grid current and noise
It might be interesting to measure the correlation coefficient of the tube voltage noise and the current noise.
Running things at a more conventional plate voltage and a significant reverse voltage on the grid would shift things around a bit: the datasheet says, for Vp 150V and Vg -1.5V, "no more than 0.3uA". No typical spec is given. I should get round to translating Dimitri's link---maybe there is more information about grid current there. But if the current is, say, 200nA, for full shot noise and 500mHy at 10kHz, we've still got about 8nV/sq rt Hz.
Still in all, for an MC stepup it's not too shabby for a hollow-state device, at least for noise, and I see low distortion and predominant second for the I source and 100k loading condition.
One thing to consider using a triode like this for MM is the current noise. I measured about 9ua of grid current with the setup. If this has full shot noise (and most of the time things are worse) it will be generating a lot of noise in a high-inductance cartridge, rapidly exceeding the voltage noise. For this example a half-henry inductance looks like |31.4k|, and the current noise density for full shot noise is about 1.7pA/sq rt Hz, hence a voltage noise density of about 53nV/sq rt Hz (!). Even in the midband a 1k resistance is yielding 1.7nV/sq rt Hz.WoW, that seems Very good to me for tubes ! I know it's using a HPF though, but hiss would be nice & lowish, for a MM anyway. I know this about MC's, but that spec would be great for MM's
It might be interesting to measure the correlation coefficient of the tube voltage noise and the current noise.
Running things at a more conventional plate voltage and a significant reverse voltage on the grid would shift things around a bit: the datasheet says, for Vp 150V and Vg -1.5V, "no more than 0.3uA". No typical spec is given. I should get round to translating Dimitri's link---maybe there is more information about grid current there. But if the current is, say, 200nA, for full shot noise and 500mHy at 10kHz, we've still got about 8nV/sq rt Hz.
Still in all, for an MC stepup it's not too shabby for a hollow-state device, at least for noise, and I see low distortion and predominant second for the I source and 100k loading condition.
Hi,
Personally I think this particular valve is all over the place and far too bothersome too tame. Especially so when you want to use some in //.
I'd rather settle for something less exotic yet more easy to keep in line when //ed.
Maybe pentode based as Dimitri suggested (thanks for that Dimitri) or if nothing else I could redesign my own work so it works with EC86s (which I like) iso ECC88s.
Too bad there aren't any twin triodes having notably higher gm than the ECC88.
That Italian design isn't bad but it leaves quite a lot on the table IMHO. Just from looking at it that is.
Pls. don't count on me too much for something other than mere thoughts. As from next month I'll be abroad most of the time so that doesn't help.
Mainly, no internet no nothing much available comms wise.
Cheers,
Personally I think this particular valve is all over the place and far too bothersome too tame. Especially so when you want to use some in //.
I'd rather settle for something less exotic yet more easy to keep in line when //ed.
Maybe pentode based as Dimitri suggested (thanks for that Dimitri) or if nothing else I could redesign my own work so it works with EC86s (which I like) iso ECC88s.
Too bad there aren't any twin triodes having notably higher gm than the ECC88.
That Italian design isn't bad but it leaves quite a lot on the table IMHO. Just from looking at it that is.
Pls. don't count on me too much for something other than mere thoughts. As from next month I'll be abroad most of the time so that doesn't help.
Mainly, no internet no nothing much available comms wise.
Cheers,
I'm inclined to agree---considering the huge parameter spreads, the grid current, and the microphonics.Hi,
Personally I think this particular valve is all over the place and far too bothersome too tame. Especially so when you want to use some in //.
I'd rather settle for something less exotic yet more easy to keep in line when //ed.
Maybe pentode based as Dimitri suggested (thanks for that Dimitri) or if nothing else I could redesign my own work so it works with EC86s (which I like) iso ECC88s.
Too bad there aren't any twin triodes having notably higher gm than the ECC88.
That Italian design isn't bad but it leaves quite a lot on the table IMHO. Just from looking at it that is.
Pls. don't count on me too much for something other than mere thoughts. As from next month I'll be abroad most of the time so that doesn't help.
Mainly, no internet no nothing much available comms wise.
Cheers,
The friend uses an EC86 as the input tube in his MM/MI preamp.
Hi,
Do you happen to know what topology his mm/Mi phono pre uses for this valve and if so if he is happy with the sound of this valve?
It's just a hunch but I feel that by using 5 or 6 or these per channel in // with pentodes as a ccs we could reach a Sn/r of roughly 70 to 75 dB. Not world shattering but good enough for most MCs I hope.
Sand ccs may add a couple of dBs to that but I'd rather go valve full stop.
Maybe even a battery supply although IME I think it's not much of an advantage with a properly designed PS.
Just some thoughts though. Feel free to add as you like. Me, I'm just watching.
Best,
Do you happen to know what topology his mm/Mi phono pre uses for this valve and if so if he is happy with the sound of this valve?
It's just a hunch but I feel that by using 5 or 6 or these per channel in // with pentodes as a ccs we could reach a Sn/r of roughly 70 to 75 dB. Not world shattering but good enough for most MCs I hope.
Sand ccs may add a couple of dBs to that but I'd rather go valve full stop.
Maybe even a battery supply although IME I think it's not much of an advantage with a properly designed PS.
Just some thoughts though. Feel free to add as you like. Me, I'm just watching.
