The STR112 turned up today also. BTW today's listening sessions confirm that the source quality transcends everything by a long margin.
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I checked my copy of Dafos and I have side2 label, so you may have a valuable record there. I still find the grooves on Dafos to be insane. Recently wife has actually been asking for records. Given she was born the same year CDs were launched I assume she is just humouring me.
Best wishes on your new addition, I've paid my dues 4 times over and I hope everything goes well.
Oh and some light reading I found whilst reading around the transimpedance concepts
Patent US4470020 - Virtual ground preamplifier for magnetic phono cartridge - Google Patents
On first scan hard pushed to find novelty.
Patent US4470020 - Virtual ground preamplifier for magnetic phono cartridge - Google Patents
On first scan hard pushed to find novelty.
I ran across something else funny today looking for the current value of the STR112. A guy bought several on ebay and commented that the square wave tests only produced tri-waves for him, I guess he didn't get that that LP is not RIAA. They say literally the grooves are exact 1kHz triangles (constant velocity). Looks like these are $40-100 when they show up, discogs last sale was at $39.95.
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well that's better than the €150 for the B&K 2010 record.
Would that be this page? Resonance Frequency
Would that be this page? Resonance Frequency
Yes, BTW Jason Statham was blowing up wooden Grados in "The Mechanic, Resurrection". How does he replace all those LP's?
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In order to keep some links together It was just pointed out to me that one of the earliest references to a damped loading was the Barney Oliver amp of 1973 http://www.hparchive.com/Manuals/Barney_Oliver_Amplifier_Manual.pdf
I also found this blast from the past. With a few tweeks would be a good candidate for a flat pre to 2kHz. LD is like the easter bunny hiding this stuff around the web
Ah, the best kept secret of all: transimpedance MM/MI loading.
Barney Oliver's stuff was great, and the tribute op-amp version is true to the spirit of that discrete preamp. It's pretty demanding of gain-bandwidth; that's how I ended up with the 'exotic' op-amp - it's necessary. There's a typo in your post, Bill - you mean 20kHz of course!
All my MM/MI pre-amps are true transimpedance these days: they present a true short circuit as a load. I came up with a very tidy circuit that takes care of the wrong LR time constant arising and converts it to 75uS in the 1st stage, whilst conserving true transimpedance loading. That is also demanding of gain-bandwidth in an op-amp, if one ever needs a genuine excuse to go exotic. I also did a valve version, using 2 stage rf pentodes, which I am particularly fond of............
I did once post the stream of consciousness that took the early rubbish concept sketches into something rather special IMO, but the latter stuff was purged from the web AFIAK, presumably for heresy........
AFAIK I have the only ones, for my own use.
It really is the only way to fly for MM/MI, IMO. Doesn't work well with all carts IME, but decent Ortofon and AT carts support it superbly IME. The LCR resonance doesn't exist, capacitive/resistive loading gone forever, sounds and measures exceptionally well.......
And, definitively, there is no effect on mechanical damping IME. Neither does the universe collapse to a local singularity.
This is yet another example of opportunity for better vinyl playback that, apparently, the lore of 'you can't do that' has kept from our reaches.......
LD
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Yes, that is the definitive and final 'Barney'. A tribute to Barney Oliver's discrete transimpedance circuit, done with an op amp.
It's not for the fainthearted, and neither was Barney Oliver's original, because the amplifier requires high gain-bandwidth so is essentially an rf circuit and rf rules apply.
Barney Oliver's circuit presents an impedance to the cartridge so that the cart's inductance provides the 75uS pole. So isn't true transimpedance.
A different circuit called 'Aurak' goes one further, and loads the cartridge with a true short circuit; fixing the wrong LR time constant arising in a cunning way. Aurak is the concept which evolved from sketches into something quite special, but AFAIK, only early versions, if any, survived the purge.
So there are two separate circuits : Barney is a tribute to Barney Oliver's 1973 discrete circuit. Aurak is a true transimpedance MM/MI preamp circuit.
So far, I think, you've only uncovered Barney..........
Both are improvements on standard loading, Aurak is the better IMO. Suppose I would say that.........!
LD
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That explains something that was worrying me. Having never needed to use a transimpedance circuit 'use it or lose it' had kicked in so I was starting again from scratch looking at what was going on. But something looked odd on the Barney and I couldn't put my finger on it.
If I can't find Aurak I am sure George will!
Anyway my conundrum for today is how this works when you decide to fit your DL-102.
If I can't find Aurak I am sure George will!
Anyway my conundrum for today is how this works when you decide to fit your DL-102.
I tried in the morning, no luck.
We are left on the mercy of Lucky
George
Don't we have enough to start? True transimpedance means a good false summing input to me, now just figure out the equalization right? I would start with an AD745 which is decomped and then start worrying about the inevitable oscillations.
Using Steven van Raalte's improved model for cartridge including mech resonance, I modified this into the cartridge being connected to a virtual ground, just to get some feeling without optimising or fine tuning.
Without too much trouble it was quite easy to get a relatively flat response.
Hans
Without too much trouble it was quite easy to get a relatively flat response.
Hans
Frankly I'm shocked at how nice my best kept LP's sound with my kickstarter phono setup. I gave all my "never to be finished" high-end TT projects away at a local swap fest.