6922

[analog_sa]

Hi Frank

>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 ?


Batteries are exacly like caps, no two are alike. If battery power were more popular there would be dozens of companies offering designer batts So, the fact that someone likes or dislikes 'battery sound' is pretty meaningless if the exact battery is not specified.
There doesn't seem to be an abundance of valve types suitable for MC duties and the power supply demands are daunting. I've sadly switched to an INA103 arrangement, dealing with 100uV doesn't give you much choice. And i would never buy a transformer without hearing it first. The ones i've heard never impressed me.

peter

 

[fdegrove]

Hi Peter,

I couldn't agree more on both counts.Still in this particular application the battery sollution is certainly not a bad idea.
The tubes for the task were around though but long gone now.
Still for a home project I'm sure something even better suited than the 6922 must still be available at a price.
Bernhard has suggested the EC8020 as a viable candidate...
Guess I'll have to dig out my old manuals.

Greetz,

 

[marjan]

It was a long, long week

but I finaly menaged to compleet one chanal of Hampton MC pre-pre. There is no chasis yet, and the grounding is probably poor (see picture 2) but this is still just a test board. Sound impresions as it can be heard on only one chanal are great. Only disturbing noise feom the speakers is low frequ. hum (grounding I supouse) at high listening level.

pict.1

 

[marjan]

pict.2

 

[analog_sa]

Only disturbing noise feom the speakers is low frequ. hum (grounding I supouse)

Not necessarily grounding. At these levels it's very difficult to have no hum without some type of screening

 

[fdegrove]

Hi,

At these levels it's very difficult to have no hum without some type of screening

Exactly...

I'd use alot thinner wire from the RCA input to the tube and output too.

Wires that thick are just acting as big aerials to their environment.

Also, for best detail resolution the tubes should be carefully matched.

Cheers,

 

[marjan]

Yes, wireing and layout tehnics is the art that require a lot of expirience. I do not have it.
Well, like I said it`s only a test board, and the hum isn`t wery loud so I supouse it can be solwed. I`ll try a star grounding shema with two local star points (one for PS and one for input stage) and one main star ground point somewhere near the mains socket.
Any sugestion or pointing to some reference, regarding layout and wireing (or anything else) will be wellcome.
thanks
rgds
Marijan

 

[fdegrove]

Hi,

Here's a good source on star earthing:

AIKENAMPS

Cheers,

 

[marjan]

Thank you Frank, great reading. It did not clearefied all my questions, but it`s a great lead to folow (for a beginer absolutly). I`ll try to draw the layout of stargronding and post it heer if someone will be willing to fast check out.

regards
Marijan

 

[marijan]

If someone is willing to check this up-thanks on advance. I`d just like to know if I made some basic mistakes in the starground layout. It`s a zipp file, too big to direct posting (btm).

thanks
rgds
Marijan

 

[fdegrove]

Hi,

Sorry to say so but it's nowhere near to star earthing.

With true star earthing every single negative connection receives its own lead to ground.

Cheers

 

[marjan]

OK, I do understand that this is not a thrue one point stargrounding, but what are the local stage ground points AIKEN article is talkig about then? PS local ground point, preamp stage ground point... , conected on central star ground point?
Are you saying Frank that this is not a thrue star grounding or you are saying that I made a totall mess out of it, useles for this purpouse? Point me to some basic and not permitable erors please.

Thank you for trying to help

rgds
Marijan

 

[fdegrove]

Hi,

PS local ground point, preamp stage ground point... , conected on central star ground point?

Everyone seems to have his own philosophy on the matter but to me a single earthing point seems to give to best results.

Since this is a MC Headamp I'd certainly recommend implementing it carefully.

Are you saying Frank that this is not a thrue star grounding or you are saying that I made a totall mess out of it, useles for this purpouse? Point me to some basic and not permitable erors please.

Yes, it's not a true star as you're combining a bus and a star ground in one.
This isn't necessarily an error, it will work, only with a little mre effort it can be made better.

Even without chassis as a shield it should be absolutely humfree.

Cheers,

 

[Zen Mod]

I'm pretty sure that you can find localy some EI ECC88 or even PCC88 for cheap (hehe-NOS);
for heating I recommend you (even for E series ) LM317 in CCS topology, naturally - elevated to some apropriate potential.
FDegrove have right (almost as usually that you must try fet loaded anodes ;
also-sort of Allan Wright's fet based inputs must be even better-if memory serves me well, 88 can sound little on cold side when is driven with smaller Ub and current.

 

[marijan]

Well. I supouse I`m not going to bother myself anymore with the MC pre section. After I puted transformers in a seperate enclosure, after I completed the second chanal of preamp, and after I implementd three point stargrounding (all high voltage grounds are conected to the minus pole of first HV filter cap with separate wieres, same at the filament section which is star point 2 and same at the signal circuit-see zipp) I don`t feel any need to change anything. This stuf is realy great. Only noise I can heer from the speaker now is one, produced by my Paravichini tube phono preamp-tube noise at silly gain levels. On the friends SS preamp there is allmost total silence at normal or higher listening levels. I`m shure that fet loaded anodes can sound bether or be quieter in this implementation, same for the one point star grounding, but based on expirience by buildng it using original schematics, I can say it`s fubules anyway. Highly recomended.

I need a chasis now.

rgds
Marijan

 

[marijan]

in test chasis

 

[fdegrove]

Hi,

Marjan,

Do you remember when exchanged some mail regarding my MC headamp?

If ever you need one for very low output MCs ( some Ortofons are really very low ouput, for instance) , then this one will provide it.

It does sound sweet and has very good imaging if you use very well selected tubes.

I also select the FETs (BF244A) for IDSS and lowest noise.

I assume you haven't seen it yet here so I post a link to it:

MC HAMMER.

BTW, glad to see the HAMPTON circuit turned out to your liking.

Cheers,