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[FS] 47 Labs - 4712 Phonocube + 4700 Power Supply

S

SamS

pfm Member
This is the High Gain version of this current amplifying phono stage.

In very good condition with a few visible marks, mostly on the PS, which have hopefully been captured in the photos. The white specs in photos on the top of the phono cube are dust.

According to 47 Labs - High Gain is for cartridges with an extremely low output level and/or high internal impedance. Since it is a current amplification device with 0 ohm input impedance, output level is determined by the output amperage of the cartridge (output voltage divided by internal impedance).

More information here:

https://www.sakurasystems.com/reference/phonocube.html

I had purchased this on PF about 7 years ago, and at the time the seller thought he was selling the Standard Gain version. But this is in fact High Gain as confirmed by Jez Arkless who analysed the circuit while fixing a grounding issue.

With my Lyra Kleos SL there is a bit too much gain which meant using an attenuating cable for more usable volume range on my preamp. I used the unit for a few years and it has sat idle since I purchased a more compatible phono stage.

In my system there is a slight hum when the volume is set very loud – noticeable only when volume cranked with nothing playing or between tracks when playing very loud. The hum is possibly a function of the cartridge spec and may ameliorate if a lower output/higher internal impedance cartridge is used.

At the time of purchase I had checked the output amperage on a few cartridges. The Phono Cube was built, as I understand it, with the Miyabi 47 in mind. So I assumed that as the ideal for the Standard Gain version. Some other cartridges I had read about in positive reviews of the Cube, so they were assumed compatible.

Miyabi 47 = 0.3/2 = 0.15 Ideal for 75dB standard gain version
Lyra Lydian Beta = 0.5/4 = 0.125 Claimed to work OK
Lyra Skala = 0.5/5.5 = 0.0909 Claimed to work OK
Benz Micro Ruby = 0.3/38 = 0.0079 No Good - would need 90dB High Gain version
Lyra Clavis DC = 0.25/2 = 0.125 Should be Ok
Lyra Kleos SL = 0.25/2.7 = 0.0926 Should be OK as similar OA to Skala

PM me if you need any assistance in checking possible cartridge compatibility. There is no UK power lead included.

Looking for £1,200 including RMSD in UK, or can collect from Chiswick, London W4 or meet up within reasonable distance.

Photos here:

www.dropbox.com

47 Labs Phono Cube

Shared with Dropbox
www.dropbox.com www.dropbox.com
 
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The grounding issue was sorted by Jez Arkless as stated above. Here is what Jez wrote me at the time:

Sorted. Bizarrely though it wasn't "faulty" as such.... After much analysis and head scratching I found what appears to be a design fault in the grounding regime. Sure enough, after removing an internal ground which theoretically was causing an internal ground loop, the hum went away. I can't believe they all hum like that which then begs the question "was it a mistake 'Friday afternoon' error in manufacture?"... I can see that as it is symmetrical one could turn it round and, maybe after returning from a toilet break/whatever, forget that you had put one ground in and do it again... Anyway theory and my experience told me it shouldn't be grounded like that and when I removed one ground to leave it as I thought it should be it works without hum...

The hum at high volume level is different to the grounding issue and much less intrusive, and not intrusive at all, at normal volume levels. As mentioned above this may be due to cartridge compatabiity as my Kleos SL is ouputing too much amperage for the High Gain version of the Phonocube. Ideally a cartridge with extremely low output level and/or high internal impedance (as per the Benz Micro Ruby from the list above) would be a better match and may ameliorate the hum, but I can't test this unfortunately.

I thought that my preamp might be playing a part in this, so I set it up with an Onix integrated I have knocking about but the result is the same, which leads me back to cartridge compatability. Unfortunately when disconnecting the power leads from the cube to the PS i managed to ham fistedly snap one of the retaining clips. I have added photos to the above link to show this. This has no effect on anything as each connector is dual clipped and the remaining clip keeps everything secure but I thought I should highlight it.

I'll also drop the price to £1,100 including RMSD.
 
Very few people have even heard of these, less have heard them. Not many phonostages get any attention from me these days, but this one always impresses due to its EXCELLENT performance.

The 47 is built on sound principles:
  • Unique equalizing circuitry that amplifies all the voltage the cartridge generates without loss.
  • Complete dual mono structure with each channel in a separate chassis.
  • Rigid and compact aluminium chassis to ensure a quick and smooth release of vibrations.
  • World's smallest number of parts --------- 25 parts per channel
  • World's shortest signal pass length -------------- 44 m/m
  • Powerful voltage regulation with high capacity transformer - 170 VA cut-core transformer +- Individual coils
  • To be upgraded into complete mono structure by adding another Model 4700.
The hum issue/none issue at high volume is most likely due to it being such high gain, but there can be multiple factors that cause hum in vinyl replay. Like how the grounding scheme of the system is working, the proximity of other devices, atmospheric interference...it's endless.

The one i heard, tested and measured returned excellent results. This is one of those devices i recommend to people who want a SS device with excellent performance for sensible money.

GLWS
 
Thanks for your input Bigman.
I was listening to a few needledrops this morning, that I had made back when the Phnocube was in situ, and they were totally captivating.

Sale is on hold as waiting to arrange a dem for an interested buyer.
 
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