I think that fdegrove has posted a design; I can't remember if it used a 6SN7 or the premium 5692 equivalent. Do a search with "fdegrove" as author and either 6SN7 or 5692 as the search term.
Ah, phooey, I thought he used a 6SN7! Sorry for the wild goose chase. But it's a really good circuit and one you ought to consider.
What do you say about a simple triode with a CCS for anode load?
A lot of diyers out there have done projects like this.
With 6SN7,5687,ECC99,etc
You are doing some experiments with 5692,too.
I like very much this idea.But which tube to choose?
12B4A is a very linear tube and it sounds very nice.
But it's too microphonic!
A lot of diyers out there have done projects like this.
With 6SN7,5687,ECC99,etc
You are doing some experiments with 5692,too.
I like very much this idea.But which tube to choose?
12B4A is a very linear tube and it sounds very nice.
But it's too microphonic!
The first problem is output impedance. The tube isn't just loaded by the CCS, it's loaded by the cable capacitance and the input impedance of the power amp. So you end up needing a buffer, thus my recommendation for a cathode follower or a fancier circuit like Frank's.
The second problem is gain. With a CCS load, the preamp will have too much.
The second problem is gain. With a CCS load, the preamp will have too much.
hmmm...
I don't need enough gain.That's why I used 12B4A.
What do you say to use the same topology as my previous preamp was but with another not so microphonic tube?
I don't need enough gain.That's why I used 12B4A.
With a CCS load output impedance increases?
What do you say to use the same topology as my previous preamp was but with another not so microphonic tube?
It's possible, but why not just use a proven design like Frank's? Getting a high current tube to work in your circuit can be a challenge and it will always be compromised by the relatively large plate resistance of a tube. In theory, you could use an enormous regulator tube like a 6336, but that's a really tough solution to an easy problem.
Yes, using a CS load will raise the output impedance. If the cathode is bypassed to ground, the source impedance will be equal to the plate resistance at the chosen operating point. In a follower, that's knocked down to something on the order of a few hundred ohms or less.
Yes, using a CS load will raise the output impedance. If the cathode is bypassed to ground, the source impedance will be equal to the plate resistance at the chosen operating point. In a follower, that's knocked down to something on the order of a few hundred ohms or less.
SY said:
Yeah. And better still, hitch it up to this, using a CineMag CMLI-15/15B and a 10k PEC log pot. 🙂
An externally hosted image should be here but it was not working when we last tested it.
se
Steve Eddy said:
How do you like the Cinemag products? They seem like a reasonably priced alternative to the Lundahls of the world. I just wish they made some of their products center-tapped.
Interesting idea.
How much do the CineMag CMLI-15/15B or the JT11-P1 cost?
I was planning in the future to build one with the S&B TX103!
But I can't afford so much money right now. 🙁
A tube preamp costs much more lower than two S&Bs.
How much do the CineMag CMLI-15/15B or the JT11-P1 cost?
I was planning in the future to build one with the S&B TX103!
But I can't afford so much money right now. 🙁
A tube preamp costs much more lower than two S&Bs.
Hi,
Errrr....Yes he did...
Only that's another circuit I posted...somewhere.
If it's the SRPP using 6SN7s then it suffer from low PSRR just like the WCF Resident (re)posted here.
The SRPP has a gain of roughly mu/2 and like to see a low fixed impedance to work with.
The WCF suffers a mild insertion loss (gain = 0.97) but can drive just about any real life load.
The two combined can work very well together and with some small tricks would make for what John Broskie calls an "Aikido" stage.
The main pros are high linearity, enough gain for those convinced they need a preamp with gain and thanks to the WCF a low Zout to boot.
On the contra side there's of course some added complexity and the added expense of feeding yet another tube. No free lunch there.
Then there's the tried and tested 6SN7 schem using a grounded cathode for gain coupled to a CF for low Zout, a recipe almost as old as tubes themselves I believe....
Is this the one you had in mind, SY?
Cheers,😉
Plugging Cinemag iron now, Steve? Howdy BTW...
Errrr....Yes he did...
Only that's another circuit I posted...somewhere.
If it's the SRPP using 6SN7s then it suffer from low PSRR just like the WCF Resident (re)posted here.
The SRPP has a gain of roughly mu/2 and like to see a low fixed impedance to work with.
The WCF suffers a mild insertion loss (gain = 0.97) but can drive just about any real life load.
The two combined can work very well together and with some small tricks would make for what John Broskie calls an "Aikido" stage.
The main pros are high linearity, enough gain for those convinced they need a preamp with gain and thanks to the WCF a low Zout to boot.
On the contra side there's of course some added complexity and the added expense of feeding yet another tube. No free lunch there.
Then there's the tried and tested 6SN7 schem using a grounded cathode for gain coupled to a CF for low Zout, a recipe almost as old as tubes themselves I believe....
Is this the one you had in mind, SY?
Cheers,😉
Plugging Cinemag iron now, Steve? Howdy BTW...
Attachments
Hi Frank,
I'm reading your ultimate preamp,right now!
Damn 30 pages are a lot of pages for a thread.
I thing 6SN7 schem using a grounded cathode coupled to a CF is the simplest and easiest design I can build,right?
I don't know why but I don't like CF!
I thing I have read somewhere that CF stages don't sound nice.
Maybe that's why I don't like them.
What do you say on this? 🙁
I'm reading your ultimate preamp,right now!
