Help diagnosing distortion problem in LP playback, please.

[MattHooper]

Folks,

Recently I've had a problem with distortion creeping in to my LP playback system.

Initially when the system is turned on, playing a record (that is in good condition) will sound clean enough, but after a few minutes distortion will start to occur, at first just barely "is it there?" level of grittiness and then it gets worse until the sound is covered in a layer of haze/fuzz, with transients distorting very obviously, like an over-driven amp. Or the type of fuzzy playback you get when a big hunk of dust got hung up on your needle. (The needle is fine, I keep it very clean).

I turn the system off, and the same thing happens the next time I use it.

Any ideas for trouble-shooting this?

My turntable and Benz Micro Ebony L cartridge and phono stage are 3 years old. Well cared for.

I don't know how it could be the stylus, which as I say is kept very clean and not sure distortion would have this type of "starts clean, becomes really distorted" character ever time.

And my tube amp/tube pre-amp seem fine: my digital source displays no distortion.

Which makes my hunch go towards my phono stage. It's a JE Audio phono stage that uses 2 small 6H30 tubes as buffer stages. I'm wondering if this might be a sign of a tube or both going south? Any other ideas?

Thanks for any input!

 

[Blumlein 88]

I think you've narrowed it down to phono stage. And yes this sounds like a tube going bad kind of thing.

That is a dual triode. Are they using one half of it for each channel or one tube per channel (two tubes total in buffer)?

If they are using two of them is the noise in both channels?

And have you moved or changed anything in the general area recently. Just as an example, a friend a few years ago had a situation like you described. He had moved a Mac Mini from one shelf to the other placing it about 15 inches closer to the phono stage. It was fine, and in time like 10 minutes would fuzz up, and begin to distort and eventually if you let keep playing motorboat. Tubes tested fine, and we swapped in another set and again same result. Somehow the Mac Mini PS was bleeding into it, and we assume oscillating at some frequency, and when some part of it got hot enough started causing issues. Moved the Mini and problems gone.

But sounds like maybe you need a new 6H30.

 

[anmpr1]

One way to find out is to insert another phono stage. You can get an inexpensive one for small dollars--20 or 25 USD. If that solves the problem then the only thing left is change the tube(s). Then, if no luck, send it back for repair. Your unit is quite expensive. I'd be on the horn to the dealer and/or manufacturer if it has a defect. A three year old phono stage shouldn't be failing.

 

[MattHooper]

Thanks for the advice Blumlein and anmpr1.

You've given me some more things to think about.

I only just recently did a purge of stuff in my house including some audio equipment. And as usual, that item that I hadn't used for years, was hanging on to "just in case" I finally got around to saying "Ok, if I haven't used it by now I don't need it." And of course, several times now within a week of getting rid of said item, I suddenly need one!

I'd recently got rid of an old Rotel phono stage which would have come in handy in JUST this type of situation. But..doh!

 

[Blumlein 88]

Thanks for the advice Blumlein and anmpr1.

You've given me some more things to think about.

I only just recently did a purge of stuff in my house including some audio equipment. And as usual, that item that I hadn't used for years, was hanging on to "just in case" I finally got around to saying "Ok, if I haven't used it by now I don't need it." And of course, several times now within a week of getting rid of said item, I suddenly need one!

I'd recently got rid of an old Rotel phono stage which would have come in handy in JUST this type of situation. But..doh!

That is some kind of law of the universe. So many times I've rid myself of items not touched for years and years. Seems in each case I then need it within 2 weeks. One such item was unused just in case for 28 years.

 

[MattHooper]

That is some kind of law of the universe. So many times I've rid myself of items not touched for years and years. Seems in each case I then need it within 2 weeks. One such item was unused just in case for 28 years.

