OK, I think I got it! Thanks a ton! I don't think I would have considered shorting the colors, but now I know not to, and the reason is clear.
Looks like my gain options are 20.8, 18.4 and 8.6 dB, 18.4 being closest to ideal for my application.
In this preamp is the magnitude of gain (per secondary taps) proportional with noise and distortion?
In this circuit does the transformer act like an active gain device? Do all single gain amplifiers (tube/SS) lacking a transformer invert polarity?
Looks like my gain options are 20.8, 18.4 and 8.6 dB, 18.4 being closest to ideal for my application.
In this preamp is the magnitude of gain (per secondary taps) proportional with noise and distortion?
In this circuit does the transformer act like an active gain device? Do all single gain amplifiers (tube/SS) lacking a transformer invert polarity?
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As long as the load on the secondary is constant (you are going to use a 600 Ohm or a 1k Ohm resistor across the whole secondary, right?) . . .
Then, for a given signal on the grid of the tube that drives the primary,
the noise and distortion is constant.
But if you have to turn up the signal to the grid to get enough signal out of the lower gain tap, then the distortion goes up (because more signal to the grid = more plate signal out of the plate).
And if the noise is from a stage that is before the grid, then when you turn up the signal to the grid, you are turning up the noise to the grid as well.
Those two together would make the signal to noise constant.
(But the additional signal level makes for more distortion).
You will not know for sure the real performance until you put that circuit into your system.
I hope that makes it clear.
Then, for a given signal on the grid of the tube that drives the primary,
the noise and distortion is constant.
But if you have to turn up the signal to the grid to get enough signal out of the lower gain tap, then the distortion goes up (because more signal to the grid = more plate signal out of the plate).
And if the noise is from a stage that is before the grid, then when you turn up the signal to the grid, you are turning up the noise to the grid as well.
Those two together would make the signal to noise constant.
(But the additional signal level makes for more distortion).
You will not know for sure the real performance until you put that circuit into your system.
I hope that makes it clear.
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When received there was no load to ground @ the input nor output. Before I hear the preamp:
Volume wiper > series 470R > single grid input; also volume wiper > 470k (.5W) > ground.
Secondary output: black (RCA body) > 640R (.5W) > orange (RCA pin); also RCA body > star ground.
Thanks for your kind help and consideration. It appears Tom followed a flawed schematic, did not follow a proper schematic, or combination thereof.
Volume wiper > series 470R > single grid input; also volume wiper > 470k (.5W) > ground.
Secondary output: black (RCA body) > 640R (.5W) > orange (RCA pin); also RCA body > star ground.
Thanks for your kind help and consideration. It appears Tom followed a flawed schematic, did not follow a proper schematic, or combination thereof.
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Outside my all custom server/streamer designed by another friend, this 5842 preamp is the most outstanding audio component I have ever owned. I can not overstate how thoroughly the 5842 outperforms my currently produced SS preamp, considered to be among the best SS at any price. I can't say MY SS preamp sounds "colored" in FR, but it just filters out so much of the music. Bass on the 5842 outperforms the SS; amazing. The 5842 has lower noise floor.
I can not thank you all enough for your kind assistance, esp. 6A3sUMMER, who's advice is priceless. My experience with this preamp before updates this week was about 15 years ago; regardless, I got a good taste of it at that time, and I feel absolutely sure it currently outperforms the old circuit by huge margin.
I respectfully request to know what R value to get for a motorized Alps Blue Velvet volume control.
I plan to also move the RCA inputs from the L side to the rear. Is there any known problem with input wires passing under the big PS caps?
Magnequest messaged me personally that he retired. In the rare case someone wanted to replicate my preamp, what OPT would you folks recommend? Price (please specify unit #).
Considering the performance, gain options, and low maintenance cost I am surprised OPT are not more common in tube line preamps. I can not more highly recommend others building this 5842 OPT preamp with tube OPS.
I can not thank you all enough for your kind assistance, esp. 6A3sUMMER, who's advice is priceless. My experience with this preamp before updates this week was about 15 years ago; regardless, I got a good taste of it at that time, and I feel absolutely sure it currently outperforms the old circuit by huge margin.
