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Old 25th October 2012, 02:34 AM   #3571
Salas is offline Salas  Greece
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Quote:
Originally Posted by Jay View Post
The tweeter uses some kind of material (still a dome) which is named, if I'm not mistaken, SELENIUM. Seems like a metal, but soft like fabric. This dome material is popular in PA speaker system.
Maybe your HF driver uses a Mylar diaphragm?
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Old 25th October 2012, 07:27 AM   #3572
abetir is offline abetir  Philippines
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Originally Posted by naf View Post
dear Salas and Shaan,
channel 1 done, current feed change by paralelling 3k3 || 2k4.. Vas current down to 14.2mA
Hi Naf,

[edit] Can you show it in the schematic? I may get hold of my 25vac transformer this coming weekend, and of course it will be close to +/-32vdc.

TY!

Last edited by abetir; 25th October 2012 at 07:37 AM.
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Old 25th October 2012, 07:40 AM   #3573
naf is online now naf  Indonesia
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Originally Posted by abetir View Post
Hi Naf,

can you show it the schematic? I may get hold of my 25vac transformer this coming weekend, and of course it will also be a +/-32vdc.

TY!
this is my change 1k2 to 1k4 by paralelling 2k4 with 3k3
r 220 increased to 267 by series 220 + 47
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Old 26th October 2012, 12:04 AM   #3574
abetir is offline abetir  Philippines
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thanks naf, will try that too, if i encounter the same abnormal heating of parts.
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Old 28th October 2012, 04:54 PM   #3575
Jay is offline Jay  Indonesia
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Originally Posted by Salas View Post
Maybe your HF driver uses a Mylar diaphragm?
i'm not sure. it must be a common thing. color is yellowish.
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Old 30th October 2012, 02:47 AM   #3576
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Just a question. Did someone have measured the common mode rejection of his SSA ?
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Old 30th October 2012, 04:46 PM   #3577
shaan is offline shaan  India
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Interesting, I am eager to know the CMRR too. But how to inject a phase-equal signal into the low-impedance inverting input(s)? Or is there other ways to check the cmrr?
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Old 31st October 2012, 12:03 PM   #3578
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Interesting, I am eager to know the CMRR too. But how to inject a phase-equal signal into the low-impedance inverting input(s)? Or is there other ways to check the cmrr?
Adding an offset to the input signal DC coupled, signal = 1/2 max level, offset = +1/V or -1/2V. That way, the signal will go from 0V to + (or - ) V.
We are not interested, here, with the rejection itself, but the distortion induced by asymmetrical signals.

Of course, we need a cap in the output before to measure the distortion. Then compare distortion with offset vs distortion without.
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Last edited by Esperado; 31st October 2012 at 12:12 PM.
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Old 2nd November 2012, 08:28 PM   #3579
mikelm is offline mikelm  England
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Quote:
Originally Posted by MiiB View Post
I have made some different outputs. from laterals to Bipolars and a combination of both.
Hi Michael, I wonder which o/p device combination you preferred in the end ? In spice I found irf610/9610 followed by BJT looks best but for a low power amp a BC546c followed by a lateral MF also works very well - this is what I'm using at present but I will upscale soon.

Quote:
Sound is very very good. I believe its the simplicity and short current feed-back path that plays a major role in this. Like less is a lot more. The SSA is for sure a strong concept. But it really does require some good housekeeping. This type of simple current feedback circuits benefits a lot from fixed working conditions. Simple voltage/resistor biasing is not good enough for current feedback, as the feedback currents will alter/modulate the working conditions . The current feed-back needs to be purely additive process, for this you need a good high impedance CCS driving the circuit.
Do you think a fixed resistor from a perfect supply would still spoil the FB operation ? In spice I see little difference . . . or do you also think the high impedance of a good CCS contributes to ideal working conditions ?

mike
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Old 2nd November 2012, 09:01 PM   #3580
MiiB is offline MiiB  Denmark
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The fixed resistor sets the working (driving) current flow in the input pair... when you inject the current from the feed back it will add to the driving current. if the current source is ideal the process will be purely additive and precise, but a 1k Ohm current source (the resistor)..is hardly ideal and so the feed back process is unlinear with amplitude. in steady state (sines) (spice) this effect will not be visible in terms of higher distortion, but in dynamic conditions with ever changing amplitude this effect is easy to understand.
Listening vise you get an amplifier with better focus and a stable character.. when inserting a CCS.

My SSA has changed quite a bit now i set the VAS current through mirrors and use Hawksford cascodes on both input and VAS.

My output is a combination of Fets and Bjts...

Last edited by MiiB; 2nd November 2012 at 09:07 PM.
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