I had a Z-Systems RDP-1 digital eq sitting on my equipment rack since the late 90's. Very expensive at the time! I fiddled with it a few times but never found that I used it. But I kept it around sort of like a life-raft 'what if I need it to adjust the sound sometime, like to tame speaker brightness' or whatever. I just never needed it. It became a running gag with an audiopal who'd ask once every couple of years 'So, have you used that RDP yet or are you finally going to sell it?" I'd say "still keeping it...just in case!"

But I needed money for new speakers last year and finally said to myself "You've never used this damned thing for 22 years...let it go!"
Sold it.

Next week, I suddenly realized I had the (at least temporary) need for the thing!

At the moment I have two JL subwoofers and their pricey analog crossover. I was never interested in subwoofers, sonically or aesthetically, but I reading hype from the subwoofer afficianados on AVS spured me to finally try and I bought them 3 years ago. After an initial half-hearted try, they've sat unused. I keep thinking "I'll try them soon, soon...." but it's such a damned hassle "doing it right" with all the room EQ etc, I can't be arsed. Again, they've turned in to a running "thing" that my pal brings up "so how are those subwoofers sounding? "

And, again, I'm getting a jones for a possible set of speakers, now scrounging around for stuff to sell, wondering if I can finally part with the subs...which I'll probably need the moment I get the new speakers and think "damn, bet the subwoofers could have fixed this problem!"

 

[EJ3]

But I needed money for new speakers last year and finally said to myself "You've never used this damned thing for 22 years...let it go!"
Sold it.[/QUOTE]

And then you try to find one and discover that it is made out of unobtanium and you can't find another one to replace it.

 

[MattHooper]

One way to find out is to insert another phono stage. You can get an inexpensive one for small dollars--20 or 25 USD. If that solves the problem then the only thing left is change the tube(s). Then, if no luck, send it back for repair. Your unit is quite expensive. I'd be on the horn to the dealer and/or manufacturer if it has a defect. A three year old phono stage shouldn't be failing.

I think you've narrowed it down to phono stage.

Dammit I'm going nuts here. I'm still somewhat of a newbie to the nuts and bolts of vinyl and just terrible with electrical theory in general. If anyone can help out...

I'm trying to grab as cheap and fast a phono stage as possible so I can swap it in to my system just to see if the distortion is coming from my phono stage.

The thing is my cartridge is a low output. Tough to find a cheap phono stage to do it right. Specs for the Benz Micro cartridge here:

Benz Ebony M Specifications:

• Output: .26V
• Stylus: 5x120µm
• Impedance: 1 ohms
• Loading range: >50 ohms
• Weight: 10.7g
• Compliance: 14cu
• Tracking force: 1.6-1.9g

My existing phono stage has very flexible settings for any type of cartridge. My settings are currently:
MC Gain: 65 dB
MC Impedance: 100 Ohm

A local fix-it shop suggested they have a cheap phono stage for MM, but with a variable gain control I could crank up to get enough level. I guess I'd have to crank the volume up on my pre-amp a lot more than normal but in theory should be a clean signal?

Alternatively, there's something like this on amazon:

https://www.amazon.ca/Preamp-Phonograph-Preamplifier-Turntable-Pre-Amp/dp/B08B3S8PJF/ref=sr_1_89?dchild=1&keywords=phono+stage&qid=1607658364&sr=8-89&th=1

Says it's for both MM and MC cartridges, but likely for higher output MC cartridges. Could it work, in a pinch?

Thanks for any help.

 

[Blumlein 88]

https://www.audiosciencereview.com/...measurements-of-emotiva-xps-1-phono-amp.7568/

Well the Emotiva will work for sure. Definitely no need to pay more than that. $199.

Do you have a recording interface with microphone input? Won't have RIAA or the best impedance, but would let you hear if there is distortion or not. Record the signal, apply RIAA digitally even with something like Audacity and hear it.

The one you link looks like they are saying MC has 6 db more gain and an MC friendly impedance. Probably marginal on the gain.

 

[MattHooper]

https://www.audiosciencereview.com/...measurements-of-emotiva-xps-1-phono-amp.7568/

Well the Emotiva will work for sure. Definitely no need to pay more than that. $199.

