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Old 14th January 2003, 09:31 AM   #261
protos is offline protos  Greece
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Since the LM3875 seems to accept balanced inputs does anyone have an idea how the Thor/Peter Daniel minimised gainclone can be converted to balanced input?
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Old 14th January 2003, 12:49 PM   #262
Previously: Kuei Yang Wang
 
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Hi,

Quote:
Since the LM3875 seems to accept balanced inputs
Any Op-Amp can "accept" balanced Inputs. Though just because it CAN be done does not mean it provides advantages.

Quote:

does anyone have an idea how the Thor/Peter Daniel minimised gainclone can be converted to balanced input?
I suspect you would do it one of the usual ways. the best solution of course is a suitable input transformer. That failing make the usual pseudo balanced input. Nelson Pass has used it a lot, it's described and shown as part of the A75 Article, part 1 page 12:

http://www.passdiy.com/pdf/A75p1.pdf

Sayonara
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Old 14th January 2003, 01:12 PM   #263
Nielsio is offline Nielsio  Netherlands
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Kuei,

Do you have any pictures of gainclones you've built?
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Old 14th January 2003, 01:51 PM   #264
Previously: Kuei Yang Wang
 
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Hi,

Quote:

Do you have any pictures of gainclones you've built?
I have worked very extensively with Chip Amp's and Op-Amp's in the 1980's when the "Gaincard" was a gleam in Kimura San's eye, mostly Pro-Audio design. A good deal DIY too, including fully active speakers with Motional Feedback on woofers and currentdrive on midrange/fullrange and tweeter, all Amp Chips (TDA2030) inverting with a "boosted bridge" circuit with TDA2030A on the woofers, subtractive crossovers and so on....

Later I did a lot of servicing HiFi/High End gear, much of this chips galore too.

These days I use Valves out of esthetical choice and nostalgia as much as for sound reasons. I still occasionally mess about with Chips, but rarely. I paid my "lehrgeld" with oscillation,circuits and all sorts of theoretical and practical issues in those long forgotten days over 15 years ago, though little has changed since then, so all this "old fogey stuff" still holds up well...

Sayonara
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Old 14th January 2003, 02:53 PM   #265
protos is offline protos  Greece
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Please forgive me Kuei Yang Wang but I'm a bit of a newbie.
Do you mean that I can drive the op-amp as is with a balanced signal from a balanced pre-amp as long as the input impedance of + and - signals is equal?
So I just add a resistor to the other signal line of Peter Daniels gainclone and I'm done?
Why wouldn't I want to drive the amp this way? You seem to have some doubts on whether balanced operation is suitable.
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Old 14th January 2003, 02:57 PM   #266
Previously: Kuei Yang Wang
 
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PS....

Here my latest "clone". It's not really a clone, but these SE 300B Amp's are inspired by Gordon Rankins Triton/Napoleon Style Amp based on the Chassis and iron of the DIY HiFisupply "Billie" Kits....

Modestly obliges me however to say that many features in this amplifier are my own and have nothing to do with Gordons Amplifiers. What I did nick from him are the Gridchok on the output valve and the use of the 437A as driver with an input transformer that offers up to 12db passive gain....

Click the image to open in full size.

Click the image to open in full size.

Sayonara

PS, these amp's sound a LOT better than a friends inverted, battery powered Gainclones, but so they should for the investment and design....
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Old 14th January 2003, 03:39 PM   #267
Nielsio is offline Nielsio  Netherlands
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So they are the ultimatisch amps for you?

Quote:
these amp's sound a LOT better than a friends inverted, battery powered Gainclones
Sound better how?
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Old 14th January 2003, 03:41 PM   #268
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Hi,

Quote:
Please forgive me Kuei Yang Wang but I'm a bit of a newbie.
Okay. I have redrawn Nelsons Schematic a little (no Circuit Drawing program at hand here) to clarify the application to an inverted gainclone (including the "unconditionally stability resistor").

Quote:

Why wouldn't I want to drive the amp this way? You seem to have some doubts on whether balanced operation is suitable.
I in general do not feel that balanced connections offer advantages, UNLESS they are executed using transformer coupling. Note also that I called the input type shown here and described by Nelson Pass as "pseudo balanced", indicating that it does not operate fully like a balanced (transformer) input.

In many cases the balanced outputs of preamplifiers incorporate extra circuitry over unbalanced outputs which usually do not help the sound. In my own system I use balanced Inputs and Outputs EXTENSIVELY, however the inputs are either naturally balanced or via transformer and most outputs are via a transformer (only VCR na d Phonostage have unbalanced outputs actually).

Sayonara
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Old 14th January 2003, 03:52 PM   #269
Previously: Kuei Yang Wang
 
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Hi,

Quote:


So they are the ultimatisch amps for you?

Nope. They are good compromises and suit my system.

Quote:


Sound better how?

Better resolution, much higher vocal integilibility, subjective better dynamics, less compression (yes - I know what compression sounds like - used studio compressors many times), better pace, swing and rythm, more musical. When listening there is a feel (in the whole system) of much less "between" the music and the listener.

I sould say that based on many other Amplifiers (SS, PP Valve and SE Valve) that I have heard at home my friends gainclone probaly comes into the top ten, in the context of my system, maybe even top 5.

I still know one amplifier whose sound I prefer in my system, the Kondo/Audio Note Japan Baransu 300B SE. The Kegon sound similar but lacks the same fine structure on musical lines and vocal clarity. Sadly I lack by far the long green to aquire said Amplifier (or a Shindo WE 300B Ltd), so I console myself with my little amps'.

Sayonara
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Old 14th January 2003, 04:13 PM   #270
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Default Balanced input paper

Good paper here on a "new" balanced input circuit:
Balanced Input

MR
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