Hum in 'Operate'

Hi I have a recently purchased PS-2a.
When switched to ‘Operate’ there is a hum which makes the unit unusable - I need it for use in my studio.
It is not a ground loop issue - the accompanying clip was recorded with the PS-2 only connected to AC & a speaker cabinet.

Hey Bluesman welcome to the community :tada:

Sorry to hear this makes it unusable. You have a PS-2A which is the latest version of the Power Station and has improvements to the power supply in terms of filtering.

I can hear the hum when in Bypass (this is noise from your valve amp), and this increases when you go into Operate because you have the noise of your valve amp plus the noise of the PS-2A’s valve amp on top.

Sometimes this can be improved by detecting and changing a tube that is particularly noisy. The noise can occur due to random variation in the manufacturing process of tubes that increases the leakage current between the cathode and the heater element.

When cables carrying small, single-ended signals are close to PS-2A’s transformers, this can also be a cause of noise because the changing magnetic fields induce a noise voltage in the conductor.

But you sound like an experienced user, so I am sure you have tried different cables and moved them into different locations to see if the noise can be improved. A photo of the setup might help to see if I can catch anything, however unlikely. And if you do have a different ECC83 you could try swapping it in: How do I change the tubes and fuses in the Power Station

However, I get the feeling that these will probably not improve things too much. When you are playing the guitar, how is the hum? It is quite hard to gauge from the audio above the true levels. Are you based in the UK? I wonder if you are close to me; you could always pop over, and we could compare it against my PS-2A. PM if interested. I am about an hour from London.

Regards,

Dan

Hi Dan

Thanks for coming back to me.

There was no amp connected when I did the sound clip – just the PS-2a connected to a speaker cab, nothing else.

I wanted to keep it as clean as possible.

I already checked the tubes, in case they had been damaged in transit but everything is fine.

The hum is audible in quiet passages when recording.

Yes, I am experienced, having produced/engineered/ performed with major acts over more years than I like to admit!

I have owned a PS-2a before (it was stolen) and it didn’t have this problem.

I’m in Bedfordshire.

Thanks again.

JV

Hey

OK, I see what you mean now. Operate does draw more power from the power supply than when in bypass mode, so this could explain it. I suppose the only thing we can really do is get it serviced to investigate what is going on. I can PM you the details of a UK based tech. or if it is still under warranty you could request the dealer organise it for you? Where did you buy it from. We are not too far either, I’m in Newmarket.

Really, stolen. Annoying …

Hi Dan

I bought it from Peach Guitars, and they seem keen to have me deal directly with Fryette so I guess there’s no point in going back to them.

I purchased this PS-2a on 18th September 2024 so it is well within warranty.
Unfortunately, I didn’t get around to using the new unit until a couple of weeks ago so didn’t spot the problem inside the return period.

Bad mistake I should have checked it.

Yes, please let me have details of your tech., I would really like to get this resolved asap if possible.

Thanks for your help, Dan.

Have a great Christmas.

Cheers JV

Hey JV

Yes, that makes sense we can support the product better than they can. I am pretty sure that to become a Fryette dealer they agreed to handle warranty repairs. So you could ask, but I’ll PM you repair tech. info anyway.

Regards

Dan

Exactly the same problem with my PS-2a. I bought it from Thomann (Switzerland) and sent it back for repair. Thomann returned it to me saying the hum is “normal”. There is also mechanical noise when switchen to the operate mode.

Is there a fix for the issue? Several forum members have reported the hum problem already.

Best
Lorenz

We would need to get our hands on one of these noisy units to evaluate it and then see how it compares to units we think are typical. With that baseline, it becomes more than conjecture and opinion and opens the possibility for investigating improvements.

This looks like exactly the same problem that another Power Station owner and myself are experiencing and discussing here (Warning: long messy thread, where we eliminate causes for the hum and figure out things along the way):

I’ve now also found reports of the exact same problem on several guitar forums.

I think it’s pretty clear by now that this must be either a bad batch (not very likely as the affected units seem to have been purchased over a period of more than a year) or an inherent design flaw (possibly only with 230V units, as all reports I’ve seen about this hum seems to be coming from various European countries).

