The Phonoclone and VSPS PCB Help Desk

[woodturner-fran]

Hi all,


happy days! No. 2 Phonoclone RC Limited is up, running and sounding pretty good!


First to let you know: I connected the PS up initially as per the other phonoclone first ie dual mono, COM posts tied together and connected to TT grounding post. Hummed like crazy - but I was expecting that!

So to solve the issue, all that was required was to connect the grounds of the inputs together. Hum diminished greatly. I actually also connected my tonearm ground wire to this point as well - and I think its a bit more hummy than the last phonoclone. However I'm going to let it run for a little and see. If you are using dual mono, it would seem that you need to tie the input grounds together. If you need to use the tonearm ground then only join it to one of the COM pins.

And where would we be without pics!!







So you can see front and back of the cases, PS layout - I made a small PCB for this for neatness (! your opinion of my neatness might be different than mine! and yes that is a little bit of left over flux, its clean now!), the boards in the second case and an overall view.

[tube 300]

Very nice cases!!
and much space inside.

I have the phono clone also running
the sound is very very good !!
But i must solve the hum problem it is not much but there is also a radio in it.
When i lift the needle from te simply red record i hear the beatles softly singing, let it be
For simplicity i build the phono clone suply in the first place with 1 transformer and do it as Richard advised on his home page
the com together on the groundlug then to the xlr and the rca's isolated.
Advice is welcome
Is this "radio problem" common ?

[woodturner-fran]

I haven't had the RF interference problem, but I notice on this one that when I turn on my tape deck a faint buzz through the phonoclone.


Listening impressions:


Sound is still developing but, after 3 hours of running it has smoothed out nicely. I haven't A-B tested yet, but it would seem that maybe its a little more dynamic, but I don't think the treble it yet quite as clear as the other phonoclone. Soundstage is very good, and very solid placement within that stage. Bass is also excellent and mids, voices float nicely. Very good overall sound, but you know what? - I think it has a bit more to give yet.

I don't know what has been said about burn in before on the phonoclone - and it seems that RJMs own one is probably the one longest built so he may be able to comment more - but from what I'm hearing a few days of patience will be rewarded.

I think it is appropriate to thank RJM here and now for a fantastic kit and design. It really is superb. And that also goes for the VSPS which is about the best MM phonostage I've heard no matter where I've gone.



On dual mono: I wonder if some of the hum issues would be eliminated if the common of both transformers were tied together before the rectifiers. I'll try it soon, but if anyone is doing this dual mono at the moment maybe they could try it? (my transformers were dual secondaries, so I joined them in series to create a centre tap which is my common)

Comments?


Fran

[rjm]

Hi guys,

Fran, Im slightly worried about your decision to go with unshielded, wooden boxes for the case .... fantastic looking as the are. The phonoclone is a high gain preamp, one would not normally attempt to use it outside of a grounded metal enclosure, likewise all the cables .. except the power umbilical .. should technically be shielded as well.

Burn in. I've gone through it more times than I care to remember, and it goes something like this: (assuming powered up 24h, listning to one record or so every day)

Day 1: horrible, congested sound for perhaps one day
Day 2-3: rapid change to the direct opposite, a hyperextended bass and treble... sounds good in a way, but maybe too much, especially the treble which is rather harsh.
Day 4: the extension recedes, to the point where you think its actually sounding rather closed in.
Day 5-14: Gradually opens up again, this time giving way to natural extension and clear sound.

By the third week, its basically 95% of its final sound I think.

tube300,

I had one person report a problem of radio interference to me. We never could solve it .. the OP27 op-amps, being bipolar, are sensitive to RF, this could be fundamenally the problem. Most people, including myself, do not experience the issue so its hard for me to test. If you cant change anything by grounding and shielding or RF beads, you might try replacing the input op-amp with a FET type, OP134 or something like that.

/Richard

[woodturner-fran]

RJM: on the cases - I'll observe, evaluate and report on hum and noise. I'm hoping they'll be OK as WAF is high!

hum is not noticeable right now at normal listening levels. I have a much treasured pair of ESL 57's and I don't drive them to trouser flapping levels, so it might not be an issue for me.


From your burn in description, I think what I'm hearing corresponds to what you have there for day 2.

good things to come!

Fran

[tube 300]

I tryed a lot of things to get the humm lower
the radio is gone i must turn the volume very high to hear it now
so thats ok.
Dont want to use a different opamp i have not a gainclone limited then anymore.
I Think the hum is only wiring things when i connect the the input and output ground together the hum halves but is stil a little to much
the com is also on the casing then .

The sound is realy amazing i am very happy with it

[tube 300]

It are the cables
The cable from te cartridge and the output cable working like antennes i can lay them so that there is no hum but if i move them only a few mm the humm get there and the radio plays louder.
If i unplug the cartridge cable the phono clone is totaly humm free
i can turn op the volume of the preamp totaly and there is absolute no humm is this a good sign or is it always quied then?
pfffffff

[woodturner-fran]

mmmm thats what I saw too.


I'm wondering if the grounding arrangement for dual mono needs to be looked at.

Tube300 - I'm not going to get to it for a few days. Could you maybe rewire yours at the phonoclone case so that the phonoclone is running from just one transformer and see if the hum goes? (ie exactly as per RJMs site?)


Fran

[tube 300]

hi Fran
Yes i did it,i have build the phonoclone exactly as the building instruction
I was started and play still with 1 transformer this must hum free first and then i try the the second one.

If you disconnect the cartridge cable do you have humm then?

[woodturner-fran]

When I was doing this first: yes, if I disconnected even one cartridge cable then the hum was gone...


BUT:

I didn't think I would get time to try this: I tried connecting the COM points together before the rectifiers - result was huge hum and buzz - so this is out.


However, I had a bit of a look again, and with some careful routing of cables my hum is now gone - or at least so small as to not be audible at even loud listening levels.

So my arrangement then: Dual mono - each side fed completely separately through 2 cables through 2 3 way XLR jacks to each board. Inputs and outputs connected as normal. Ground of both inputs (ie RCA sockets) are connected together and also to the TT ground lug. Careful arrangement of my non shielded interconnect results in v. small noise. My tonearm cable is shielded - moving this doesn't affect hum. Interconnect from PC to preamp is non -shielded and here is where my noise is getting in.

I think I will have to shield it too.

My cables are DIY silver with eichmann bullets. An easy way to shield, if your cables are DIY is to use the copper braid from TV coax and connect to ground at one end only. Or leave a fly-wire and connect to the TT ground lug.

Fran