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Designing a universal diff-in/diff-out Head Amp
Designing a universal diff-in/diff-out Head Amp
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Old 27th January 2019, 09:28 AM   #171
billshurv is offline billshurv  United Kingdom
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Designing a universal diff-in/diff-out Head Amp
Ah. Fairy nuff.
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Old 28th January 2019, 11:41 PM   #172
billshurv is offline billshurv  United Kingdom
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Designing a universal diff-in/diff-out Head Amp
Scott will find this funny. Chatted with my Technics owning Guinea Pig (ToGP). ToGP was horrified even by the idea of a headshell mounted doohickey so I'll make him one that goes at the mixer end. I reckon you could build the circuit into an XLR connector if you were more delicate than I am.
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Old 29th January 2019, 12:27 AM   #173
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by billshurv View Post
ToGP was horrified even by the idea of a headshell mounted doohickey
Of course.
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Old 31st January 2019, 11:07 PM   #174
billshurv is offline billshurv  United Kingdom
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Designing a universal diff-in/diff-out Head Amp
Tonights Dumb question(tm) on the balanced version. How matched do the FETs need to be and what needs to be matched. I realised I have a number of LSK170 about to come free which would make initial lashups easier.
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Old 1st February 2019, 12:07 AM   #175
scott wurcer is offline scott wurcer  United States
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If your doing source followers with a relatively large drop on the source resistors you don't need to worry much about it.
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Old 1st February 2019, 12:41 AM   #176
billshurv is offline billshurv  United Kingdom
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Designing a universal diff-in/diff-out Head Amp
Thank you. I thought that was the case, but wanted to double check before I unsoldered the wrong FETs
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Old 12th February 2019, 08:54 AM   #177
Rick PA Stadel is offline Rick PA Stadel  United States
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Hi Bill,

You may also want to include a rectifier or two. Phantom-powered toys not only get hot-plugged, but a lot of recent gear provides a switch for the 48V -- and it won't always be a nice, polite 2 volts-per-second ramp.

Such fun discovering this project and getting caught up. Hope I'm not too late for your Mouser order.

Regards,
Rick
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Old 12th February 2019, 09:05 AM   #178
Rick PA Stadel is offline Rick PA Stadel  United States
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Umm -- come to think of it, maybe just a 15 or 18V zener from Q1* emitter to ground should be adequate for both ramps.

* referring to the 2nd schem, Hans' post #156

All the best,
Rick
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Old 12th February 2019, 10:02 AM   #179
billshurv is offline billshurv  United Kingdom
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Designing a universal diff-in/diff-out Head Amp
Rick, all my projects are slow time at the moment around other things at the moment so nothing missed out. As soon as I get something working will go off to my test subject to see if he can get it to work without breaking it and likes it. This will be the balanced version.
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Old 12th February 2019, 03:08 PM   #180
Hans Polak is online now Hans Polak  Netherlands
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Quote:
Originally Posted by Rick PA Stadel View Post
Umm -- come to think of it, maybe just a 15 or 18V zener from Q1* emitter to ground should be adequate for both ramps.

* referring to the 2nd schem, Hans' post #156

All the best,
Rick
Rick,


I fully agree with the 18V zener on the SE version.
The diff version already has a zener, no accidents waiting to happen over here.


Hans
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