Hum on Tube Amp - Can't find source

@jea48 + @dpop

It looks like the one I posted.

Mine is a TPS3A111000 (no superseded by TPS3A111002)

https://mall.industry.siemens.com/mall/en/us/Catalog/Product/?mlfb=US2%3ATPS3A111002

Thus:

voltage code: 120/240V, 10,3W

100kA per phase

EMI/RFI filtering (sine wave tracking), Ground integrated monitoring, Protection modes L-N, L-G, N-G, L-l

(whatever all of that means!)

@zombiedad swapped the KT77 also swapped the 7044 and 12ax7 from one unit to the other.

I suspect that 12ax7 is the problem.  Speaker wires are AQ Rocket directional 18" long

I don't think is the Rocket cable.   Try swap the 12ax7 also.   I didn't swap my small tubes.  just removed the KT88 and put in all 4 KT120.  Problem solved.  Dead quiet.  

@zombiedad I should have some tubes delivered tomorrow for the swap.

Let's hear!

@ervikingo

The unit was biased and received a complete test. Unit passed all factory specs.

I’m assuming you sent it in, because of this problem? If it came back with a clean bill of health from Manley, it sounds like this problem was not taking place when they had it on the bench, otherwise I’m quite sure Manley would have contacted you about it (yes, no, maybe?).

The sound in that video sounds like “motorboating”.

holmz you beat me to it

@jea48 Are you trolling with a lure too 😂

@dpop I sent it because when I received them they had non OEM inline fuse holders and one was DOA.  I spoke with the seller and agreed that they should go to Manley for repairs/return to original configuration and any other repairs.

I paid for checkup and a couple of tubes that had the key broken.

Manley have been great.  They have followed the journey on this and offered suggestions.  The non conforming tube was brought up by them today/yesterday.

I didn't read every post, just the first half of them. I'm going to say that it's the transformers themselves. I had this problem with my Luxman integrated. It was dead quiet for several years after I bought it, then developed a low hum. It is always the same, comes from the amp, not the speakers, and is independent of any controls or devices. The fix is new transformer(s), which is expensive, and not a guaranteed remedy.

@builder3

ervikingo reports: "there is no mechanical hum on the amps; I have noise on speakers."

@ervikingo 

they had non OEM inline fuse holders

Curious as to how they got that way in the first place (I'm sure we'll never know)?

Thanks, I should've taken the time to read everything carefully.

would speaker feedback do that? IRS Beta 

@ervikingo 

Have you tried connect a different pair of speakers on your Manley Snappers?

@imhififan @ervikingo

Have you tried connect a different pair of speakers on your Manley Snappers?

Another good point. The manual states: Recommended Speaker Load: Optimized for 5 ohms

Do you know what impedance your speakers are rated ervikingo?

Once the noise starts you can’t bias them as the voltage cycles.

To me, this is the most concerning factor in this whole scenario.

Here’s a few other tidbits from the manual:

-For the power tubes in our amplifiers, after a few years if you notice a small revolt going on where several of the output tubes are misbehaving or getting hard to bias, you might consider doing a full re-tube.

-Three tube types that are electrically and plug-socket compatible with the 12AT7A dual triode include the 6021, 6679, and the ECC81 (I find it a little interesting that they made no mention of a 12AX7 here).

-Never operate the amplifier without a speaker load, or suddenly disconnect the speaker load while the amplifier is producing a signal. This risks punch-through of the enamel insulation covering the transformer’s internal magnet wire. Permanent damage to the output transformer may result 

-Additionally, it is best to cut power to the Snapper when not in use rather then leaving the power on indefinitely. This will enhance tube and system life.

 

imhififan @ervikingo

Have you tried connect a different pair of speakers on your Manley Snappers?

Another good point. The manual states: Recommended Speaker Load: Optimized for 5 ohms

Do you know what impedance your speakers are rated ervikingo?

Once the noise starts you can’t bias them as the voltage cycles.

To me, this is the most concerning factor in this whole scenario.

Here’s a few other tidbits from the manual:

-For the power tubes in our amplifiers, after a few years if you notice a small revolt going on where several of the output tubes are misbehaving or getting hard to bias, you might consider doing a full re-tube.

-Three tube types that are electrically and plug-socket compatible with the 12AT7A dual triode include the 6021, 6679, and the ECC81 (I find it a little interesting that they made no mention of a 12AX7 here).

-Never operate the amplifier without a speaker load, or suddenly disconnect the speaker load while the amplifier is producing a signal. This risks punch-through of the enamel insulation covering the transformer’s internal magnet wire. Permanent damage to the output transformer may result 

-Additionally, it is best to cut power to the Snapper when not in use rather then leaving the power on indefinitely. This will enhance tube and system life.

With the motorboating clue, it would not be unthinkable that those small tubes are involved.
Do these have coupling capacitors?

