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Old 14th September 2010, 12:13 PM   #1421
quan is offline quan  Australia
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Hi Richard, i am pleased to report that using the new grounding scheme has worked a treat the hum is fixed.
I have learned a few things- it must be use with shielded interconnect, keep the PC3 away from any nearby transformer otherwise it will hum like crazy.
Once again thank you for your help Richard.
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Old 15th September 2010, 10:19 AM   #1422
rjm is online now rjm  Japan
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That's great!
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Old 21st September 2010, 03:59 PM   #1423
dezzz is offline dezzz  Denmark
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Finally, after spending its teenage years in storage, my PhonoClone RC Limited has been installed in a temporary chassis. This being my first venture into MC, I thought that I would test the RIAA with the already mounted MM Ortofon OM 10 Cartridge, just to see if anything would object. The result is as espected, low fidelity, but what has me concerned is the very low audio level. The phonoclone is hooked up to a GainClone and then a pair of Jordan JX92s. Not a powerful system, but still the output from this RIAA and with the high (4mV) output MM cartridge is very low.

I would have expected the opposite, a very distorted and loud output. Are my expectations plain wrong, or should I hold out with the purchase of a Denon DL-103 until after my inevitable mistakes have been rectified?

Hope you can help!
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Old 23rd September 2010, 12:29 PM   #1424
rjm is online now rjm  Japan
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Your phonoclone is working just fine, the problem is your testing method. The phonoclone circuit does not work with MM cartridges. Not at all. The gain will be too low even for the higher output signal, and the frequency response will not be correct. Remember the impedance of the cartridge is a vital parameter in the operating point of the phonoclone circuit, setting the gain of the first stage as R2/Zcart.
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Last edited by rjm; 23rd September 2010 at 12:36 PM.
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Old 23rd September 2010, 12:39 PM   #1425
dezzz is offline dezzz  Denmark
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Thank you for an expensive reply :0)
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Old 27th September 2010, 08:25 AM   #1426
Jezza56 is offline Jezza56  Australia
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Default VSPS circuit board

Hi, Im an newbie to electronics I want to build the phono amp, have downloaded the single side board and put it up using Eagle, I do not understand the dotted lines going from V++ and V-- to the op amp why are they broken lines

Rergards Jezza
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Old 27th September 2010, 06:14 PM   #1427
dezzz is offline dezzz  Denmark
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Another DL-103 + PhonoClone is born, in this case spun by a Pro-Ject Xpression MkII. After initial problems, with a loud hum resulting from improper isolation of the input RCA from the chassis, the analog voice of Tom Waits is now more haunting than ever. This being my first MC adventure I have nothing relevant to hold either component up against, perhaps only a temporary ignorance, but sofar a blissful of the kind so I am very satisfied. Thank you for putting this kit together RJM!
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Old 28th September 2010, 02:07 AM   #1428
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Richard Murdey
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@Jezza56

Click the "ratsnest" button to fill the polygon shapes used to define the ground plane. In Eagle you can draw traces as lines and as shapes. The shapes are shown as dotted outlines when you first load the .brd file.

@dezzz

Thanks for posting. It's nice to hear from people who don't have problems once in a while! Posting photos to the Phonoclone thread is also encouraged.
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Old 29th September 2010, 06:21 PM   #1429
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I've just finished building this design and using +9V -9V from batteries.
I have had initial problems achieving the correct gain setting on the input stage, but this is almost resolved, barring a little bit of tweaking perhaps. I have a Linn Troika working nicely withb it, which in itself is quite an achievement due to the low output voltage of 0.2mV and low cartridge impedance of about 3.5 ohms.
The typical solution for a Troika is to use a 10:1 step-up transformer before a "normal" MC phono stage.

R2 is currently set at 100 ohms and is quite stable. I am very surprised about the sound. Detailed, but very assured.
The reason I had initial problems, because I read that most users would be Ok using 1.5K. I realise now that this value is critical, also experimented succesfully by increasing R6 marginally to add a tad more weight to the bass.
MY kEF 107s sounded a little bright when using 670 + 47k values. Closer to 750k appears to be a better balance. I know this is not true RIAA, but Kef 107s extend the bass response using the Kef Kube. I am finding that I have a nice balance now without using the Kube ( always been sceptical of the benefits of the Kube )
I initially used a 1.5K value for R2, because I was mistakingly looking at a specification for a Troika and approximating based on the recommended output impedance, duh ! I immediately realised my calculations were considerably out, when hearing huge amounts of volume with my valve amplifier at a low level.
The opamps are dual type BB OPA2134. I bought them for 1.85 + VAT from CPC. All the other parts I had were found from parts bins where I work. I am using an old hard disk caddy for a Seagate disk which was used for our old Sun servers, it has the IEC power connector and switch, just had to remove the insides, a very short mains cable attaches the 9V supplies, so they're external to make for easy charging. A little crude, but for me it is mainly about the music, and this phono stage has saved me a fortune, and the Troika is singing much to my amazement.

So , would like to say a big thank you to RJM and how much your effort is appreciated.

With the Troika being such a low output , I may need to increase the gain a little until I'm getting a more normal sensitivity for my amplifier ( volume control needs to be beyond 12 o'clock )
I think 150 ohm for R2 may be ample. Will definately have to think about a gain switch if using my Dynavetor DV-20X.
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Old 29th September 2010, 11:14 PM   #1430
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Set R2 for 150 ohms. Now, the gain is more than ample for the Troika.
Is the recommendation to avoid values below 500 ohm, a general recommendation that covers the majority of cartridges ? It does not seem appropriate for the Troika.
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