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Pioneer PL-990 turntable clipping, [moved from General Audio/TOS #6]
claudiod
post Sep 1 2013, 12:03
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Hi, this is my first post on this forum but I've been a long-time reader.

I have a question.

I'm converting my parents' records to digital with this setup:
- Pioneer PL-990 turntable with line level output (it has an integrated preamp unfortunately, but since I only have a bunch of old records to convert I'd like not to buy a new one for now)
- Olympus LS-5 recorder (PCM, 24 bit/44kHz)

recorder is connected directly to the line level output from the turntable

transfers from 33rpm records are perfect (after a bit of click removal)

but 45rpm have a clearly audible distortion (possibly because the volume is higher?), which is also clearly seen in the attached sample, and a bit weird: only the positive half of the wave is clipped!

http://www.hydrogenaudio.org/forums/index.php?act=attach&type=post&id=7616
(sample converted from 24bit to 16bit to reduce size for uploading)

My question is: where is the clipping more likely to happen?
1) in the cartridge
2) in the integrated pream
3) in the recorder

I would discount a problem with the recorder, since I tried to add a -10dB attenuator to no avail.

So, is it 1 or 2?
If it's 1, I guess I should look for a new cartridge with a lower output level
If it's 2, I could try to bypass the integrated preamp by soldering a new output right after the cartridge and before the preamp; but before modifying the turntable, I'd like to hear some opinions

Thanks



This post has been edited by claudiod: Sep 1 2013, 12:05
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[JAZ]
post Sep 1 2013, 13:27
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Usually, when you see clipping only on one side of the waveform, that indicates that the needle is not centered and so it can't move as well on one side.

Inspect the needle and verify that it is centered (you might be able to center it with your fingers).


It is not completely out of the question that it's the preamp, but since the sample is not available (error in the url? or maybe you didn't submit), i wouldn't know for sure.
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claudiod
post Sep 1 2013, 14:00
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Thanks for your answer

Sorry, there was an error in my link; now it should work:
http://www.hydrogenaudio.org/forums/index....ost&id=7616
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Apesbrain
post Sep 1 2013, 14:11
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You could try transfering at 33.3 and then adjusting to 45 in digital domain. Some related information is here although it deals with 78s:
http://manual.audacityteam.org/man/Recording_78rpm_records
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claudiod
post Sep 1 2013, 21:36
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@JAZ: there's no way to centre the needle, however I removed and replaced it, after moving it a bit with fingers, and it seems it's centered, but still clipping

@Apesbrain: I already tried that. There's perhaps a tiny improvement, but still clipping.

I'll try to intercept and record the signal before it reaches the preamp just to see if the problem is the preamp, and I will let you know here.
Although I am starting to fear the problem could be in the cartridge (which is not replaceable, just the needle is)

Meanwhile, thanks for your suggestions

This post has been edited by claudiod: Sep 1 2013, 22:08
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AndyH-ha
post Sep 2 2013, 03:27
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While anything is possible, Pioneer had a relatively simple job: match the built-in phono preamp to the phono cartridge. There is no excuse for clipping to occur within that system. Cartridge outputs certainly vary but they vary mainly with cartridge design, they don't become higher with aging.

You say this clipping is audible. Is it audible when confined to an analogue system, i.e. when you feed the TT output to an amplifier-speaker system?

Can you try recording with any other ADC?

Does this off-center clipping happen with all 45s?
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claudiod
post Sep 2 2013, 07:18
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It seems to me that clipping is audible even on my analogue amp.

As a test, I can try recording with my computer's on board card; or with an analogue tape recorder, and then to my ADC from there (never had any clipping transferring tapes). Will try both and let you know.

It happens with 18 out of 20 45s that I tried. The other two are recorded at a lower level.
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mzil
post Sep 2 2013, 07:45
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Try playing a 33 1/3 RPM record at 45 RPM. If that has no problem and sounds/records cleanly, then it could be your collection of 45's were damaged from playback on a poor quality/dirty needle/misaligned stylus record-player in the past, which etched distortion into the groove walls permanently, I'm afraid.

