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Discrete opamps.
Discrete opamps.
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Old 19th May 2019, 01:46 PM   #11
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by canvas View Post
Some of the characteristics are quite impressive.
Like BJT's with 40 pico-amp Ib or 260dB Aol?
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Old 19th May 2019, 01:57 PM   #12
canvas is offline canvas  Taiwan
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Quote:
Originally Posted by scott wurcer View Post
Like BJT's with 40 pico-amp Ib or 260dB Aol?
Hi Scott,

Yes, these sounds impressive to me. I've only seen few bjt op amps with less than 50pa Ib. And the 260dB Aol? Never heard. Perhaps they are exaggerating. I don't know. You're an expert. Would love to hear your opinion about it.

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Old 19th May 2019, 02:17 PM   #13
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by canvas View Post
Hi Scott,

Yes, these sounds impressive to me. I've only seen few bjt op amps with less than 50pa Ib. And the 260dB Aol? Never heard. Perhaps they are exaggerating. I don't know. You're an expert. Would love to hear your opinion about it.

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I meant BJT not FET, 40pA is not possible so it must be a confusion. All the illustrations are CAD drawings so who knows?
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Old 19th May 2019, 03:01 PM   #14
Mark Tillotson is offline Mark Tillotson
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On the other hand i bet they measured its noise with a ne5532/34 based sound card or analyzer as they couldn't get lower than the ne532/34 noise itself.
Input noise measurements are done with decent amounts of gain, so the noise behaviour of the output stage of the device (and of the measuring equipment) will not confound the reading.
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Old 19th May 2019, 03:20 PM   #15
dreamth is offline dreamth  Romania
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Which makes for the fact that they could measure much better for a discrete op-amp so they should be thankful for giving them a chance to cheat
It looks like these guys never read this:
http://leonaudio.biz/double.balanced.mic.amp.notes.pdf
Nobody trying to make a hybrid should skip Graeme Cohen's document.
And this too:
http://www.forsselltech.com/media/at...ts/JFETMP1.PDF
http://www.forsselltech.com/media/at...ike_Preamp.PDF

Last edited by dreamth; 19th May 2019 at 03:41 PM.
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Old 19th May 2019, 03:51 PM   #16
Mark Johnson is offline Mark Johnson  United States
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Discrete opamps.
FYI, Douk Audio also sells chassis with huge heatsinks, suitable for class A amplifiers, on eBay. I bought one and built a First Watt M2x in it. Good mid-grade quality and corresponding mid-tier prices. Here's the one I bought, the JX085 (link)

What the photo in the eBay listing does NOT show, is that the front panel is engraved with the words "PASS ALEPH AMP CLASS A". I consider this a little misleading; the photos in the listing are carefully arranged so the engraving is out of frame. The one head-on picture is lighted so no shadows fall in the engraving and you can't see it or read it.

Those are the kind of folks you're dealing with when you buy from Douk Audio.

(It turns out I don't actually care very much whether the case is or is not engraved; this has no effect upon the sound of the amp . But I do think it's not a completely honest way to advertise goods for sale).
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Old 20th October 2019, 10:34 PM   #17
keantoken is offline keantoken  United States
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I can't find any information on this SX-22B except for this Ebay listing which gives Audience as the source???

SX22B Discrete Dual Op Amp HiFi Preamp Board Integrated Module Replace 4558d for sale online

Where is the SPICE model?

I do find this opamp, which has much reduced specs:

Dual Discrete Op Amp HiFi Audio Preamp Operational Amplifier OPAMP replace ad827

Quote:
The whole frequency band is very average with accurate and soft high frequency, full mid-frequency, flexible and strong low frequency. The sound is near to gallbladder machine and LP records.
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Last edited by keantoken; 20th October 2019 at 10:39 PM.
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Old 22nd October 2019, 04:22 AM   #18
PRR is online now PRR  United States
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> The sound is near to gallbladder machine

Gallbladder machine?

I've had gall pain. You do NOT want this.
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Old 22nd October 2019, 02:45 PM   #19
Mark Tillotson is offline Mark Tillotson
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I suspect it means an ultrasound scanner - IM products from ultrasound extend into the audio spectrum perhaps.
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Old 22nd October 2019, 02:47 PM   #20
jan.didden is offline jan.didden  Europe
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This: The whole frequency band is very average probably means 'very flat'.

Jan
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