ricardo wrote:
Wanna link to some High End (?) circuits which you feel have lower noise, lower current bla bla and better "balance"? That would be a constructive contribution.
Sorry to say, but I find your response to my open questions, meant to give a constructive contribution, rather harsh.
Answerring your bla bla question first, it makes no sense to put a Ferrari engine in a Fiat 500. That will make the product unbalanced.
Designing a pre amp with great care by making a fully balance design and striving for ultra low noise is not a quick and dirty job and needs quite some attention.
As cart current is one of the design criteria, it seems quite logical to pay attention to this aspect with the same care and attention.
Whether or not 100uA cart current can be allowed is a question that is not supported in the specs of any cart manufacturer.
So the easy way is to go as low as possible, just like was done with the extremely low noise.
So with high grade I mean: Low noise, low cart current, low phase distortion from 20-20kHz, accurate Riaa curve, high overload margin, very few caps in the signal path etc, etc.
Only when all these criteria are met, you have a balanced design.
What may be a fact of life for you, will not be perceived by others when things are not outspoken.
It did nor read before about you having tested many elements.
The design in this thread is from the beginning concentrated on a MC preamp, so only MC carts are of concern here.
Your opinion that all elements can have 100uA is a point that I missed in your posting.
And I only read about testing harmonics but not at all about all the listening you have done in a team.
It would therefore be interesting to hear whether you contacted Cart suppliers and if any to hear what their response was.
But whatever may be true, when the supplier does not guarantee this possibilty, why take the risk?
I contacted the supplier of my Benz LP Cart and their response was: the lower the better, but no more than in the low nA region.
For that reason I will never take the risk to allow 100uA, although their answer may be much too conservative.
Wanna explain what is low end or low grade about 5532?
It is low grade with respect to high grade RIAA preamps, the way I have explained at the beginning of this posting.
For a Riaa preamp 65dB SNR A-weighted is about the border where noise becomes noticeable from the speakers at normal listening levels, so this value must be seen as a lower limit.
This 65dB is for a MM ref 5mV@1kHz and for a MC ref 0.5mV@1kHz.
To have some room for Carts having less output, a target value of 75db SNR A-weighted seems appropriate.
Now coming to the 5532: For an MM its voltage noise is perfectly adequate but the current noise spoils this figure.
The input short circuited gives very nice noise figures, but the cart connected tells another story.
For that reason a Fet op-amp like the opa2134 or even better the opa1642 are to be preferred.
And for an MC application it voltage noise is to high to meet the 75dB.
Hoping the discussion can be continued in a more amicably manner.
Hans