Born Again Vinylista Phono Stage

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izzy wizzy
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#106 Re: Born Again Vinylista Phono Stage

Post by izzy wizzy »

From that, I gather, 40dB gain would get you a decent level with the cart you use. Would that be about right? A valve phono, done right will not overload.
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#107 Re: Born Again Vinylista Phono Stage

Post by Cressy Snr »

izzy wizzy wrote: Sat Aug 21, 2021 12:19 pm From that, I gather, 40dB gain would get you a decent level with the cart you use. Would that be about right? A valve phono, done right will not overload.
Yep,
40dB is the minimum I’d accept.
46dB (x200 approx rounding up) would be even better. You are then looking at about 0.7V rms into the power amp for the 3.5mV output of the cartridge.
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#108 Re: Born Again Vinylista Phono Stage

Post by IslandPink »

I reckon I've got about 50dB with my 2x D3a phono, which is slightly over the output of a CD player, so that sounds right.
You're not going to get 46dB from ECC88's without three gain stages, so I think you need to cast the net wider in terms of valves.
I am of the opinion that the first valve of a phono amp is about solving a number of electrical engineering issues, and that the second valve, plus component choices, has more use for adjusting the 'flavour' of the sound.
The first valve if chosen correctly, is all about providing a natural sound through the RIAA, and dynamics and transparency.
The key is to get a decent current ( > 10ma ) and a low output impedance of eg. < 3k. This means you can make your RIAA a fairly low impedance, eg. 25k or 20k, and still have it driven properly without the colourations you get if you overload the driving valve.
This lower impedance for the network then means , in turn, that you -
1. drive small signals through the coupling cap transparently
2. Overcome the Miller capacitance of stage 2 and avoid a HF roll-off, even with a high gain second stage

From there you have options , either another high gain, high current valve, and a direct output ; or a high gain low current valve like ECC83 or 5751, or 6SL7, followed by a cathode follower. In this second case you can choose to split the RIAA as the circuits above.

If you need anything extra, I'm more than happy to buy a few valves for you.
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#109 Re: Born Again Vinylista Phono Stage

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IslandPink wrote: Sat Aug 21, 2021 1:02 pm I reckon I've got about 50dB with my 2x D3a phono, which is slightly over the output of a CD player, so that sounds right.
You're not going to get 46dB from ECC88's without three gain stages, so I think you need to cast the net wider in terms of valves…

…If you need anything extra, I'm more than happy to buy a few valves for you.
First of all thanks Mark for that generous offer. I think I may be OK though: depends on what people think.

So I have :
Half a dozen NOS 12GN7 Philips
Four EF80
four 6SL7GT Sylvania.
Four 6AU6.
Too many 12AT7 to count.

Is there anything in there in terms of triode strapped pentodes that could be pressed into service as the first stage?
Trioded 12GN7 with CCS load has a gain of 39, according to Pete Millett’s tables.
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#110 Re: Born Again Vinylista Phono Stage

Post by IslandPink »

Worth looking at that, yes. You'd need something like ECC83 afterward ( and CF ) to give the gain.
They are high current/transconductance, I don't know how quiet, but likely pretty good, you had some nice quality ones if I remember correctly. Would be good to make an estimate of the Miller cap for triode mode first.
If not OK, then pentode mode, you could probably use a fairly low anode load and still drive a low-Z network, but you'll need to get the G2 supply clean... Nick can help !
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#111 Re: Born Again Vinylista Phono Stage

Post by Cressy Snr »

IslandPink wrote: Sat Aug 21, 2021 2:23 pm Worth looking at that, yes. You'd need something like ECC83 afterward ( and CF ) to give the gain.
They are high current/transconductance, I don't know how quiet, but likely pretty good, you had some nice quality ones if I remember correctly. Would be good to make an estimate of the Miller cap for triode mode first.
If not OK, then pentode mode, you could probably use a fairly low anode load and still drive a low-Z network, but you'll need to get the G2 supply clean... Nick can help !
Cheers Mark. Yes the 12GN7 I have are decent quality. Might be getting somewhere now, and thanks Stephen for laying out the processes and the pitfalls to watch out for. Thanks Nick for helping to narrow my focus. I’d still have been all over the place but for you three.

I’ve got a decent path to go down now, I think.
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#112 Re: Born Again Vinylista Phono Stage

Post by Nick »

The d3a's I was going to send to Paul but he didn't need are still boxed up.
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#113 Re: Born Again Vinylista Phono Stage

Post by Cressy Snr »

Nick you have a PM.
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#114 Re: Born Again Vinylista Phono Stage

Post by izzy wizzy »

If you look at the ton of phono stages out there, what Mark laid out seems to be the destination of many many folk that have trodden this path.

It's very hard to beat a high gm triode/pentode front end driving an all in one EQ with a series first R of about 20k; it's hard to go lower Z easily without sacrificing too much gain. IMHO, the d3a is one of the best at this job. E810F is another. I favour pentode but this is where flavour comes in. A lower Z EQ like this will give you the jump you are after over those with series R 10x higher. Dynamics is why I tend to the pentode over the triode but it's easy peasy to try both. This is where you can also tune for flavour.

I favour 5687 following. No CF required after. Again, there may be others to try here.

There have been many follow this recipe (triode d3a, 5687) but of course this is your machine and everyone is after something slightly different. This combo is super quiet.
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#115 Re: Born Again Vinylista Phono Stage

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Cressy Snr wrote: Sat Aug 21, 2021 6:07 pm Nick you have a PM.
Game on !
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#116 Re: Born Again Vinylista Phono Stage

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Yep, d3a low imp single RIAA to 5687 is a hard act to improve on without inductors IMHO.
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#117 Re: Born Again Vinylista Phono Stage

Post by Cressy Snr »

Nick wrote: Sat Aug 21, 2021 9:29 pm Yep, d3a low imp single RIAA to 5687 is a hard act to improve on without inductors IMHO.
I’ve got a few 5687s. :)
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#118 Re: Born Again Vinylista Phono Stage

Post by IslandPink »

That might not be enough gain, though, if resistor loaded.
C3g would be cool for the second stage. I could spare a couple.
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#119 Re: Born Again Vinylista Phono Stage

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EC88? nah
Last edited by Cressy Snr on Sat Aug 21, 2021 10:32 pm, edited 3 times in total.
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#120 Re: Born Again Vinylista Phono Stage

Post by Cressy Snr »

IslandPink wrote: Sat Aug 21, 2021 10:01 pm That might not be enough gain, though, if resistor loaded.
C3g would be cool for the second stage. I could spare a couple.
That might be good too. I used to have four but they are long since sold.
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