You know I think you should write a book.. 😀
On the turntable thing, as imperfect as the TD-124 is I would not trade either of them for anything else. Torque is where it is at.. I like those outmoded idler driven things, and have a 401 too that I need to get working. Working on putting together a gifted 3 phase drive for a Papst Aussenlaufer motor.. Should be very interesting around here over the space of some months. Next week off to Montreal for some immersion in Francophone culture and a good hifi show..
On the turntable thing, as imperfect as the TD-124 is I would not trade either of them for anything else. Torque is where it is at.. I like those outmoded idler driven things, and have a 401 too that I need to get working. Working on putting together a gifted 3 phase drive for a Papst Aussenlaufer motor.. Should be very interesting around here over the space of some months. Next week off to Montreal for some immersion in Francophone culture and a good hifi show..
Hi,
But you fail to see the analogy between the TT and electronic design?
It's not all that different, it's all about energy, damping and reflection.
Ciao, 😉
But you fail to see the analogy between the TT and electronic design?
It's not all that different, it's all about energy, damping and reflection.
Ciao, 😉
As Kevin has heard me say at least once already, my head spins! OK so we're at 1uF for the screen cap, bypassed by 0.1uF (even though the schematic doesn't show the bypass). The higher quality the better, though I'll no doubt start with something less than perfect...
Thanks for all the work, Kevin, and for the input Frank, RajkoM and others.
Thanks for all the work, Kevin, and for the input Frank, RajkoM and others.
Guess I should have said something, yes I definitely see the turntable analogy - the energy and drive of the TD-124 are what drew me to it in the first place. The platter mats I use are a combination of cork, rubber and lead in one case, and in the other cork and two different types of rubber. They seem to provide the sort of damping and reflection control I am looking for. (George Merrill products in both cases, sadly the cork, rubber and lead version is no longer available.) I like Ortofon SPUs.. (Dynamic presentation and great detail particularly higher up the line)
Hi,
Think of the electrically opposite of impedance matching. You want to sink energy and make it hard for it to return to source.
Most of all, know that in order to sink energy the mechanical impedance should be higher, not lower.
Think mechanical diode and pick up any book on it. Think Tiptoes, spikes etc.
After that, I won't need to write my book. it's too obvious.
My mistake, Carl. Thanks to RajkoM for the eye opener and for Kevin to be bravely be the man he is.
Ciao, 😉
Think of the electrically opposite of impedance matching. You want to sink energy and make it hard for it to return to source.
Most of all, know that in order to sink energy the mechanical impedance should be higher, not lower.
Think mechanical diode and pick up any book on it. Think Tiptoes, spikes etc.
After that, I won't need to write my book. it's too obvious.
My mistake, Carl. Thanks to RajkoM for the eye opener and for Kevin to be bravely be the man he is.
Ciao, 😉
Capacitors
It seems that the Russian MGBCH-1 1uF/500V shunted by a 0.22uF PIO (ancient 1999 vintage from Angela Instruments) is about the best combination I have heard for screen bypass duties so far..
I also tried a pair of 8yr old unbypassed Solen Fast Caps 2uF/400V tonight and there was extremely audible/pervasive distortion - it was so bad I didn't even finish the first cut on the album before ripping them out.. I did not check them but I suspect they were leaky and upsetting the screen voltage as I can't think of another likely explanation.. At some point I will check them - I expect something will be obvious.
It seems that the Russian MGBCH-1 1uF/500V shunted by a 0.22uF PIO (ancient 1999 vintage from Angela Instruments) is about the best combination I have heard for screen bypass duties so far..
I also tried a pair of 8yr old unbypassed Solen Fast Caps 2uF/400V tonight and there was extremely audible/pervasive distortion - it was so bad I didn't even finish the first cut on the album before ripping them out.. I did not check them but I suspect they were leaky and upsetting the screen voltage as I can't think of another likely explanation.. At some point I will check them - I expect something will be obvious.
Hi,
Just an observation:
These are both PIO caps AFAIK, right?
