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Old 6th March 2003, 12:20 AM   #11
jam is offline jam  United States
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Frank,

Ah! Ha! A response. All I need is a schematic if a line stage to drive a transformer to obtain a balanced out. I suppose a reasonably low output impedence is in order. ( your choice of topology ) .

If you worked for Goldman how come you are in the tube camp?

I also find low feedback or circuits with no global feedback are a lot more critical of the power supply. Care to comment?

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Old 6th March 2003, 12:55 AM   #12
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Default IN A JAM...

Hi,

Quote:
All I need is a schematic if a line stage to drive a transformer to obtain a balanced out
That's not too hard to do, a single ended stage driving a trannie is rather easy...tell us the gain you need...hold on, you don't mind starting a thread in the tube section for that, do you?

You'll get much more input that way and some advice from me on regulated PSUs to boot...

Quote:
If you worked for Goldman how come you are in the tube camp?
Well, that's a long story...we were never employed by Goldmund as such...see it as a take over "avant la lettre".
It is an interesting, yet sad story on how some brilliant people lost a fortune not realising the immense opportunity they had...
A fascinating story in high-end history.

As for the tube part...well if you look at the fact that some contributors such as J.C. Verdier, Jean Hiraga and yours truly were tubes guys already before we entered this mechanical engineering task, you may understand it a little better.

If you ever get the chance to buy the "L'Audiophile" collection of magazines in English (I don't know if you read French) you may find it a treasure throve even to this day.
The only thing in the Anglosaxon world that came close was the British mag "Hifi-Answers" under Jimmy Hughes.
Lucky for me I have met all of them in person and maybe one day I'll write about these people for I feel those were really pioneering days.

Cheers,
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Old 6th March 2003, 01:12 AM   #13
jam is offline jam  United States
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Thumbs up Frank's the Man!

Most excellent idea ...Frank.

I speak no French so where do I purchase copies of the English version of L'Audiophile?

Tubes?.......6DJ8's or 6SN7's perhaps you choose.

I shall call the preamp Franken Tube in honor of it's designer (that being you).

Maybe you can teach us old (solid state) dogs a few new tricks.

Regards,

Jam
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Old 6th March 2003, 01:23 AM   #14
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Default Frankenstein.

Hi,

Quote:
I speak no French so where do I purchase copies of the English version of L'Audiophile?
Unfortunately other than a few articles on the Kaneda preamp (remember?) I am not aware of translations...maybe my work should start there?

Quote:
Tubes?.......6DJ8's or 6SN7's perhaps you choose.
O.K...so an active preamp with some 15dB of amplification feeding a transformer would be your ticket?

I assume you need to feed a balanced amp?

Cheers,
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Old 6th March 2003, 01:31 AM   #15
jam is offline jam  United States
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Frank,

Yes my amp has a balanced input, but if possible let it be an option for other members of the forum.

Regards,
Jam
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Old 6th March 2003, 02:16 AM   #16
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Default Dull sound?

Quote:
I have expressed the same feelings not so many time ago in the solid state forum...the shunt feedback sound to may ears much more dull.
Hi Jorge,
Like many others have said , I repeat that the actual implementation of a circuit can affect its 'sound'. To make a general statement that shunt feedback is 'dull' would probably not be correct.
My shunt implementations, do not have 'dull' sound but different sound. HF is present just like the series feedback implementation.But it sounds different . It sounds smoother - not really duller!
About the speaker signals ( back emf?) going back into the previous stage : If this 'did' happen it's effect would depend a lot on the output impedance of the previous stage. Besides I was under the impression that significant back emf in a speaker happened significantly at LF.
Note that zero negative feedback circuits can also sound"dull". There is no way the speaker back emf can cause this ( by going back to the input).
So give "shunt' a chance. maye be you will have to spend more time listening to such circuits. Not all will be good implementations. So give it time and have fun. That's what it is all about !
Cheers.
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Old 6th March 2003, 02:43 AM   #17
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Default The missing link!

Hi ashok!

I have spent much time studing the speaker interface and his relation to sound quality!Is that interface that explain the dramatic diferences betwen amps!

When i talk about dull sound i don't mean that there are no highs...but more a sensation of intermodulation.

But you don't need to belive in me ...try this:

In a valve amp suitch the ground reference of the output transvormer for the amp became inverting...then conect the feedback resistor to the grid of the first tube.
After this conect another amp via a 8 oHms resistor to the output.Put same music or sinusoide in this second amp and put the volume control at a medium level.
Then you can see at the grid of the first tube the sinusoide or the music that the second amp is feeding.(see with a osciloscope).
That second amp simulate the EMF of the speaker.
Is obvius that that voltage that apears at the input grid will enter in the preamp or cd...even if the ouput impedance of the preamp is low,but the open loop impedance is not! then this parasitic voltage will be processed!

Better than listening to people...is to do some experiences!

Cheers

jorge
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Old 6th March 2003, 02:59 AM   #18
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Default feedback tests

Hi Jorge,
You are right about the signal being visible at the input. more accurately you will find a current flowing in the feedback resistors caused by the signal being injected at the output of the first amp.
You should also find this happenning in a voltage series feedback circuit - that is current flow in the feedback resistors.

I will think about the effect of this in both cases. It may not be as simple as it looks. Right now I have to run. Lots of work today. I will post again later. Thanks for your views.
Cheers.
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Old 9th March 2003, 06:46 AM   #19
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Default Update.

I must admit that I did not do any thinking.
I did glug , glug , and lots of listening.
I noticed that the voltage shunt feed back had what seemed to be "darker" spaces between sounds ! Know what I mean ?
In addition on track 5 of The best of Four Play, there is a powerful transient drum . This has tremendous attack even on the voltage shunt circuit and in addition it has 'weight'. There is also a long decay that I cannot hear easily on the voltage series feedback circuit. It is not due to the electronics as it is probably more than a second - sounds like a huge leather skinned drum !
Played quite loud I am not missing much of the 'bite ' which I earlier said that shunt feedback did not have.
There is certainly more weight in the sound. It's simply more tuneful!

If this test were conducted with a low level opamp it might not show similar results because the circuit configuration would be different and the effect of the speaker impedance would be missing. Just a thought .

Now I will be listening to Koji Kitaro and Yani and see how the system sounds.


Cheers.
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