A delayed answer
Mr. Curl
I would suggest to use a test record with a single frequency tone recorded at two-three different modulation velocities on different tracks and follow the procedure detailed on the second post of this page:
Turntable Forum • Shure V15Vx + JICO SAS antiskate measurements ± brush
George
Mr. Curl
I would suggest to use a test record with a single frequency tone recorded at two-three different modulation velocities on different tracks and follow the procedure detailed on the second post of this page:
Turntable Forum • Shure V15Vx + JICO SAS antiskate measurements ± brush
George
Wayne, I just re-read your review. I was impressed. You had a lot in this issue to compete with. And then reviewed by Dick Olsher, a tube nut at that. Obviously, you did really well, and perhaps 'listened' to exchanges here more than many.
Engineer to engineer, I would like to ask if you are still really happy with the electronic volume control that you designed?
I have been afraid to try, but Alps refuses to make the quad motor-drive pots that we use for the Para JC-2 preamp, so we are stuck with an alternative sooner or later. Of course the CTC Blowtorch used TKD super-pots, but they are priced out of sight, too! Parasound refuses to have anything to do with them at this point.
It is refreshing to see somebody here directly in competition on this thread. I know you have been here, but I just could not 'place' you, before. Now I know.
Engineer to engineer, I would like to ask if you are still really happy with the electronic volume control that you designed?
I have been afraid to try, but Alps refuses to make the quad motor-drive pots that we use for the Para JC-2 preamp, so we are stuck with an alternative sooner or later. Of course the CTC Blowtorch used TKD super-pots, but they are priced out of sight, too! Parasound refuses to have anything to do with them at this point.
It is refreshing to see somebody here directly in competition on this thread. I know you have been here, but I just could not 'place' you, before. Now I know.
The linked method provides quasi static results (long term “drag”)
For monitoring short term effects (as the effects expected from the cartridge reading dynamic music grooves), you’ll need a TT with two tone arms:
Find a 45rpm single and glue it (using double side tape placed at the label area) over a 33.3 rpm test record that has a single tone track close to the outer radius. Put the combo on the platter. Set TT speed at 33.3 rpm
The cartridge of one arm will read the music from the 45rpm record and the cartridge of the other arm will read the test record track.
For good synchronisation, use only one channel from each cartridge. One for to feed the L Input and the other to feed the R Input of the RIAA preamplifier.
Feed the output of the preamplifier to a sound card and make a stereo recording.
Study/measure the frequency variation of the steady tone (test record groove) on one channel that is caused by the varying modulation (music record) on the other channel.
George
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John, do you have an objection to using motorised stepped attenuators?
A quick search brought up this - http://www.bentaudio.com/DLFILES/STEP-REM-R1.pdf
A quick search brought up this - http://www.bentaudio.com/DLFILES/STEP-REM-R1.pdf
I know some folks like to keep their lp12 as original but it can be improved quite a bit although Linn take the urine with their upgrade prices. Here's a wee something you might like to check out, better than Linn's version and far cheaper too.
Won't be long now ! 10 Sole VII's ready for powder coating..
Won't be long now ! 10 Sole VII's ready for powder coating..
John I still like the NJR part it performs very well is repeatable, reliable and available. That last one is pretty important especially if you do any volume. I remember minimum 1K orders at Threshold for Alps or Noble pots and that was over twenty years ago. The Threshold T2 used a reverse feed 12 bit R2R that worked well but took lots of space and customers could hear relays clicking I suppose fet or CMOS switches could do it but didn't appeal to me at the time.
An interesting shunt was used on the earlier X stuff but used lots of parts and cost $$ at the patent office and that whole thing left me
. I think the compactness and precision trimming help on the NJR. It is just a volume control but as you know all those details matter at the level you work.
An interesting shunt was used on the earlier X stuff but used lots of parts and cost $$ at the patent office and that whole thing left me
. I think the compactness and precision trimming help on the NJR. It is just a volume control but as you know all those details matter at the level you work.
Brilliant, although many of us do not have a TT with >1 tone arm. Have you done these tests? If so, what did you find? I have always suspected that such effects would be swamped by the inherent lack of rotational stability of a typical TT.
Also, isn't that test effectively doubling the drag from the styli? Still, an ingenious method to measure something that is often talked about but seldom measured.
For to answer your question, spend a day to build a simple/cheap/good second arm which can even be mounted without any modifications, outside of your TT plinth: The Altmann DIY Tonearm
Nominal rotational velocity offset and long term rotational instability is a subject of the drive-system/platter-inertia combination. It is easily measured but is not easily acoustically detected or annoying.
Short term rotational instability is difficult to measure but is acoustically noticeable and I see that it is to be attributed (if I exclude the case of a malfunctioning feedback system on DD with a light platter) to the record/mat/platter interface.
This interface is asked to fight with some daemons: Torque transfer, mechanical vibrations, acoustical vibrations (i.e. transmition, isolation, absorption functions to be exercised in various and controlled degrees).
A solution that is optimum for one function is detrimental for the others.
Therefore Scott’s provocative question “How does it do on piano?” applies here too.
With TTs, there is a bunch of mechanical elements –masses/springs/compliances, distributed within the materials or discrete at the interfaces-that have to be functionally balanced in amplitude, frequency, phase.
It is the compounded effect of all these that we perceive as “better on this”, “worse on that”, in the end always “different on some aspects”.
As soon as you start digging, you will realise there is no such a thing as a “typical TT”, nor there is a “best overall” one.
I enjoy the music of vinyls on my (and others) TTs.
I measure for to spot the gross problems and try to attenuate them.
I read, experiment, modify for to get a comprehension of the limit in effectiveness of the applied “solutions”.
George
I agree. My apologies.Sometimes it's difficult to tell in this thread...
I admit my sarcasm needs work.
I also admit that your statement is not entirely inaccurate.
For me:
1. There are no valid repeatable test regimens yet used in industry to determine the full bandwidth ground loop current susceptibility for audio equipment. Whitlock does force pin 1 current, but limits bandwidth and still considers only IR drop, to date never considering the inductive mutual coupling. While I've posted on at least 3 sites a complete descriptor with diagram of the setup, I've seen nobody take it up.
2. There are no valid repeatable test regimens yet for measuring full bandwidth ground loop currents created by audio power equipment.
3. Everybody assumes the output section of a source component is impervious to ground loop currents, which is incorrect. While it may not amplify the coupled signals, it will still present it to the input of the next piece of equipment.
4. The distinction between bench testing of an amplifier using well isolated test gear, and that of amplifier operation in situ using equipment which is not well isolated is lost to most. I've provided test diagrams of that as well over the years.
5. Very few people account for the sensitivity of humans to ITD at the 2 to 5 uSec level, and confuse that entity with an inverted bandwidth of darn near half a Mhz. To produce any semblance of soundstage, ITD and system generated ITD errors must be considered.
So, yah...you're right...there is a "modicum" of truth to your observation. We do not test some entities we are sensitive to, but my remarks cannot be applied in a blanket fashion to all things.
Cheers,
jn
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