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Old 21st January 2013, 03:23 PM   #9121
Salas is offline Salas  Greece
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41.1dB
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Old 21st January 2013, 05:46 PM   #9122
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So here we have Rev2 calculator.

This one incorporates a simulator for the 1st stage of the folded cascode built with two K170 in the input.

If it passes the sieve, I can add a sheet with info for the 2SK369 buids.... just need some input on possible Idss / Vp data.

It is interesting to experiment with different Idss... if we choose an Idss higher than 8mA, the value on the trimmer becomes negative, indicating we must increase Vdd or slightly lower R13.
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Old 21st January 2013, 06:11 PM   #9123
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It is interesting to experiment with different Idss... if we choose an Idss higher than 8mA, the value on the trimmer becomes negative, indicating we must increase Vdd or slightly lower R13.
Glad I could contribut

Am i right that the current through that branch is limited in that is proportional to the total resistance. If limited to 10ma through the branch, and youhav a jfet taking up 8-9mA, then you do not have enough left to drop a voltage across the collector of the bjt, as it is getting eaten up by the Jfets, the Jfets Rs, and the forward drop of the bjt base. Increasing the B+ voltage increases the total available current in proportion with the increase in voltage/resitance.

reading that again, it makes no sense, but i think its close
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Old 21st January 2013, 07:03 PM   #9124
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Its nice if some of you grasp the works and can predict/tune for different biasing semis but in general for the most builders try stick to the given IDSS and B+ region as in the recommended circuits, and they will work right up.
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Old 21st January 2013, 07:07 PM   #9125
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Originally Posted by RCruz View Post
So here we have Rev2 calculator.

This one incorporates a simulator for the 1st stage of the folded cascode built with two K170 in the input.

If it passes the sieve, I can add a sheet with info for the 2SK369 buids.... just need some input on possible Idss / Vp data.

It is interesting to experiment with different Idss... if we choose an Idss higher than 8mA, the value on the trimmer becomes negative, indicating we must increase Vdd or slightly lower R13.
Should be following reality for gain quite well this revision. Try verify on your builds too.
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Old 21st January 2013, 07:47 PM   #9126
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Its nice if some of you grasp the works and can predict/tune for different biasing semis but in general for the most builders try stick to the given IDSS and B+ region as in the recommended circuits, and they will work right up.
Grasp might be a bit strong, but then again, grasping does seem to define what i do most days here, pretty well Building my second will be strictly by the book, as it is so much easier when you follow directions. Plus, I have a feeling that you have put a lot of time into getting it ready, and that includes tweaking it to a happy medium, sound wise. The calculator by Rcruz will be a nice and handy tool . On the second build, I am adding a selector switch to be able to tune the input resistor. Easier than resoldering smd over and over again.
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Old 21st January 2013, 08:05 PM   #9127
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You are right.... if you follow the pdf, you can be sure to get the most out of it.

Hi Salas

Thank you, I will verify my builds using a test disk at 1kHz

This was fun and I really am learning a lot.
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Old 21st January 2013, 08:40 PM   #9128
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Some DMMs are happier below 500HZ when the level is not several volts. My Fluke 17B is not reliable beyond 500Hz while my 87V is till 20KHz. The HFNRR record is testing single tone at 300Hz though. Me I use calibrated level PC FFT or my calibrated arb gen and DSO of course but with DMMs and disc if something comes up weird try factoring the procedure well. Stay at same track area and check quick enough, have good anti skating also.
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Old 21st January 2013, 08:53 PM   #9129
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Perfect..... allready did it in the past and detected a difference in output of my previous cart with 1kHz.

Now I will use 300Hz
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Old 22nd January 2013, 11:23 AM   #9130
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All is up and running now with much better numbers with added Rs on second stage. I have most of the parts for the second build and had a question as to PSU caps. RCruz, you stated that you were surprised to notice the effect of the PSU cap selection. Would you elaborate. My brothers version has Nichicon KG. I was considering the same or similar, with the addition of a large motor run before the SSLV. Any recommendations here?

Also, how about an idea of testing the RIAA curve. I have pc Based scopes and partially functioning Tek 465
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