I think it’s time someone at Fryette take a much closer look at this, instead of trying to come up with alternative explanations for this hum. The hum is clearly originating from inside the Power Station, and will almost disappear if you remove the top lid. Then, if you move the top lid closer to the top of the unit, without actually touching it, the hum will gradually increase as you move the lid closer. And yes, the hum is present with no amp connected. The hum is 100% definitely originating from inside the Power Station itself, and almost certainly coming from the power transformer.

To me this strongly suggests a severe design flaw. The Power Station is utterly useless to me with this kind of noise level. Shipping the unit off for a repair (AGAIN…) obviously won’t fix anything if it’s a design flaw rather than a faulty unit. We need Fryette to step up and sort this out ASAP, as the situation isn’t really acceptable with this many reports of the exact same hum.

Personally I’ve already purchased a Tone King Iron Man II instead, as I quite frankly don’t see a solution to the problems with the Power Station anytime soon. I would still like to get it fixed of course, and I hope Fryette will come up with a solution so I can at least sell it with a good conscience. As it is, it’s really not worth anything to me.

I will be happy to send mine to Fryette for evaluation if they cover the shipping costs both ways, but I will not pay international shipping costs AGAIN without some kind of guarantee that the problem will be fixed. I’ve already wasted close to the equivalent of $100 on this already, when I had to ship the unit to a different country and back for a repair that didn’t happen (there are no Fryette dealers in my country unfortunately so I had to purchase it from abroad). Not to mention the cost of the Power Station itself… which is just gathering dust now, as it’s utterly useless.

Hi Trerik,

Unfortunately, I don’t have my PS-2 anymore. Last time we spoke, I said,

I am currently without a PS-2 but will be getting one in a month or two. When things have moved forward here, I will get in touch with you again.

Also, I cannot cover the costs personally, so I would need approval from the shop for the shipping. Please standby.

Regards,

Dan

I would also be interested to know if anyone have measured the plate current and plate voltage in their Power Station. When I did this (during the troubleshooting we did in the other thread I mentioned) I found two things:

  1. With the readings I got (using bias probes from Eurotubes) I calculated 54% of maximum dissipation. In a guitar amp this would be extremely “cold”, but for all I know this could be perfectly normal with the Power Station. It does seem to be designed rather differently than a guitar tube amp output stage, for a more “neutral” tone and possibly to accommodate a wider range of tubes/bias. I have not been able to get a confirmation from Fryette about this.

  2. The stock tubes in mine were (Fryette labelled) JJ 6L6GC. The plate voltage I got (504V) slightly exceeds the maximum plate voltage for a JJ 6L6GC (as listed on JJs spec sheet). I’m no electronics engineer so I have no idea if this is cause for concern, but I have not received any response from Fryette about this. I know that some 6L6GC-based guitar amps from the 70s have considerably higher plate voltages than this, but tubes were generally far more robust back then…

I’m not saying this is causing the hum (I think it’s probably unrelated) but I would still like to know if this seems right.

Ok, thanks for the update. It will be interesting to see if you experience any hum with your new Power Station. It does seem to affect quite a few units that have been purchased recently around Europe.

Thanks for your understanding Trerik, next time I talk with the shop, I will bring this up.

Probably biasing a little cold makes sense so that the Power Station does not impose too much personality on the signal. Regarding the 504V plate voltage: the line voltage can fluctuate -10% – +6% and how long the PS-2A has been running makes a difference too because as the wiring gets hotter, the resistance increases, causing voltage sag. Tubes are pretty resilient to this kind of thing. So this does not jump out at me as a serious issue. That said I will check!

Regards,

Dan

Thanks!

Just to be clear:

I will of course be happy to pay shipping costs if the Power Station can be repaired. But this is looking more and more like something that probably can’t be fixed by a local tech at a dealer. At least not without more information from Fryette. The other poster in this thread who shipped the Power Station back to Thomann, and was told the hum was “normal” is an example of this. The hum is definitely not normal. But without more information from Fryette it will probably be a waste of time and money to send the Power Station for repairs that won’t happen.