Something like a broken solder trace could easily be involved to create a situation where the amps is motorboating - maybe even from trying to account for DC.

@ervikingo 

I wonder if sending the tubes out to be tested might not be a bad idea?

TC Tubes

Desert Amplifier Repair

I did try with my other speakers (Aerial 8b) and noise is present. 
 

thanks for the info on tube testing!

I’ll read that Audio Asylum post now. 

@jea48 

"Manley Snappers Blowing Tubes (over and over)"

Great catch (although at the same time, possibly a red flag)!

@ervikingo 

I did try with my other speakers (Aerial 8b) and noise is present. 

Good to know. OK, can cross that off the list. 

Here’s some highlights from the jea48 linked Tubes Asylum discussion:

-check the bias as they power up, and let them settle in for a bit (like 20 mins) for a final check.

-do not buy new tubes for hi-fi amps from guitar tube suppliers. Buy them from hi-fi tube dealers. Tubes (even matched quartets) sold by most guitar outlets are specially selected to distort early (low transcoductance tubes), therefore they run out of bias adjustment pretty quickly on a HI-Fi amp and there goes another tube!

-Manley has checked out the amps (one of them twice) and says there isn’t anything wrong with them.

-I have one Snapper that has been back to the shop once. It seems to be holding its own ok in terms of not blowing tubes. The other amp is a different story. It just came home from its second trip to the shop and after two hours of use, blew its B+ fuse and two of the tubes, separating the center post of the two tubes from the tubes themselves.

-Try plugging the monoblocks directly into the wall outlet and check the bias to see if you have better bias stability (bypassing any power conditioners).

-When you pull output tubes in and out on a regular basis, we have a tendency to stretch out the tube pins and even can cause tiny stress cracks on circuit board..Now this leaves you with low bias or intermittent bias or no bias voltage many times therefore causing tubes to burn up. I don’t know how much technical knowledge you have on this kind of stuff, but I would re-solder the tube socket connections and tighten the pins inside the sockets or even replace the sockets with better ones

-Manley’s have not-so-good sockets in them.

-yanking tubes in and out of both amps, he could very well have bad sockets in both or loose solder connections at the very least

-We are rebiasing the amps each time we replace the tubes. We recheck the bias every few hours and the amps have never held bias well. We are terrified of damaging the output transformers, power supplies, speakers, and everything else. My husband and I have been audio enthusiasts for almost 30 years and the hobby is becoming more stressful than fun with the problems we have had with these amps. We have spent many thousands of dollars (money we don’t have) replacing tubes by the octet since we bought the amps, not to mention the shipping back to Manley.

Did you fix it?

Replace the tubes

Did you try your system in another home?

Monday morning update.  I couldn't wait for the "good tubes" to come for testing.  I ordered one from Amazon (overnight delivery!) and the noise is completely gone.  Its scary quiet!

I ordered new 7044 as one of them is not up to par (still some noise).  I moved the 12 AT7 from one amp to the other and there was noise on the other amp; moved the 7044 from the quiet amp to the other and the noise is gone.

Huge lessons learned:

- there are a lot of enthusiasts out here who are willing to help

- @atmasphere is an awesome resource 

- start with the basics; I have spent weeks and $$$ chasing after the noise and never thought to check if the prior owner had used the proper tubes

I'll post again once both 7044 and 12AX7 have been replaced with the 12AT7.

Please accept my most sincere thanks for your help (and for the humor...  trolling with the motorboating sound...!)

"I have replaced the tubes and both amps were just tested at the factory."

You're telling us the factory didn't notice you were using the wrong tubes?

Sheesh.

@ervikingo

The 7044 tube is the Driver tube...

I would strongly suggest you tell the vendor you buy them from you need each section of the Triode tightly, closely, matched. Pay extra for each tube if you have to.

I doubt you will get that from Amazon.

.

@jea48 UHUM.  I didn't order the 7044 from Amazon.  Only a 12AT7 as a tester (TungSol) while the good ones arrive from Manley (7044 and 12AT7).

@dweller regretfully they did not.  The spec'd tubes for the Snapper changed and they now use the 12AX7, my vintage didn't.  Occam's Razor

@jea48 since we are on this, any recommendations on tubes or suppliers?

12AT7, 7044, EL-34, KT77?

Buy tubes at Upscale they will guide you one step at a time . The tubes from Amazon sellers I bought they did not last except the 6n23 tubes from Caufied guy from California. Grant fidelity sells quality tubes but pricey.

I have had good luck with The Tube Store over the years.

we need a "Like" button on this forum

Was following and good to read it appears to be sorted out. . . .

Excellent outcome I was going to say I had a hum issue that turned out to be a dirty tube pin glad your tube replacement got it sorted.

