Hi,
And this dinosaur isn't afraid of using gas references for his MC stage either LOL....
Dead quiet too...He,he.....
But, that's not the point. The point is the music, the pleasure of listening to it.
Anyhow, the whole thing has been on my mind for what seem to be decades.
I know what can be done and what can't so don't expect the (musically detached) detail retrieval of a SS design using J-fets or other magical ss devices.
What you should have is a you are there experience. There in the studio, there at the recording venue. Whichever is appropriate.
You get the picture...........
Cheers,
And this dinosaur isn't afraid of using gas references for his MC stage either LOL....
Dead quiet too...He,he.....
But, that's not the point. The point is the music, the pleasure of listening to it.
Anyhow, the whole thing has been on my mind for what seem to be decades.
I know what can be done and what can't so don't expect the (musically detached) detail retrieval of a SS design using J-fets or other magical ss devices.
What you should have is a you are there experience. There in the studio, there at the recording venue. Whichever is appropriate.
You get the picture...........
Cheers,
Careful. I could rope you in to the redesign of my Radford.
As for fun, I took the lid of a preamp PSU I made aged 19 mainly out of bits from an old tek scope I found in the skip at Uni. That was a fun I really should never repeat!
Hi,
How about a mu follower 6C45s in // driving a single 6C45 direct coupled into a WCF driving a passive riaa network which could be dc coupled (a la Jermey Epstein?) into another (high gm wcf) stage driving a pot and cable?
PSU would be fully valve rectified and series regged. I'd use gas voltage reference and cascode error amp as per my usual recipe (a high precision one for the first stages, yes these do exist) filtered by an eleoctrolytic cap followed by polyprops of high Q.
Just a thought though.......
Cheers,
How about a mu follower 6C45s in // driving a single 6C45 direct coupled into a WCF driving a passive riaa network which could be dc coupled (a la Jermey Epstein?) into another (high gm wcf) stage driving a pot and cable?
PSU would be fully valve rectified and series regged. I'd use gas voltage reference and cascode error amp as per my usual recipe (a high precision one for the first stages, yes these do exist) filtered by an eleoctrolytic cap followed by polyprops of high Q.
Just a thought though.......
Cheers,
Hi,
We probably do. I didn't do any maths on this, it was just a basic outline of how I'd go about it.
Nothing carved in stone though.
Well, I always put the highest gain stage first and yes, the mu-follower's good PSSR is an added bonus. Although given the //ed valves it won't be all that great though. OTOH the regulated PS should be sufficient. (I'd think)
The reason I'd use a WCF to drive the RIAA correction is that it allows for a low breakout resistor which should reduce overall noise. Just an idea though.
A possible problem with high gm valves like this is a propensity to oscillate, adding grid stopper will increase noise so, once again, no free lunch.
Any thoughts are most welcomed, guys.
Cheers,
We probably do. I didn't do any maths on this, it was just a basic outline of how I'd go about it.
Nothing carved in stone though.
Well, I always put the highest gain stage first and yes, the mu-follower's good PSSR is an added bonus. Although given the //ed valves it won't be all that great though. OTOH the regulated PS should be sufficient. (I'd think)
The reason I'd use a WCF to drive the RIAA correction is that it allows for a low breakout resistor which should reduce overall noise. Just an idea though.
A possible problem with high gm valves like this is a propensity to oscillate, adding grid stopper will increase noise so, once again, no free lunch.
Any thoughts are most welcomed, guys.
Cheers,
Hi,
Absolutely correct, Piano3.
It's an idea that stuck with me after comparing my own phono preamp (design publicized on this forum, active/passive RIAA, SS rectification) to Dusan Klimo's Merlin pre (passive RIAA and valve rectification) which uses classic resistor loaded gain stages dc coupled into cfs throughout.
Much to my surprise the differences were very small.
My design being ever so slightly more dynamic, more lifelike sounding. Especially on well recorded piano recordings (a la Decca anno early Sixties). Other than that hard to tell the difference really.
Naturally we have to keep in mind that both designs date back from the late Eighties.
Surely we can do better than that now. I know I can but MC cartridges levels demand a far more rigorous approach if you want to do it using valves (and avoid as much sand as possible along the way).
Anyways, thanks for the reply.
Cheers,
Absolutely correct, Piano3.
It's an idea that stuck with me after comparing my own phono preamp (design publicized on this forum, active/passive RIAA, SS rectification) to Dusan Klimo's Merlin pre (passive RIAA and valve rectification) which uses classic resistor loaded gain stages dc coupled into cfs throughout.
Much to my surprise the differences were very small.
My design being ever so slightly more dynamic, more lifelike sounding. Especially on well recorded piano recordings (a la Decca anno early Sixties). Other than that hard to tell the difference really.
Naturally we have to keep in mind that both designs date back from the late Eighties.
Surely we can do better than that now. I know I can but MC cartridges levels demand a far more rigorous approach if you want to do it using valves (and avoid as much sand as possible along the way).
