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Old 11th April 2013, 06:23 AM   #121
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Quote:
Originally Posted by pinnocchio View Post
What about 70um copper thickness?
Pretty sure it's impossible. AFAIK, no PCB manufacturer in Vietnam could offer 2oz copper thickness.
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Old 11th April 2013, 07:46 AM   #122
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Quote:
Originally Posted by keantoken View Post
The feedback connection to D3 and D4 makes the stability under clipping very complex and conditional. I can't predict what will set it off but it seems dangerous.

Also, if the Cj of the zeners is significant compared to the 4148's, then you will probably have charge pumping through the 4148's causing some strange dynamic frequency-dependent distortion. Whether this is is perceived as distortion or as some "special sound quality" is another matter. If you flip the D+Z around, it'll be the 4148 that's reverse-biased rather than the Zener, so its small capacitance will be more guaranteed and charge-pumping reduced. The original Goldmund actually does this IIRC, and although it doesn't look right it still works. If you choose to switch the protection back to the output I suggest to put 2 diodes in series with R19 so it's value can be decreased - because with the Goldmund protection scheme the gate voltage at clipping is Vz+Vd+(Ivasmax*R19).
HI!

i see it!
thanks
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Old 11th April 2013, 02:12 PM   #123
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Quote:
Originally Posted by quanghao View Post
after I copy Goldmun Telos 2500 Amplifier, I was successful and not only that, on the basis of development, diy, and little understanding, learning and experience inherited their predecessors,
Quanghao also to design an amplifier with circuit diagram here. Please see

Thanks all
This thread originated with the idea of copying the relevant features used in the excellent-performing OPA637 op-amp, but applied to a higher-supply-voltage power amplifier. While in the process much is lost along the way with stage gains and slew-rate, etc., there's anopther aspect that was lost at the beginning and remains lost. I'm referring to the bootstrapped cascode stage used by the OPA637.
Click the image to open in full size.
In the figure, circuit A. on the left is the form you're using, and B is an improved form that I'm suggesting. [sorry guys, I'm still figuring out how to make stored Flickr images work properly here, but you can right-click and see the image]

Unfortunately, JFETs do not have as low an output conductance as we'd like, and furthermore, the JFET output conductances in a transistor pair are not matched. Anytime you change a JFET's Vds you're going to get a change in Vgs. This is bad for amplifier distortion. Burr-Brown solved this by insuring constant Vds for the input JFETs.

Removing this feature might not be so bad for an inverting amplifier, because the input stage is always at ground, but you're using the usual non-inverting feedback configuration, which runs the input stage common-mode voltage through the input-signal voltage range.

Last edited by winhill2; 11th April 2013 at 02:28 PM.
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Old 11th April 2013, 03:10 PM   #124
lineup is online now lineup  Sweden
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I agree with you winhill2.

I have been inspired of this thread about a OPA637 clone.
So, I have a slightly modified '637-amplifier' in my SPICE.

It is almost same input stage as you suggest, version 'B'.
Instead of Zener diode I use a resistor = R7 (15k) to generate a 15 Volt cascode.

Regards
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File Type: jpg OPA637_input.jpg (35.7 KB, 85 views)
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Old 11th April 2013, 03:23 PM   #125
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Quote:
Originally Posted by lineup View Post
I agree with you winhill2.

I have been inspired of this thread about a OPA637 clone.
So, I have a slightly modified '637-amplifier' in my SPICE.

It is almost same input stage as you suggest, version 'B'.
Instead of Zener diode I use a resistor = R7 (15k) to generate a 15 Volt cascode.

Regards
did you test the sound of it?
thanks
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Old 11th April 2013, 03:44 PM   #126
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keantoken helped me run this amplifier simulator, and give very good ideas for it.

Thank you very much
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File Type: jpg keantoken TEST it.jpg (281.9 KB, 135 views)
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Old 11th April 2013, 04:42 PM   #127
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Quote:
Originally Posted by lineup View Post
I agree with you winhill2.

I have been inspired of this thread about a OPA637 clone.
So, I have a slightly modified '637-amplifier' in my SPICE.

It is almost same input stage as you suggest, version 'B'.
Instead of Zener diode I use a resistor = R7 (15k) to generate a 15 Volt cascode.

Regards
Excellent lineup, it's very similar what I used in my TT amp, minus zener.
BR Damir
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Old 11th April 2013, 06:08 PM   #128
lineup is online now lineup  Sweden
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Yes, I remembered it from your TT amp.
I think it is close to the best way to do
a floating Cascode of the input stage.

My 637-Amp is promising.
I might even post it in this thread.
But I will work a bit more to perfect it.
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Old 12th April 2013, 03:52 PM   #129
Oland is offline Oland  Russian Federation
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Smile Much reminds

Quote:
Originally Posted by quanghao View Post
keantoken helped me run this amplifier simulator, and give very good ideas for it.

Thank you very much
Much reminds

AEM6000_Audio_Amplifier_Module.pdf

poweramp.pdf
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Old 14th April 2013, 06:12 AM   #130
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[QUOTE=Oland;3451480]Much reminds

i seen it!

yes!
i was test ti, but i not like the sound of it!

thanks
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