and distortion requirements... (and component quality.
I usually get run out of town as a heretic by the guitar amp guys for my hi-fi leanings and the use of SS regulators and oil caps though.
Consequently, I have built up triode instrument amps and they sounded too spongy... gotta be a pentode for me.... or UL. but seriously, if anyone has tried a gyrator on the plate of a pentode in parafeed, I'd be thrilled to know the results.
There have been some good threads on this very subject recently which have only just died down. There are more knowlegable contributers to those than me. Go back a page or two on the Tube listings and you will find them. I suspect you will need to consider plate chokes - which brings you back into the big bucks again.
Good luck.
Shoog
Good luck.
Shoog
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