Damn 30 pages are a lot of pages for a thread.
I thing 6SN7 schem using a grounded cathode coupled to a CF is the simplest and easiest design I can build,right?
I don't know why but I don't like CF!
I thing I have read somewhere that CF stages don't sound nice.
Maybe that's why I don't like them.
What do you say on this? 🙁
Hi,
He, he...You have Jam to blame for that....
Anyway, no need to read all those pages.
Most of it is about a phonopreamp, what's left deals with the WCF as a buffer linestage.
Most of it stems from prejudice, the remainder founded on the fact that there are some "classic" designs out there with really lousy linestages using half-*ssed CFs...
Add the fact that a CF is about 100% local feedback and just about everyone has read "somewhere" that feedback is Dr.Evil in person and you get the picture.
IMHO, if you don't need a CF then don't use it....But that goes for just about anything really.
You can't go wrong by keeping things as simple as need be.
So, to answer your question more ad rem:
If you want something that could be up with the best and don't need to drive your neighbour's silly snob-amp then my vote would go for Brett's 12B4A preamp assuming you want some gain and have (or are going to) an amp with a Zin ranging from 50 to 100K.
No 500pF/m interconnects spanning 10m runs either.
12B4As are plentyful and cheap so if you need to put 8 aside out of a dozen because of microphony (I still have to find the first microphonic 12B4 from my NOS stash) then you'll probably still cheaper of then having to buy NOS 5692s anyway....
If you want the low Zout and some gain then the 6SN7 comes to mind.
Everyone who's ever built it was pleasantly surprised but if you're on a budget I'd advise to build in the possibility to use the 12V heater version as well.
That should at least cover the octal varieties nicely.
Another option is to use the loctal based 7N7 but I have no experience with those.
Plenty of tubes to pick from if you stick with what's electrically equivalent, from noval through loctal. No sweat.
If no gain is required and you want to concentrate the budget around a high quality volumecontrol and still want to be able to drive difficult loads then the WCF buffered volctrl may be your thing.
Of the three discussed so far, it does like a very clean, stiff PS as it's PSRR is rather abismal.
Note that all circuits usually benefit greatly from a decent PS as this has far more impact than people seem willing to admit.
Needless to say possibilities are endless.
Cheers, 😉
He, he...You have Jam to blame for that....
Anyway, no need to read all those pages.
Most of it is about a phonopreamp, what's left deals with the WCF as a buffer linestage.
Most of it stems from prejudice, the remainder founded on the fact that there are some "classic" designs out there with really lousy linestages using half-*ssed CFs...
Add the fact that a CF is about 100% local feedback and just about everyone has read "somewhere" that feedback is Dr.Evil in person and you get the picture.
IMHO, if you don't need a CF then don't use it....But that goes for just about anything really.
You can't go wrong by keeping things as simple as need be.
So, to answer your question more ad rem:
If you want something that could be up with the best and don't need to drive your neighbour's silly snob-amp then my vote would go for Brett's 12B4A preamp assuming you want some gain and have (or are going to) an amp with a Zin ranging from 50 to 100K.
No 500pF/m interconnects spanning 10m runs either.
12B4As are plentyful and cheap so if you need to put 8 aside out of a dozen because of microphony (I still have to find the first microphonic 12B4 from my NOS stash) then you'll probably still cheaper of then having to buy NOS 5692s anyway....
If you want the low Zout and some gain then the 6SN7 comes to mind.
Everyone who's ever built it was pleasantly surprised but if you're on a budget I'd advise to build in the possibility to use the 12V heater version as well.
That should at least cover the octal varieties nicely.
Another option is to use the loctal based 7N7 but I have no experience with those.
Plenty of tubes to pick from if you stick with what's electrically equivalent, from noval through loctal. No sweat.
If no gain is required and you want to concentrate the budget around a high quality volumecontrol and still want to be able to drive difficult loads then the WCF buffered volctrl may be your thing.
Of the three discussed so far, it does like a very clean, stiff PS as it's PSRR is rather abismal.
Note that all circuits usually benefit greatly from a decent PS as this has far more impact than people seem willing to admit.
Needless to say possibilities are endless.
Cheers, 😉
Hi,
To my mind the easiest and most elegant way to go about it is to use what I nickname the "see-saw" circuit.
It offers the advantage of AC current balance, something worth keeping in mind if you want to find out why some CFs don't sound too good when sitting on a common rail supply.
Cheers, 😉
To my mind the easiest and most elegant way to go about it is to use what I nickname the "see-saw" circuit.
It offers the advantage of AC current balance, something worth keeping in mind if you want to find out why some CFs don't sound too good when sitting on a common rail supply.
Cheers, 😉
Attachments
pedroskova said:
I've found them to be every bit as good as the Jensen equivalents.
Talk to 'em. They're very amenable with regard to doing custom work. I wanted to use both their CMMI-10C and their CMLI-15/15B and was thinking of mounting them topside and wanted them to be the same size. They put the CMLI-15/15B in a C size can for me for just the difference in the cost of the cans.
Center taps shouldn't be a problem and if memory serves, when I was ordering mine, they asked if I wanted any center taps.
se
resident said:
The JT-11P-1 sells for $70 each in 1-3 quantity. The CMLI-15/15B was something like $54 and that was for one I had them mount in a C size can instead of the B size can.
I'll have to dig through my EMail and see if I can find the original quote.
se
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