changing filter cap values
- Thread starter tman
- Start date
Re: changing filter cap values
When i asked where was it installed, i was talking about where in the circuit.....not where on the chassis.
If it was installed in the typical location of a Pi Filter, they might have removed a 400 Ohm resistor that would offer more "Sag" than the choke they installed.
Three Caps in //.?
I have seen enough.
Good Luck Guys
Yes...that is exactly what it means. A choke is a short to DC. No, i absolutely do not have a degree in electronics, but i Do Know the definition of an inductor.
When i asked where was it installed, i was talking about where in the circuit.....not where on the chassis.
If it was installed in the typical location of a Pi Filter, they might have removed a 400 Ohm resistor that would offer more "Sag" than the choke they installed.
Three Caps in //.?
I have seen enough.
Good Luck Guys
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Re: changing filter cap values
Yeah, now I remember why I keep my mouth shut about these things. I'll just ask a very simple question, then I'm done. Why do you think it's reffered to as a 'choke"?
ZZ if you don't get it, go look at the schematic. Do I need to post it for you, and can you even read it?
I was asked to help with this, and this is the exact reason I stay out of these threads, and away from this forum. You could hve been the man to build every bridge in the world, but one post in this forum, and you don't know **** about bridges.
Yeah, now I remember why I keep my mouth shut about these things. I'll just ask a very simple question, then I'm done. Why do you think it's reffered to as a 'choke"?
ZZ if you don't get it, go look at the schematic. Do I need to post it for you, and can you even read it?
I was asked to help with this, and this is the exact reason I stay out of these threads, and away from this forum. You could hve been the man to build every bridge in the world, but one post in this forum, and you don't know **** about bridges.
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GoldenVulture
Braindeadologist
Re: changing filter cap values
To answer the question. I'm guessing this is the mod he's using. Also, it's two caps [100uf] in parralell on the plate feed and one on the screen feed.
Yes...that is exactly what it means. A choke is a short to DC. No, i absolutely do not have a degree in electronics, but i Do Know the definition of an inductor.
When i asked where was it installed, i was talking about where in the circuit.....not where on the chassis.
If it was installed in the typical location of a Pi Filter, they might have removed a 400 Ohm resistor that would offer more "Sag" than the choke they installed.
Three Caps in //.?
I have seen enough.
Good Luck Guys
To answer the question. I'm guessing this is the mod he's using. Also, it's two caps [100uf] in parralell on the plate feed and one on the screen feed.
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GoldenVulture
Braindeadologist
Re: changing filter cap values
You can't tell them anything, GV. Not even if you prove it. He doesn't understand what the choke is being used for.
"If, on the other hand, you are selecting a choke for a capacitor input supply (such as the typical Marshall or Fender design), then the requirements are relaxed quite a bit. The purpose of the choke in these type supplies is not for filtering and voltage regulation, but just for filtering the DC supply to the screen grids of the output tubes and the preamp section."
You can't tell them anything, GV. Not even if you prove it. He doesn't understand what the choke is being used for.
"If, on the other hand, you are selecting a choke for a capacitor input supply (such as the typical Marshall or Fender design), then the requirements are relaxed quite a bit. The purpose of the choke in these type supplies is not for filtering and voltage regulation, but just for filtering the DC supply to the screen grids of the output tubes and the preamp section."
Re: changing filter cap values
That one was on me. I got in a rush and just glanced at the schematic.
See how easy that is?
To answer the question. I'm guessing this is the mod he's using. Also, it's two caps [100uf] in parralell on the plate feed and one on the screen feed.
That one was on me. I got in a rush and just glanced at the schematic.
See how easy that is?
LLL
New member
Re: changing filter cap values
This thread has reached the 1000% win mark.
Lemme say something:
All you posters pretending you know tube amps - keep in mind your "advice" could literally hurt someone.
Pretend with everything else to get your "forum cred", but when it comes to the high voltages found in tube amps, leave that up to the experienced, FFS.
This thread has reached the 1000% win mark.
Lemme say something:
All you posters pretending you know tube amps - keep in mind your "advice" could literally hurt someone.
Pretend with everything else to get your "forum cred", but when it comes to the high voltages found in tube amps, leave that up to the experienced, FFS.
LLL
New member
Re: changing filter cap values
It's called common sense. There are a couple in this thread talking out of their ass... not the kind of subject to be pretending to be knowledegable in.
It's called common sense. There are a couple in this thread talking out of their ass... not the kind of subject to be pretending to be knowledegable in.
GoldenVulture
Braindeadologist
Re: changing filter cap values
If you want to reassure yourself about what your doing, this is a good reference.
- http://www.valvewizard.co.uk/smoothing.html -
- http://www.valvewizard.co.uk/index.html -
If you want to reassure yourself about what your doing, this is a good reference.
