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Ampeg PF-50T Humbuster
- Thread starter mnats
- Start date
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- Tags
- ampeg ampeg pf-50t pf-50t
I've done this mod on 2 of my custom USA-assembled Heritage PF-50Ts (the third was quiet already). Awesome job and Thank You, mnats and Bertr!
One thing: I have noticed that people use a 220 micro cap. Fine, but a 100 micro will work just as well. It's just that I did not have one in the box (And Mnats did the original mod with 100 micro with no shortcomings). 47 micro will probably be fine. I have seen that configuration with 2*10, 2*22 micros in bias circuits (SLO100 / JCM800). 220 does not add much compared to 100. I would take 100 as standard (only for space and consistency of the values in the bias circuit).
No problem at all with 220 though, the tranny and diode can easily take the charging.
No problem at all with 220 though, the tranny and diode can easily take the charging.
interesting, I might try emailing loud support. I'm not expecting much but if I can somehow get the hum removed without voiding my warranty, I will go that route first. maybe there was a revision and I just missed it.See, guys? Told you that they knew already but nobody believes me!
Yes I agree, I have tried 100uf and 220uf and cant hear any difference. Thanks for the good info.
Warranty schmarranty! I can't stand the idea of you guys having quieter PF50T's than me any longer, and Hodgy's endorsement of this mod just put me over the edge. I'm taking the plunge. So have we agreed upon which method is best? Mnats seems to think Bertr's method is easiest and most efficient, but the idea here is maximum reduction of noise, so since I'm not doing it myself, doesn't matter so much which method is easier...I'm sure it will all be easy for Birddog.
Just use Bertr's method. There won't be any audible difference and it avoids having to remove the PCB which is a pain to do...
I would not call it my method: It's a variation of the original... Mnats, you really did build the car, and I just found a way to put the wheels on quicker (Out of sheer lazyness to ... remove the PCB!).
Well I think that's very cool that you guys did it, so whoever did what, thank you! I still struggle to notice it on gigs, but I do hear it at home. And I do remember one gig where I went to the board with it and the sound tech said I had a hum he couldn't get rid of. I thought it was something he was doing since I used it the night before with no problem. Now it makes sense to me 
I'm wondering if a "stock" vintage B15 is dead quiet or ? In the early days of HiFi solid state amps the cork sniffers disliked them partially because the lack of tube amp hum made the new-fangled amps seem "sterile".
Vintage B-15's are no noisier than any well made SS amp. They're actually some of the quietest running amps you'll ever hear when they're in good working condition.
Thank goodness for you guys!
I bought a Oliver Powerflex 500 and had a little "cleanup" work done on it. It is about as quiet as an unplugged tv. I loved the sound (my first all tube amp) so much, I bought a pf-50T to use. I won't be dragging that 50some year old Oliver amp out of the house very often.
The hum on the Ampeg is definitely audible enough, you certainly wouldn't mic it for a recording. Am considering returning it. But since I got it on "clearance" for a steal it might be worth modding....
I bought a Oliver Powerflex 500 and had a little "cleanup" work done on it. It is about as quiet as an unplugged tv. I loved the sound (my first all tube amp) so much, I bought a pf-50T to use. I won't be dragging that 50some year old Oliver amp out of the house very often.
The hum on the Ampeg is definitely audible enough, you certainly wouldn't mic it for a recording. Am considering returning it. But since I got it on "clearance" for a steal it might be worth modding....
I just took mine into Birddog for this mod. He said it will be a piece of cake.
Might be a while. He's also doing a fret dressing on my main bass and replacing a couple pots on my 69 SVT so don't sit by the computer waiting.I'll be patiently waiting for the results and follow-up...
Working for cake! That’s not bad for a half hour’s bench time.
Yes, I would say it's definitely worth modding (check my previous post in this thread on page 2).
My experience last November emailing LOUD about this major problem with an otherwise great amplifier proved fruitless. YMMV.
So, sure, they know (knew) about it JimmyM. They're just not going to do anything about it. They suggested I should feel free to do the mod and void my warranty (not that I needed their permission). So, I did. It was about 10 minutes of trivial bench-time.
Now that Yamaha has purchased Ampeg, perhaps they'll be interested in revving the circuit board to take care of the problem for future units.
Anyway, I'm loving mine since the mod. I can understand why you would consider returning it without the mod.
BTW, as far as I can tell, there's no such thing as a Heritage PF-50T. At least as far as availability to the general public goes.
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