Do you have a recording interface with microphone input? Won't have RIAA or the best impedance, but would let you hear if there is distortion or not. Record the signal, apply RIAA digitally even with something like Audacity and hear it.

The one you link looks like they are saying MC has 6 db more gain and an MC friendly impedance. Probably marginal on the gain.

Thanks. Emotiva not available, more than I want to spend in this case.

So the one I linked to should work, but just turning up the volume on my pre-amp? Maybe I'll grab that one.

 

[anmpr1]

Dammit I'm going nuts here...

Didn't realize you had a low output MC. If you have the HP-10 phono stage then you add another level of complexity. Evidently each phono stage (MC and MC) are separate circuit boards. Thus I was going to suggest you buy an inexpensive MM cartridge and see if you can reproduce the fault. But since the high and low gain amplification stages don't share any common circuitry (I think) then that wouldn't help. That is, your MM may be fine, but the MC could be faulty.

The tubes in the HP-10 are not for amplification [this is not uncommon in phono stages and it is done to reduce S/N--I have a Bellari that uses an opamp with tubes for 'conditioning', and a PAS-3 mod that uses a JFET for initial amplification before sending the signal to the tubes for final amplification].

I would try @Blumlein 88 suggestion and replace tubes and see how that goes. If no luck then it would be back to the dealer or factory.

 

[Robin L]

My first thought is "so, you're really hearing IGD for the first time". However, you might want to check the stylus on the cartridge under a microscope. When I had a LP rig, I played LPs hours upon hours, every day. So the tips of the stylus wore out pretty fast. And the sound you're describing aligns with what I was hearing when the stylus gave out. Of course, when the turntable is an old AR XA, chances of stylus damage are pretty high. That $20 Grado that was floating around in the 1970s was a lifesaver many times. I'm sure you're real careful, but the stylus assembly of a phono cartridge is really delicate. But you already knew that, right?

 

[EJ3]

If it's the stylus I would think that the distortion would be there immediately upon stylus touching down on the LP. Not wait a few minutes and then start distorting.

 

[raindance]

A stylus won't deteriorate after a few minutes of listening. Of course there's always the possibility that your records were cleaned with something that gunks up the grooves/stylus. The workaround for this is to get a record that isn't your favourite and try wetting it with water before playing it. If the issue clears up when playing wet then your records are full of gunk.

Did you confirm if the distortion is in both channels or just one?

 

[anmpr1]

Preamp tubes should last (almost) forever. Especially if (like in this case) they are not used for primary amplification, but only to 'condition' the sound. Then, you wouldn't expect them to be operated at full rated voltage. But tubes do go bad. All tubes.

6H30 are not the cheapest preamp tubes the company could have used. You're probably looking at sixty to seventy dollars for two. A quick search lists average life for this tube between 4-10 thousand hours of use.

Tube gear--the gift that keeps on giving (or is it taking). LOL

 

[MattHooper]

Didn't realize you had a low output MC. If you have the HP-10 phono stage then you add another level of complexity. Evidently each phono stage (MC and MC) are separate circuit boards. Thus I was going to suggest you buy an inexpensive MM cartridge and see if you can reproduce the fault. But since the high and low gain amplification stages don't share any common circuitry (I think) then that wouldn't help. That is, your MM may be fine, but the MC could be faulty.

The tubes in the HP-10 are not for amplification [this is not uncommon in phono stages and it is done to reduce S/N--I have a Bellari that uses an opamp with tubes for 'conditioning', and a PAS-3 mod that uses a JFET for initial amplification before sending the signal to the tubes for final amplification].

I would try @Blumlein 88 suggestion and replace tubes and see how that goes. If no luck then it would be back to the dealer or factory.

