Hi,
Yeah, wouldn't that be great?
A dedicated MC phono stage would be quite something.....
As for the russiaqn valves, I was thinking about the 6S3/6S4 (what's the difference?) based on it being their equivalent of the EC86 but looking at the USSR sheets it doesn't seem to be a true equivalent or am I missing something?
Cheers,
Yeah, wouldn't that be great?
A dedicated MC phono stage would be quite something.....
As for the russiaqn valves, I was thinking about the 6S3/6S4 (what's the difference?) based on it being their equivalent of the EC86 but looking at the USSR sheets it doesn't seem to be a true equivalent or am I missing something?
Cheers,
Hi,
Yeah, wouldn't that be great?
A dedicated MC phono stage would be quite something.....
As for the russiaqn valves, I was thinking about the 6S3/6S4 (what's the difference?) based on it being their equivalent of the EC86 but looking at the USSR sheets it doesn't seem to be a true equivalent or am I missing something?
Cheers,
I remember thinking about the EC86 when I was designing what ultimately became the Muscovite and was somewhat horrified at the cost.. The 6S3P/6S4P are really somewhat closer to a 5842/417A in most respects. I really like them - no failures, quiet, and long lived. (I like them for other more subjective reasons as well related to their distortion spectrum and I suppose their cost.)
The 6S3P is intended to be the bottom tube in a cascode, and the 6S4P the top, otherwise they are very similar parametrically with some differences in inter-electrode capacitances.. They will operate to several hundred MHz in a properly designed circuit. I settled on one for both positions as the inductance of the internal pinning arrangement is not relevant for audio applications.
I've found a few types are near impossible to source while other types are practically given away. I am a big fan of some less popular Russian types which often have no western analogs and are stellar performers.
Not too bad, but at the upper limit of what I generally want to spend except for tubes like the D3A.. lol I'm not finding a lot of correlation of merit with what the tubes cost - I guess buying Russian tubes has changed the value/performance equation for me.. lol
Edit: My recollection is that the 6S3P is actually significantly more linear and has slightly higher transconductance than the EC86, it was also much cheaper.. (The EC86 seems a bit cheaper now than I remember.)
The EC8010 might be an even better choice if there are any to be had. The D3A is a serious contender here as well except that the supply seems to be drying up..
I was thinking of running several tubes in parallel.. I'm still gravitating towards the 6S3P-EV for its consistency, low noise and low cost.
The 6S45P is worth a serious look..
Edit: My recollection is that the 6S3P is actually significantly more linear and has slightly higher transconductance than the EC86, it was also much cheaper.. (The EC86 seems a bit cheaper now than I remember.)
The EC8010 might be an even better choice if there are any to be had. The D3A is a serious contender here as well except that the supply seems to be drying up..
I was thinking of running several tubes in parallel.. I'm still gravitating towards the 6S3P-EV for its consistency, low noise and low cost.
The 6S45P is worth a serious look..
Hi,
A formidable valve indeed. I've never had the chance to work with it so don't look at me for hands on experience lol.
Curious to see how closely the track each other, if not it may turn out quite an expensive route to take.
I think I can still get D3A at a reasonable price if taken by +/- 100 if there's any interest.
EC8010 will probably be off the charts though......
Cheers,
A formidable valve indeed. I've never had the chance to work with it so don't look at me for hands on experience lol.
Curious to see how closely the track each other, if not it may turn out quite an expensive route to take.
I think I can still get D3A at a reasonable price if taken by +/- 100 if there's any interest.
EC8010 will probably be off the charts though......
Cheers,
Hi,
Given that this is going to be a MC input stage I'm hoping to do better than 0.3microV of noise.
This is still quite a bit higher than the noise from a low input impedance xformer but hopefully n-number of //ed valves and a very stiff PSU will make it possible.
Cheers,
I'm achieving something close to 80dB snr (calculated) with the current transformer based set up and the Muscovite, so I think we need to do better than 0.3uV
Measurements indicate the phono stage is very quiet. (I would have to dig for the number)
The noise floor of my solid state head amp is below the noise floor of my home brew FFT hardware and subjectively is silent.
With an output of 250uV to 300uV @ 5cm/sec I hope we can do better than 0.3uV residual noise. This equates to a snr of potentially only 40dB which is going to be too low I think.
It does seem like paralleling tubes with very low rp and low internal noise mechanisms is the way to go. I'm currently looking at a head amp, but truthfully it probably makes more sense to increase the front end gain by 20dB or so and do it in a dedicated mc phono stage which is what I understand you are talking about.