- http://www.valvewizard.co.uk/smoothing.html -
- http://www.valvewizard.co.uk/index.html -
GoldenVulture
Braindeadologist
Re: changing filter cap values
utahere:
Yeah your a world of practical advice and knowledge .
- http://guitaramped.com/forum/tube-amps-f19.html -
Two whole threads.
What ?
utahere:Yeah your a world of practical advice and knowledge .
- http://guitaramped.com/forum/tube-amps-f19.html -
Two whole threads.
:foot:
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LLL
New member
Re: changing filter cap values
I'm not talking about myself, but since you inferred:
I bought a JTM45 reissue back in 2003. I replaced the garbage PCB with a full PTP board loaded with proper JTM45 (mid 60s) component values.
I populated said board myself and wired it up.
I also replaced the OT and loaded it with Mullard preamp (12AX7 x2), a Mullard CV4004 (military version of the 12AX7) in the PI... and a pair of Valve Arts KT66s. And a NOS 5AR4 for the rectifier.
I also replaced the stiff filtering (50+50uF, 100+100uF IIRC) with period correct, "saggy" 16+16uF in the preamp and 32+32uF in the power section.
The result was night and day versus the crappy stock config. So I basically rebuilt the amp.
I also learned how to properly bias my amp with a multimeter... and of course, how to properly discharge those big caps anytime I went poking around. This involved soldering a 1-Ohm resistor to each power tube (pin 8 on the octal IIRC) so I could measure.
3 years ago, I decided to change my JTM45 into something more akin to a JTM50. I changed the tone stack and some other values to be more Superlead circuit-like (after some testing of different values) , modded it for EL34s (EHX 6CA7s to be exact) and set the bias circuit so it would work with my variac (running at 100v).
I also modded a 1959S (Marshall's first re-issue) to be shared cathode instead of split. (pretty easy one-wire mod).
etc
I've been modding tube amps since 2003. So yes, I am a world of practical ****ing advice and knowledge.
This guy's about to do serious (and potentially dangerous) surgery on his amp... playing with the filtering, no less.
I didn't see anyone say, "hey, be careful in there" (well, I did)...
So, how about yourself? Why don't you tell the forum all about your tube amp building/modding experience? (no googling, now)
What ?
Yeah your a world of practical advice and knowledge .
- http://guitaramped.com/forum/tube-amps-f19.html -
Two whole threads.
:foot:
I'm not talking about myself, but since you inferred:
I bought a JTM45 reissue back in 2003. I replaced the garbage PCB with a full PTP board loaded with proper JTM45 (mid 60s) component values.
I populated said board myself and wired it up.
I also replaced the OT and loaded it with Mullard preamp (12AX7 x2), a Mullard CV4004 (military version of the 12AX7) in the PI... and a pair of Valve Arts KT66s. And a NOS 5AR4 for the rectifier.
I also replaced the stiff filtering (50+50uF, 100+100uF IIRC) with period correct, "saggy" 16+16uF in the preamp and 32+32uF in the power section.
The result was night and day versus the crappy stock config. So I basically rebuilt the amp.
I also learned how to properly bias my amp with a multimeter... and of course, how to properly discharge those big caps anytime I went poking around. This involved soldering a 1-Ohm resistor to each power tube (pin 8 on the octal IIRC) so I could measure.
3 years ago, I decided to change my JTM45 into something more akin to a JTM50. I changed the tone stack and some other values to be more Superlead circuit-like (after some testing of different values) , modded it for EL34s (EHX 6CA7s to be exact) and set the bias circuit so it would work with my variac (running at 100v).
I also modded a 1959S (Marshall's first re-issue) to be shared cathode instead of split. (pretty easy one-wire mod).
etc
I've been modding tube amps since 2003. So yes, I am a world of practical ****ing advice and knowledge.
This guy's about to do serious (and potentially dangerous) surgery on his amp... playing with the filtering, no less.
I didn't see anyone say, "hey, be careful in there" (well, I did)...
So, how about yourself? Why don't you tell the forum all about your tube amp building/modding experience? (no googling, now)
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GoldenVulture
Braindeadologist
tman
New member
Re: changing filter cap values
Well thank you LLL for your concern and other advice I appreciate it and I do my work with a tech so we do it together so I can learn at the same time and we do drain everything down before any mods at all.And thank you GV for the insight on what to do and I will try both ways you suggested and let you know what I go with either removal of one cap and 2 power tubes or lower cap values. I will keep you guys posted on what worked and what sounded best.
Well thank you LLL for your concern and other advice I appreciate it and I do my work with a tech so we do it together so I can learn at the same time and we do drain everything down before any mods at all.And thank you GV for the insight on what to do and I will try both ways you suggested and let you know what I go with either removal of one cap and 2 power tubes or lower cap values. I will keep you guys posted on what worked and what sounded best.
GoldenVulture
Braindeadologist
Re: changing filter cap values
Try the pair first, they feed to the third one via the choke.
LLL
New member
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