Anyways, thanks for the reply.
Cheers,
Hello..well i am very interested also, but probably have very little knowledge i can add, but i would like to share my limited experience.
It would seem a fully hollow state with no step up transformer MC phono stage is perhaps the holly grail for the few, but perhaps abandoned by the many as unachievable, though i hope it can be done.
My initial interest in a valve MC step up was sparked by an article published in i think Sound Practices magazine in the 80s, TU-BE or not TU-BE. A circuit similar to Franks excellent MC Hammer but using only one ECC88 per channel or 2 parallel sections per channel with Fet CCS as load.
The ECC88 valve was operated at zero grid voltage, with both cathodes grounded, and signal directly into grids with no stoppers, if memory is correct supply voltage was low at around 12V on the anode. I did build it and it sounded very good, though not completely quiet with a 0.3mV cartridge a DL103.
I was using this head amp into a Curcio Daniel, set for mm gain, the combination of Head amp and Daniel in mm gain option was quieter though less transparent than Daniel alone set for mc gain. I used the combo happily for many years, no issues with grid bias current, at least that i was aware off.
The Curcio Daniel used a fairly text book single ECC88 in cascode at the front end with an un bypassed cathode resistor 390R for mm and 100R for MC. I always wondered how it would sound were i to add the Head amps parallel ECC88 to the lower section of the Daniels cascode. That would be 3 parallel ECC88 sections under the one remaining ECC88 section. My hope would be that this arrangement would have the low noise of the Head amp into mm stage, but retain the transparency of a 2 stage phono amp. Of course i never got around to building it, but later found out that is what ARC did in one of there reference phono preamps, Maybe the reference 3 perhaps?
Now we have the Russian valves available. I am told that a pair of 6C45p arranged as a mu follower is quiet enough for MC duty. But i would think that 3 stages of amplification would be required? Thats assuming fully passive RIAA equalisation which i personaly would prefer.
What about starved plate? i read that pushing high current to achieve high gm is not perhaps best for low noise at audio frequency.
One wonders how a valve such as the 6C45p behaves at low currents and low anode voltages?
It would seem a fully hollow state with no step up transformer MC phono stage is perhaps the holly grail for the few, but perhaps abandoned by the many as unachievable, though i hope it can be done.
My initial interest in a valve MC step up was sparked by an article published in i think Sound Practices magazine in the 80s, TU-BE or not TU-BE. A circuit similar to Franks excellent MC Hammer but using only one ECC88 per channel or 2 parallel sections per channel with Fet CCS as load.
The ECC88 valve was operated at zero grid voltage, with both cathodes grounded, and signal directly into grids with no stoppers, if memory is correct supply voltage was low at around 12V on the anode. I did build it and it sounded very good, though not completely quiet with a 0.3mV cartridge a DL103.
I was using this head amp into a Curcio Daniel, set for mm gain, the combination of Head amp and Daniel in mm gain option was quieter though less transparent than Daniel alone set for mc gain. I used the combo happily for many years, no issues with grid bias current, at least that i was aware off.
The Curcio Daniel used a fairly text book single ECC88 in cascode at the front end with an un bypassed cathode resistor 390R for mm and 100R for MC. I always wondered how it would sound were i to add the Head amps parallel ECC88 to the lower section of the Daniels cascode. That would be 3 parallel ECC88 sections under the one remaining ECC88 section. My hope would be that this arrangement would have the low noise of the Head amp into mm stage, but retain the transparency of a 2 stage phono amp. Of course i never got around to building it, but later found out that is what ARC did in one of there reference phono preamps, Maybe the reference 3 perhaps?
Now we have the Russian valves available. I am told that a pair of 6C45p arranged as a mu follower is quiet enough for MC duty. But i would think that 3 stages of amplification would be required? Thats assuming fully passive RIAA equalisation which i personaly would prefer.
What about starved plate? i read that pushing high current to achieve high gm is not perhaps best for low noise at audio frequency.
One wonders how a valve such as the 6C45p behaves at low currents and low anode voltages?
Hi,
Thank you for your contribution.
You know, that circuit should be dead quiet. Certainly so with a cart such as a Denon Dl103.
I've never had any noise issues even with low output MCs at all with the MC head amp driving my own MM preamp.
That said this is not ideal from a playback point of view.
Hence this thread. And yes, I think a 6C45 could do a better job at retrieving more detail from the vinyl record.
I hope Kevin will find the time to sort this valve out. Once that's done we're in business and anything else will be relatively easy to design.
I'm pro passive RIAA provided it is driven properly.
Cheers,
Thank you for your contribution.
You know, that circuit should be dead quiet. Certainly so with a cart such as a Denon Dl103.
I've never had any noise issues even with low output MCs at all with the MC head amp driving my own MM preamp.
That said this is not ideal from a playback point of view.
