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Old 16th June 2013, 10:18 PM   #661
RNMarsh is offline RNMarsh  United States
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Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by jacco vermeulen View Post
Wow! That's IT! Not exactly the 100 version but plenty of useful projects and info on how things worked and what the parts did. Then I started using the parts to create other circuits/ideas. later, i got a pencil soldering iron and eventually a VOM and scope and made my first test equipment -- a transistor characteristic tester... all with analog meters monitoring every terminal's current flow at different R's etc and then I could calculate the HFE etc. Installed in a red lunch box. Who knows... it might still be at my mothers house somewhere --- she just turned 93 !! I was always impressed by magic and learned some tricks... still do some... electronics seemed like magic to me... something that caught my curiousity to learn how it works.. the trick to it.

Thx-Dick Marsh

Last edited by RNMarsh; 16th June 2013 at 10:29 PM.
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Old 23rd June 2013, 12:57 AM   #662
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I had the time to listen to the amplifier, but as I recently sold my DAC, I had to rely on my m-audio soundcard to do all the listening, so this made the task rather difficult.
Still, I can say that the amp sounds very very promising! It is very natural sounding, with perhaps a touch of warmth, fast and punchy, with excellent reproduction of tones. Soundstage is earthy and expansive, intruments feel real, palpable. I will be able to develop more when I find a proper source.


In the meantime, I made some measurements, here are the results...

Let's begin with sine/square wave tests on the scope.

From left to right: 10Hz, 10kHz, and 100kHz square wave output. I didn't install the input filter cap to allow full bandwitdh.
Attached Images
File Type: jpg Marsh headamp_10Hz.jpg (148.8 KB, 720 views)
File Type: jpg Marsh headamp_10kHz.jpg (212.4 KB, 707 views)
File Type: jpg Marsh headamp_100kHz.jpg (160.1 KB, 692 views)

Last edited by CaféNoir; 23rd June 2013 at 01:00 AM.
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Old 23rd June 2013, 02:33 AM   #663
RNMarsh is offline RNMarsh  United States
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Those are picture perfect square waves. You will like the sound even better with a good DAC, I am sure. Thank you for sharing your results !!

-Richard
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Old 24th June 2013, 01:26 PM   #664
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Thank you for publishing such an interesting design. I am impressed with the performance of the circuit, especially in relation to its simplicity.
Now I am curious how the performance could be improved further, did you manage to build the 12 transistor version you mentioned in your article?

Below, sine wave and clipping behavior...
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File Type: jpg IMG-20130414-00209.jpg (313.3 KB, 505 views)
File Type: jpg IMG-20130414-00205.jpg (172.7 KB, 479 views)
File Type: jpg IMG-20130414-00206.jpg (194.3 KB, 87 views)
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Old 24th June 2013, 06:26 PM   #665
sonidos is offline sonidos  United States
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+1. It helps to know this. Wow...can't wait to call this one done!
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Old 27th June 2013, 12:26 PM   #666
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Hi All,
CafeNoir was right nearly all my are within 20% and I have 2 sets within less than 10% of each other. :-)
I hve built 2 PSUs for the amps and have (at last) got round to soldering all the resistors on Samuel's boards also matched the 2sa1930/2sc5171s. Now about to order the caps, some more 2sa/2sc (just to see if I can get any closer matches) and the rest of the semi cons from Mouser (now I have the min order value).
I will be using AAVID THERMALLY ML26AAG heat sinks and mounting the SA/SC s horizonally to the back of the sinks to keep the e b c configuration correct. i.e. mount them with correct config verticaly, bend legs thro 90 degs and mount heatsinks to them with the sides pointing upwards. The sinks then overhang the board a bit but I have plenty of space.
I am using the boards the correct way up too (liked all the clear componet printing) and so I am reversing SA/SCs mounting Sounds more complicated than it is I will post some pix when all sorted.
So onward and upward
Pingushome
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Old 30th June 2013, 08:43 PM   #667
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Hi,
Construction so far, have to reorder R11/14 and still waiting Mouser order for the caps etc.
Pix not great on my phone.
The second is how the heatsinks will mount when the devices are soldered up and mounted to the bottom of the sinks. They will then be clear of any other bits on the board
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File Type: jpg DSC00060.JPG (225.0 KB, 207 views)
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Old 13th July 2013, 10:42 PM   #668
RNMarsh is offline RNMarsh  United States
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See post #40 for typical THD results you will obtain.

Thx-RNMarsh
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Old 15th July 2013, 01:30 AM   #669
RNMarsh is offline RNMarsh  United States
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Note the results in #40 are for 33 Ohm load and therefore higher Z loads, will result in even lower THD.

-RM
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Old 29th July 2013, 06:19 PM   #670
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Folks from Burson sent me this review of a bunch of headphone amplifiers -- the Marsh Headphone Amplifier would certainly be in the first ranks: Innerfedility Soloist Review Summary
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