Not saying this is actually the case here but PIO caps have a knack for reducing harshness in the upper midrange somehow.
IOW, they're the ideal cap for pentode (or any other stage's odd order harmonic predominance) camouflage.
No idea if you have the kit to actual perform this analysis but a distortion spectrum taken from that stage should show mostly odd order distortion. Something that won't be cancelled out at the output either in a typical preamp.
Somehow I have the impression you already know this and I just hope you won't blame me for pointing it out. In fact I am rather annoyed, embarrassed to point it out. (Hmmm, it sounds more polite, less direct if I'd say it in French somehow) 😀
Shall we do an all triode, Mega Muscovite, fully balanced preamp? Y compris l'etage a bobine mobile, please.....😱
Ciao, 😉
Just an observation:
These are both PIO caps AFAIK, right?
Not saying this is actually the case here but PIO caps have a knack for reducing harshness in the upper midrange somehow.
IOW, they're the ideal cap for pentode (or any other stage's odd order harmonic predominance) camouflage.
No idea if you have the kit to actual perform this analysis but a distortion spectrum taken from that stage should show mostly odd order distortion. Something that won't be cancelled out at the output either in a typical preamp.
Somehow I have the impression you already know this and I just hope you won't blame me for pointing it out. In fact I am rather annoyed, embarrassed to point it out. (Hmmm, it sounds more polite, less direct if I'd say it in French somehow) 😀
Shall we do an all triode, Mega Muscovite, fully balanced preamp? Y compris l'etage a bobine mobile, please.....😱
Ciao, 😉
mine is all triode, fully balanced (10 tubes) and fully Muscovite.......
Frank, have you any idea why PIO might lessen the effect of odd harmonic distortion?
Frank, have you any idea why PIO might lessen the effect of odd harmonic distortion?
Kevin, since you only need 1uF, have you tried K71-4 easily availably cheaply on ebay? I doubt that the nominal 250V rating would be a problem.
Hi,
Just an observation:
These are both PIO caps AFAIK, right?
Not saying this is actually the case here but PIO caps have a knack for reducing harshness in the upper midrange somehow.
IOW, they're the ideal cap for pentode (or any other stage's odd order harmonic predominance) camouflage.
No idea if you have the kit to actual perform this analysis but a distortion spectrum taken from that stage should show mostly odd order distortion. Something that won't be cancelled out at the output either in a typical preamp.
Somehow I have the impression you already know this and I just hope you won't blame me for pointing it out. In fact I am rather annoyed, embarrassed to point it out. (Hmmm, it sounds more polite, less direct if I'd say it in French somehow) 😀
Shall we do an all triode, Mega Muscovite, fully balanced preamp? Y compris l'etage a bobine mobile, please.....😱
Ciao, 😉
Indeed they are both PIO caps..
The second stage is the dominant distortion source in this design.. The most recent measurements show 2nd @ -63dBr and 3rd @ -95dBr this is with a 1kHz fundamental. (Attached)
Measurements of the 6J9P were pretty impressive in terms of distortion, but I neglected to save the graph. It is a well made tube with good internal geometry. The distortion was stupidly low ..
Notice the pentode 1/F noise is all done by 200Hz, interestingly enough a reduction from 15mA of plate current to ~10mA of plate current resulted in a reduction of 1/F noise of 10dB. I was surprised.
I've attached a recent measurement graph with some trepidation as I am definitely having problems with pick up of line frequency harmonics in low level measurements with external devices. I see this to some extent with any device connected to the measurement setup. The source seems to be leakage currents from the computer PSU, but using an isolation transformer does not significantly affect it. Lifting the safety ground on the server is not something I am willing to do, lifting all other grounds does help to a significant extent.. I plan to try some WE REP111C between the sound card (balanced I/O) and Millett sound card interface providing full isolation between the interface and the front end/DUT.
My system is all unbalanced and my Schick tone arm does not support balanced operation, however both of my other arms do, one is a modified SME 3009 Series II, the other a clone of the 3012 Series II/R which I built from a kit and a lot of SME parts.
