I was toying with the idea of playing with preamplification in the headshell. Does anyone have a feel for how much mass I could add before things are unmanagable? I have a Grado in an MMT arm at exactly 10Hz resonance now. The setup is in storage so I can't fiddle with it now (I also forgot the brand of the headshell but it is some kind of premium carbon fiber thing).
With the right SMT parts it seems like you could do it at under a couple grams. On the down side, you'll have extra wires for power, and the caps I'd want to use for even half the RIAA eq wouldn't be itty bitty SMT ceramics, but larger films. Fortunately there are lots more SMT part options now than even a couple years ago. IMO, it's a good idea to investigate, along with putting the pre in the table itself. I know that's been done commercially.
As Conrad says, it should be possible with SMD parts to keep the circuit under a couple of grams. I do think you should leave any RIAA equliziasion out of this circuit, and just make it as a clean buffer with gain of e.g. 20-40dB. Resistors in the receiving end could bring signal down to what normal RIAA circuits accepts.
My thoughts are going more to shielded cables and a piece of mu copper around the shell
My thoughts are going more to shielded cables and a piece of mu copper around the shell
Conrad Hoffman said:
SMT caps are problematic, but you can get 1206 NPO now up to .1u and I think I remember higher. I was thinking of a phantom power arrangement similar to the Schoeps transformerless mic circuit. There are several external sound devices with P48 and balanced inputs. You could also try RIAA in software or a hybrid approach.
Certainly one could do that - at least to fit a single gain stage - even if your setup seems not to be perfect for this task (low compliance MC like SPU, Denon DL103 and the likes that benefit from high mass arms).
As I'm currently working on my phono, I would be more sceptical regarding shielding. Even a simple alu-box is probably already too heavy and without shielding it's likely to pickup lots of noise so there's no net benefit.
But being the person you are, you already thought about that
Have fun, Hannes
As I'm currently working on my phono, I would be more sceptical regarding shielding. Even a simple alu-box is probably already too heavy and without shielding it's likely to pickup lots of noise so there's no net benefit.
But being the person you are, you already thought about that
Have fun, Hannes
Hi,
Clearaudio did this as a commercial product in the late 80s, if I remember correctly. It was a thickfilm-asic based on a discrete design.
I think that a single gain stage to lift the voltage levels on a higher niveau could be a benefit already. This would leave out the problem of finding good, tiny sized caps for the playback-equing to a second stage off of the tonearm/headshell and would introduce very little additional mass.
jauu
Calvin
Clearaudio did this as a commercial product in the late 80s, if I remember correctly. It was a thickfilm-asic based on a discrete design.
I think that a single gain stage to lift the voltage levels on a higher niveau could be a benefit already. This would leave out the problem of finding good, tiny sized caps for the playback-equing to a second stage off of the tonearm/headshell and would introduce very little additional mass.
jauu
Calvin
Building an initial gain boost into the headshell is likely worth the effort, but speaking from experience, trying to EQ or A/D at the headshell may very well create a cure that results in worse consequences than the disease that it is supposed to cure.
I'd suggest building a SMD JFET front end into the headshell (2 leads in, 2 leads out), and integrate the rest of the circuitry (whatever it is) with the tonearm 5-pin cable connector. The SMDs wouldn't alter the f0 resonance (at least not by much), and you wouldn't need to hack the tonearm's wiring loom, so the work would be easy and the bearing friction of the tonearm wouldn't be impaired.
regards, jonathan carr
I'd suggest building a SMD JFET front end into the headshell (2 leads in, 2 leads out), and integrate the rest of the circuitry (whatever it is) with the tonearm 5-pin cable connector. The SMDs wouldn't alter the f0 resonance (at least not by much), and you wouldn't need to hack the tonearm's wiring loom, so the work would be easy and the bearing friction of the tonearm wouldn't be impaired.
regards, jonathan carr
I'm wondering how good noise performance of above A/D-converter is. Unshielded and in the vicinity of a turntable motor I cannot imagine it to be great.
EDIT: Hi Jan, how do you mean that? One can certainly use ground planes for shielding, but that's protecting only from one side - leaving the other 5 open to nature
Have fun, Hannes
EDIT: Hi Jan, how do you mean that? One can certainly use ground planes for shielding, but that's protecting only from one side - leaving the other 5 open to nature
Have fun, Hannes
Hannes
You said it your self
We make so many efforts with our gear and circuits (balanced cables, double shielded wires, groundplanes and many other things) to prevent noise, and then we still have four completely unprotected 0.5-1" long wires connecting the headshell to the pick-up
It is here I'm thinking of doing some tests with some shielding teckniques
You said it your self
We make so many efforts with our gear and circuits (balanced cables, double shielded wires, groundplanes and many other things) to prevent noise, and then we still have four completely unprotected 0.5-1" long wires connecting the headshell to the pick-up
It is here I'm thinking of doing some tests with some shielding teckniques
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