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Analog Playback
Topic: Zero Ohm Loading

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Posted by Romy the Cat on 11-13-2011
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I run both of my Reference and Daily tonearms into my “End of Life Phonostage”. As I told I do not know any way to commutate signals at phono level signal and I just re-plug the phono cables at the phonostage’s input. I have no problem with that as I never need my Reference and Daily tonearms at the same time.  The cartridges my Reference and Daily tonearm use Otophone Jubilee and SPU Classic , they are fine to be loaded into the same impedance, I use 73R.

My mono tonearm is a different animal. I use Otophone SPU Mono and even it is MC cartridge but it has essentially MC loading characteristic.  For this Mono tonearm I use a separate phonostage. It is essentially another 834PT with external choke-regulated PS but with no air-caps.  This phonostage loads Otophone SPU Mono to 23K and it goes sound very nice. However, it make signal do not flow over my Expressive Technology transformer that sits in input of “End of Life Phonostage”. 

So, I wonder if it possible somehow to load the cartridges that want to see 47K into 70R and to pass the signal by my reference phonostage? I wonder if I use some kind of good impedance-matching 1:1 little transformer and still to take advantage of the “End of Life Phonostage” capacity.  Does anybody come across any very-small, phono-level impedance-matching transformer? Probably it would be better do not have 1:1 but rather a small step down as the SPU Mono has some excessive gain.

The Cat

Posted by Bud on 11-13-2011
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Knowing your love of transient speed in transformers I think you would do best with a small Lundahl device. They are Per's pride and joy. If you want to skew towards information transform, with a slight "softening" of leading edge performance I can help out.

Posted by Romy the Cat on 11-14-2011
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Yes, I understand Bud that anything might be done but I do not want any DIY solution. To deal with all of the shielding, with grounds… I do not want to be involved into all of it. Also, the transformer shall sit at the RCA exit jacks of phono cable. So, the size and the quality of construction is the key in this hall idea. It needs to be RCA-RCA small adapter or ideally a small transformer on tube-shape core hidden inside the RCA male connector or cable. If something like this already exist and available with 30 days home trial then I wools go for it. I will not do construction of my own devise; I would rather to use my current separate phonostage. The maximum efforts that I would put in this project is to open a UPS box.

Posted by Paul Costa on 11-17-2011
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Romy

Here is something that looks like what you describe,  I do not know if it is the quality or performance you are looking for.  But he does offer a 30 day in home trial. 

http://www.blueberryhillaudio.com/products/analog-evolution.html

Posted by Romy the Cat on 11-17-2011
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Thanks, Paul.

I never saw this company. I did call today to the guy who run it and had longer conversation with him then I intended. Size and shape wise it was exactly what I was looking for. Unfortunately he does not do matching transformer but only step up transformers. I am sure that it would be possible to get him the enclosure and to have someone to wind the transformers but I do not want to commit myself with a custom project with unpredictable results.

BTW, this Blueberry Hill Audio Company has a very elegant in my view idea: a 75dB gain phonocorector built in-line, of cause with external power supply.

http://www.blueberryhillaudio.com/products/analog-evolution-evo-VI.html

The guy who runs the shop told that it has passive correction, interesting, isn’t?  I have no idea how it’s all sound but this open a Pandora box for the concept of phono cable with built in RIAA correction. I like it. The company runner told me something that is kind of strange: he assured me that his phonostage designed in a way that cartridges that run into it do not require any loading matching. I do not know if he not truly understood what he was saying it I am a just a Moron. In my understanding cartridge loading is not the responsibility of correction but the way to damp mechanical resonances in cartridge coil. He however assured me that he knows all of it and his phonostage is made in unique way to deal with it. It is kind of regretful that I have no interest in phono correctors or I would look into it.

Rgs, The Cat.

Posted by Serge on 11-21-2011
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Well, I think it may be something like Tominari of Dynavector used to do with his Phono stage a while ago. He considered the cartridge as a current source which sorts of 'unloads' it.
http://www.dynavector.com/products/amp/e_pha200.html

Posted by Romy the Cat on 11-21-2011
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Ah, the current source!! Serge, you must be right. Ironically I did hear about this method of extracting cartridge signal by Dynavector when I used tier 507 arms but I forgot about it. If am not mistaken the Dynavector is not a phonostage by just voltage extractor that need to driver another MM-level devise with RIAA circuit. As I understand the Blueberry Hill unit is a full phonostage, with current to voltage converter, RIAA and the driving buffer. I never heard those types of correctors; it would be interning to try them. The current source is good, the coil in cartridge become infinitely damped. However, I do not know if the people who design the cartridge and tonearms rely upon the cartridge resonances. I do not think they do, otherwise it might be necessary to have different type of specially cartridge in order to get from the Dynavector/ Blueberry type of phono devises their optimum performance.

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