Marsh headphone amp from Linear Audio

[jamato8]

What is the output power of this amp? I am driving the HE1000 V2 right now, not easy to drive and this amp is doing an excellent job of it!

 

[osscar]

Hi,
My MARSH amplifier with +-14V PSU can delivery about 2W @ 35 ohm (9V rms ) - and 1W of these 2W will be pure class A ( with 120mA bias per transistor) and then ir will switch to class AB

 

[jackinnj]

Sheridan Whiteside is on Turner Classic Movies with Bette Davis this week.

(Inside joke)

 

[Rush]

Sheridan Whiteside is on Turner Classic Movies with Bette Davis this week.

(Inside joke)

When acerbic critic Sheridan Whiteside slips on the front steps of a provincial Ohio businessman's home and breaks his hip, he and his entourage take over the house indefinitely.

I want in!

Rush

 

[jackinnj]

I want in!

I only need refer you to the esteemed Dr. Marsh's photographic avatar which has a striking similarity to that of Monty Woolley.

"The Man Who Came to Dinner" is a holiday favorite of mine. 1942.

Monty Woolley, Cole Porter etc. were a bunch of Yale guys who had a great time together! The movie also stars Betty Davis.

 

[Rush]

I only need refer you to the esteemed Dr. Marsh's photographic avatar which has a striking similarity to that of Monty Woolley.

"The Man Who Came to Dinner" is a holiday favorite of mine. 1942.

Monty Woolley, Cole Porter etc. were a bunch of Yale guys who had a great time together! The movie also stars Betty Davis.

Yes it is!

Ha!

Rush

 

[31697B]

How is the listening? Has some others' finished and ready to give listening impressions?


THx-RNMarsh

 

[31697B]

Have others been listening for any affects from different power supply designs?

I will use this for my HPA ---->


View attachment hpa_psu_sch (2).pdf



THx-RNMarsh

 

[Mark Johnson]

Might want to install an RC noise filter between each zener reference diode and its output driver. I use those nifty 3-terminal Feedthru Caps that TDK makes for RF applications. Fortunately they sell feedthrus in values > 4 microfarads.

 

[Mark Johnson]

(And in the Appendix of my Linear Audio v.10 article, I offered equations and data showing that it's safest to set the ratio (C18/C19) >= 15). As you woulld imagine, soft copy download is not free; Jan D. charges €2,99 at the webstore.

_

 

[jackinnj]

Parenthetical -- LT1210 wasn't around when Walt did the Audio Amateur "Regulators" article, i.e. 1995 -- it makes a good "rail driver" for PSRR measurement.

 

[31697B]

I read your article, MJ. Will add them Thx.

and a bypass on the zeners.


-R

 

[31697B]

All happy and content listening to music


-Richard

 

[31697B]

My friends in Bangkok, Thailand (Magnet Audio Tech) built this all out effort from the article in Linear Audio. Everything on one PCB. Fine workmanship.









THx-Richard

 

[jamato8]

My friends in Bangkok, Thailand (Magnet Audio Tech) built this all out effort from the article in Linear Audio. Everything on one PCB. Fine workmanship.


View attachment 747262






THx-Richard

Excellent!

 

[Mark Johnson]

Did they include the circuit design modifications suggested here in post #1589?

 

[jackinnj]

Richard -- did they include the headphone comp which was an integral component of the article?

fwiw - looks great!

jack

 

[31697B]

The suggestions came after their layout. But they can change it fast anyway... thats just prototype.

NO! They didn't include HP Comp. :-( Maybe we should do it ourselves?

Shortly afterwards several people started playing with the idea and now there are some headphones that do it, I believe, semi-automatically.

I am listening with Senn. HD-800 phones now and they are 300 Ohm. These phones are really excellent.


-Richard

 

[31697B]

All my topologies are inherently linear, fast, wide bandwidth. Today, I got around to measuring the BW.

With the original transistors I tried, the BW = 5 MHz at -3 dBv





THx-RNMarsh

 

[Mark Johnson]

Let's see, 5 MHz bandwidth at a gain of 4X (12 dB), is a GBW product of 20 MHz. Almost as good as the FET input opamps Jan Didden used in his 1995 Super Regulator, the AD817 (GBW= 50 MHz) and the AD825 (GBW= 41 MHz). We need to remember that the ICs are voltage feedback amplifiers but the headphone amp is a current feedback amplifier.

These chips cost about five dollars each if you pay extra for thru-hole packaging: Mouser link

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