The Phonoclone and VSPS PCB Help Desk

[AndrewT]

Originally posted by amt
Ok, I didnt have an appropriate resistors on hand so I popped in some 1000uf caps instead. The DC now reads +/- 19VDC which is great.

Hi,
were you trying to measure the DC from the PSU without fitting any smoothing caps after the rectifiers?

[woodturner-fran]

Yes, the advice is good. Do lower the first gain to 300R. Also, you can put a small cap across some of the terminals of the opamps. I jsut can't remember right now, but if you look up the phonoclone thread and go back through the last 10 pages you will find it.


Fran

EDIT: here is the post:

tube 300:

See this:

http://www.diyaudio.com/forums/show...7413#post667413

He adds a 220pF between pins 2 and 3 of the first op amp stage I think and it solves his problem. Could you try that? I won't get at this for a few days. If it works, I think I will do it to both of mine as well.


Pin out here:

http://www.analog.com/images/Produc...605OP37_fbl.gif


Fran

[amt]

Great! Some insight into the problem.

The Linn cable has been replaced with shielded 4wire Cardas "headphone" interconnect. It didnt seem to make a difference with the hum but did cut the RF noise.

And I did check the PS without the caps. My bad I now see.

So, I will first drop the input impedence to 5 ohms and cut the gain on the first OP27.

Now Im not clear as to the 200pf cap usage. Do they go on only the inputs OR the outputs or both? Can they be connected at the RCA input or do they need to be on the other side of the input resistors, near the pins? And do the caps on the outputs go between the +/- on each RCA jack or between the L/R +?

amt

[woodturner-fran]

The cap is actually soldered to the pins of the opamp itself. I think when I did mine I had the opamp mounted in a socket and I soldered the caps to the legs of the socket rather than the opamp. I think it helped but the biggest help was dropping the gain on the first stage.

I also tried some op37 but it made no difference (thought maybe the 27 were oscillating or something).

As far as I know (and you would want to check this) the cap on the inputs is soldered at the back of the RCA jacks.

Fran


EDIT: this all happened a while back and I can't remember the conversation exactly but I think I reacall that RJM thought that the input phono leads were acting as an antenna and thats how the hum was being picked up. I n my case if you held the leads in your hand and moved them around you could go from no hum to lots of hum. But it was never stable. Soldering the caps to the opamps and reducing the gain really sorted it out.

[rjm]

Phonoclone 3

Phonoclone 3

[wrankin]

Hey gang,

I am looking at building a VSPS using just point-to-point wiring and some perf/project board. I noticed that there are some wonderful examples of these efforts earlier in this thread, but they tend to only show the pretty component side of the board. Does anyone have examples of the underside of the board that show wiring and layout?

If there are examples and I just missed them, a URL or even a post number would be great.

Also if anyone has suggestions about things to watch out for when doing a non-PCB implementation, I would love to hear about it.

Thanks,

-bill

[juluska]

this is a photo of my first attemp to build the vsps. It works but the sound wasn't as good as i wanted, so i did a second pcb in about 60% the space of the first and now the sound is as good as any other preamplifier i've heard.

[johnsonlam]

Sorry for breaking in ...

For my humble opinion, you need to change the output coupling capacitors to "highest grade as possible" in order to have a good sound.

Also try AD828 for fast, better treble sound.

That my VSPS, sounds good ("approved" by many friends).

http://picasaweb.google.com.hk/lh/ph...s_TPpeLBRVO9Aw

[rjm]

The AD828 brings some interesting traits to the table. The only thing to watch out for is the bandwidth will be about 10 times higher than the OPA2134 etc. More rigorous bypassing - a small low inductance capacitor placed directly next to the power pins - may be required for stability.

Output caps: whatever works for you. Suggest downsizing to 1 uF or 2.2 uF for the really expensive ones and save a little money.

For your viewing pleasure: the beta version of the Phonoclone 3 boards, currently being made by the Christmas elves at Olimex. I have a couple of spares if anyone is feeling adventurous and can't wait for me to build one and report the results. $40 for a pair of double sided boards.

[Tandren]

Hi Richard,

If still possible I like to have one pair of the new Phonoclone 3 boards. I have all the components for the Phonoclone 2 apart from the 10V regulators which seems hard to find in Sweden. The new version helps me get around this problem. Payment via Paypal?

Cheers,
Thomas