The Phonoclone and VSPS PCB Help Desk

[DARIO1997]

Hi Rjm, i have Denon DL103 with VSPS and transformers Peerles 15095.
Have you comparated the phonoclone 3 with VSPS?
Can I improve the sound if I replace the VSPS/Peerless15095 with Phonoclone-3, or replace only the VSPS with the VSPS 300?
Regards, Mario.

[protos]

Using a 103R and r2 is the standard 1.3k if I remember.
As I said the main problem is hum not rf hash now
I connected another turntable yesterday with a simple 103 and there was huge hum problem.Must have been a combination of other problems because I can't imagine the phono stage is to blame.

[Tham]

Hi Rjm, started my built for my Supex 909 cart with 0.25mV output...what would be the recommended R1 & R2 value (part kit comes with a BOM that had R1 at 47R and R2 at 1K)? I have 47K for R7 now. Is that value critical?

[protos]

I further investigated the source of hum and noise by switching various cmponents around or off.My conclusions:
1.The phonoclone is extremely sensitive to magnetic coupling from adjacent transformers etc.Not the circuit itself which is quiet when disconnected from source but when a cartridge plus cables are connected this becomes a source of noise injection.For example the input (cartridge/cable) picks up the transformer hum from the valve amp in the shelf below(about 35cm).This i tested with a headphone amp connected to the output of the phonoclone so I could see the effect of switching the main amp on or off.The valve amp was not connected at all to the phonoclone.
2.The cables themselves are a source of noise.If one moves the input or output(!) cables around a higher pitched buzz increases or decreases.These cables are not close to any transformer or other equipment .I was surprised how moving the output cables affected noise levels .
3.Trying different ac mains grounding or taking components off the system did not affect hum levels.So it is basically the circuit which when connected to source becomes a sensitive type of antenna for noise including RF which is still around if volume is at very high levels.
Now I wonder if there is something wrong with my circuit or do others experience similar problems? As I said before the phonoclone is playable and most of the the time the hum problems are covered by the surface noise of vinyl and of course the music but it is there when you lift the cartridge.

[northernsky]

Hi,

just added 330pF caps to input IC1. The RF noise is reduced a lot, but there is still some hum.

As in the case of Protos the noise is very low and cannot be heard from the listening position.

When I listen to the music by the CD player the noise is much lower, but a bit is still there. So, I am also going to add the caps to the input of my lm3875 Gainclone.


Renato

[rjm]

Note this post, a really stunning build of the Phonoclone 3. The builder, Insides, says his is completely silent, as is most often the case.

http://www.diyaudio.com/forums/analo...ml#post1966207

Yet a number of you run into hum and noise problems, and even if your Phonoclone might not look quite as nice as his does I believe the responsibility lies with me rather than you. I think you've connected everything correctly, just that something, some oversight on my part in the design, is such that the Phonoclone does not "play nice" on 100% of systems or 100% of situations.

One point, directed at protos: the input cables are not noise sensitive so much as without the cartridge load attached the gain of the first IC stage is zero. The output noise is reduced by 30 dB or so, and whatever ground loops or oscillations present are killed also. To make a proper comparison you should replace the input cables with a dummy input load of 10 ohms or whatever your cartridge impedance is.

Even after 4-5 people reporting these sorts of problems to me I am still no closer to figuring out what the cause is, and why it should only crop up in such rare situations.

The phonoclone should be quiet, with only a soft "rush" of Gaussian noise heard when the volume is turned up. By definition it will be noisier than the CD player, but you should never be able to hear anything at normal listening levels unless your ear is right next to the speaker or the room is fantastically quiet.

My advice is unchanged: attack the problem step by step. remove the input cable and replace with dummy resistors, disconnect one channel from the power supply, change the ground connection from the board to the case from the COM to the IN- instead. Lower the gain by reducing R2. Try a 47 ohm resistor between COM and EARTH in the power supply. Try different phono cables / cartridge.

It's frustrating work. Oscillations and hum will change with every change you make, but this doesn't always mean that the change is directly influencing anything. When oscillating the circuit becomes hypersensitive to external stimuli of any kind. Basically you have to cut things out until it stops and then add things back one at a time until it starts again.

[northernsky]

Hi Rjm,

I am also completely satisfied with the Phonoclone! Thanks to you, the music out from the Denon DL-103 +phonoclone is much more real than by my previous MM cartridge and commercial phono-pre

Renato

[rjm]

Thanks, but with the DL-103 in particular you should not have any trouble at the default settings which makes it all the more frustrating. Though if it is truly very low level it could be something simple like pickup from the turntable motor...

If you learn anything more about the source of the noise or how to silence your phonoclone please let me know.

[protos]

Hmmmm, I just noticed yesterday that one channel is giving all the hum problems.What I mean is that if I leave only the left channel connected there is no hum at all.When the right channel connects the hum starts in both channels.This is very suspicious and points to some internal grounding problem.I will investigate further.

[northernsky]

Hi,

just to complete the information.

My amp is an audiosector gainclone (2 monoblocks). The first tests I did with an ipod cable to the amp (without the ipod).
When I connected a simple passive pre to the amp with shielded cables the rf noise almost disappeared.

The situation now with the phonoclone (and small caps at the IC1 input) is that I hear a very low rf noise with the input selector to CD. The noise slightly increase when I select the phonoclone pre and the phonoclone is turned on.

This is the reason why I think the the noise could vanish when I connect also in the amp the cap to the op-amp input.

One more thing: I have a Rega P3 turntable which has not the ground cable.

Renato