advertisement


Naim Gain stage - Feedback vs Gain

P

pm1961

pfm Member
I vaguely remember reading that somebody experimented with the value of the feedback resistor in the gain stage with good results.

If I remember the logic correctly, reducing the feedback increased the gain (and quality?) but its natural limit was the overall stability of the circuit.

Has anybody any details of experimenting with this?

Cheers,

PM
 
A combination of a 6K8 and the existing 1K will virtually halve the gain of the stage. To ensure stability, a 47pF ceramic or silver mica cap across base and collector of the ZTX214 will guarantee the stage doesn't do it's usual impression of an RF signal generator.
 
Does your answer infer that you believe the gain is already as high as stability would allow and there's nothing to be gained by decreasing the feedback?

Is that cap across the trannie a "good thing" irrespective of any other changes?

Cheers,

Paul
 
In the main, with any given circuit, as the feedback is increased, the stability is degraded ( there are phase shift issues which are responsible for oscillation ). With the gain stage in question, it's a very good idea to fit that small cap and indeed, after many years of doing just that, I had to smile when Salisbury followed suit. Funnily enough, I've just finished work on an Ixo which when powered up, raved away like a good 'un - the caps put paid to that malarky.
 
Les

You mentioned Salisbury........they don't mention you (at your request) so do the honourable thing and return the compliment.

Regards

Mick
 
You know Parry, I've never been targetted by a stalker before - I must say it's really quite flattering to learn that I must be treading on a few toes .........
 
Les

It is very simple really. I shall remind you every time you mention Naim.

My PC flashes when it happens so its dead easy and very effective.

If you don't mention them, my pc dosen't flash.

The ball is in your court as they say.

Regards

Mick
 
Originally posted by Mick Parry
My PC flashes when it happens so its dead easy and very effective.
Click to expand...
Mick

A couple of strobe lights and Klaxons in and around your home would surely be more appropriate.
 
Gee Mick, I bet Les is shaking in his boots.....not!

This is the DIY section, Les is offering useful advice, why don't you just PISS OFF!!!
 
I'm sure everyone's impressed by your flashing Michael. Speaking for myself though, I prefer to roll my own.......
 
Rusty

To answer your eloquenty put question, Les can answer as many questions as he likes and I hope he answers hundreds. All I am doing is drawing attention to the fact that he is once again having a snipe at Naim.

He has asked them never to mention him so he should do the decent thing and not mention them.

Regards

Mick
 
My PC flashes when it happens so its dead easy and very effective.
Mick,

you realy do need help.............theres a nice place just down the road from me 'The Priory', where all the rich nutters go for special treatment................

you would be more than welcome and only 3k per night, nothing to a man of your means........I'm sure in only a week or two they would have you back on the road to Salisbury.

Salisbury
Salisbury
Salisbury
Salisbury
Salisbury
Salisbury
Salisbury
Salisbury

Had enough yet Mick, ....No........

Salisbury
Salisbury
Salisbury
Salisbury
Salisbury
Salisbury
Salisbury
Salisbury

Graham
Click to expand...
Click to expand...
 
You mentioned Salisbury........they don't mention you (at your request) so do the honourable thing and return the compliment.
Click to expand...

A little perspective please – as I understand it Les has informed Naim that he does not want mentioning on their forum, a place where, as far as I am aware, he does not have any right of reply. This situation has absolutely nothing to do with pfm, plus no one who works for Naim is banned on this forum, they have full access to state their case here if they don’t like something Les says. These are very different situations.

Tony.
 
A combination of a 6K8 and the existing 1K will virtually halve the gain of the stage. To ensure stability, a 47pF ceramic or silver mica cap across base and collector of the ZTX214 will guarantee the stage doesn't do it's usual impression of an RF signal generator.
Click to expand...


Are we talking R9 and R14 here Les?


BTW Les, huge thanks for all your help over the last 2 years, I couldn't be happier with the results.

Steve.
 
Originally posted by LesW
A combination of a 6K8 and the existing 1K will virtually halve the gain of the stage. To ensure stability, a 47pF ceramic or silver mica cap across base and collector of the ZTX214 will guarantee the stage doesn't do it's usual impression of an RF signal generator.
Click to expand...

Les,

I take it this is the same position as the 33pf cap you used to recommend (on the Analogue Addicts mailing list IIRC)?
 
BTW Les, huge thanks for all your help over the last 2 years, I couldn't be happier with the results.
Click to expand...

I second that.
Les has been a tremendous help for me, whether he mentioned Naim or not.
Yair
 
Yup, Les is a great chap, which he's proven to me a number of times now. He's not the fastest of the bunch, but that isn't always the most important thing now, is it?

-=> Mike Hanson <=-
 
Seconding for Les!

Mick, Les DID NOT mention Naim as you stated. He mentioned Salisbury.

Perhaps you should train your evaluations when to react and when not and get your PC to service if you have asked it to bling when Les mentions Naim. It is a faulty thing as it is blinging on Salisbury, too. Or perhaps it blings even for Les? Get it checked if you lean on your PCs evaluations. It may spoil your reputation (?).

This time Les did not really put Naim anything much into shame and there was no reason for you to come in the middle. BTW what are you doing in the DIY side? After all this is for tinkerers, ehh?

We all have our personal shortcomings and you would not stand such a stalker yourself on your neck, would you? Les has done massive positive contribution for most of the DIY people here.

We all know how splendid amps Naim manufactures and how good after sales service they are offering. They speak by themselves. Les is in his own class and Naim do not give a toss about Les or anybody else, I bet. No reason to make too much hassle on it here either.

Oz
 
You must log in or register to reply here.


advertisement


Back
Top