The Phonoclone and VSPS PCB Help Desk

[rjm]

stueyh:

The VSPS, like most phono stages, doesn't have as large an output as a typical CD player. So the volume level will have to be set a little higher to get the same loudness.

If for whatever reason the compensation is unacceptibly large (I'd say more than a quarter turn) then the gain of the VSPS can be increased up to 50dB as you point out. Technically noise and distortion increase somewhat, and bandwidth decreases... but I've gone as high as 55dB and not noticed any audible degradation in sound.

Whether that will be sufficient with the lower output level Denon DL110 depends on your amplifier and speaker sensitivity. I would suggest it should be OK, but as I said at the beginning please understand that you shouldn't expect the volume level to be the same as if/when you listen to CDs.

btw: The Phonoclone, on the other hand, is a bit of a rarity in that it easily produces a 2V line-level output with even the lowest output moving coil.

cjunk:

Happy to hear you fixed the RFI problem. You asked me by email how quiet my Phonoclone was. I would say average to quiet. You should expect about 20dB higher noise floor than the amplifier by itself, just because of the high sensitivity. At normal listening levels I can hear no noise for the speakers. With the volume all the way up there is audible hiss and fustle, but no hum whatsoever.. and no local radio stations!

I tried to point out in the building pages that the circuit common (COM) connects to the phonoclone chassis (and the turntable) but is NOT connected to the power supply chassis which is earthed. Disconnecting COM from the power supply case might help the RFI somewhat.

-Richard

[rjm]

to stueyh :

pics please!

Actually to anyone who is building either the Phonoclone or VSPS, you are most welcome to send photos of complete or in-progress projects to me by email. My yahoo account can accept full-res pictures with ease, up to 10 Mb per email, so don't be shy!

-rjm

[naz]

Could I ask folks what they are using for C4-C7? I'm trying to decide what to go with. I have some Panasonic FC's at 220uF that I was going to use for C8-C11. I'm just looking for some good starting suggestions I guess? I can always upgrade down the road

Naz

[stueyh]

No probs, I'll take some later.

[steenoe]

Could I ask folks what they are using for C4-C7?

Naz, I will use Wima FKP2's as RJM suggested. I might try some other types later on. I used FKP3 in the P2P VSPS I made earlier, and they sounded pretty good.

Steen.

[rjm]

naz was asking about C4-7, the bypass or decoupling capacitors placed on the output of the regulator. This is probably the part with the widest possible variation, as you could go with nothing at all (the regulator and op-amp are so close that even the datasheet 0.1 uF isn't needed) up to, well, I've seen people put up to triple bypass 2200uF+0.1uF+0.001uF in similar situations.

I went with a 100uF electrolytic on the basis that I didn't want to use a (possibly inductive) film cap, and I didn't want to use a big, slow electrolytic. 100uF has a reasonably low impedance over the frequencies of interest in this circuit. (And I could use the same cap for the input and output, a plus.)

Some brave person might want to substitute a tantalum cap, perhaps 4.7 or 10 uF in this position. Or, for amusement, try it first with no bypass caps and then add an electrolytic in the 47-220 uF range, see what if any difference it makes.

In terms of brands you either go with a generic model, a low impedance model, or a audio model. There probably isn't much difference between brands within those three classes. While I favor low impedance types, 47 labs probably uses generic parts.

naz: I'd use those 220uF FC's for all C4-C11 and not give it much further thought until I was ready to really play around with it later.

-R

[naz]

Thanks rjm

I will try using all 220uF FC caps for now and see how it goes, my other idea is to pick up some Elna Cerafine caps and drop those in.. I guess the best idea is just to get something in there so I can start listening to it..

Naz

[Tazzy]

RJM, could you confirm that you recieved an email from me (from dennis AT turnhout DOT net)?

[needlz]

Hey all... I just built my phonoclone and a 12V powersupply. I never used a bridge rectifier before and bought this one (bought 2 but am only using 1) from partsexpress...
http://www.partsexpress.com/pe/showd...number=050-060

I am getting weird DC readings from it's output and am assuming this is because it's not full wave rectification... I am trying to build my powesupply like this...
http://www.geocities.com/rjm003.geo/...phono_dia2.gif

Can I wire 2 of these together to get full rectification or should I just get something like this from mouser?
http://www.mouser.com/index.cfm?hand..._pcodeid=52602

[rjm]

I'm using the exact same 400V/25A bridge rectifier in my Phonoclone now.

You can use one or two. Hooked up correctly - carefully check the package for the terminal identification - they work great. Actually I really like the sound of these parts.

Without more info, I have no idea what you mean by "weird DC readings", but don't forget that until you actually hook it up to the Phonoclone there is no capacitance in the power supply, so the output is just a rectified AC wave, with no smoothing. You can still verify the polarity, though, even if you cant measure the true DC output until you have capacitance and ideally a load there.

-rjm