MPP

[Hans Polak]

I have to say that I use a balanced transimpedace phonostage with 4 low noise Opamps in parallel as the frontend. Because of strong feedback the input impedance is very low.

Well, a virt gnd input is exactly what a transimpedance amp is supposed to present.

Hans

 

[jan.didden]

I have to say that I use a balanced transimpedace phonostage with 4 low noise Opamps in parallel as the frontend. Because of strong feedback the input impedance is very low.

Your Linear Audio article (Vol 0) - Down the rabbit hole?

Jan

 

[Joachim Gerhard]

Andreas, that is plainly true.

 

[Joachim Gerhard]

The problem with the testers is, that they have precious little time for a review.
In the old days Audio had at least 30 employees to produce the magazine.
Now there are maybe only 5 people and freelancers.
The Art of good testing is mostly lost and forgotten nowerdays.

 

[Joachim Gerhard]

Jan, I have to read my own article again but the idea for such a stage is not new.
In the old times we called it Dolphin.
Hesener made a Layout years ago.

 

[Joachim Gerhard]

Here is the Dolphin.

 

[jan.didden]

Jan, I have to read my own article again but the idea for such a stage is not new.
In the old times we called it Dolphin.
Hesener made a Layout years ago.

Attached ;-)

Jan

 

[al2002]

Joachim, thanks for posting your results. Very useful.

 

[as_audio]

11687 : drawing errors already addressed ? Not sure.

 

[FdW]

Here is the Dolphin.

Dolphin was placed under NDA and not yet lifted.

 

[Joachim Gerhard]

True ! Diagram 11683 only shows the idea to parallel Opamps at the input for less voltage noise.
That idea is not new. See Elektor Supra 2.
I have not seen that in a transimpedance stage though.
The Dolfin as such is much more complicated or should i say sofisticated.

 

[Joachim Gerhard]

Jan, in the Rabbit Hole article i paralled the opamps out of another reason.
4 times the current drive compared to a single opamp to drive the low impedance feedback network without overload.
Later it showed that i build a much too heavy german tank.
One opamp per side works as well because of the miniscule signal at that point.

 

[Hans Polak]

Here is a Dolphin for sale from € 1613,77 for € 68,00

Ruffel Price Hike Dolphin Mm Mc Phono Amplifier Movement Ruffel Price Hike Dolphin Mm Mc Phono Amplifier Movement [224554934607] - €68.00 -

Hans

 

[Joachim Gerhard]

The discount is amazing. I would buy it for fun.

 

[as_audio]

Waning, Hans are you joking ? This is a fraudulent website.
The "offer" is created by your search using old Ebay etc ads.

 

[as_audio]

... Diagram 11683 ...

Please explain why you consider this a "balanced transimpedace phonostage"
(11677, 11678).

 

[Hans Polak]

Waning, Hans are you joking ? This is a fraudulent website.
The "offer" is created by your search using old Ebay etc ads.

Is the world already that bad ?

Hans

 

[Joachim Gerhard]

Yes

 

[Joachim Gerhard]

Interestingly the 25Ohm groundlift resistor is Not in the Noise Budget

 

[wiseoldtech]

About the time I bought the SME 3009 SIII* that I ended up never using to try on high compliance cartridges I had an audio technica AT-34 bayonet mount. Given it's compliance and the weight of AT arms fo the time that was about 6.7Hz. Clearly AT were not worried about low resonant freqency. I kinda wish I hadn't sold that cartridge as it really did perform well.
*5.5g with the standard wand.

With a resonance of 6.7Hz, I'd employ a Sallen-Key filter (thanks to Rod Elliot) to the RIAA preamp outputs to eliminate anything below 18-20Hz.


I've installed them on my various TT setups with excellent results.
No more airborne feedback issues at high volume, no rumble worries, and you don't even miss the woofer-pumping of a warped record, it's gone.
With those issues solved, the amp's power can concentrate on the music.



Project 99 - Infrasonic Filter