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Schematic for Pro-ject phono box
Schematic for Pro-ject phono box
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Old 4th November 2008, 10:41 AM   #131
raffells is offline raffells  Wales
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Join Date: Dec 2007
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Default update

well , a week after 4562 are installed (thanks folks) the performance has stepped up a gear.Just a hint of hi end sonics now with mostly vishays installed.Its tempted me into further mods...Also needs a smidgeon more gain probably due to lower distortion.
Also cannot optain those 12pf silver mica or polystyrene caps anywhere?..
Turning my attention to the power supplies ,split rail design I have spent some time on the web seeing conflicting technical advice.?
This ranges from,Do not add any smoothing caps down the line nearer to opamps as it can increase noise ? to stick to smaller values of 100nf or even 1 mf.
The other question relates to the single 47mf cap on the input rail.
To Increase value or bypass with 470nf? or both.
Im also looking at the DC filtering prior to wallwart ac power supply. Report if effective later.
Note :I think this is already sounding better that the stock revised models.
Im tempted to adapt my slightly better headphone power supply for this project.

Any comments?..
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Old 19th January 2009, 05:50 PM   #132
raffells is offline raffells  Wales
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Default more help needed?

Well Im pretty happy now that things have run in and Ive transferred it in to a MK2 Box.
A couple of technical questions,
Im still picking up some hum from the wallwart power supply mostly.Any suggestions how to shield it,and should I consider screening the power wire ?..
One probplem is the position of the 16V socket in the new Mk2 case.
Its nearer the input than I would like.
Ive twisted the wires when inside the box but it makes only a tiny difference.
The massive 1.2M resister has been upgraded by some people to 1.32M what is the purpose/advantage. Difficult to get that value.
I did try the 220mf to lower the bass roll off but Ive better quality caps at 100mf and have replaced them.Fairly important sonic effect..
Still could do with some advice re that 47Mf on the power rail.Could I go up to 220? Is it worth bypassing with smaller polyprop,same applies to the 2200ms.
Many thanks If theres anyone still out there..
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Old 24th February 2009, 11:37 PM   #133
vardenis is offline vardenis  Lithuania
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Join Date: Sep 2008
Could moderators enable emailing option for me?
I'd like to mail mzperx.
Thanks in advance
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Old 5th October 2016, 11:45 AM   #134
RogerGustavsson is offline RogerGustavsson  Sweden
diyAudio Member
Join Date: Aug 2004
Location: Huskvarna
Looking for a schematic of the Pro-Ject Phono Box, the version sold today.


Last edited by RogerGustavsson; 5th October 2016 at 11:49 AM.
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