Ampeg PF-50T Humbuster

[AboutSweetSue]

Hi AboutSweetSue,

a certain note rattling instruments on the wall to me indicates room resonances. In my case the main culprit is the E at 82Hz.
By "D" do you mean the note at 73Hz? You can check out your room here: Invalid Link Removed
Just type in the measurements of your room and if you get a red or purple bar at or close to 73Hz (or wherever your D is) you have your answer.
In that case no amount of screw-tightening/gluing/fiddling will help. Only a notch filter, generally cutting bass (on the amp or with an HPF) or turning (way) down. Or moving to a bigger room. Physics is a harsh and cruel mistress I'm afraid.

Edited to include: you could also make/buy bass traps tuned to the problematic frequency, but that can get expensive and impact the looks and usability of your room quite a bit...

Have a nice day,
Walter

I took the cage off last night, tapped on the top of the amp a few times, found that the ringing was coming from those purple housings with the spring inside. I took them off, put them back on, and it seems to be fixed.

It seems these Ampegs generate a lot of noise. The PF-115he rattled at the lid, fixed it easily with a new gasket, the front plate w/logo rattled, fixed it with a good push, and now this PF-50t is rattling. All seem to be easy fixes, and I’d rather fix these noise issues rather than sell due to these being such great sounding, cool bass amps. I don’t believe I have a hum. The amp sound quiet enough to me. (I put my ear to it last night, quieter than my class Ds)

As for the room, it’s an old house with wood floors, wood trim. It’s not ideal, but, like you said, the rattling can be controlled with adjusting the eq.

 

[beans-on-toast]

Repositioning the springs like you did can help. Those covers are shields, they shield the tubes from external fields and noise. They also help cool the tubes by dissipating heat.

The ones that the amp comes with should work.

For a better tube shield, look for an IERC 6020B. They have fingers that hold the tube, a different type of spring. They push on.

This is an example of the spring fingers for a different model shield.

 

[JimmyM]

Repositioning the springs like you did can help. Those covers are shields, they shield the tubes from external fields and noise. They also help cool the tubes by dissipating heat.

The ones that the amp comes with should work.

For a better tube shield, look for an IERC 6020B. They have fingers that hold the tube, a different type of spring. They push on.

This is an example of the spring fingers for a different model shield.
View attachment 3257304

Do they come in purple?

 

[beans-on-toast]

Do they come in purple?

You can get these tube shields in any color as long as it’s matt black.

Matt black radiates heat way better than the other end of the scale, white. That’s why they use it. In you have to have purple, the darker the better in terms of radiant efficiency.

Interesting to note, Yamaha’s corporate color is violet. That’s a kind of purple. Can’t see them wanting to change the color to black.

History of Logo - About Us - Yamaha Corporation

 

[Garret Graves]

Partial update: As far as my Sweetwater rep knows, the PF 50T that I was sent is new from Ampeg, he has inquired with them about the mod, and whether they have stopped adding the mod, or whether they sent a shipment of older PF 50's they had sitting around. Earlier in this thread, it seemed as if Sweetwater orders had shipped out new, pre modded units- this may no longer be the case, FYI will let you know more when I do

 

[Garret Graves]

Further Update- Yamaha/Line 6 has gotten back to Sweetwater rep. They do NOT do the mod at the factory. Like has been mentioned here, it is hit or miss as far as whether the amp is noisy or not- some are, some aren’t. I don’t know what happened in Mr. Beers case- perhaps the dealer he buys from did the mod in house, and he mistook it for factory? The mods can be performed by dealers without voiding the warranty! Sweetwater has done the mod, Sweetwater will also simply check whether the amp is noisy or not out of the box when asked. My rep is collecting more info, and I will most likely be sending it back to them for either a swap for a naturally quiet unit, or they will perform the mod for me, no charge, and no void of warranty. So there you have it! Buyers beware- do not expect to see mods coming from the factory up to this point- future, who knows. The rep he talked to at Yamaha was familiar with the story, btw.

 

[Garret Graves]

Contact your retailer and tell them the hum is unacceptable, Ampeg has a fix and you want an amp with it in place.

Their mod is not implemented the same as the one found here. They should fix it or give you an amp that does have the update.

There is no factory update, please read my latest post FYI
Edit- it is possible that European market received an update, voltage and hz relates are different there. According to Yamaha convo with Sweetwater, no factory mod is done- dealers can do the mod and it won’t void the warranty

 

[beans-on-toast]

There is no factory update, please read my latest post FYI
Edit- it is possible that European market received an update, voltage and hz relates are different there. According to Yamaha convo with Sweetwater, no factory mod is done- dealers can do the mod and it won’t void the warranty

Hopefully they will eventually revise the PCB with an updated bias circuit.

Whether it's a factory change or a service center performs the mod, it amounts to the same thing.

Generally when a service center performs an update under warranty, the procedure is supplied by the manufacturer as a technical note. If Sweetwater is authorized to perform the mod, then it'll be taken care of for you. The alternative is you returning the amp for a refund which I imagine they would prefer to avoid.