Perhaps at some point we can do an all balanced Muscovite with MC input stage included. SY has however beat us to the punch with his latest design in Linear Audio..
(Note: I usually forget to reset the scaling when I change ranges output level here is roughly 1.4Vrms relative to 3mV input, and there is a small uncertainty in the input level as well)
Attachments
FFT
I have done two measurements using an attenuator to reduce the 1.1V output of the generator to approximately 6mVrms. One measurement is just the external loopback with no external ground paths deliberate or through the parasitics of other devices to mains or mains ground, the other is with a SINGLE external ground point
I do my measurements with all external grounds lifted in order to eliminate ground loops, and I may try powering the DUT (Muscovite Mini) through an isolation transformer the next time I have it on the bench in order to eliminate parasitic coupling through the mains. (Maybe)
At more typical signal levels this stuff would be in the mud, doing phono stage measurements it is a real problem, and I am still trying to come up with a good solution.
The source of all of the nasties seen is the supply in the PC that does the measurements. For safety reasons I am very adverse to modifying the supply and I am not sure in any event that it would help.
Ferrites helped substantially with HF nasties which were also present. The front end is well shielded and this alone was a rather substantial improvement - I am going to see what other things I can do with grounds to help this issue.
Bear in mind that all of this crap is relative to a fundamental at 6mVrms..
I have done two measurements using an attenuator to reduce the 1.1V output of the generator to approximately 6mVrms. One measurement is just the external loopback with no external ground paths deliberate or through the parasitics of other devices to mains or mains ground, the other is with a SINGLE external ground point
I do my measurements with all external grounds lifted in order to eliminate ground loops, and I may try powering the DUT (Muscovite Mini) through an isolation transformer the next time I have it on the bench in order to eliminate parasitic coupling through the mains. (Maybe)
At more typical signal levels this stuff would be in the mud, doing phono stage measurements it is a real problem, and I am still trying to come up with a good solution.
The source of all of the nasties seen is the supply in the PC that does the measurements. For safety reasons I am very adverse to modifying the supply and I am not sure in any event that it would help.
Ferrites helped substantially with HF nasties which were also present. The front end is well shielded and this alone was a rather substantial improvement - I am going to see what other things I can do with grounds to help this issue.
Bear in mind that all of this crap is relative to a fundamental at 6mVrms..
Attachments
Hi,
That's not really what I wrote even though, subjectively speaking it is what one perceives.
What PIO caps do very well is absorb mechanically induced distortions.
Again subjectively, they seem to pass the audio frequencies rather well (LF) but seem to suppress anything much above it in a rather gentle and gradual slope.
Short of actual DA and DF measurements, it's anybody's guess. That said, it's one of these loose end audio things I guess, i.e measurements not correlating to actual listening tests. One more in the cue....
Ciao,😉
P.S. I'd be more than interested to learn about your balanced phono pre.
Ten valves for the amplifying stages is quite feasible indeed. Of course you don't want to start counting the number of valves I'd add to the PS.....
Not that I want to make either Tim de Paravicini or J.C. Verdier jealous in any way by outnumbering the valve count.
One final word: Power supply.
PPS: Apo's to KevinKR for all the OT lately.
That's not really what I wrote even though, subjectively speaking it is what one perceives.
What PIO caps do very well is absorb mechanically induced distortions.
Again subjectively, they seem to pass the audio frequencies rather well (LF) but seem to suppress anything much above it in a rather gentle and gradual slope.
Short of actual DA and DF measurements, it's anybody's guess. That said, it's one of these loose end audio things I guess, i.e measurements not correlating to actual listening tests. One more in the cue....
Ciao,😉
P.S. I'd be more than interested to learn about your balanced phono pre.
Ten valves for the amplifying stages is quite feasible indeed. Of course you don't want to start counting the number of valves I'd add to the PS.....
Not that I want to make either Tim de Paravicini or J.C. Verdier jealous in any way by outnumbering the valve count.
One final word: Power supply.
PPS: Apo's to KevinKR for all the OT lately.
