PV10 to PV10A output stage convertion

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rdl1970
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PV10 to PV10A output stage convertion

Post by rdl1970 »

Hallo to everybody.

My idea is to lower the output gain (38 dB) of my PV 10 so that i can rotate my volume pot over 8 o'clock position! :D

I studied the output stages of the PV 10 and PV 10A and realized that the only difference is that the 5751 and 12AT7 tubes of the PV10 has been replaced with two 12AU7 (within a couple resistors and caps).
You can check this in the attached schematics and part list.

Is there anybody that tried and succeded to do this?

Any suggestion?

Thank you in advance.

Regards

Roberto
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PV10 parts list.pdf
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Re: PV10 to PV10A output stage convertion

Post by admin »

Haven't tried it myself as I don't own the unit. However, a simple solution would be to use an RCA plug attenuator. Not sure what the effect it would have on sound quality but it's an easy way to lower the volume on the cable connection side.

I added the files you posted to our master database of schematics/manuals/etc, thanks!
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Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
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Re: PV10 to PV10A output stage convertion

Post by jeffreybehr »

Roberto, your goal is valid--almost all home-amplification systems have too much gain and hence too much overload and noise. C-j writes that the line section of the '10 has 31.5dB of Voltage gain; http://www.conradjohnson.com/It_just_so ... -PV10.html

Concentrate on V4, as V5 is wired as a output-impedance-lowering cathode follower. I'd merely replace the 5751 with a 12AU7. It's safe to do so and will give you an indication that the decreased gain from that switch is worth your time.
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rdl1970
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Re: PV10 to PV10A output stage convertion

Post by rdl1970 »

Hallo Guys.
Thank you very much.
I tried with a line attenuator but they sound quality decreased so much....
I'm about to swap the 5751 with a lower gain tube such as a 12au7.

I'll let you know.
Roberto
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Re: PV10 to PV10A output stage convertion

Post by GEORGE ABRAHAM »

I tried the AU7 switch to the 5751 but the gain reduction was minimal. Looks like resistors may be the only way to go to cut gain.
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Re: PV10 to PV10A output stage convertion

Post by admin »

Have you tried the attenuator on the input? Maybe you get lucky and the sound quality does not take a hit...
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Re: PV10 to PV10A output stage convertion

Post by AnotherJohnson »

This thread from 2016, which was resurrected this week, piqued my interest because of the gain issues.

Looking it up, factory gains from CJ range from 18 dB to 31.5 dB. That’s a huge range, but there were several PV10 versions, and it appears to have been a staple of CJ for more than a decade. By the end of the use of the 10 designation, it appears that they’d even abandoned the balance control.

I used to suggest the Rothwell attenuators to tame gain, but I agree that they are not a good choice in systems that aren’t already hobbled by other shortcomings.

I’m not sure why 31.5 dB seemed like a good idea to anyone … not even “at the time.” What would that match well with? Was there some CJ amp with 20dB of gain that they were designing to?

Impedance matching impacts gain marching. Maybe there was something they were trying to achieve. Does anyone know?
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Re: PV10 to PV10A output stage convertion

Post by AnotherJohnson »

Here’s a review covering the period from the first release to the last (two reviewers- Corey Greenberg and Sam Tellig.)

https://www.stereophile.com/tubepreamps/790/index.html

The reviews focus on the idea that, if you have to have a cheap preamp, this might be a good choice. The build quality and parts choices were a compromise. Stronger recommendation for the first release (Greenberg) than the last (Tellig).

The 6, 9, and 10 never floated my boat. I had the 5, 8, and 11, and loved them all.
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
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Re: PV10 to PV10A output stage convertion

Post by AnotherJohnson »

Here’s the PV10 that interests me.

https://www.investopedia.com/terms/p/pv10.asp

And with this PV10, I want as much gain as possible. 🤣🤣🤣
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
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Re: PV10 to PV10A output stage convertion

Post by goonybird »

I have same issue and used rothwell attenuators. But since bought an ev1 phono and with my audio technica art 9 output 0.5mv, the volume is perfect. I think the issue is more likely the higher output of cd players so that would be the best place for attenuators.
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