@ervikingo, so glad to hear that the hum is gone. Now it’s time to enjoy some music. 

Yes, with the significant other "quarantining" due to Covid, I moved to the music room since last Monday!

Have put hours enjoying music!

The (financial) downside is that i hit the vendors:

- Have 2 quads of EL34's scheduled for delivery today.  With those, every single tube on the amps is new

- Waiting for the PS Airlens to be released so in the meantime I ordered (and received) a Wiim Pro

- Ordered a budget DAC to go with it (Topping D90SE MQA) which should be delivered later in the week

Currently running the Wiim to my trusty but dated spec'd Theta Gen V and alternatively to the onboard DAC on a Lexicon MC-1.

Have to say, the Wiim sounds good!  On A/B tests from my CD transport to the same DAC there is a discernible difference (improvement).

With the motorboating clue, it would not be unthinkable that those small tubes are involved.

@holmz The 12AX7 has more gain than a 12AT7. This can affect the amount of feedback that exists in the amplifier and can also affect something called 'phase margin'. If the amp was designed to use a lot of feedback and was a bit to close to the limits of its phase margin, by adding the slight extra gain of the 12AX7 it could have pushed the amp over the edge. So an oscillation is entirely possible, simply on account of the 12AX7. This is why it can be so important to use the tube for which the amp is designed.

merits repeating: "atmosphere: This is why it can be so important to use the tube for which the amp is designed."

@atmasphere being a guy in the land of 10k lakes, motor boating should be natural. 😎 (but it’s probably ice fishing season now,)

I was pretty sure that the hum reducer gear, and power conditioning approach, was not likely to lead to a solution… and the amps not having RCAs hooked up precluded a ground loop being possible.

And some version of an Ishikawa chart would have been helpful here.

In any case… it is a great outcome for the OP, and should be useful for others.

being a guy in the land of 10k lakes, motor boating should be natural. 😎 (but it’s probably ice fishing season now,)

@holmz 

My understanding is the two happiest days in the life of a boat owner is the day he buys it and the day he actually is able to sell it. I find bicycles are much easier to manage except for that N+1 thing (N= the number of bikes needed).

@atmasphere yeah… shopping for a gravel/adventure one now.

Crickey, they can be around the price of 3-4 of the mono blocks.

ha ha ha. I dont own a gravel but own 3 Orbea mountain bikes N+2

@ervikingo Hope your hum is still a non-issue.

I'm anxiously awaiting the delivery of my first tube monoblock amps.

I had a hum issue with my solid state amps, even with all new electric dedicated 20amp lines and audio grade outlets. Thank god a single humX fixed the issue, but I'm kinda nervous about my new amps since I won't be using dedicated and newly run outlets.

I'm probably gonna have new 20amp lines run with audio grade outlets placed once I know where I'm gonna have my amps set up more permanently, but just kinda nervous.

Well see... I'm also probably gonna ask the dealer I bought my amps through to lone me a puritan 156 with ultimate cable to A/B things should there be an issue. 

Does it happen only with those amps or just with ANY tube amp? Because if this is the case you may need a new house. 

Do the P.S. Audio Power Plants eliminate hum from tube amps? Know first-hand the heartbreak of Tube hum (Prima Luna Prologue Premium w/Klipsch LaScalla II).

This would be a godsend.

Put together any tube amp and the hyper efficient Klipsch Lascalas (or Klipschorn) and that efficiency will dredge the bottom of the amp's circuit mercilessly revealing the slightest hum, Paul Klipsch must not have minded this issue. (Early on he used tube amps until later Crown SS)  Admittedly, all is forgiven and forgotten once the music is playing. However, pauses or gaps in the stream of music and HELLO there's the hum again! Being OCD, i.e. today's audiophile, and introduce said hum, and no matter how minuscule it can become deafening. Like most who are in this spot we have applied every tweak possible. And we have had a measure of success. But tube amps use tubes. Tubes are a moving target  They are like candles gradually burning out. As a consequence, noise can increase here and there among the family of tubes as they interact with each other. The last couple days, after a month of nearly continuous (nearly) silent operation, no matter what I did, the hum had once again risen above my personal limit. After doing my due diligence and double checking the common culprits, I was defeated. Then on a whim I rotated the power tubes leaving the same but moving the big ones around. Hum GONE! Why is that?  

Interesting change in what little "hum" I have left after Raven upgraded the grounding loop system. I just I'm OCD about a totally black background. I rearranged my room where now I sit 3 feet further back from speakers. For some reason I'm now out of reach of a low frequency "hum" that I can reacquire audibly if I lean forward those 3 feet! In the meantime the soundstage and detail etc. are all still excellent. Weird but nicely so. My volume goes up a tad at this increased distance which also helps. (I have an off topic quick question...does anyone know the best DB's on the Lascalas where they produce their best sound? 70? 80? 90?)