I need to go off and work out the range of mV per mH. I reckon that there is only a 2:1 variation on this.
Use the calculation model that I have published today and you will see what happens with gain when inserting a 500K resistor.
I can't imagine someone doing this, but the model gives the right answer anyhow.
I'm somewhat flabbergasted by your unwillingness to cooperate in something where you had no cooperation whatsoever, despite my offering to correct all possible errors.
That makes that this addendum is sentenced to death.
Hans
Only got half the data (and some of it not entirely sure I can trust without measuring myself) but appears I was wrong. The range of normalised output in terms of mV/H varies considerably across the history of cartridges but modern ones seem to have all clustered together. For a x-section of currently available or recently discontinued cartridges the output is 6-10mV/H.
For some of the freeky old skool stuff I have the range is 22-45mV/H. But this was from the era when low inductance was the rage.
Need to find some more figures, and no idea if this means anything or not.
For some of the freeky old skool stuff I have the range is 22-45mV/H. But this was from the era when low inductance was the rage.
Need to find some more figures, and no idea if this means anything or not.
That's where I started, but figured the compromise of gain variation between cartridges was worth the simplicity of the arrangement in this topology.
Besides, I sort of think as a matter of principle, cart output V ought to correlate with L...……
LD
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I made the preamp sound like the ( fleetwood Mac ) CD with the same LP.
The preamp is not RIAA compliant but the sound is like a $20k MC cart and RIAA preamp except it has lower noise. The cart + preamp are RIAA compliant.
You may find the L and R response from your cartridge is not equal requiring slight differences in preamp EQ.
The preamp is not RIAA compliant but the sound is like a $20k MC cart and RIAA preamp except it has lower noise. The cart + preamp are RIAA compliant.
You may find the L and R response from your cartridge is not equal requiring slight differences in preamp EQ.
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With 500k for either resistor the DC gain is 60dB rather than 20dB so I'm not sure what you think is the "right" answer.
Excel doesn’t think, it calculates. And gain is completely dependant on the cart used.
So saying gain is 60dB with 500 k is like saying “all cars are blue”.
Use the model, select a cart and you will get your answer.
That’s an imteresting observation, possibly meaning that there is a tolerance in Lc and/or Rc making them slightly different between L and R.
With 47k preamp this is moot, but with an Aurak it becomes obvious.
Hans
I have seen many measurements on the internet of supposed L and R, but I am not sure I trust them. Hopefully from the measurements people have been doing here we can extract some measurements to compare to spec.
For example numbers I found done on a std LCR meter for AT150 generator
Spec 530R 356mH
measured 677R 378mH
That's enough in a 2L-R setup to put the pole 40Hz out which is significant. But the measurements are as likely to be off as the cart.
For example numbers I found done on a std LCR meter for AT150 generator
Spec 530R 356mH
measured 677R 378mH
That's enough in a 2L-R setup to put the pole 40Hz out which is significant. But the measurements are as likely to be off as the cart.
Bill,
even when your LCR meter might be a bit off, but a relative measurement between L and R will give a good indication how close the two channels compare.
Hans
Another factor helps mitigate such imbalance in Aurak: variation in R and L are correlated - they arise from the same piece of wire and are codependent upon physical parameters like number of turns.
For the case of a cartridge with 5% correlated mismatch between L&R channel inductance and resistance, with Aurak that maps on to about a 0.5dB mismatch in channel level, not eq.
0.5dB shift in level is the same as for standard 47k loading, if channel output correlates directly with coil inductance.
Either with Aurak or standard loading, normal variation ought not to be a factor in a healthy cartridge. 0.5dB channel level mismatch is trivial in audio terms.
Aurak isn't particularly sensitive to variation in cartridges or between channels - but then neither is standard loading.
LD
Hans, that was not the two channels I showed, that was manufacture spec vs an actual measurement. Let me trawl for 2 channel comparisons.
Yes, that's enough to be audible, about a 1dB shelf lift above 500Hz. Not terrible, but enough to present a problem, I think.
Maybe one does need to measure and choose R=2L-Rc from the result.
LD
I've got a half decent meter for measuring R on some samples, but not hooked up an inductance measuring jig. It's on the list. Hookup and measure with a test record will be quicker and possibly as good for these purposes.
Bill, my English must be very confusing. Yes I fully understood that you showed Spec's versus one channel.
That's why I tried to suggest to compare both channels. 😀
Hans
@Scott
I thought you were talking about two different problems, but it was probably just the gain change that you tried to mention all the time in case of using two unequal resistors giving a certain value in parallel.
In the example I gave, the difference in overall gain between 4k2//5k4 and 4k7//4K7 is only 0.1db, but f.i. a 3k//10K will make a difference of 2.8dB when using a 500mH+1000 Ohm/180nF combination.
The larger the difference between the two, the more gain you get.
But this is all taken into account in the Excel model I provided.
Aurak, technical reference as addendum to Cart. Dyn. Behav.
Hans
In hindsight, I think I misunderstood your message because of the word "exact".
I thought you were talking about two different problems, but it was probably just the gain change that you tried to mention all the time in case of using two unequal resistors giving a certain value in parallel.
In the example I gave, the difference in overall gain between 4k2//5k4 and 4k7//4K7 is only 0.1db, but f.i. a 3k//10K will make a difference of 2.8dB when using a 500mH+1000 Ohm/180nF combination.
The larger the difference between the two, the more gain you get.
But this is all taken into account in the Excel model I provided.
Aurak, technical reference as addendum to Cart. Dyn. Behav.
Hans
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Hans: I am running into a case where I cannot remember what I googled in the past to find the threads where people did compare channels. I will do some resistance measurements tonight as a starter.
I am not so sure it is moot with 47k. The audio frequency capacitance resonance means that differences, especially in "L" will cause some very strange phase shifts between left and right above 5kHz. Far far larger than the effects of 1% component matching in the RIAA network that people worry so much about.
That's OK I just thought a way to set gain (normalize all carts to say 20dB @ 5mV) and not use any extra R might be a useful data point. As I said I have not looked at enough carts to see if L, R, and sensitivity wash out.
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