yep.
built one many years back.
not the best there is, but also not so bad.
mlloyd1
built one many years back.
not the best there is, but also not so bad.
mlloyd1
Given that loading resistors are easily changed or shock horror replaced with a pot how is that a problem. The inductance is published for all reputable brands and for the disreputable ones can be measured. I don't see a problem there. The problem is where they have engineered the cantilever resonance to prop up the falling HF response which seems to be the case with some carts these days.
Hans, I was a bit fast - of course you're right.
Let use this opportunity to update my collection of RIAA amplifiers. I have added two more, the active version with two inverting amplifiers, and version with passive eq AND two inverting buffers. The latter is particular appropiate for OP amps with common mode distortion issues, i.e. "cheap" audio OP amps. Again, I have chosen the impedance level high enough to such that virtually all OP amps may be used - even TL072
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I have not taken neither input offset voltage nor input bias current into account. For some OP amps you might find it necessary to include a capacitor after either the first or the second OP amp. Eg. if the first OP amp has a 3mV input offset voltage, that will be amplified to 3V at output of the last OP amp.
Or if the input bias current of the first OP amp is 500nA, the output will be 500nA*47k*1000 = 2.4V.
I have not taken neither input offset voltage nor input bias current into account. For some OP amps you might find it necessary to include a capacitor after either the first or the second OP amp. Eg. if the first OP amp has a 3mV input offset voltage, that will be amplified to 3V at output of the last OP amp.
Or if the input bias current of the first OP amp is 500nA, the output will be 500nA*47k*1000 = 2.4V.
> loading resistors are easily changed ... how is that a problem.
For mass-consumer systems around 1960, such fiddling was not generally acceptable. This led to the idea of standardizing the resistance, and semi-standardizing the total capacitance, and letting the cart designer find an optimum.
In a 2016 DIY thread arguing many different topologies and techniques, yes, it would be silly to strain at this gnat.
For mass-consumer systems around 1960, such fiddling was not generally acceptable. This led to the idea of standardizing the resistance, and semi-standardizing the total capacitance, and letting the cart designer find an optimum.
In a 2016 DIY thread arguing many different topologies and techniques, yes, it would be silly to strain at this gnat.
The problem is that the published inductance figures are very often not accurate, and are not exactly the same for L and R. See Chapter 13 of Burkhard Vogel's Sound of Silence 2nd edition, where he measured some cartridges.
Thank you, I'll add that to my list to get when I have funds.
But is this any greater problem than the fact that many manufacturers of phono stages have no idea what the capacitance of their input stage actually is?
but of course the shame in all this is that it would be easy to measure all of this with a PC if decent test records were still made. These seem few and far between these days.
But is this any greater problem than the fact that many manufacturers of phono stages have no idea what the capacitance of their input stage actually is?
but of course the shame in all this is that it would be easy to measure all of this with a PC if decent test records were still made. These seem few and far between these days.
Are you talking about shunt RIAA feedback? With series feedback the impedance of the RIAA network can be as low as you can drive with the opamp/s of choice, and this has no effect on the input impedance at the non-inv input, so no noisy buffer required.
Well you have no common-mode distortion, but with 5 mV signals that's not an issue anyway. But you have added another stage with its noise & distortion. To me that's troublesome.
if you want to use OpAmps, go active. Here is a good example:
The VinylZone: Analogue Addicts Phono Pre
If you want to go passive, I'd use an open loop discrete circuit. Two gain stages (each about 30-40 dB max) and a buffer for output. Provide for enough headroom.
But it is more difficult and expensive to do. Gain adjustment (MM/MC) can be made in first gain stage, increasing / decreasing degeneration. That will get you about constant headroom, and the noise penalty for higher output cartridges is not critical.
I have no idea about tubes, did never use them.
The VinylZone: Analogue Addicts Phono Pre
If you want to go passive, I'd use an open loop discrete circuit. Two gain stages (each about 30-40 dB max) and a buffer for output. Provide for enough headroom.
But it is more difficult and expensive to do. Gain adjustment (MM/MC) can be made in first gain stage, increasing / decreasing degeneration. That will get you about constant headroom, and the noise penalty for higher output cartridges is not critical.
I have no idea about tubes, did never use them.
I have yet to hear a plausible reason (audibility being the least) to not use an LM3886 for low power amps. Yet there are tons of discrete schematics and amps, books and threads about this around.
When designing with Op Amps you have boundaries that are difficult to overcome with passive EQ, and I would not do it. Thus I wrote he should use active EQ.
When going fully discrete and open loop, passive EQ is a nobrainer regarding headroom and noise.
No buffer between the two voltage gain stages, using the high impedance nodes to place the RIAA network.
Much more fun than just using an Opamp and hook some caps and resistors around it.
And it sounds better, to my ears. But thats my statement, and no, I will not enter in such discussions.
Allow me; here are three:
1) Poor distortion performance as normally used.
2) Poor reliability if used anywhere near ratings.
3) Tendency of manufacturer to make duff batches that fail after about 3 months.
#1 can be overcome, as you imply.
#2 is probably true of anything- leave some safety factor.
#3 I hadn't heard. Was there some well known incident that occurred?
One thing that would be nice is a really in-depth section on phono grounding. Exactly how/why does hum get picked up and the best strategies to avoid it. Some turntables have a ground lead, some don't. How do they get away with it?
#2 is probably true of anything- leave some safety factor.
#3 I hadn't heard. Was there some well known incident that occurred?
One thing that would be nice is a really in-depth section on phono grounding. Exactly how/why does hum get picked up and the best strategies to avoid it. Some turntables have a ground lead, some don't. How do they get away with it?
How would you go about it?
No it isn't true of anything. Compare the reliability of power transistors with power-amp ICs. It's hard to come up with figures but I've a lot of experience with both and the difference must be at least an order of magnitude and probably more. You would need one hell of a safety factor.
Probably best not to name names until everybody's dead, but I have known it happen at two manufacturers, several years apart.
This is speculation but I suggest it might be that you can get away without a ground lead if the cartridge is electrically screened. We are currently looking at the issue here:
http://www.diyaudio.com/forums/analogue-source/300382-what-would-you-want-see-book-electronics-vinyl-replay-douglas-self.html
If anyone has a notion of what % of cartridges are unscreened we would be very glad to hear it.
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