Best,
I haven't seen the schematic (nor heard the preamp) but he is very traditional. He did mention a choke load in the plate of the EC86, and what type of resistor the 270 ohm grid stopper wasHi,
Do you happen to know what topology his mm/Mi phono pre uses for this valve and if so if he is happy with the sound of this valve?
It's just a hunch but I feel that by using 5 or 6 or these per channel in // with pentodes as a ccs we could reach a Sn/r of roughly 70 to 75 dB. Not world shattering but good enough for most MCs I hope.
Sand ccs may add a couple of dBs to that but I'd rather go valve full stop.
Maybe even a battery supply although IME I think it's not much of an advantage with a properly designed PS.
Just some thoughts though. Feel free to add as you like. Me, I'm just watching.
Best,
. I presume that drives a passive interstage network for the EQ.He did mention once that the overall polarity was inverting, when I suggested a sandy pre-pre that was inverting itself, and it is three stages, so we can suppose that all tubes are common-cathode. And I know he listens to advice from one of the Audio Note UK guys about having too many of the same tubes in a system ("sonic signature buildup" concerns) so we know that the EC86 is the only one.
Hi,
Just thought i would bump this thread, has anyone built anything yet?
I have made a start, just need to finish the powersupply, but as usual got a little side tracked
I have opted for a simple configeration i am reasonably familiar with.
CCS fed Glow tube shunt regs, one per channel. Mu follower stages, 2 stage passive eq. Valve line up 6C45pi X2, ECC88, 6n6p. Heater arrangement has been a bit of a nightmare. Construction allows for easy modification which will probably be needed
More details soon, when outboard PS is finished, if it performs at all.
Just thought i would bump this thread, has anyone built anything yet?
I have made a start, just need to finish the powersupply, but as usual got a little side tracked
I have opted for a simple configeration i am reasonably familiar with.
CCS fed Glow tube shunt regs, one per channel. Mu follower stages, 2 stage passive eq. Valve line up 6C45pi X2, ECC88, 6n6p. Heater arrangement has been a bit of a nightmare. Construction allows for easy modification which will probably be needed
More details soon, when outboard PS is finished, if it performs at all.
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Looks very good. In truth I had forgotten about this thread. I've not done anything since I last posted and those 6C45 have sat languishing in my parts cabinet. Work continues to keep me very busy for the moment and I am also in the throws of a small run of expensive DHT linestages and am about 50% done, hope to finish by mid 2017.
I've mostly abandoned the world of SPUs and now rely mostly on a Windfeld on a heavily modified Souther Linear tracker, so the problems of low output MC remain of interest.
I don't know if or when I will look at pursuing an all tube MC again, it does seem like a hybrid cascode might be the better approach noisewise. LSK jfet? Possibly slightly higher output LOMC are another option to consider to ease noise requirements. (Hanah?)
I've mostly abandoned the world of SPUs and now rely mostly on a Windfeld on a heavily modified Souther Linear tracker, so the problems of low output MC remain of interest.
I don't know if or when I will look at pursuing an all tube MC again, it does seem like a hybrid cascode might be the better approach noisewise. LSK jfet? Possibly slightly higher output LOMC are another option to consider to ease noise requirements. (Hanah?)
I can’t believe this thread is 9 year’s old! Well, here goes. For what it’s worth, and if anyone is even remotly still interested I did eventually just this year get the preamp fired up. It’s been sat on the things to finish shelf for 9 years.
I took the plunge and ordered a custom transformer with 4 independent heater windings, and a single HT winding. Outboard PS is a simple crcrc HT supply, with 4 dc heater supply’s connected to the preamp via a 12 core umbilical.
Results? Well I can report the single 6c45p input tube is very surprisingly unearthly quite! That’s with a common or garden Denon DL103, overall gain of this pre is a high 65db with ecc88/6n6p or up to 70db with 2x ecc88s. Out of the 8 x 6c45p I have, all 8 are very quiet, no rushing noises, heater crinkles, popping or microphonics other than a dull dong when provoked with a finger.
I have not tried 4 sections of ecc88 in parallel so I cannot compare, but I have tried 2 sections of ecc88. To my ear and memory a single 6c45 is much quieter and much better behaved, even with very quiet music passages noise is totally unobtrusive, well below record surface noise, what noise there is, with ear close up to the speaker is quite low pitch, possibly due to the RIAA eq.
Of course this thread was about a dedicated mc head amp, the 6c45 has perhaps too much gain for a stand alone head amp, but it does make a great mc front end tube.
Cheers
I took the plunge and ordered a custom transformer with 4 independent heater windings, and a single HT winding. Outboard PS is a simple crcrc HT supply, with 4 dc heater supply’s connected to the preamp via a 12 core umbilical.
Results? Well I can report the single 6c45p input tube is very surprisingly unearthly quite! That’s with a common or garden Denon DL103, overall gain of this pre is a high 65db with ecc88/6n6p or up to 70db with 2x ecc88s. Out of the 8 x 6c45p I have, all 8 are very quiet, no rushing noises, heater crinkles, popping or microphonics other than a dull dong when provoked with a finger.
I have not tried 4 sections of ecc88 in parallel so I cannot compare, but I have tried 2 sections of ecc88. To my ear and memory a single 6c45 is much quieter and much better behaved, even with very quiet music passages noise is totally unobtrusive, well below record surface noise, what noise there is, with ear close up to the speaker is quite low pitch, possibly due to the RIAA eq.
Of course this thread was about a dedicated mc head amp, the 6c45 has perhaps too much gain for a stand alone head amp, but it does make a great mc front end tube.
Cheers
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