I can't fathom why Sweetwater is shipping an amp out that has a known issue and there is a fix available. It shouldn't be up to the client to discover it and raise the issue.

 

[Garret Graves]

Hopefully they will eventually revise the PCB with an updated bias circuit.

Whether it's a factory change or a service center performs the mod, it amounts to the same thing.

Generally when a service center performs an update under warranty, the procedure is supplied by the manufacturer as a technical note. If Sweetwater is authorized to perform the mod, then it'll be taken care of for you. The alternative is you returning the amp for a refund which I imagine they would prefer to avoid.

I can't fathom why Sweetwater is shipping an amp out that has a known issue and there is a fix available. It shouldn't be up to the client to discover it and raise the issue.

Amen to all that. I would encourage you guys to please go over your earlier posts with an edit. I was very encouraged when I read in here that the factory kicked out an update and would be getting a noise free unit. This is not the case, and you can set the record straight and give people a heads up.

 

[Martin Beer]

My amp was bought in the UK and dispatched from the UK distributor, Polar. So it may be that the mod is specifically carried out for the UK market with our 50Hz AC, and possibly at the distributor rather than factory level.

 

[ENG4]

Best $2.17 I ever spent. I really liked my PF-50T before, but love it now, Thanks Gents!

 

[Garret Graves]

View attachment 3267506
Best $2.17 I ever spent. I really liked my PF-50T before, but love it now, Thanks Gents!

Good job there! My replacement from Sweetwater is on the way- they performed the mod in the shop for me, and will on request. I'll crack it open and take a shot of it.

 

[agedhorse]

Best $2.17 I ever spent. I really liked my PF-50T before, but love it now, Thanks Gents!

I sure hope you have some electronics safe adhesive under that cap...

 

[ENG4]

[QUOTE="agedhorse, post: 22152313, member: 68399"]I sure hope you have some electronics safe adhesive under that cap...[/QUOTE]
I'm going back in to clean up one of the joints and plan to apply your thought, appreciate it...

 

[Garret Graves]

Received my replacement PF 50 with the mod done by Sweetwater, and it has no hum! Hallelujah to that! The one problem is during shipping the right side transformer on the top has popped out of its mounting bracket and is loose. Looking at it, I should be able to bend the four tines on the mounting bracket straight, push them through the corresponding holes, bend them back and done- comments?
Thanks

 

[JimmyM]

Received my replacement PF 50 with the mod done by Sweetwater, and it has no hum! Hallelujah to that! The one problem is during shipping the right side transformer on the top has popped out of its mounting bracket and is loose. Looking at it, I should be able to bend the four tines on the mounting bracket straight, push them through the corresponding holes, bend them back and done- comments?
Thanks

Will work just fine.

 

[Garret Graves]

Here is the mod as done by Sweetwater. Zero audible hum (at bedroom levels, but a bit when cranked) and a marvelous sounding amp, I love it. I also ‘fixed’ the transformer mount issue myself. Unplugged the two molex connectors to give it a little play, unscrewed the 4 bolts from chassis to release the mounting plate, straightened the tabs on the sheath of the transformer, put them through the plate, bent them closed as best as I could, remounted to chassis, plugged the molexes in, closed it up, played my bass. Now I can join the Portaflex club!

 

[beans-on-toast]

Here is the mod as done by Sweetwater. Zero audible hum, and a marvelous sounding amp, I love it. I also ‘fixed’ the transformer mount issue myself. Unplugged the two molex connectors to give it a little play, unscrewed the 4 bolts from chassis to release the mounting plate, straightened the tabs on the sheath of the transformer, put them through the plate, bent them closed as best as I could, remounted to chassis, plugged the molexes in, closed it up, played my bass. Now I can join the Portaflex club! View attachment 3276237

Good going with the transformer. When you plug in and turn up to playing level, how quiet is quiet?

 

[Garret Graves]

Good going with the transformer. How quiet is quiet?

I hear a tiny amount of hum when cranked up, no hum at all at bedroom practice level in my speaker , nor through my cans which are fed through the transformer out into my board. What I do hear is a small amount of hiss, but its nothing unusual. The first PF50 I had had a very noticeable hum through everywhere, and it was wearing on me, frankly. This quiet PF50 is to die for, my first all tube amp (I have the Aguilar DB751 hybrid that I love to death too). What inspired me to give it a try in the first place, was at a recording session, and the studio has a B-15, from the 60's-OMG it was love at first note for me. So I'm a very happy camper now in spite of the long journey to this point), I'll gig with it and record with too, anticipating many years of use with it down the road.

 

[Garret Graves]

I edited my last two posts after noticing small amount of hum when cranked up gain and volume. I didn’t note any hum when in bedroom and gain and volume are around 3-4. As you pass 5 on volume, you can hear hum, but it is still very low, and so far below playing volume, that I only mention it as a technicality. With the mod, hum is no issue of note as far as I’m concerned, and I’m quite picky