I'm not sure whether 4 // 6S3P would be sufficiently quiet, but I think the 4 // 6S45P are more likely.
I think the rp has to be extremely low, and 1/f noise is going to be a huge concern..
Hi,
Yes, it is important to have a high gain as early on as possible to lift the signal straight out of the mud.
Another question that remains is whether or not it is worth it to go balanced throughout the phono stage or not. In theory it should be an improvement but is it worth the extra pecuniar expense....
6C45 has been on my mind too and it sure looks the part but...How about grid current etc?
Looking back at my original design using the //ed 6DJ8s and its ccs it suddenly seems hard to improve unless you forget about any existing MM phono preamp and rethink the whole thing from scratch and design a MC only phono stage.
At least that's my opinion.
Hopefully the curves of the 6C45s will tell us more.....
Cheers,
Yes, it is important to have a high gain as early on as possible to lift the signal straight out of the mud.
Another question that remains is whether or not it is worth it to go balanced throughout the phono stage or not. In theory it should be an improvement but is it worth the extra pecuniar expense....
6C45 has been on my mind too and it sure looks the part but...How about grid current etc?
Looking back at my original design using the //ed 6DJ8s and its ccs it suddenly seems hard to improve unless you forget about any existing MM phono preamp and rethink the whole thing from scratch and design a MC only phono stage.
At least that's my opinion.
Hopefully the curves of the 6C45s will tell us more.....
Cheers,
Claimed worst case grid current is <3uA after 3000 hours of use, I would think this is sufficiently low? I've almost always used transformers where this is a non-issue, but I do have a bipolar transistor multi-tan chip based head amp which also has not caused any problems.
Grid current is a consideration, but I believe perhaps mistakenly that a few uA of current is not going to be a problem.
I'm thinking a pair paralleled to start per channel.. I wanted to do a standalone head amp, but I see nothing but problems and poor performance with that approach including managing the rather excessive gain without schemes that could feed damaging warm up transients back to the cartridge or generate additional unwanted noise, or just not sound very good. Guess I am not being very creative here..
Seems like another stupid cascode or a mu-follower might be the way to go.. Perhaps a cascode with dissimilar triodes top and bottom or horrors sand on top.. lol
You know as I think about it a D3A seems like a viable option in triode connection as part of a cascode or mu-follower.
Grid current is a consideration, but I believe perhaps mistakenly that a few uA of current is not going to be a problem.
I'm thinking a pair paralleled to start per channel.. I wanted to do a standalone head amp, but I see nothing but problems and poor performance with that approach including managing the rather excessive gain without schemes that could feed damaging warm up transients back to the cartridge or generate additional unwanted noise, or just not sound very good. Guess I am not being very creative here..
Seems like another stupid cascode or a mu-follower might be the way to go.. Perhaps a cascode with dissimilar triodes top and bottom or horrors sand on top.. lol
You know as I think about it a D3A seems like a viable option in triode connection as part of a cascode or mu-follower.
Hi,
A single mu-follower stage using one 6C45P triode per channel can take an MC cartridge with an output as low as 0.25mV....
The reason I questioned that valve however is that I don't know the grid current generated at Vg close to 0. That and it also doesn't seem to be linear at that bias either.
EC86 and D3A (triode) however should be fine at that operating point. There are other valves too mostly DC amplifiers.
All in all I don't see the problems you seem to see but I may be missing something........
Maybe I should do a write up on my original headamp and explain why I want to do better?
Cheers and mucho respect K. ,
A single mu-follower stage using one 6C45P triode per channel can take an MC cartridge with an output as low as 0.25mV....
The reason I questioned that valve however is that I don't know the grid current generated at Vg close to 0. That and it also doesn't seem to be linear at that bias either.
EC86 and D3A (triode) however should be fine at that operating point. There are other valves too mostly DC amplifiers.
All in all I don't see the problems you seem to see but I may be missing something........
Maybe I should do a write up on my original headamp and explain why I want to do better?
Cheers and mucho respect K. ,
Hi,
Here's a link to the original pre preamp:
http://www.diyaudio.com/forums/analogue-source/252588-mc-head-amp-stage-s-using-tubes.html
IIRC the xformers would be 30VAC ones and not 12.6VAC as shown on the drawing.
Cheers,
Here's a link to the original pre preamp:
http://www.diyaudio.com/forums/analogue-source/252588-mc-head-amp-stage-s-using-tubes.html
IIRC the xformers would be 30VAC ones and not 12.6VAC as shown on the drawing.
Cheers,