The Phonoclone and VSPS PCB Help Desk

[rjm]

Originally posted by rambojj
Sorry, rjm. But OPA134 is a single Op Amp. OPA 2134 is dual.

He said he was using the NE5534. That's a single.

But thanks for pointing out that typo. I don't know how that one slipped by undetected for so long.

[AndrewT]

opa134 is single opamp, opa2134 is dual opamp.

[rjm]

Yes, yes my head knows that. It was my fingers that didn't.

(The 2134 and 134 is easy and obvious, the 5532 and 5534 is something I often have to look up because I keep forgetting which is which...)

[rjm]

The web page is now fixed.

[jermo]

oh balls, thank you! I'm pretty sure I asked for a 5532, the writing on these things is really faint so I didn't bother looking until I posted. This is why I came to the forums I knew the answer was out there!
I'll go get the proper op amp today, put it in there and tell you how it goes.

[jermo]

not that you need to be told because it was pretty obvious what the problem was, but it works!! now I just need to break it in I didn't break in the caps before I put them in so it definitely sounds a bit harsh, thank you so much for this!

[fluffhead]

Finally killed the hum and it sounds great! There was a ground loop, which seemed obvious to you all but took me a while to figure out where. It seems the layout of the circuit (specifically the order the components connect to the ground) is more important then I first thought. Thanks again for the help!

[faxurda]

Here my VSPS Phono .. I love it

Thanks RJM

http://s296.photobucket.com/albums/m...Phono%20Stage/

[rjm]

Originally posted by rambojj
After building the VSPS I am interested in building a Phonoclone.
The RIAA Caps are not the same as the caps from the VSPS. There I used 4 x 1nF per Channel and 732kOhm, 100kOhm + 4,99kOhm and 2,2kOhm for the RIAA. At the Phonoclone there are 2.90nF RIAA (2.2nF||0.68nF). Why?

Sorry for the delay attending to this.

First, while it makes sense to use the Allen Wright fourth time constant in the VSPS, is does not make sense to use it in the Phonoclone, so its not even suggested as an option in the Phonoclone circuit documentation.

Second, the slight differences in resistance and capacitance are just tweaking the response for different tradeoffs in frequency balance and ease of construction.

Option 1. (VSPS parts) 732K 105K 1n 3n

result: slight treble upturn of 0.25 dB. May be audible in the phonoclone, which for reasons beyond the scope of this discussion has a tendency to peak the treble response anyway. I stopped using this version early on and substituted one of the two following alternatives:

Option 2. (Phonoclone "accurate" parts) 750K 110K 1n 2.9n

result: this is near-perfect, if you go to the trouble of measuring and hand selecting selecting the capacitors to 1%. In in a bag of 100 10% silver mica caps though, you may be unlikely to find any 1.00 nF capacitors, as a batch tends to be all low or all high, but within the marked tolerance: the good ones are removed at the factory to be sold to the military or marketed in other non-consumer channels. This has been my experience anyway. 1% mica caps are expensive and hard to find.

comment: a number of people still don't seem to realize that the RIAA accuracy depends on the most outlying value. Improving the resistor from 1% to 0.1% tolerance will make no useful difference if the capacitors are 5% off.

Option 3. (Phonoclone, practical parts) 768K 110K 1n 3n

Rather than messing around a a futile search for 1% 1.00 nF and 2.80 nF caps, this version gives up and just uses 1.0 nF caps throughout. They'll be some variation, and it's worth channel matching the caps, but it probably not worth fussing over it more than that.

P.S. attached zip file contains plots of the phonoclone simulated response for the different options above. The treble and bass cutoffs are also included (assuming 4.7uF C3, 10K load, OP27 and 30dB gain for both stages). It's a pretty accurate simulation of the real world frequency response.

[northernsky]

It works! My VSPS stereo version is now working. I solved the troubles I had last week,
a stupid error of course: I inverted the V+ and V- connection coming from the PSU.

And the sound is very good to me. Just few minutes of listening and the vynil records sound better than by using the phono pre built in in my integrated amp (an expensive commercial YBA Integré).

Thank you to the people who helped me and in particular to rjm for his project. Now I only need to put the board in a case


thank you again

Renato