Schroder sq and the new talea

Dear Ralph,
The cartridge I was using was not a LOMC, but a LOMI cart that likes to "see" a capacitive load of 400-600pF and a resitive load of 4,7kOhm. I had asked Thom if it was feasible to use the Atmasphere "all the way", but got a negative answer(or so I understood). Should have asked you, but didn't see you around that day. My bad, sorry.
Could you please explain what exactly you meant by "a phonosection being susceptible to ultrasonics"?
When loading a cartridge that's connected to the phonoamp via a transformer, both the upper end of the frequency response and therefore phase response and the gain of the transformer are affected(see graphs on intactaudio.com -
http://www.intactaudio.com/forum/viewtopic.php?t=945&sid=efdd3b82186d4bfef1d24cdbbd192f9d)
As far as I understood Thom, you rely solely on tubes(12AX7) for your 66db of gain. While I don't know how you get this much gain out of a tube input phonostage other than through paralleling input tubes, I take my hat off if you did so without paying a noise penalty.
The prototype phonostage had a gain of 40db, the prepre in use provided an additional 30db(4,7kOhm load). I'm sure the clicks on the volume control are 2db apart for "regular" use. Where I ended up having to set the volume(Joel chose to start out at rather low volumes, fine with me though I had preferred to raise the playback level by 3-6db), the clicks seemed farther apart. But even if we had both used the Atmasphere preamp, 2db steps are too coarse for level matching/a valid comparison.
As said before, lots of things to be learned here. Next time we'll do better :-)

Cheers,

Frank

We use 12AT7s for phono gain. You can't get bandwidth with 12AX7s.

Installing the afore-mentioned values on the loading terminals of the preamp would have done the trick.

With higher impedance cartridges like this, the loading does become more of a damping issue, as higher impedance cartridges do ring much like transformers and have to be damped in a similar way.

With LOMC, the impedance is so low (50 ohms, often a lot less) that the artifacts of ringing are entirely ultrasonic, often well in excess of 100KHz. They can be sometimes quite surprising in amplitude, if a tuned circuit (depending on what resonant frequency that might be achieved with the inductance of the cartridge, capacitance of the cable, and aspects of the input of the preamp itself) results. If you think about this as RF being injected into the input of the preamp, it can be easier to understand. If the preamp has a problem with that, the loading resistor may become quite critical, as it interacts with the resultant tuned circuit.

We get around the noise issue by use of a differential balanced phono section (which was the first of its kind ever done), which employs very effect constant current sources. It can have as much as 12 db less noise than an equivalent single-ended phono circuit.

Dear Atmasphere,

I still believe that true value in the sense of the word has nothing to do with declaration or point of view of people but with its inherent quality.

This seems inherently contradictory. There is no 'objective' viewpoint to be had; we are all humans and assign value and create stories about 'quality' in an arbitrary fashion. Rome did not prevail because of a sword; it prevailed, and that's all there is. Once you assign reasons, you are making up stories.

"Rome prevailed, and that's all there is. Once you assign reasons, you are making up stories." ?
Oh yeah ?
Sounds to me like the G.W. Bush way to simplify existence and the world as much as possible, so that ultimately nothing is left that can't be either bought, explained to a 3 year old child or bombed ....
I took the example of an outstanding ( if historical ) technical device with superior performance - rooted in superior knowledge of its creator, unique materials used and recognized both in its time and by history.

This sentence should be something every audio designer would like to see written about himself and his creations - right ?

Now the point should be clear.
It was to illustrate just that specific point - not to discuss Roman empire's history nor the reason for it's military and strategic success.
Finally and just BTW: Rome did not prevail of a sword alone, but in military history the roman gladius I was talking about is long recognized as one of the very few truly outstanding ( read: graced with inherent value ...) weapons in history.
In a line with the english longbow, or the japanese Katana.
It "helped" to shape the world we are living in today.
There is such thing as inherent quality - the fact that it is so rarely found today is sad, but no proof for it's absence in reality.
I for one do look for inherent value in audio components.
That these birds are so rare is not my fault.

Atmasphere, If you are right then physical science is not
possible. Frege stated that science needs the sence as well
as reference by its statemens. Every single particle physicist knows the 'meaning' of Higs particle. Ie the contribution of this particle to the theory. But non of them knows if this 'name' has a reference. So we in Europe have build this colider for 2 billion Dollars in order to
(possible) answer the question about reference. If we do not succeed then the whole theory will colapse.I need not to defend Dertonarm, he is much smarter then I, but his
opinion is in accordance with physical science. One can
dispute his wording (inherent value of objects) but not
his physical inclination. The nature does not care about our feelings nor about our thinking. The arrogance of homo
sapince is self-deceit. Our 'mother náture' don't care about us.
Regards,

Thank you for your reply Ralph! Now everything makes a lot more sense to me. LOMI carts indeed can't be compared to LOMCs based solely on their output figures. But with correct loading one can achieve an incredibly wide bandwidth(flat beyond 70kHz +). Not that there is any usable info imbedded in the grooves(nor was it ever present on the master), at least one sees no nasty (MC)peak between 15 and 30kHz and the phase shift near the upper end of the audio band is minimal.

Have a great weekend,

Frank