So my tech just reduced the grid voltage to -38V from -35V, while that’s not the typical way to bias it was just a quick test to see if it would work.
That means the tubes are running colder, reducing the grid voltage (making it more negative) is equivalent to reducing the current at the cathode which is what typically is measured when biasing.
Keep in mind I have PS-100, so things might be different, hope that helps
Thanks for the clarification!
I suspect these units are in fact supposed to be biased a bit colder than a typical guitar amp, but I still think mine is biased surprisingly cold (and also has a slightly higher plate voltage than JJ 6L6GCs are rated for).
I have no idea if this is cause for concern, or if this is normal with the Power Station. I’m tempted to try a set of slightly higher “rated” tubes, to presumably make them run slightly hotter with the factory bias setting, which should also slightly reduce the plate voltage. This might be worth a try for a potentially VERY easy fix, but to be honest I don’t think it will solve anything. I don’t see how this should affect hum that SEEMS to be “leaking” into the audio signal path from the transformer.
But then again, if I understand you correctly you only started getting this hum after the tech biased the tubes slightly colder… Right?
I’m just going to chime in to address a few issues I see here, starting with a question:
When listening to this hum in your video, where is the front panel volume control set? Ok, on to the issues.
There have been no significant changes in a few years to the design or transformer specs of the PS-2 except the addition of the XLR connector making it the 2A.
A preamp tube with excess cathode leakage can cause noticeable hum with the volume on zero. So, that’s worth having a look at.
The bias is factory set, so bias is not adjustable. That said, higher IP rated power tubes will pull more current on the power supply, which in extreme cases, could cause a detectable increase in hum. A simple way to measure this is to read the AC voltage at the speaker out with an 8 ohm static load connected, volume set to zero and unit set to Operate. A typical reading is 1mVAC or less. Maximum acceptable is 3mV, but typical is 1 to 2mV in production.
Power tubes that are not well matched will cause a bit more hum at the output jack, so to get it as low as possible, make sure your set is well matched.
With no amp connected to the Amp In jack, the noise will be within spec. If you are turning the volume all the way up, you will hear an increase of residual hum, but since this is not a practical level for any purpose, there is no reason to set it that way. If you are evaluating with the volume full up, This may be why the repair shop is saying it is within spec.
You may experience a more noticeable level of hum with a UK or EU model due to the lower line frequency. Still that would only be noticeable with the volume up high. That said, we test those units at 50HZ line frequency, so they are capable of passing the 1-2mVAC noise spec.
This is a compact assembly and the power transformer is very close to the top cover. Therefore, it is normal that the transformer may cause the top cover to resonate a small amount. We test for that here too. This is not considered a design defect. It’s simply a lot of performance packed in a very small package.
Finally, if you are in the UK, buy from a dealer in the UK. The Thomann units are specified for 230V operation. UK units are specified for 240V. Using an EU model in the UK will push the plate and filament voltage up around 5% . That could possibly aggravate noise issues.
Hope you find this useful.
Dave
I have already tried replacing the tubes, with a matched pair that tested more or less the same. The hum was not affected at all.
I’ve tried this as well. There may have been a SLIGHT difference that would have had to be measured rather than heard, which means it was negligible in this context.
The power tubes are matched, I tested them. The phase inverter tube has matched triodes. The replacement tubes I tested were also matched. When measuring the bias it was also “matched” across the two output tubes. With the factory bias the %maximum dissipation was considerably lower (and the plate voltage a bit on the high side) compared to how I would bias a guitar amp, but maybe this is normal with the Power Station?
Not really relevant. The is a SLIGHT increase in hum when turning up the volume, but it is negligible compared to the difference in hum with/without the top lid installed. Without the top lid, the Power Station is very quiet. With the top lid the hum (centered at 50 Hz) increases by around 20-30 dB (I don’t remember the exact numbers, but basically a LOT). There’s also a smaller peak centered a bit lower, probably around 50 Hz.
I beg to differ. If this is actually how these Power Stations are supposed to work, I would say they have a major design flaw.
I’m not in the UK like the OP. I use 230V and purchased a 230V Power Station.
So while your comments are interesting, and maybe useful to some Power Station users, they don’t really solve anything regarding the hum issue.
