PV10A Pre Amplifier to PV10B

[goonybird]

Just acquired a late model PV10A (two knob version)
Looking at circuit diagrams for the PV10A and PV10B both appear similar apart from minor component additions/changes eg adding desirable bypass caps
Problem is that the PV10B schematic shows a Zener Diode D27 off V4a (V5a?) but the parts list doesn't give a value other than "Znrdiodeboard"
any idea what value these diodes are ?
many thanks

[admin]

Not sure if this is it, but you can pull a spec sheet off for the D27:

https://www.datasheetarchive.com/zener% ... sheet.html

[goonybird]

Hi Thanks. The D27 is the CJ schematic reference number not the actual diode item number.

[admin]

Oh, that's a bummer. Are there any markings on the actual diode that you can perhaps reference for the values?

https://www.techwalla.com/articles/how- ... odes-value

[goonybird]

On the PV10B Z27 is actually a supplemetary board with multiple diodes and a capacitor for each channel, which looks like it is C18 on schematic.This board replaces both C18 (47pf) and R30 (3.3k) off V4a (V5a) Can anyone help with circuit diagram and values on this board.?Picture off internet of PV10B Z27 board

[admin]

I can't read the values off the picture you posted but capacitor and resistor values are typically easy to read off the components. Color coding on diodes (and resistors) should be able to be obtained by close examination of the components. Are you not able get find these color codes when opening up your unit and looking at the components with a magnifying glass?

[AnotherJohnson]

Where’s Roberto when you need him?

[Big Dog RJ]

He's busy enjoying those fine tunes!
Cheers Robbo mate

[roberto]

Right here..hola amigos,

The color codes are basically for resistors and some European small caps. Tantalum and ceramic caps. Diodes, I guess not. The number stated in their body usually is the guide for their specs. Zener diodes or Schottky diodes are marked with letters and numbers. Resistors are usually on colours.

I will replace the Zener diodes with the same direct replacement. A little more power dissipation will not harm. On semiconductors, like transistors, the collector current, the working collector voltage and the power wattage dissipation a little bit more, will not harm at all.

How can I help?

[roberto]

Seeing the picture 2, the resistors color is not right. I will test all them to see if they are into only 1% of tolerance value. Also, the non plated tube color at the right, I don't know if it is OK. All tubes, as far as I know, should exhibit a silver mercury color inside. Also, a black color of the left tube tells me that is burned...I will replace both tubes...even that the preamp sound (I hate to assume) is (OK?)
The picture No 1, tubes and resistors look unburned...they, physical looking ok, but not the ones at second pic in the bottom.

I do not have the diagrams for the PV10A and PV10B. Write to the CJ service dept to find out more about it.

Gee, I don't know without having both in my test bench to find out what's wrong.

Happy listening!

[roberto]

He's busy enjoying those fine tunes!
Cheers Robbo mate

Woof Woof, big dog RJ,

I am enjoying my system very much. Just add my Linn LP-12 with a Magneplanar Unitrack unipivote tone amp, and a Denon 103R cartridge. I am using a Vincent phono preamp, and soon as I get more funds, I will have a CJ...digital gear sounds great to my ears.

Happy listening!

[Joe Appierto]

"Also, the non plated tube color at the right, I don't know if it is OK. All tubes, as far as I know, should exhibit a silver mercury color inside."

You could very well be right, Roberto. On the other hand it could be an RCA clear top.

[goonybird]

Just to clear some confusion - the pictures are of PV10B off the internet. Not my unit, I have a PV10a which has been serviced before buying by a known quality tube specialist in leicester UK
I have changed the 12At7 which was an unknown chinese make, for a Pinnacle ECC81 (12AT7) NOS I had in my box of old tubes.
I don't need to add the zener board but would have been nice for completeness to bring a PV10a up to full PV10B spec.
So far fast diodes and bypass caps have arrived, and I might leave it at that.

[roberto]

"Also, the non plated tube color at the right, I don't know if it is OK. All tubes, as far as I know, should exhibit a silver mercury color inside."

You could very well be right, Roberto. On the other hand it could be an RCA clear top.

Right on Joe,
All factories might vary the way of build the vacuum tubes...but on the other hand, the silver color inside is a getter, to absorb the oxygen that might be left inside the vacuum tube. I think that I said something not too accurate regarding the silver (barium) color. You might have a tube working good without the silver barium coat.

Goonybird,

Do you have the PV-10B specs on hand? I have a dear friend who owns one PV-10AL (line stage only, no phono pre inside) and works great. Definitively owns the Conrad Johnson signature sound. Looking at the diagram, and the components value, most of them are very are similar, do you think that the PV-10B really sounds better than the PV-10A?

Happy listening!

[goonybird]

I don't know if the PV10b actually sounds better but then look at what mods they (CJ) did. Mainly added small value bypass capacitors to the main coupling capacitors. That is sound engineering sense, so for little cost seems worth it. Also notice tapping the main board produces a lot of resonant noises, one culprit being the 4700mf electrolytic(it rattles!) , so will replace this. Other than that it will be looking for the lowest noise 12AX7's in the phono stage. Looking at JJ gold ECC803s (which apparently are very low noise) hope to lower the valve "rush"

[AnotherJohnson]

My experience with guitar amps is that tube rush can go away with break in.

I’m usually too impatient to wait it out with audio gear. But tubes do change during their first 50 hours or so of use. The change can go in either direction.

[roberto]

What is better? This is one of the most difficult question to answer in our beloved hobby. I had many audio gear in my hands, or should I say ears, and I can say that there are goods from the same company, that I did like better previous models than the newer models, or viceversa. Better is what I do like. What makes my feet to tap the floor along with the rhythm of the music. Better is the stage, size of the instruments, the harmonic texture of them, the timbre and enjoy those wonderful tunes out there. There are so many different parameters in the audio gear, that first, you have to trust your ears, even that they can be fooled. This happens in our immediate memory. The long term memory is the one that we have to use. This long term memory is the one that I do trust.

On the other hand, what sounds different not necessary is better. On Conrad Johnson, what fascinates me is that all models have the magic of CJ. This magic is a truly transparency, with a palpable naturalness that is very difficult to achieve. At this moment in my system, I don't want to do any change. It is just giving to love. I am really enjoying my sound quality.

When the bug is bothering you, this could be because something is telling you to do a change...I love my work. There are so many different audio options and combinations here. I just had the pleasure to listen Avant Garde speaker. Wow, what dynamics. The percussion instruments are fantastic...but the truth is, they are not for me. Also had the pleasure to listen Focal...and Sonus Faber...great sound too.

I must confess, I am a planar speaker guy. This is my liking. Who knows, I might change too.

Happy listening.