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Gyrator loaded Son of ZV9/F3
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Old 12th February 2018, 09:53 AM   #161
juma is offline juma  Germany
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What I like might not be the same what you like.
Those parts are cheap, circuits are simple and all can be easily built in point-to-point manner so you can test them and decide for yourself what suits you the best...

BTW there is a 2sk170 on your PCB but the circuit uses BS170 - those are very different parts, check everything thoroughly ...
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Old 12th February 2018, 10:18 AM   #162
maouna is offline maouna  Greece
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I will build and try both.Will 2sk170 work instead BS170? Pins are the same though.I already have 2 pieces 2sk170 maybe genuine.BS170 bought from ebay have a chance to work?

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Old 12th February 2018, 11:46 AM   #163
juma is offline juma  Germany
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Quote:
Originally Posted by maouna View Post
...Will 2sk170 work instead BS170? ...
No.
2sk170 is JFET (depletion mode device) and BS170 is MOSFET (enhanced mode device).
No need to buy parts on ebay - BS170 is current production and can be bought from reputable companies like Mouser or Digikey:
BS170 ON Semiconductor / Fairchild | Mouser Deutschland

BS170-D75Z ON Semiconductor | Diskrete Halbleiterprodukte | DigiKey
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Old 13th February 2018, 11:31 AM   #164
juma is offline juma  Germany
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Quote:
Originally Posted by maouna View Post
...I already have 2 pieces 2sk170...
If they are genuine Toshiba and have Idss in range 8-15mA you can use them nicely - in fact, you can add a pair of Lateral MOSFETs and you'll have a great power amp.

Single rail power supply, no input cap and the output cap is inside feedback loop (gain = 20dB, R13/R3 ratio). P1 sets the output stage bias (0.5 - 1A depending on your preferences/heatsinks) and P2 sets half of the power supply voltage at the + pin of C4. Both pots can be single turn, start setting them at middle positions (give capacitors few seconds to get charged before you start). To set the I_bias insert 0R1 resistor between plus pole of power supply and Drain of Q5. Watch the voltage drop across that resistor and set it with P1 to 50-100mV.
Z_in is determined by R2 (10k) so it will need the preamp with Z_out of less than 1k. Together with JFET's parasitic capacitance R2 builds an effective low pass filter that makes amp immune to RFI without compromising amp's freq./phase response. Amp's Z_out is very low (DF>100).
Output power depends on supply voltage (20W at 8R with 45V PSU and 10W at 8R with 30V PSU - with 4R load power gets doubled).
Amp sounds smooth, live and clean and it's simple enough to build point-to point.
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Old 13th February 2018, 01:41 PM   #165
marconi118 is offline marconi118  Germany
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brilliant as always Juma, reminds me the fetzilla but simpler and with gyrator has to sound lovely.
will try it P2P
is there a way to increase the Zin a bit? and decrease gain? increase R2?
can I use BC547B instead? does hfe matters for cascoding?


OT. is your SuSy amp inv. OPA549 still the preferred AB class amp?
Is there a cheaper replacement for OPA549? BB ICs are really expensive....

Last edited by marconi118; 13th February 2018 at 01:56 PM.
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Old 13th February 2018, 02:57 PM   #166
juma is offline juma  Germany
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There is an error in post #164. Gain is set by R13/R2 ratio, not R3 (it's there just to avoid Gate going positive re. to Source).

Quote:
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... is there a way to increase the Zin a bit? and decrease gain? increase R2?
You can try 22k for R2 - half the gain, double Z_in. Somewhat narrower passband.

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Originally Posted by marconi118 View Post
can I use BC547B instead? does hfe matters for cascoding?
Yes. Not much

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Originally Posted by marconi118 View Post
OT. is your SuSy amp inv. OPA549 still the preferred AB class amp?
No, but I still have it - sounds great with Rogers LS3/5A

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Originally Posted by marconi118 View Post
Is there a cheaper replacement for OPA549? BB ICs are really expensive....
Not that I know.
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Old 13th February 2018, 03:14 PM   #167
marconi118 is offline marconi118  Germany
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what cals AB amp has replaced your Susy inv amp?

need an AB amp for low power consumption but still sunding not bad
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Old 13th February 2018, 03:25 PM   #168
juma is offline juma  Germany
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Quote:
Originally Posted by marconi118 View Post
what cals AB amp has replaced your Susy inv amp?
That one won't get published soon.

Quote:
Originally Posted by marconi118 View Post
need an AB amp for low power consumption but still sounding not bad
Try LM3886 - not bad for sure. Low consumption guaranteed. Cheap too...
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Old 13th February 2018, 03:55 PM   #169
marconi118 is offline marconi118  Germany
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simple GC with LM3886 is my last ressort...
do you have somithing else, still cheap to propose?

Back on topic, is it possible to use the full mosfet with shade feedback version MOSFET-trioda Mju folover verzija - Solid State - diyAudio.rs

to drive latreal mosfets? will it sound different than the one with bf862 cascoded?
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Old 13th February 2018, 04:25 PM   #170
juma is offline juma  Germany
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No.
Yes.
Yes.
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