Hi Trerik,
I think what David is saying is that he is quite confident that your PS-2 is operating the same as everyone else’s. If there is a hum issue above and beyond that, then the best course of action would be to ship it to Fryette in the USA for an investigation and a service—without having the unit in front of us, there is not much more we can do here.
I really sympathise with the difficulties you have had and the trouble you already experienced trying to get it looked at in the EU. I understand that you would prefer to avoid the expense of shipping it to the USA. I cannot see an alternative at this point.
Regards,
Dan
Just two things, but my suggestion regarding checking/servicing will follow.
Please provide your test method and test equipment used with which you established that there is a 30dB difference in hum with cover on vs off. What I am looking for is the test point at which you measured this dramatic difference and the equipment that yielded this measurement.
You seem to be implying that a power transformer mounted onto a chassis must absolutely not induce any resonance in that chassis at the line frequency of operation. If I am understanding you correctly, then practically every guitar amplifier known to man is afflicted with a major design flaw.
That said, we engaged in an extensive test routine in an attempt to verify your issue . Our service tech in Germany was present via video conference call to observe and verify our results. Therefore, now that he is fully immersed into this subject, I would feel confident that he if fully qualified to make a reasonable assessment of your unit.
Seriously? That’s just silly. I own close to 20 guitar/bass tube amps, as well as lots of analog studio rack equipment, and none of them have this level of hum, not even remotely close. Also, none of my guitar tube amps have the transformers inside a tight fitting, surrounding metal “cage”. I only experience this problem with the Fryette Power Station (and far less with the top lid off) so either it must be faulty, or it must have a design flaw that makes it useless for my intended use (recording). When several other Power Station users, on this forum and on other guitar forums as well, are reporting the EXACT same problem, you must surely understand why I suspect the latter? Because surely they can’t ALL be faulty, can they? Anyway, I’m not interested in starting an argument over technical specifications, I’m not qualified for that. I’m only interested in how it performs in real life situations, and unfortunately it performs very poorly. I want to establish whether this is normal behavior for this product, because if that’s the case it is quite simply useless to me and it’s not worth wasting any more time pursuing possible solutions if they don’t exist.
I’ll admit my method for evaluating the hum isn’t very scientific, or adequate from a technical perspective. But I’m quite frankly not interested in that. The only thing that matters to me is how the Power Station performs for my intended use (recording guitars/bass in my recording studio) and unfortunately it has turned out to be useless for this, due to the level of hum it adds to my recordings.
Please see the attached screenshots when monitoring the signal through my DAW. There is one screenshot with the Power Station in bypass, one with the PS in operate mode with the lid off and finally one in operate mode with the lid on. The level of hum with the lid on is unacceptable for recording.
These screenshots were made with NO AMP connected to the Power Station. All the hum is originating from the Power Station.
The Power Station is connected to a single speaker cab, miked with a Sennheiser 421, straight to an ultra-clean micpre with the mic pre gain set for typical, moderate recording levels and no further processing. The same mic pre gain was of course used for all these three tests.
The VOLUME on the Power Station is all the way down. Raising the volume doesn’t actually affect the hum at all until the volume knob is almost all the way up, and even then only marginally. This of course means that the signal-to-noise ratio gets far worse at lower volumes, and reducing the volume is after all the whole point of this product.
The DEPTH knob actually affects the hum more than the volume knob, but still only marginally. In these examples the depth knob was at noon. None of the other knobs/switches affect the hum at all.
Lifting the ground on the Power Station increases the hum, but only very marginally. On the attached screenshots the ground was NOT lifted, as it shouldn’t be with no other electrical devices physically connected to the PS.
The only thing that significantly changes the level of hum is when I remove the top lid.
With the Power Station in bypass there is no hum whatsoever.
The level of hum I’m getting with the lid on is VERY audible on recordings, particularly with clean guitars and bass, which is of course totally unacceptable.
The attached screenshots are taken with a guitar speaker. With typical guitar speakers the hum rolls off under 150 Hz. When used with a bass speaker the hum doesn’t start to roll off until around 50 Hz, which makes it even worse.
A device that raises the noisefloor this much, and in the form of a strong, very audible peak of hum, is useless for recording. I can’t imagine this amount of hum would sound very nice when mic’ed through a large PA system either.
Based on the attached pics, do these noise levels seem normal for the Power Station?
