6922

[marjan]

I did not want to include the personal taste regarding sonical caracteristi`s of hi-fi ( high end - whatever) equipment in tread like that, but it is a fact. In theory some products or designs can look georgeus and not discusionable. Lot of them does sound great too. But when we leave the circuit discusion level moving to the completed product, we can talk about the sonical efects that the component is able to deliver. Perception of sonical caracteristic`s is subjectiv. That is why my question on the start of the tread regarding choice of the tube included "based on personal expirience with that tube". What I`m trying to say is that every aproach will be sonicly satisfying for some and the oposit for some one else. Every aproach shoud go along with the demands we have to a given component in the therms of reliability, stability, and most natural reproduction of the recorded meterial a supouse. To give a judgement of the design or aplication of dif. parts in it, I supouse it should be built first, so you can test, listen and make your owne opinion. That is helpfull and good to share.
Since there is a debate about diferent aproach, not only about PS and regulation of it, but about using diferent tubes from single triode, paralel double to the chain of two or even more double triods (aybe it woul`d be good to use, let say two perfectly matched sigel oens in paralel conection or even more of them, since you (a supouse) do not hawe two perfectly matched sections in one double). Obviously it is possible to use diferent tues in a input stage of such of design. ECC88/6DJ8/6922 is like to be prowen as the most comon (the best?).
I`d like to refrase my question leeding us to the start point of design.
Which electrical parameter`s of the tube are the most important in such a design? What are the ideal tehnical operating carasteristic`s of the input tube if you are planing to design MC step up modul. Knowing that, designeing and disision`s about chousing aproach, woul`d be much easier. I know that ansver to that, demand wide global knowlidge on the field of ellectronic and acoustic, butI`d like to see a kind of short imagenary data sheet of the tube it woud be ideal for the purpouse.
rgds Marijan

[dice45]

Marjan,

sorry for having gone off-topic, but Frank did ask me and i thouhgt i'd answer, did not intend to threadjack your thread.

Apart form the fact such thing as facts do not exist i agree with you.

To your QQ:
I doubt parameters alone can determine what tube to use. But one thing is sure: the higher the tube's transconductance, the lower the thermal noise. Shot noise is unaffected by transcondictance, but thermal noise reduces by 3dB each time the count of the parallelled tube section is doubled.
The ECC88 is a very good choice as it has enough transconductance and runs from low B+, not all such tubes do that or are spec'ed and documented for that. It is not a good choice as it gets noisy soon, apart from whizzing (which can annoy much) shot noise increases.

The tube for your purpose must have high transconductance, ultra low microphonics, and with a current souce you need a µ of 10 atleast, with anode resistor a µ of 20 .
It should be able to run with low or zero grid bias like the ECC88.
But before i would use parallelled sections, i would use a tube with twice the transconductance.
5842 or EC8010 e.g. and these tubes also are proved to have good sonics.

The ECC88 has not an ideal transfer characteristics curve, already decreasing slope in the negative bias area, it generates more k3 than most other audio triodes. But for MC swing (signal amplitude) that does not count at all.

You must try out which tube works best for you. Not much experinece out there

[dice45]

Klaus,

Originally posted by lohk
any comments about this hybrid SRPP circuit ?
Does anybody know more about the ominous "solid source" ?

to me this looks like an integrated CCS with R3 as current sensing resistor, acting as active load for the tube. With SW1 open, this stage will have gain of 33. Like the µ of the tube. Sw1 closes neg. feedback loop.

To me this looks not like an SRPP. The CCS simulates an almost infinite resistance so R3 is irrelevant as far as output swing is concerned.

[lohk]

Here is another MC prepre with a 6922 / ECC88.
I found it in the net somewhere, but I think it is similar to a schematic published in the (long dead) german mag ELRAD in the late eighties.
(smaller sized gif)

[lohk]

Another 6922 / ECC88 MCprepre, designed by Dusan Klimo, found at Frederico Paolettis pages.
(gif, converted from postscript)

[marjan]

Frank
supouse that I`m using 230/100V EI transformer for anode suply
would it still be sutiable at 30VA rating, one chanal each (I found them in a local store at resonable price)? You mentioned that 100mA is moore than enough. And at home I stil have some EI I could use for heater suply230/12V-10VA trans. OK no OK?

Bernhard
I did not try to get specific numbers regarding parameters of the tube. I just wanted to know what demands (in parametric form) designer of the circuit is puting in front of the thube which is intended to be in use as the MC input stage in the MC step up modul. Your ansvers are helpfull enough to me.
Thank`s

Lohk
thank you for posting those shematics

BTW, what would be a diference betwin using one double ECC88 triode in paralel section conection and two matched (sutiable for the purpouse) single triode`s allso in paralel conection. Any benefit or any diference from second variation at all?
rgds to all

[fdegrove]

Hello Marjan.

100V secondary is too much really for a 30VDC you require.Sorry.

[fdegrove]

Marjan,

Whilst browsing I noticed no one actually answered the last part of yr. q.
Regarding any diffs in using separate single triodes or twin ones:

I see more drawbacks in using separates ones from virtually all angles of design:more sockets ,wiring etc.
If you really want to get as close to perfection as possible on the tubes here I would select them with both sections paralled for high Gm and low noise after I gave them a couple of days of burn in.
Maybe a good dealer could do this for you ?

Greetz,

[fdegrove]

Hello Peter,

Does this bring back memories?

Sorry for the late reaction,I was trying to put Marjan on track.
Regarding the circuit you talk about...I tried the same work arounds as your self.
I gave up on the batteries for practical reasons no more applying now.In short the battery supply for the 24V B+ would surely be worthy of consideration.
After all other than the heater supply,the anodes only consume 1 mA per tube.(In this particular application.)
You could still integrate a choke AND a CCS.
I would still decouple the batteries with a few mF of polyprops though.
Listening tests done by the French L'Audiophile team suggested the batteries they used for tests on the development of the "Le Monstre" transistor amp were rather dirty sounding in the highs.
Admittedly it was a rather over the top expirement.
Have you considered other valve based solutions ?



To Lock,

Thanks for this Dusan Klimo circuit.Having met the designer on several occasions and moreover having listened to his designs I came to respect his work a lot.
I think his circuit is a very good compromise considering the combination with his Merlin preamp.
Very possibly one of the best prepre's I've seen on paper.
Unfortunately I never had the chance to listen to it.Did you?

Greetz,

[marijan]

Hi frank
I`m in the proces of soldering parts for my MC pre-pre already using basic design.

Still trying to get proper output caps. I have 1uF Wima MKP`s for now. Dont know if they will be perfect for this aplication but for the testing purpouse they`ll do. Thinking of bypasing them with the 100p Micaas but I can see diferent opinions about that on some treads -I`ll just try. I supouse I`ll have to open my purse and get some oil caps or similar.

Tubes. I just wondered if there is any benefit of using single`s in parallel mostly becouse it is easyer to find matched par than double with matched sections, but I supouse that it not to critical parameter, so I`m going for parall. double. I shoud finish the projectin week or two. I`ll post my impresions.
regards
Marijan