We need to know if there’s a known solution to a problem which at this point unfortunately seems to be quite common with the Power Station. I will not waste more money on shipping costs without knowing for certain that it can actually be fixed.

Of course, there seems to be a lot of happy Power Station users out there too, which gives me hope that it can actually be fixed. The evidence strongly suggests that something must have changed at some point, either a change in the design or a bad batch of components or something…??? I think it’s very interesting that all the complaints about hum seem to come from people who purchased their Power Station in Europe. Maybe there’s a problem with the power transformer for the 230V units? Did you start using a different transformer, or a new batch of transformers at some point? As far as I can tell the hum definitely seems to originate from the power transformer, but I could be wrong of course…

Hi Trerik,

I would be delighted to say to you, “ship it and I will fix it.”. The truth is that I cannot really guarantee that. The first thing I need to do is assess how your PS-2A performs relative to another unit. What I can say is, “ship it and I will investigate it”.

This investigation might reveal an issue, and at this point, I do give you the benefit of the doubt; you sound very experienced with gear! However, it might reveal your PS-2 performs the same or better than the reference Power Station! In this case the problem comes down to each individual’s perception of what is noisy and what is too noisy for a given use case.

There has not been any change to power transformer design or manufacture as far as I am aware.

I will bring this up next time I meet with the shop.

Regards,

Dan

I am having the same issue with my PS-100, after it decided to cook itself and blow a fuse, the tech reduced the bias and it works again with the tubes that were in it. However when it is placed in operate, without any input, just a speaker cable to a cabinet it produces the same hum in the clip in this thread.

My unit is also 230V

@Cyphers: Are you saying it didn’t have a hum initially but developed a hum after the tech reduced the bias? That’s interesting. We have already established that the tubes in mine (and another poster’s) Power Station have significantly lower Ip ratings than the tubes in Dan’s Power Station, which seems to be working fine. Maybe this is actually a bias issue? It doesn’t seem very likely to be honest, but stranger things have happened.

I’ve already mentioned that mine seemed to be biased VERY cold (and with a corresponding plate voltage that seemed a bit on the high side). .

When I tested replacing the tubes I went out of my way to use tubes that tested the same as the stock tubes, to avoid any bias issues. Maybe I should try tubes with a higher test rating, to get a slightly “hotter” bias (and corresponding lower plate voltage, which did seem a bit on the high side in mine…).

But I’m no amp tech…

Dan: Any comments on this?

Hi @Trerik, this is @Cyphers orginal post – he was talking about reducing the plate voltage to help prevent tubes from blowing fuses. Some new tubes are on their way to him (or will be… Gil needs to respond to him about that :slight_smile: ).

The hum issue and the blowing tubes issue are seperate.

Hum is normally caused by energy from the power supply leaking into the audio signal; this is unrelated to bias. For example, heater filaments can couple/leak energy into the cathode, and it then becomes audible.

@Trerik thanks for waiting I will get back to you in a day or two about your noise issue.

Thanks Dan.

But it seems to me that he says the hum appeared after the tech reduced the bias? Or is there another thread where his problem is discussed in more depth?

But reducing the bias would actually make the tubes run “hotter” (and slightly lower the plate voltage). Which was exactly what I was thinking about testing, by simply using a pair of stronger testing tubes.

I got the terminology mixed up a bit in my previous post. I always get confused when people talk about lower/higher bias. Do they actually mean lower/higher bias or do they mean running the tubes colder/hotter? Lots of people seem to actually mean the latter, even though it’s wrong. Lowering the bias will of course make the tubes run tubes “hotter”. So I guess you could say that a lower bias is also a “hotter” bias. Which isn’t very intuitive unless you know what’s really happening inside a tube.

I could of course try installing both a pair of tubes with slightly higher test ratings and a pair of tubes with slightly lower test ratings and see what happens… I’m sure I have both somewhere in my studio. I can always “borrow” a pair from an amp for testing purposes. But I’ll wait until I hear from you again.

But yeah, like you said, this probably won’t affect the hum at all, so it’s probably not worth the hassle. At least I don’t see HOW it could affect the hum. I’ve seen what happens with both over- and under-biased amps, and hum is not a typical symptom. At least not in guitar amps.