Power Station in bypass:
In operate mode, lid off:
In operate mode, lid on:
I have this exact issue with my ps-100 that I’ve just received. Also trying to work out if it’s normal.
It’s exactly the sound of transformer hum of the unit amplified as soon as you hit operate. On bypass the amp has some gain/volume hiss but otherwise quiet and without hum.
Finding out whether this is “normal” or not (according to Fryette) won’t really help you at all if the hum still makes the Power Stations useless for your intended use.
Based on the posts here, and on other guitar related forums, there certainly seems to be an inherent hum issue with many of these units. Just out of curiosity, is yours a 230V unit too? Because all the complaints I’ve seen so far seem to be with 230V units.
If you purchased yours brand new, and still have the possibility to return it for a refund, that’s probably your best option at this point, because Fryette seems to have gone quiet on this topic, and show no signs of trying to resolve it.
To be fair, they have offered me to take a look a mine if I cover the cost of both the repairs and the shipping costs from Europe to the USA (and back) but they have also made it clear that they can’t guarantee a solution. Which means that this isn’t really an acceptable solutions for me at all. Especially when people who have returned their Power Station to the dealer for repairs have been told the hum is “normal”.
There’s also a lot of custom paperwork involved, so unless Fryette can guarantee a solution it’s simply not worth the cost&hassle of shipping it to the USA. And to be honest, if they can’t find a solution to this problem, which is affecting LOTS of Power Station users, without me sending them mine, they’re either not trying very hard, or the product has a serious design flaw that simply can’t be fixed.
Either way, your best option (if possible) is probably a return/refund. Sadly that ship has sailed for me, so I’m stuck with a useless (and rather expensive) Power Station.
Hello from Germany,
a few more comments and observations from my side.
I’ve had five Powerstations here over the last months. Four PS-100 and one PS-2A (all 230V).
I own two PS-100 at the moment and I love them. 
However they all have a quiet hum out of the speaker on operate regardless of whether an amplifier is connected or not (you can hear it in the attached sound file I just recorded with my iPhone in front of the speaker).
I always thought this is normal.
I use them mainly to play live with my bands, so this is not a big problem for me.
After your post I really wonder if the 110V versions are all dead silent and only the 230V versions have that hum? Can someone with a 110V version confirm that they don’t hear a hum when they switch to operate?
Greetings
Jens
Hi Jens,
Thanks for this question, would you just give full setup description of how the audio file was recorded. What amp was connected, the volume levels, etc?!
Regards
Dan
Hello, Dan!
Over the last few years, there have been a lot of complaints from PS-2 owners about hum on various internet forums. All of these problems concern units with 230V power supply.
For example, here is exactly the same problem. It is described in great detail:
Why hasn’t Fryette solved this problem yet?
I created a separate thread on this forum and asked if there are any owners of 230V units without hum problems. Not a single person responded.
I would really like to buy a PS-2a on Thomann, but I don’t want to face the same problem.
Please help all PS-2a owners who live outside the US.
Thank you so much!
Hey Aosha,
I noticed the other thread, I did not reply because I don’t have a US voltage Power Station. But let’s see what happens.
This sums up what we think at present Hum in 'Operate' - #23 by DavidPhelge
Regards
Dan
Unfortunately we have already ruled out all the possible causes for the hum mentioned in that post.
Hi Trerik,
I perhaps need to catch up with this, but what Dave posted seems pretty common sense to me. Maybe there are some details to look at. The main issue I have is that I can’t really comment without an actual unit in from of me.
dan, we are not talking about you personally.
We are talking about Fryette as a whole, which says: “we are absolutely not worried that all owners of PS-2 and PS-100 230v around the world have encountered a hum problem.”
It is quite obvious that this is the same problem for everyone.
And it is quite obvious that if Fryette wanted to, it would have looked at the behavior of the device in Europe with 230V long ago. For example, your engineer from Germany, whom you mentioned, would have delivered the device from the Thomann store, which is also in Germany. This «problem” is resolved in a few days.
But Fryette simply does not care.
Great technical idea, but a terrible company and a terrible product.
People will continue to buy Tone King/Aracom/something else or change PS to Tone King/Aracom/something else.
Why do you even pretend that you work for other markets besides the US? This only ruins your reputation.
Although, you probably don’t care about your reputation either.
2 posts were split to a new topic: Power Station crackle sounds
