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Chip Amps Amplifiers based on integrated circuits

Joe Rasmussen "Trans-Amp" - 40 Watt Transconductance "Current Amplifier"
Joe Rasmussen "Trans-Amp" - 40 Watt Transconductance "Current Amplifier"
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Old 4th December 2019, 10:15 PM   #451
lohk is offline lohk  Europe
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While this address does not work (here?) the direct one works (see above). The problem may be not https but something else.
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Old 4th December 2019, 10:51 PM   #452
Joe Rasmussen is offline Joe Rasmussen  Australia
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Quote:
Originally Posted by lohk View Post
The problem may be not https but something else.
This is where the actual Gif graphic file is stored on my website and this is what is used when I upload it in a message:

"https://www.customanalogue.com/diy/Trans_Amp_Schema_Wiring_Caution.gif"

Copy and paste the URL address and you have direct access to it. How diyaudio.com deals with this is beyond my control, does the graphic get stored elsewhere (on a Dutch .nl website?)?
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Old 4th December 2019, 11:28 PM   #453
lohk is offline lohk  Europe
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Yes, this is what I did. It is very easily to add it here:
Click the image to open in full size.
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Old 5th December 2019, 01:51 AM   #454
planet10 is offline planet10  Canada
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Joe Rasmussen "Trans-Amp" - 40 Watt Transconductance "Current Amplifier"
The entirety of webspace is in transition to all https:

dave
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Old 9th December 2019, 04:10 PM   #455
Ken Newton is offline Ken Newton  United States
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Quote:
Originally Posted by Joe Rasmussen View Post
Hi Ken

You have probably seen that PCB on my website.
Yes.

Quote:
So Ken, this new (dangerous word these days) amplifier is all about the current. Even that front-end is about current, the input stage converts the source voltage to current, then the 900V Power MosFets are driven via their Sources as the inputs. There is absolutely zero voltage swing on the Gate that is normally used as input, so the non-linear capacitance there has no effect.
I, too, am a fan of the grounded-gate. As you know, it's very common in RF applications, but is rarely used in audio (except as a cascode, of course).

Quote:
I was very lucky, through a personal contact I was able to get the circuit computer modeled by one of the world's best, the head of Power Electronics, part of SpaceX. He actually designs the guidance systems in Elon Musk's rockets, indeed Musk's right-hand electronics guy.
You are very fortunate to have access to leading-edge engineering talent like that. Does this gentleman also happen to be an audio enthusiast?

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I am 68 today (I don't celebrate birthdays) and in my life this has been the single largest project and really only finished last month.
Happy Birthday, just the same!

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I will be doing some measurements soon that will show distortion on the current of an amplifier that does not show up on the voltage side. A crude measurement has already been done, but needs to be done more critically and documented right, as well as capturing the distortion on the acoustic side of the speaker. I have about twenty people that the results will be shared with and we will have a private discussion online where the trolls cannot shout it down with noise.

Keep in touch if you have an interest in the above. My email address is publically known joeras@customanalogue.com and I trust you, so I can fill you in on those measurements.

Cheers, Joe
I'm naturally curious and attracted to new ideas, so, yes, I'd be interested in being apprised of intriguing breaking developments.

Off topic. I'm curious about your perspective on volume controls, about your preferred form/implementation. There are so many differing approaches, and I don't recall reading your thinking about it. I'm currently working on an DIY preamp and would value your input about this. I don't want to hijack this thread, so, perhaps, PM me, or point me to any prior published comments of yours about this, if that's not too inconvenient. Thanks, Joe.

Last edited by Ken Newton; 9th December 2019 at 04:15 PM.
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Old 19th December 2019, 06:48 AM   #456
Joe Rasmussen is offline Joe Rasmussen  Australia
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Hi Ken

Sorry, been busy putting finishing touches on the new amp. I will now find out just how good it is, having put some into certain hands for honest feedback.

Quote:
Originally Posted by Ken Newton View Post
I, too, am a fan of the grounded-gate. As you know, it's very common in RF applications...
Not an RF guy, but not hard to understand it works with RF.

