The Phonoclone and VSPS PCB Help Desk

[rjm]

ran_ph

100uA is the maximum current flowing out of the adj terminal, and you can ignore it for this discussion unless you make R2 extremely large. The max voltage normally seen by C2 is Vout*(R2/(R2+R1) i.e. pretty much all of Vout. The voltage rating on C2 should be equal or greater than Vout. Personally I prefer to be safe and rate all the caps for 25V. You can't use a 6.3V part there, at any rate.

BT

one point I forgot re the VSPS ultra, the input ground can be attached either to the bottom pad of R2 (safest bet) of the original IN- pad. Shouldn't matter which.

-rjm

[rjm]

For the guys who recently got a Phonoclone PCB and a bag of parts in the mail, this is approximately what it should look like when the board is finished.

C1: the 102G cap is 1nF
C2: the 222G is 2.2nF and the 681 is 0.68nF, in parallel they total 2.88 nF.

you can also use 4x 1nF caps for 1nF and 3 nF respectively.

I've sort of settled on Matsushita carbon film resistors for the R5, R6, Riken Ohm for R1 and R2, and Takano carbon composition for R3, R4 and R7, R8. I will probably make a full parts kit available for the next batch order, including the resistors for the first time.

I'm also considering offering 25A bridge rectifiers and silver mica RIAA caps. Though neither of these are cheap, they are the parts I'd use myself, so it only seems fair to add these to the order list.

-Richard

[bearddavid]

Hi There,

As one of the recipients RJM refers to in the post above I thought I'd just mention that my PhonoClone boards and parts arrived last Sunday and that my PhonoClone is now singing sweetly!

It's spread out on the bench as present - I haven't even begun to build a case but the initial results are very encouraging, I think I have a little too much gain with R2 at 1K5 (I'm using an Ortofon Kontrapunkt b 470uV 5OHM internal DC resistance and recommended load 50-200 Ohms) -- any suggestions for an R2 value to give me a little less gain and suite this cartridge ?

Thanks


Dave.

[rjm]

Each time you half the value of R2, you drop 6dB of gain. Perhaps try 680 ohms and adjust further as needed.

/R

[bearddavid]

Thanks Richard,

I'll give it a go and report back.

Dave

[Panelhead]

Richard,
Are there nonmagnetic silver mica caps available in Japan for the RIAA? I plan on using a 3000 nfd I found over here, but it is huge.
The inductance cannot be very low. It is heavier than the circuit board I suspect.

George

[Panelhead]

Got carried away. Did see some 0.1 ufd silver micas locally. The leads look like welding rods.

George

[rjm]

Um, are we talking about the same thing?

The RIAA caps in the Phonoclone are in the order of 1 nanoFarad, and silver mica caps are typically about 10x8x4mm in size, depending on the actual voltage rating and capacitance of course. Only a little larger than film/foil types, in fact.

I believe most brands have tinned copper lead wire, so I dont expect them to be any more magnetic than, say, any other cap you might use.

And old but interesting article on capacitor "sound" : Capacitor Types (of course other factors like inductance may be important, this page just looks at voltage hysteresis)

Polystyrene and polycarbonate appear to be in the same class as silver mica, for what its worth I think any of those would be fine in this application.

/R

[Panelhead]

Originally posted by rjm

Most are real small. The 3000 pf ones I found are pretty large. Those have copper leads.
CDE is the brand most readily available here. Almost all of them have steel leads. So do some of the SAHA, Sang,San, ADM, and others. Sometimes the makings are identical, a few are copper, the majority steel.
It used to be better, maybe 50% were steel, now 90% are. I keep a magnet in the car for capacitor and resistor shopping.
In Japan they may still have a lot of copper leaded ones. The Soshin brand are real nice, but hard to find here. All I have seen have copper leads.
The 0.1 ufd 500v silver mica cap I mentioned is almost three inches long, inch deep, and a half inch thick. Welding rod is a little big, maybe wire coat hanger size leads. A monster size cap. All to get 0.1 ufd.
I guess rather than try the big 3000 pf, I will take your advice and parallel values to make a 2900 pf. This will be lower inductance. And the leads should fit through the circuit board without reaming the holes.
This is an issue with using old parts to build things. The leads were larger on some of the passives 30 - 40 years ago. They will not fit the holes if drilled for modern parts.


George










Um, are we talking about the same thing?

The RIAA caps in the Phonoclone are in the order of 1 nanoFarad, and silver mica caps are typically about 10x8x4mm in size, depending on the actual voltage rating and capacitance of course. Only a little larger than film/foil types, in fact.

I believe most brands have tinned copper lead wire, so I dont expect them to be any more magnetic than, say, any other cap you might use.

And old but interesting article on capacitor "sound" : Capacitor Types (of course other factors like inductance may be important, this page just looks at voltage hysteresis)

Polystyrene and polycarbonate appear to be in the same class as silver mica, for what its worth I think any of those would be fine in this application.

/R

[rjm]

No, really.