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Marsh headphone amp from Linear Audio
Marsh headphone amp from Linear Audio
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Old 21st April 2019, 03:19 AM   #1611
Mark Johnson is offline Mark Johnson  United States
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Marsh headphone amp from Linear Audio
Have some people at Lawrence Livermore explain the "risetime bandwidth equivalency" relationship to you. They can start with the Wikipedia article.

You will discover that 20 ns risetime corresponds to a bandwidth of 17.5 MHz. Congratulations, when going from FETs to bipolars your bandwidth only dropped 12%, from 20 MHz to 17.5 MHz.

At that time in history, Elantec and Comlinear were shipping all bipolar Current Feedback Amps whose bandwidth was 80 MHz. Soon National and AD would enter the fray with even greater bandwidth at even lower power.
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Old 21st April 2019, 03:46 AM   #1612
RNMarsh is offline RNMarsh  United States
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Yep. Like I said, it was the same Tr as the generator. So i dont know how fast it actually was. 20ns is not its Tr. It was faster. With the devices I used 50 years ago, it should be near 100Mhz.

If you read back -- you will see that i preceeded them in CFB amp topology and in fact the designers called me on the phone to discuss it when i was at LLNL... before they completed their design because they had been working on similar circuit and was about to go to patent app when my article came out. This is well before any IC shipments. They got my phone number from Ed Dell (TAA) and called me at my office at LLNL. They were really upset.

They modified the circuit slightly and got patent. They added a diode to make 2nd stage a current mirror. This is all old news... i have described this before in detail and in publication. Now the speeds using CMode topology are in GHz range with MOSFET etc.




THx-RNMarsh

Last edited by RNMarsh; 21st April 2019 at 04:15 AM.
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Old 26th April 2019, 03:03 AM   #1613
eljoantonyn is offline eljoantonyn  India
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OFFTOPIC:
I need to contact Jack (jackinnj) and he's not responding to PMs. May be he's away ?
Anyone know ?
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Old 17th May 2019, 05:41 AM   #1614
RNMarsh is offline RNMarsh  United States
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Hmmm still no response from Jack?



-RM
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Old 17th May 2019, 01:29 PM   #1615
jackinnj is offline jackinnj  United States
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Marsh headphone amp from Linear Audio
Quote:
Originally Posted by RNMarsh View Post
Hmmm still no response from Jack?



-RM
I got back to him -- perhaps the issue is shipping to India which is $14.
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Old 18th May 2019, 04:00 AM   #1616
eljoantonyn is offline eljoantonyn  India
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I got the communication from Jack today.
I'm dealing with some issues in my company and when I'm free, I'll mail him back.


Thank you jackinnj & RNMarsh.
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Old 19th May 2019, 04:39 AM   #1617
eljoantonyn is offline eljoantonyn  India
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I'm hoping that all of the components can be had from mouser
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Old 19th May 2019, 03:28 PM   #1618
rsavas is offline rsavas  Canada
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I see that Mouser has all the semi's in thru hole.
Does anyone have a pcb for this design?
I was thinking of making one, I will buy the article from LA.
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Old 19th May 2019, 03:58 PM   #1619
Carl_Huff is offline Carl_Huff  United States
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Quote:
Originally Posted by rsavas View Post
I see that Mouser has all the semi's in thru hole.
Does anyone have a pcb for this design?
I was thinking of making one, I will buy the article from LA.
I've been working on one. It is self contained with a wallwart power supply. I designed it to slip into a 100 x 160mm Hammond extruded aluminum enclosure. I haven't actually built one yet but expect to soon.
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Best Regards,
Carl Huff
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Old 19th May 2019, 04:44 PM   #1620
rsavas is offline rsavas  Canada
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Looks good Carl.
Might want to move the inputs (or have the option) to the other end further away from the AC input. Might not be enough room for the connectors/pots you have chosen :-) just an idea.
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