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Originally Posted by Ken Newton View Post
You are very fortunate to have access to leading-edge engineering talent like that. Does this gentleman also happen to be an audio enthusiast?
No, but his Dad is and that is how I was able to make the connection.

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Originally Posted by Ken Newton View Post
I'm naturally curious and attracted to new ideas, so, yes, I'd be interested in being apprised of intriguing breaking developments.
This one will scramble your brains because it tries to make you think in a very different way. But I have good support and encouragement. This is a subject that I believe has found its time. So hopefully fairly soon I will get back to you.

Quote:
Originally Posted by Ken Newton View Post
Off topic. I'm curious about your perspective on volume controls, about your preferred form/implementation. There are so many differing approaches, and I don't recall reading your thinking about it. I'm currently working on an DIY preamp and would value your input about this. I don't want to hijack this thread, so, perhaps, PM me, or point me to any prior published comments of yours about this, if that's not too inconvenient. Thanks, Joe.
A most vexing topic.

These days I use the volume control in the Sabre DAC and I find it really excellent. They knew what they were doing here.

Around 15 years ago I posted somewhere on diyaudio.com about this tiny little pot, mechanically not the strongest and not 1/4" shaft:

Click the image to open in full size.

Uses silver-carbon, sounds very neutral and difficult to fault, other than they can have a bit of a short life - depends how they are treated.

I tried to find that 2004 thread... ?

50k Ohm Logarithmic (A) Double Gang 9mm Potentiometer | Jaycar Electronics

Cheers, Joe
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Old 19th December 2019, 11:30 PM   #457
Ken Newton is offline Ken Newton  United States
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Quote:
Originally Posted by Joe Rasmussen View Post
A most vexing topic.

Uses silver-carbon, sounds very neutral and difficult to fault, other than they can have a bit of a short life - depends how they are treated.

I tried to find that 2004 thread... ?

50k Ohm Logarithmic (A) Double Gang 9mm Potentiometer | Jaycar Electronics

Cheers, Joe
Silver-carbon? Interesting, that's a pot. composition description which I haven't seen before. I assume this is distinctly different from the track material composition utilized in typical carbon potentiometers?
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Old 20th December 2019, 02:47 AM   #458
Joe Rasmussen is offline Joe Rasmussen  Australia
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Quote:
Originally Posted by Ken Newton View Post
Silver-carbon? Interesting, that's a pot. composition description which I haven't seen before. I assume this is distinctly different from the track material composition utilized in typical carbon potentiometers?
Yes, quite different.

So I did try all those different potentiometers

Read Post #202 by KT and mine #203.

EDIT: I found the thread:

Pot ex Tawan - Photo - ignore my ugly Pinky!
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Old 20th December 2019, 11:50 PM   #459
Ken Newton is offline Ken Newton  United States
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Joe,

Thanks, those those detailed reposnses. Do you know whether the silver-carbon composition is standard for an Alpha pot., or is it instead some specially produced unit from them?
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Old 21st December 2019, 03:28 AM   #460
Joe Rasmussen is offline Joe Rasmussen  Australia
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Quote:
Originally Posted by Ken Newton View Post
Joe,

Thanks, those those detailed reposnses. Do you know whether the silver-carbon composition is standard for an Alpha pot., or is it instead some specially produced unit from them?
Hi Ken

It has been such a long time ago, but I remember seeing the pot for sale by Jaycar (I used to do some testing consultancy for the ower of the company) and it took a lot of digging and find it on a less than obvious part of Alpha's website. Not remembering the exact words, but something about carbon "substrate" containing silver. So I bought one and tried it - and it was the best "pot" I had ever heard, clean and no obvious colourations.

I have now used about a hundred of them. I test them for channel balance before I use them. But over that 15 year period I have had to replace some, they are mechanically not the strongest and they can go noisy - I don't think the like DC from. say, grid-leak current from a tube. So if you have a bad input tube and measured mV there.
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