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Old 20th June 2009, 10:49 AM   #531
kffern is offline kffern  Australia
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3 pm is unlistenable on either phono stage.
I can't take it over 10:30 to 11:00 with the headphones on (HD650 - not the most efficient either)
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Old 20th June 2009, 10:53 AM   #532
kffern is offline kffern  Australia
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Quote:
maybe you can test the following: comparing the noise from connecting preferrably the same cartridge through the different phono stages at a level (these levels may be different for both phonestages) that normally is the loudest you use, but then without lowering the cartridge to the vinyl.
I thought this is what I have done already before I tried messing about with the 2 arms on different phono stages.
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Old 20th June 2009, 11:40 AM   #533
JBdV is offline JBdV  Netherlands
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Musical Fidelity X-LPS V3 MM/MC Phonostage (This is yours ???)

SPECS:

MC input
Sensitivity:> 350V for 350mV output at 1kHz
Input impedance: 100 Ohms
THD: < 0.01% at 1kHz, 350mV out
Input overload margin: 30dB
Signal / Noise ratio: > 65dB unweighted > 74dB 'A' weighted


So gain is 1000 not sure what the gain of your PC3 is.

Noise level is not spectacularly low, so PC3 should be able to beat that.
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Old 20th June 2009, 12:13 PM   #534
brianco is offline brianco  Ireland
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You don't describe the type of 'noise'. Is it just an awareness that something is turned on, or is it a specific type of noise? Is the earthing identical on both arm/cartridge combinations? Are you using the same phono cable between pre amp and P3? And the same preamp input?


I ask the above to narrow down the possibilities - however it seems to me that the comparisons which you have made do not allow for the many variables between the two arm/cartridge/wiring combinations.

I think that you should stick to one arm, one cartridge and one set of leads. I know too well that eg to change even between exact same type items at this end of the chain can have an enormous subjective difference. The best example of close match I had was when delighted with a Fidelity Research FR 64S arm, I bought the slightly lower mass 64FX(?) for use on a second TT. Using the same Ortofon SPU the subjective difference in tonality and noise was greatly in favour of the 64S type - which had different wiring and slightly different mass. I then put that arm in the same arm collar on the second deck and the magic was restored! THe design and dimensions of both arms are I believe identical.

If you then think that the P3 is noisy, try and get it as close as you can to the PU arm, with the shortest possible leadouts from the arm. Then orientate it for the lowest noise - if there is any. THen do exactly the same with the MF unit in place of the P3.

What the P may in fact have done is highlight a previously unsuspected problem elsewhere in your system/setup.
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Old 20th June 2009, 02:26 PM   #535
kffern is offline kffern  Australia
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Quote:
however it seems to me that the comparisons which you have made do not allow for the many variables between the two arm/cartridge/wiring combinations.
I think my mention of later using both arms has confused the issue.

My initial observation with the P3 was made with the same arm/cartridge combination as the MF. The only variable was the phono lead which in the case of the P3 is DH labs BL-1 hardwired to the board and shield connected to earth at the preamp end. The MF was connected with a home made VDH D102-III with shield to ground one end.
I guess that will be my first line of attack - connect the shield at source / disconnect shield or just fit phono plugs ?

I did use both arms with both phono stages with the same observations.

Quote:
You don't describe the type of 'noise'.
The kind of noise you get when you turn up the volume to max with any MC phono stage - a kind of electronic hash is the only way I can describe it.
I will hook it up to another system (Bryston) first and check tomorrow.

Thanks,
Kffern
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Old 22nd June 2009, 02:46 AM   #536
rjm is offline rjm  Japan
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On noise:

Some while ago I posted the noise output of my phonoclone 3.

phonoclone_noise_2496_new_54.wav

Download it and give it a listen. Your noise should sound like this, more or less. The absolute volume will depend on a number of things, so don't worry about that so much as the character of the sound.

Without getting technical, just consider the phonoclone 3 noise on its own, in the following way:

Is it completely silent at normal listening levels?
Is the noise at high volume settings free from hum on buzz?

A correctly working phonoclone 3 should return affirmative to both queries.

Getting (a little) technical, looking at the v8 X-LPS specs, the gain is 60 dB, the S/N is given as >100dB A-weighted. If you've set the phonoclone gain to 60 dB as suggested in the worksheet, the noise levels should be very comparable unless the X-LPS uses a discrete transistor input stage ... which it very well might ... or you've messed up the phonoclone in some way... which is unlikely if it sounds fine and is quiet at normal listening levels.

Got all that?

/R

P.S. the phonoclone 3 output noise is the datasheet value for the OP27, i.e. the only way to do significantly better is to use a lower noise device for the input stage. Changing the power supply / regulation / filtering / bypass / circuit values cannot lower the noise further. You can't do much better than the OP27 when it comes to op-amps, the obvious road is instead to move to discrete transistors, low noise JFETs typically.
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Old 22nd June 2009, 09:16 PM   #537
JBdV is offline JBdV  Netherlands
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I rechecked my noise level again and when I disconnect the headshell the noise is very very low: I can cannot hear any noise from the speakers at 3.5 meter normal distance at a very high volume level that I rarely use at all.(really very loud!!)

However when I reconnect the headshell I just can hear a little noise under the same conditions.

I am using a DL304. Anybody able to explain why connecting the cartridge increases the noise level?

By the way I am also looking for a nice binding post on the PC3 for the earth connection of the cartridge.
Any suggestions?
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Old 23rd June 2009, 12:31 AM   #538
rjm is offline rjm  Japan
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Quote:
Originally posted by JBdV
Anybody able to explain why connecting the cartridge increases the noise level?
The cartridge sets the gain, remember.

Noise is proportional to circuit gain, and the phonoclone circuit gain is the sum of the output stage (30dB) and the input stage, 20log(R2/cartridge Z), normally also 30 dB..

Removing the cartridge makes the first stage gain nominally zero (-inf dB), and the circuit noise falls by 30 dB to be defined by the output stage op-amp only.

/rjm

P.S. Heading off a question that would naturally arise from my previous post on noise: If a transistor input stage would have lower noise, why don't we add a transistor input stage to the phonoclone?

While the input transistor would have a device noise lower than the input transistors of the OP27 or similar, the trick is designing the transistor input stage to have comparable stability, PSRR, CMRR, and distortion characteristics to the op amp. I'm always open to ideas, but I seems to me this would be relatively difficult. I'm not familiar enough with transistor amplifiers to be able to design such a thing, at any rate.
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Old 23rd June 2009, 12:39 PM   #539
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Quote:
By the way I am also looking for a nice binding post on the PC3 for the earth connection of the cartridge.


I bought this



Renato
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Old 23rd June 2009, 01:23 PM   #540
rjm is offline rjm  Japan
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In general a stainless M4 bolt with the body sticking out through the case will do the trick.
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