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Old 24th June 2013, 02:03 AM   #71
kevinkr is offline kevinkr  United States
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Confusing..
Volken let me know if you want to replace the file.
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Old 25th June 2013, 07:13 PM   #72
volken is offline volken  Netherlands
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Quote:
Originally Posted by VaNarn View Post
Hi Volken,the file is named Jensen 0.32 no.41,but opened up the description is for a Siemens T42 !
Sorry for the confusing here is the correct file !
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Old 17th July 2013, 02:13 AM   #73
kevinkr is offline kevinkr  United States
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Picked up a NIB SPU Royal N recently on Audiogon and installed it on an 18gm Audio Technica Technihard today. Rather pleased with the result. Despite rumors to the contrary I've not found the fact that it has a Replicant stylus the least bit problematic at least in this head shell. I regard this as a rather significant improvement over my Meister Silver, better tracking, noticeably cleaner sound, more detail, refinement and much less tracing noise. (Noting that the difference between the Meister Silver and a GM E II is about as great.)
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File Type: jpg royal n 3.jpg (188.3 KB, 189 views)
File Type: jpg royal n 4.jpg (170.2 KB, 189 views)
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Old 18th January 2014, 01:51 AM   #74
kevinkr is offline kevinkr  United States
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Default Partridge 973A as MC SUTs

Recently acquired a set of Partridge 973A mu-metal core microphone step ups as I was feeling a bit too cheap to spring for another pair of Lundahl LL1941 for the second TD-124/SME-3009 Series II/SPU GM E II/Muscovite Mini phono stage.

These transformers are 1:16 and the seller claimed a primary dcr of 2 ohms and an impedance of 30 ohms..
The secondary impedance is claimed to be 40K and the dcr of about 250 ohms.

I did not bother measuring the dcr of either winding.

I did rather quickly determine that they sounded grossly inferior to the LL1941 when driven by my Ortofon SPU GM E II with a source impedance of 6 ohms.

A 30 ohm primary impedance reflects to the secondary at 7.7K so I am not at all sure where that 40K ohm figure comes from and is indeed much higher than is reported for the 1:12 version for example. (This raised my suspicions)

Something not quite right here.. I decided to measure the transformers terminated into 40K and a number of lower values to see how these transformers behaved.. The source impedance was 6 ohms, and the drive level just shy of 10mV. (I figured why not as they weren't clipping and the extra snr could not hurt.)

The results were, umm.... interesting.. See below..

The measurements were performed over a frequency range of 20Hz to 90kHz as a swept sine. (The measurement system is flat to better than +/-0.1dB from 20Hz - 90kHz)

The conclusion is that in my system with the low capacitance inputs provided by the muscovite mini that a 20K load across the primary rather than the habitual 47K is advisable.

IMHO these transformers have an overstated reputation for excellence and sonically and in measurements do not live up to the hype - they are billed as punching way above their price class which they do or don't depending on point of view. I had frankly expected better performance based on the hype - something approaching the LL1941 which I did not get. They are pleasant sounding if a bit wooly on the bottom end, they sounded a bit odd, hollow at times which the proper loading seems to have fixed.

Frankly if you are going to spend $1K - $2.4K on an SPU the LL1941 at twice the cost of the 973A is a better long term investment.

Something else I have been strongly reminded of lately is how much input capacitance and cable capacitance can affect the performance of an sut. (think resonances and slew limiting amongst other effects.) Finding the right combinations takes time.
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File Type: png 973A_40K_load_192khz.png (15.2 KB, 139 views)
File Type: png Good_973A_20K_load_192khz.png (15.1 KB, 135 views)
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Old 18th January 2014, 05:12 AM   #75
VaNarn is offline VaNarn  Australia
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Default Testing devices with mu-metal cores.

Devices such as transformers and tape recorder heads should not be subjected to D.C. as low level residual magnetism will effect the l.f. performance.A demagnetizing process under the influence of a slowly decaying A.C. field is needed to correct this problem.
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Old 18th January 2014, 05:30 AM   #76
kevinkr is offline kevinkr  United States
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Yep, they spent 16hrs being degaussed before I even wired them up, and there is no dc present at the input of the pre-amplifier. No idea obviously about their past life.
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Old 18th January 2014, 03:57 PM   #77
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Quote:
Originally Posted by VaNarn View Post
Devices such as transformers and tape recorder heads should not be subjected to D.C. as low
level residual magnetism will effect the l.f. performance.A demagnetizing process under the
influence of a slowly decaying A.C. field is needed to correct this problem.
With a modern DMM not an issue at all. It's just mA or even µA with a proper quality DMM.
Just have the SUT laying around one night or play music for some minutes and all "magnetism"
will have gone completely. Transformer core materials are intended to NOT keep any magnetism.

BTW, old Neumann condenser microphones run with with DC supplied. The transformer "sees"
this DC. Have studio engineers been stupid for decades? While DC in general is not a good thing
for any kind of transformer, we should keep a sense of proportion here.
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Old 18th January 2014, 04:19 PM   #78
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I've certainly not had any issues with residual magnetism in the cores of any transformers I've used. The remanence of materials used in transformer cores should be pretty low. My power amps are all SE and the cores do not have a significant persistent magnetic field around them when off.

The real point of my post was to express my disappointment in the performance of these transformers - had there not been so much hype surrounding them I would have been a lot happier with their performance. There are some who claim that they perform better than devices costing many times more, and IMLE this simply is not the case. They are ok, and probably better than any new at the price I paid, however they are not even close to being in the same league as the LL1931 or 1941 which cost roughly twice as much.. I've not heard the permalloy versions so I can't say whether or not they are comparable. I would say they are considerably better sounding than the UTC A-11 or Cinemag CMQEE 3440A in around the same price range, but neither of these no matter what you do to them IMO is really satisfactory for use with an SPU and even worse with higher impedance cartridges like the DL-103, but again I suppose it is a matter of taste, and the characteristics of the rest of the system..
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Old 18th January 2014, 04:30 PM   #79
limono is offline limono  United States
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Now , I have a dilemma of finding a proper transformer for my CG25i MKII mono cart with 1.5mV ,6 Ohm coil and >100 Ohm preferred load . Something 1:4 would be nice . Any candidates you know off ?
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Old 18th January 2014, 04:39 PM   #80
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The output is high enough you should probably run it direct, just make sure it is properly loaded into 100 ohms.

The only other option I can think of that might work is the Partridge 977 which is 1:6, just make sure it is loaded properly - some experimentation on the bench is recommended, and a pre-amp that can handle 9mV @ 1kHz and up to 90mV @ 20kHz...

Possibly Jack Elliano at Electra-Print could wind you something suitable in a 1:4 step up..
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