Hence this thread. And yes, I think a 6C45 could do a better job at retrieving more detail from the vinyl record.
I hope Kevin will find the time to sort this valve out. Once that's done we're in business and anything else will be relatively easy to design.
I'm pro passive RIAA provided it is driven properly.
Cheers,
Hi.
It was certainly usably quiet, but i always felt a dedicated all tube MC phono stage would be a better more transparent solution than an add on head amp.. and doable.
You have probably already seen these curves comparing 6C45p and 6DJ8 at low voltages i hope its ok for me to post them here, and a link to the website.
Nuova pagina 2
Cheers.
It was certainly usably quiet, but i always felt a dedicated all tube MC phono stage would be a better more transparent solution than an add on head amp.. and doable.
You have probably already seen these curves comparing 6C45p and 6DJ8 at low voltages i hope its ok for me to post them here, and a link to the website.
Nuova pagina 2
Cheers.
Hi,
My sincere apologies for not contributing to this thread as I should.
Various health probs, aging brain cells etc I guess.
Nonetheless, I would be delighted to see anyone of you to develop this further as I'm sure it can be done.
Health permitting I will in all modesty give outlines that to my mind may yield best performance.
I suggest thinking //ed mu-followers with a low noise high Rp valve acting as a ccs and so forth.
Think about integrating this into a MC phono stage only, think about how to best drive a passive RIAA stage.WCF cathode followers spring to mind.
Think about the best possible PS using valves, lots of them and how to avoid PS interstage cross talk etc.
Think big and outside the commercially available, etc., etc.
Think like I do and you won't see problems only music at the end of the road.
Everything seems impossible until someone does it. This particular challenge is easy, trust me.
Of course, this is for die hard, valves only, music first idiots like myself...
Best to you all,
My sincere apologies for not contributing to this thread as I should.
Various health probs, aging brain cells etc I guess.
Nonetheless, I would be delighted to see anyone of you to develop this further as I'm sure it can be done.
Health permitting I will in all modesty give outlines that to my mind may yield best performance.
I suggest thinking //ed mu-followers with a low noise high Rp valve acting as a ccs and so forth.
Think about integrating this into a MC phono stage only, think about how to best drive a passive RIAA stage.WCF cathode followers spring to mind.
Think about the best possible PS using valves, lots of them and how to avoid PS interstage cross talk etc.
Think big and outside the commercially available, etc., etc.
Think like I do and you won't see problems only music at the end of the road.
Everything seems impossible until someone does it. This particular challenge is easy, trust me.
Of course, this is for die hard, valves only, music first idiots like myself...
Best to you all,
Hi Frank, just utterly maxed out. My favorite (and only) employer is keeping me really busy these days, that in combination with other factors leaves me exhausted at the end of the day..
I hope to pick it up again eventually.. Not very active in audio at the moment other than listening in the evenings when it is not too hot to run the GM70 amps.
As an aside I did have some odd thoughts about CCS parafeed with some 6S45P-E and some 5:1 amorphous core step downs I just happen have knocking around. Yeah I know we were supposed to get away from transformers.. lol
I hope to pick it up again eventually.. Not very active in audio at the moment other than listening in the evenings when it is not too hot to run the GM70 amps.
As an aside I did have some odd thoughts about CCS parafeed with some 6S45P-E and some 5:1 amorphous core step downs I just happen have knocking around. Yeah I know we were supposed to get away from transformers.. lol
Apparently I am not the only one...
Use a schottky diode for bias and a CCS with a parafeed transformer is what I was thinking as a first step to have a look at the sonic merit of the 6S45P-E..
As posted in a previous post Nuova pagina 2 this is some of the way there. (since frames are used I was not able to directly link, click on 6C45 battery link)
One of the thoughts I had about DL-103 is that its DCR is quite high, in fact in a lot cases it may be the limiting factor for SNR as the johnson noise generated by this resistance is significant. I calculated all of this at some point and was somewhat surprised. My SPUs are all quieter than the last DL-103 I had with output levels in the same region.
Use a schottky diode for bias and a CCS with a parafeed transformer is what I was thinking as a first step to have a look at the sonic merit of the 6S45P-E..
As posted in a previous post Nuova pagina 2 this is some of the way there. (since frames are used I was not able to directly link, click on 6C45 battery link)
One of the thoughts I had about DL-103 is that its DCR is quite high, in fact in a lot cases it may be the limiting factor for SNR as the johnson noise generated by this resistance is significant. I calculated all of this at some point and was somewhat surprised. My SPUs are all quieter than the last DL-103 I had with output levels in the same region.
It should be somewhat quieter in theory, but of course one has to test it to know one way or the other, and I have Frank's syndrome, and too much on my plate.. lol I've got a lot of noisy D3A too, not sure what the story is.. lol
Note that I will no longer design with the D3A since they seem to be getting a bit hard to get, and having only 30 or so I am concerned about finding enough to keep my amps running. (A lot of them will not work properly in these amps)
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