Also, another thing comes to mind. I don't believe your machine has a tracking force adjustment , but a common malady of distortion comes from using too small- rather than too heavy- a downward tracking force. What happens is the stylus is unable to maintain proper contact with the groove walls and instead gets "bashed around", smashing against the walls rather than tightly clinging to them. [This can cause permanent groove wall damage, too.] It happens especially during loud passages where the groove motion is large and forceful, and you did mention that quiet records sounded OK, right?

Can you play these bad sounding 45's on an alternate TT to verify they are in good shape and don't have distorted grooves?

This post has been edited by mzil: Sep 2 2013, 08:17
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claudiod
post Sep 2 2013, 18:00
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There's no doubt that my 45s are in less than ideal condition: they are all late '60s / early '70s records played for many years on a mono portable turntable.
They don't skip, so I wound't grade them Poor (P), but certainly no more than Good (G).

So I am expecting some permanent distortion, but why a very regular clipping on just half wave and not just irregular damages now and then?

I will try your suggestions as well later when I get home, thanks.


This post has been edited by claudiod: Sep 2 2013, 18:14
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mzil
post Sep 2 2013, 20:03
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In theory, the Westrex 45/45 system we now use on stereo records was specifically concocted so that the existing mono record players could play the new stereo records (albeit in mono) and the new stereo players could play the old mono records as well, however the old styli had a heavy tracking force (like even 5 to 8 grams, I've heard) and they were only designed to wiggle laterally, never vertically/orthogonally. I've read that for some time the new stereo records came with a warning label advising against mono record player playback, but then they stopped.

" (However, many monophonic styli had such low vertical compliance that they plowed through the vertical modulation, destroying the stereo information. This led to the common recommendation never to use a mono cartridge on a stereo record.) "

Source

This post has been edited by mzil: Sep 2 2013, 20:07
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claudiod
post Sep 2 2013, 20:56
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Here are the results of some tests I did (as required):

- recording with another ADC (internal PC soundcard) and with an analogue tape recorder: still clipping;

- recording 45 rpm at 33 1/3 rpm: still clipping;

- recording 33 1/3 rpm at 45 rpm: not clipping;

- placing a -10 dB attenuator between the turntable line out and the recorder: still clipping;

I don't know how to interpreter the results, except excluding a problem with the recorder: it's the cartridge or preamp or damaged records

If I find the courage to bypass the preamp, I will post the results here (I opened the turntable back, and it wouldn't actually be difficult to solder a new output before the preamp, but since the cables coming from the cartridge are very tiny and very closely spaced on the preamp circuit board, I am afraid I won't be able to re-solder them back as good as before after the experiment).
Thanks for your help meanwhile.
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mzil
post Sep 2 2013, 23:31
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QUOTE (claudiod @ Sep 2 2013, 15:56) *
- recording 45 rpm at 33 1/3 rpm: still clipping;

- recording 33 1/3 rpm at 45 rpm: not clipping;


33 1/3 rpm records always sound good, regardless of actual playback speed.
45 rpm records always sound distorted, regardless of playback speed.

Conclusion: The 45 rpm records you are playing are damaged, sorry.

This post has been edited by mzil: Sep 3 2013, 00:01
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claudiod
post Sep 3 2013, 13:24
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"Conclusion: The 45 rpm records you are playing are damaged, sorry."

Possibly. But I wouldn't discount the fact that:
- 33 1/3 are pressed at a lower level to start with (at least that's what I observed with all of my records), and they never actually reach a level near to clipping level, even when played at 45;
- clipping is very regular on one side of the wave, not just a random distortion;
- why aren't my 33 1/3 damaged as well? (used with the same turntable for years); perhaps because of the lower speed?

Well, I can buy a random new 45 record to test.

This post has been edited by claudiod: Sep 3 2013, 13:27
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mzil
post Sep 3 2013, 16:24
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^Yes, buying a brand new 45 record and seeing if it has the same distortion seems like the logical, next test. Please report back your findings so we will all learn what's up.