Hi,
Haven't seen it yet but I guess it's full of sand? (sorry, SY)
I did stress the importance of PS? You did mention the importance of PS isolation for your TT, right? It's either brute force or high precision electronics, correct?
So, what's keeping us from totally isolating our all valved electronics from the vagaries of the mains and by the same token our circuitry from its PS? Nothing but our ignorance and laziness.
Any circuit is only as good as the PS it is attached to.
Here's the deal: I'll do the philosophy, you'll do the math.😀
So, here's my contribution Do everything in life as if it were the last thing you'd do.Take pride in what you do.
Ciao, 😉
Haven't seen it yet but I guess it's full of sand? (sorry, SY)
I did stress the importance of PS? You did mention the importance of PS isolation for your TT, right? It's either brute force or high precision electronics, correct?
So, what's keeping us from totally isolating our all valved electronics from the vagaries of the mains and by the same token our circuitry from its PS? Nothing but our ignorance and laziness.
Any circuit is only as good as the PS it is attached to.
Here's the deal: I'll do the philosophy, you'll do the math.😀
So, here's my contribution Do everything in life as if it were the last thing you'd do.Take pride in what you do.
Ciao, 😉
Last edited:
Just snagged a quad from alexer1 in ukraine, hopefully shipping is not a problem.
As long as there is a tube in the socket the screen voltage will typically be in the range of 140 - 150V so I don't anticipate a problem. The supplies are all tubed and take roughly 30 seconds to come up..
Frank, nothing startling in my balanced phono except that it is variable eq as my big interests are mono LPs and 78s all the way back to the beginning. Therefore the eq filters are split over 2 stages. Input stage differential pairs 6s3p-ev, second stage trioded 6j9p-e and output stage 6n6p. Balanced topology helps with miller capacitance which is proportionally rather high following the upper time constant filter, unavoidable even using the lowest reasonable value series resistor. I would regard the data sheet values of Ca-g as fairytales at audio frequencies. All differential pairs have bjt cascode ccs tails returned to -ve supply via individual regulators. No tubes in PSU; instead, each stage has its own mains x-former and choke input supply with no regulation at all; it is my experience that differential pairs don't really care.
You've heard it before, but I guess I will share the tiresome latest finding on capacitor quest 2014.. 😛
OK, tonight I installed a 250V Erse PulseX 1.0uF cap in place of the Russian PIO/Angela combo I had in there. The highs sound much more extended, quicker almost as if an overhang at the end of each note has been removed, things are more delineated.. More low level and background detail is audible. It is brighter and brasher sounding as well, but imaging is much better.
I guess I would ascribe the change to what I would hope is a measurable improvement in slew rate, but I have not, and have no immediate plans to measure it. The positive change in HF presentation would however point me in that direction.
So for anyone building one of these on the cheap it would seem that the Erse at a couple of bucks each would be both an economical choice and a reasonable performer.
OK, tonight I installed a 250V Erse PulseX 1.0uF cap in place of the Russian PIO/Angela combo I had in there. The highs sound much more extended, quicker almost as if an overhang at the end of each note has been removed, things are more delineated.. More low level and background detail is audible. It is brighter and brasher sounding as well, but imaging is much better.
I guess I would ascribe the change to what I would hope is a measurable improvement in slew rate, but I have not, and have no immediate plans to measure it. The positive change in HF presentation would however point me in that direction.
So for anyone building one of these on the cheap it would seem that the Erse at a couple of bucks each would be both an economical choice and a reasonable performer.
Hi,
That correlates very well with my (subjective) findings.
To me these old style PIO caps are excellent as input caps on a tube rectified PS where they filter and damp HF nasties pretty well.
Other than that, nice "liquid" midrange but a bit muted highs.
Anyway, glad to see you tried it out. 😎
Ciao, 😉
That correlates very well with my (subjective) findings.
To me these old style PIO caps are excellent as input caps on a tube rectified PS where they filter and damp HF nasties pretty well.
Other than that, nice "liquid" midrange but a bit muted highs.
Anyway, glad to see you tried it out. 😎
Ciao, 😉
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