The "stock hum" was horrible on mine and didn't require any measuring tools (other than a pair of ears
). No hum what so ever after it was fixed as a warranty service.
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Ampeg PF-50T Humbuster
- Thread starter mnats
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- ampeg ampeg pf-50t pf-50t
The "stock hum" was horrible on mine and didn't require any measuring tools (other than a pair of ears
). No hum what so ever after it was fixed as a warranty service.
You can tell by taking a look inside the amp. The first post has a link to pics with and without the fix. Be careful not to touch anything inside though. If you're not familar with electrical safety concerning tube amps read this before you pop the cover off: Safety
Oh, wow, sorry for the generalization. I don't have the mod and have always thought the stock hum was perfectly acceptable... extrapolating is never a good idea I guess.
The "stock hum" was horrible on mine and didn't require any measuring tools (other than a pair of ears
No need to apologize
It's sure a bit confusing since it seems that some amps hum a little, some are OK and some are horrible like mine was. Good news is that they're reasonably easy and cheap to fix yourself or just have them fixed for free under warranty.
Is there a way to tell by S/N if a unit came from Ampeg with the mod? And if needed, will ampeg do it under warranty after 2 years?
No idea for the S/N. But if you look at post 285, Marc had it done at very reasonable cost at the service center.
Ampeg is now Yamaha.
As far as I know them (from a branch other than musical instruments), they really like their stuff to work properly. Ask and quote the experience of Marc.
Ampeg is now Yamaha.
As far as I know them (from a branch other than musical instruments), they really like their stuff to work properly. Ask and quote the experience of Marc.
Close to about 2 years ago I had tried the PF-50T. Had to have it shipped rather than make the drive the GC.
I got one with a bad hum, sent it for another, got another bad hummer.
I was pretty disappointed. I decided to take another route. I would like to give this amp a try but People are still reporting this issue?!
I think Ampeg would care about its reputation a bit more. Especially with so many other brands competing for top bass dog these days.
I got one with a bad hum, sent it for another, got another bad hummer.
I was pretty disappointed. I decided to take another route. I would like to give this amp a try but People are still reporting this issue?!
I think Ampeg would care about its reputation a bit more. Especially with so many other brands competing for top bass dog these days.
Yamaha has been selling through old stock from LOUD, and I don't think they've been manufacturing any of their own products yet save for the Heritage 50th Anniversary SVT. And Yamaha has a reputation for not releasing things till they're 100% with the design. I thought LOUD did an overall good job, but they did occasionally let things slide that Yamaha wouldn't have.
Order through Sweetwater, tell them you are aware of the hum issue and want a bench tested/modded unit, and you will get a quiet one!
I´m glad that I found this thread. Bought a PF20-T last week, and it had the 50Hz hum. I fixed it with Bert's mod modified to pf20-T. Made a sim and found that 10kOhm would do the trick. Did not have a 100uF 100V, but two 100uF 50V, so I put them in series. Works fine so far.
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- Feb 12, 2006
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- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
2 x 100uF in series becomes 50uF. You might want to review your math
I knew that, check my circuit for the sim.2 x 100uF in series becomes 50uF. You might want to review your math
But it will give me 100V.
Johan, thank you for this, I’ve been waiting a while for someone to post a pf20 mod. I just did it (with the 220uf 100v cap) and it worked a treat, much appreciated.
Just fixed my PF-50 and I just want to say thank you to all those responsible. Mine was pretty noisy (Australia, 50Hz supply). Now it’s silent and even I could do the mod.
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Doner Designs
Steve Doner
- Jun 2, 2012
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- Doner Designs is an alias for Steve Doner
I’ve had mine a few years now and it’s a keeper. Without this mod I would have sold it by now for sure. I’m pretty fussy about about noise though. Glad I was able to keep it because it’s a fantastic amp and DI. Being able to operate without a load makes it incredibly versatile.The "stock hum" was horrible on mine and didn't require any measuring tools (other than a pair of ears
So I've had a pf50t for 2 years and the hum started to annoy me more and more. I'm so glad I found this thread, got the mod in directly and more than happy again with the "reborn" pf50t. Thanks a lot mnats and bertr!
Je suis tellement content de cet ampli ! Je l'ai utilisé pour un concert de rock dans un grand bar avec deux 12" DIY... quel son !! Et j'avais encore pas mal de place...
Vraiment un grand merci à ceux qui ont pris le temps de créer ce changement !
Vraiment un grand merci à ceux qui ont pris le temps de créer ce changement !
Hey Johan and mpkeire,
It's been a while you posted these but here is a question. I recently bought a PF-20T but it looks like it is all the way back from 2015. I would like to make the humbuster mod and I understand from your posts that a 10k resistor as well as a 100uf (or 220uf) 100V cap would do the trick.
I just wonder where exactly on the board of your PF-20T's you are soldering the end of the cap. I am asking about the end that goes to the ground (JMP14 on the PF-50T board). Johan - I cannot somehow see clearly in your second photo. I asked for the schematic of the amp from Ampeg, but I am not sure they will share it with me.
Thanks in advance.
Alper
It's been a while you posted these but here is a question. I recently bought a PF-20T but it looks like it is all the way back from 2015. I would like to make the humbuster mod and I understand from your posts that a 10k resistor as well as a 100uf (or 220uf) 100V cap would do the trick.
I just wonder where exactly on the board of your PF-20T's you are soldering the end of the cap. I am asking about the end that goes to the ground (JMP14 on the PF-50T board). Johan - I cannot somehow see clearly in your second photo. I asked for the schematic of the amp from Ampeg, but I am not sure they will share it with me.
Thanks in advance.
Alper
I just took care of the mod on the my PF-20T after exchanging messages with Mako (mnats) and Bertrand (Bertr). Actually, Bertrand got out of his way by sending a detailed explanation of each step in a Word document. I would like to take this opportunity to thank both of them one more time here!
In my initial attempt, I totally forgot about the directionality of the cap--the idiot me--and soldered the (-)ve end to the ground. I turned the amp on, and of course the bias pot did not work. The light in front of the amp started blinking between red and violet, and after a minute or so, there was some smoke coming out of the amp.
I turned it off immediately and waited for half an hour to make sure all the caps were discharged; and when I looked at the burnt cap, I realized my mistake. As I had already voided the warranty, I simply said "what the hell," and without much hope, I just wanted to give another try. I am glad I had ordered two of the same caps, so when I soldered the other one with the correct directions, the amp started fine and it sounds like charm now!
By the way, it is with the 10k resistor (9.72, more precisely in my case) after Johan's mod and a 220 uF 100V cap.
Cheers,
Alper
Alper
In my initial attempt, I totally forgot about the directionality of the cap--the idiot me--and soldered the (-)ve end to the ground. I turned the amp on, and of course the bias pot did not work. The light in front of the amp started blinking between red and violet, and after a minute or so, there was some smoke coming out of the amp.
I turned it off immediately and waited for half an hour to make sure all the caps were discharged; and when I looked at the burnt cap, I realized my mistake. As I had already voided the warranty, I simply said "what the hell," and without much hope, I just wanted to give another try. I am glad I had ordered two of the same caps, so when I soldered the other one with the correct directions, the amp started fine and it sounds like charm now!
By the way, it is with the 10k resistor (9.72, more precisely in my case) after Johan's mod and a 220 uF 100V cap.
Cheers,
Alper
Alper