This post has been edited by mzil: Sep 3 2013, 16:25
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botface
post Sep 4 2013, 09:01
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Are you sure it's clipping and not mistracking that's causing the distortion. Mistracking on one channel only usually points to the bias/anti-skate setting being incorrect if the cartridge is installed properly. I'd start by going back to basic turntable set up. EG :
- make sure it's on a level surface.
- ensure the cartridge is parallel to the sides of the headshell.
- make sure the overhang is correctly set.
- set the tracking force to somewhere near the top of the recommencded range
- set bias/anti-skate

All this assumes the stylus is in good condition
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mzil
post Sep 4 2013, 15:36
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Other than "make sure it's on a level surface", he has no control over that stuff. There is no counter weight, no overhang control, no cartridge alignment in general, no tracking force control, no anti-skate control, no detachable headshell, no detachable cartridge...

Other than keeping the needle clean, there's not much that the owner can do.
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Juha
post Sep 4 2013, 18:13
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QUOTE
My question is: where is the clipping more likely to happen?
1) in the cartridge
2) in the integrated pream
3) in the recorder


1) in the cartridge or
2) in the integrated pream
...

So, is it 1 or 2?
If it's 1, I guess I should look for a new cartridge with a lower output level
If it's 2, I could try to bypass the integrated preamp by soldering a new output right after the cartridge and before the preamp; but before modifying the turntable, I'd like to hear some opinions

I would start by trying another cartridge (database: http://www.vinylengine.com/cartridge_database.php ).
If that don't fix the issue then a new pre-amplifier or modifications for the integrated one.

Juha
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mzil
post Sep 4 2013, 19:37
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Cartridge replacement is not an option:

Pioneer PL-990 manual
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Juha
post Sep 4 2013, 23:24
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QUOTE (mzil @ Sep 4 2013, 21:37) *
Cartridge replacement is not an option:

Pioneer PL-990 manual



So the way to go is to try if lowering the output voltage from cartridge helps anything.


Juha
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DVDdoug
post Sep 5 2013, 19:59
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I assume your parents don't still have their turntable, or that their stereo doesn't have a "tape" output?

Personally, I think it's time to "start over"... It feels like you are in a hole with that set-up and it's time to stop digging... Check Knowzy.com for USB turntable ratings & recommendations.

Most 45s didn't sound as good as LPs... But if you are getting acceptable sound out of one channel, it's probably worthwhile fixing the bad channel.

How many 45s are we talking about? Maybe just look for MP3s... For the price of a $200 turntable you can buy 200 MP3s, you'll get better quality, and you'll save lots of time. If there are some songs you can't find on MP3, maybe you can find a CD (used if you want to minimize cost) or maybe you can just live with the distortion on those (hopefully few) records...

QUOTE
So, is it 1 or 2?
If it's 1, I guess I should look for a new cartridge with a lower output level
If you have to solder to the new cartrige, I wouldn't do it. Cartridges are not designed to be directly soldered-to, so you risk damaging a brand new cartridge.

QUOTE
If it's 2, I could try to bypass the integrated preamp by soldering a new output right after the cartridge and before the preamp; but before modifying the turntable, I'd like to hear some opinion
If you already have another preamp, it could be worth a try as long as you are willing to risk damaging the turntable. If you have to buy a preamp and it doesn't solve your problem, you risk end-up spending money on a preamp you don't need.


P.S.
WAIT....
Before you replace the cartridge or preamp... Swap the left & right connections at the cartridge or at thejpreamp input. If the clipping switches to the other channel, that proves both preamp-channels are capable of good sound and the problem is with the cartridge. If the problem remains in the same channel, the problem is in the preamp.

From what you've said, that will still require soldering, but have you opened the thing up to see if you can swap the preamp inputs around (or bypass the preamp) without un-soldering & re-soldering?