I respectfully request to know what R value to get for a motorized Alps Blue Velvet volume control.
I plan to also move the RCA inputs from the L side to the rear. Is there any known problem with input wires passing under the big PS caps?
Magnequest messaged me personally that he retired. In the rare case someone wanted to replicate my preamp, what OPT would you folks recommend? Price (please specify unit #).
Considering the performance, gain options, and low maintenance cost I am surprised OPT are not more common in tube line preamps. I can not more highly recommend others building this 5842 OPT preamp with tube OPS.
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I have learned not to trust my own ears alone. My significant other's ears are a lot better than mine. When my SO doesn't like it my SO just gets up and walks away. The SO had similar superlatives for the this 5842 preamp: "feel engaged right away," "feel like you're a participant in the music," "turns on a different part of my brain," "romantic," "like there's a black background behind the performers."
It's seems strange to say a tube preamp sounds more neutral than a very good SS preamp, but that's my story and I'm sticking to it. The 5842/OPT line preamp just let's so much more music through.
I bet this preamp would make a believer out of many persons who have sworn off preamps in favor of DAC direct to power amp.
Here's the circuit I listen to now with 6A3's edits, minus the PS.
It's seems strange to say a tube preamp sounds more neutral than a very good SS preamp, but that's my story and I'm sticking to it. The 5842/OPT line preamp just let's so much more music through.
I bet this preamp would make a believer out of many persons who have sworn off preamps in favor of DAC direct to power amp.
Here's the circuit I listen to now with 6A3's edits, minus the PS.
An externally hosted image should be here but it was not working when we last tested it.
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Hi audiowize,
I would love to jump on a reply to that Q if I just knew what it meant!
I want to swap a motorized Alps Blue Velvet volume control for the 22-detent Alps pot installed now. But beyond that it would take a heck of a lot of convincing for me to modify anything else that potentially changes the audio performance of this puppy!
Ca. 2005 I compared this 5842 sans recent upgrades vs. the then-$6k SRP Jadis JPL, a true work of art, brass face plate, etc. At that time, minus the mods from this last week, the 5842 sounded, IIRC, more grounded and precise, but the Jadis sounded bigger, grander, etc. As th4 5842 is now, I estimate it outperforms a stock JPL throughout. This 5842 gave my system a moderate dose, even with speakers only true 91 dB, of that extreme density and texture of Border Patrol's 300b mono blocks driving 100 dB+ Volti Audio speakers by Greg Roberts.
This 5842/OPT line preamp exceeds my high expectations.
Reviewer Srajan Ebaen's review states that Nagra's tube/SS preamp (ca. $13k) outperforms my SS preamp by only a narrow margin. If that's accurate, and maybe it is, then this 5842/OPT must outperform the Nagra by big margin.
The 5842 doesn't make my SS sound "broken" per se, but much more of a caricature in direct AB: robotic, mechanical, etc.
I would love to jump on a reply to that Q if I just knew what it meant!
I want to swap a motorized Alps Blue Velvet volume control for the 22-detent Alps pot installed now. But beyond that it would take a heck of a lot of convincing for me to modify anything else that potentially changes the audio performance of this puppy!
Ca. 2005 I compared this 5842 sans recent upgrades vs. the then-$6k SRP Jadis JPL, a true work of art, brass face plate, etc. At that time, minus the mods from this last week, the 5842 sounded, IIRC, more grounded and precise, but the Jadis sounded bigger, grander, etc. As th4 5842 is now, I estimate it outperforms a stock JPL throughout. This 5842 gave my system a moderate dose, even with speakers only true 91 dB, of that extreme density and texture of Border Patrol's 300b mono blocks driving 100 dB+ Volti Audio speakers by Greg Roberts.
This 5842/OPT line preamp exceeds my high expectations.
Reviewer Srajan Ebaen's review states that Nagra's tube/SS preamp (ca. $13k) outperforms my SS preamp by only a narrow margin. If that's accurate, and maybe it is, then this 5842/OPT must outperform the Nagra by big margin.
The 5842 doesn't make my SS sound "broken" per se, but much more of a caricature in direct AB: robotic, mechanical, etc.
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