Actually you just reminded me of the two different amplification sections in the HP10! And now it seems more plausible to me that it could be one of the tubes. I was thinking it used 2 tubes, one for each stereo channel, and that it seemed a bit implausible that both tubes might crap out at the same time. But if it's only one tube per amplification section (MM or MC) then one tube crapping out seems possible. (It also means that one test would be to swap out the tube from the the MM to the MC section...though I've got some new tubes being delivered).

I ordered that cheap phono from Amazon so don't know if that will help.

 

[raindance]

So the only thing in common between both channels is the power supply, so I'd suspect that one of the power supplies, likely for the tube circuitry but you never know, is either collapsing (tube circuitry) or becoming asymmetrical (this could be likely for the solid state circuitry, for example a +/- 15 volt supply that loses one half).

 

[MattHooper]

My first thought is "so, you're really hearing IGD for the first time". However, you might want to check the stylus on the cartridge under a microscope. When I had a LP rig, I played LPs hours upon hours, every day. So the tips of the stylus wore out pretty fast. And the sound you're describing aligns with what I was hearing when the stylus gave out. Of course, when the turntable is an old AR XA, chances of stylus damage are pretty high. That $20 Grado that was floating around in the 1970s was a lifesaver many times. I'm sure you're real careful, but the stylus assembly of a phono cartridge is really delicate. But you already knew that, right?

Thanks. This set up has played records very cleanly, from front to back, for the 3 years I've owned it. The distortion would occur on clean tracks, first tracks on the album. And it comes and goes. A track that had a very distorted vocal a few days ago played cleaner last night.

I wish I had a microscope for the stylus. It's been about 3 years of playing maybe an average of a record a day or two. So it could be nearing the end of life. I don't really have experience with this except for the previous micro seiki turntable given to me by my father-in-law in the 90's (which he'd bought early 80's). It was still on the same cartridge as from the 80s, sounded pretty clean (a tad gritty), and never got distorted like this.

Worringly, the phono stage is from a company in Hong Kong and the proprietor is not returning emails. (With COVID, one's mind goes to darker scenarios for why someone seems to disappear). Hope I don't end up with a boat anchor.

 

[anmpr1]

Worringly, the phono stage is from a company in Hong Kong and the proprietor is not returning emails.

That is the big problem with buying long distance. For inexpensive 'throw away' items it's not that big of a deal. For costly items it's always a concern. There are no guarantees as to business viability. I've owned plenty of gear from manufacturers that are no longer around. That seems to be the story with audio.

Is there a solution? Say what you will about them, but that is one reason McIntosh is what it is. And has been for 70 years. With tubes I own Dyna based gear. There exists a thriving upgrade path and continued support for them. On the other hand, my expensive Counterpoint tube preamplifier went south, years ago. Not worth the trouble--gave it away.

 

[watchnerd]

Folks,

Recently I've had a problem with distortion creeping in to my LP playback system.

Initially when the system is turned on, playing a record (that is in good condition) will sound clean enough, but after a few minutes distortion will start to occur, at first just barely "is it there?" level of grittiness and then it gets worse until the sound is covered in a layer of haze/fuzz, with transients distorting very obviously, like an over-driven amp. Or the type of fuzzy playback you get when a big hunk of dust got hung up on your needle. (The needle is fine, I keep it very clean).

I turn the system off, and the same thing happens the next time I use it.

Any ideas for trouble-shooting this?

My turntable and Benz Micro Ebony L cartridge and phono stage are 3 years old. Well cared for.

I don't know how it could be the stylus, which as I say is kept very clean and not sure distortion would have this type of "starts clean, becomes really distorted" character ever time.

And my tube amp/tube pre-amp seem fine: my digital source displays no distortion.

Which makes my hunch go towards my phono stage. It's a JE Audio phono stage that uses 2 small 6H30 tubes as buffer stages. I'm wondering if this might be a sign of a tube or both going south? Any other ideas?

Thanks for any input!

When I use my tube phono stage, I've had that happen with dodgy tubes that are starting to die.

Swapping tubes made it go away.