This post has been edited by DVDdoug: Sep 5 2013, 20:24
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mzil
post Sep 5 2013, 20:37
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Considering this turntable has been in continuous production since at least 1996, it is strange how there are no other reviews or webs accounts of the design's internal preamp being easily overloaded or "clipping on 45s only, regardless of actual speed selected, yet not 33 1/3 records, again, regardless of the actual speed selected to play them".

It's groove distortion, I'm confident, and these 45 records will have the same problem if a substitute stereo pickup turntable is used to play them.

This post has been edited by mzil: Sep 5 2013, 20:38
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Juha
post Sep 6 2013, 09:38
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QUOTE (mzil @ Sep 5 2013, 22:37) *
Considering this turntable has been in continuous production since at least 1996, it is strange how there are no other reviews or webs accounts of the design's internal preamp being easily overloaded or "clipping on 45s only, regardless of actual speed selected, yet not 33 1/3 records, again, regardless of the actual speed selected to play them".

It's groove distortion, I'm confident, and these 45 records will have the same problem if a substitute stereo pickup turntable is used to play them.


You assume every single product is equal (It's not rare case that device is build using wrong value/faulty components ... I have an example: My ESI DuaFire audio interface has wrong components in its RIAA stage --> RIAA EQ is totally wrong --> no one else has reporded this issue).


Good to hear that you found the cause for clipping.


Juha
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mzil
post Sep 6 2013, 21:00
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QUOTE (Juha @ Sep 6 2013, 04:38) *
QUOTE (mzil @ Sep 5 2013, 22:37) *
Considering this turntable has been in continuous production since at least 1996, it is strange how there are no other reviews or webs accounts of the design's internal preamp being easily overloaded or "clipping on 45s only, regardless of actual speed selected, yet not 33 1/3 records, again, regardless of the actual speed selected to play them".

It's groove distortion, I'm confident, and these 45 records will have the same problem if a substitute stereo pickup turntable is used to play them.


You assume every single product is equal (It's not rare case that device is build using wrong value/faulty components ... I have an example: My ESI DuaFire audio interface has wrong components in its RIAA stage --> RIAA EQ is totally wrong --> no one else has reporded this issue).


Good to hear that you found the cause for clipping.


Juha

I'm not sure I understand your point. Is it?

A. All Pioneer PL-990 turntables must have a design flaw which distorts on at least some 45s [the OP reports it occurs on several] but nobody since its release in 1996 has ever verbalized this problem on the web.

B. The OP has a broken PL-990, and if brought to a repair center this problem could be fixed [or at least swapped out with another one that works properly] which would cure the recording problem.

C. Other [please explain]

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Juha
post Sep 7 2013, 07:08
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QUOTE (mzil @ Sep 6 2013, 23:00) *
I'm not sure I understand your point. Is it?


My poin is that there always are 'monday pieces' for sale and it's possible that the design is wrong in the 1st place or because of faulty components.

BTW, was there a reason OP took off the sample file (given link opens error page)?


Juha
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claudiod
post Nov 5 2013, 15:59
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Hi, I'm the OP. Sorry for the long delay.

I eventually tested my turntable with some new 45rpm records and I am embarrassed to admit that the problem is gone! So - as some of you rightly guessed - it is all of my old records that are damaged!

Now, I am still wondering why only the 45rpm and not the 33rpm were damaged (both were played on the same old mono turntable for 30+ years), and why only half side of the wave is damaged. Probably due to mechanical reasons such as different speed and centrifugal force?

By the way, I didn't remove the sample, I don't know why it's no more available, sorry.

As someone suggested, I already bought many CDs (I don't like mp3s) and found most of the A-sides on greatest hits collections. The problem are the B-sides which are more difficult to find, and I am surprised at how good many B-sides where back in the sixties. Often even more interesting than the A-side. I will look for another copy of the 45rpm on eBay.

Now I feel this thread title is a bit unfair towards Pioneer - as it turned out my basic inexpensive turntable is not so bad after all - and I wish I could edit the title to something like "45rpm records clipping".

Thank you all for your help.

This post has been edited by claudiod: Nov 5 2013, 16:02
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