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Old 19th September 2013, 05:10 PM   #691
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Quote:
Originally Posted by RNMarsh View Post
So, the question still remains and is this: How would we prove this approach will reduce the cartridge distortion going into the preamp via test and measurements?

Thx-RNMarsh
By using a test record, establishing a reference FFT with a standard MC pre, and comparison with various amplifiers, including the subject of the article. You could also use an actuator rather than a test record.

For the transformer I would imagine one could use the Sowter as in SY's HMN phono pre, but backwards.
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Old 19th September 2013, 06:46 PM   #692
RNMarsh is offline RNMarsh  United States
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Hi Jack ---
well i dont own a phono system... maybe you can get a follow-up article done on this potentially important angle. If it shows what we expect and hear, then it will change phono design forever more. Better late than never.

In any event - it would be best moved back over to the MC forum you started awhile ago.


Thx-RNMarsh
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Old 1st October 2013, 07:21 PM   #693
RNMarsh is offline RNMarsh  United States
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Default THD with headphone as load -

While checking the thd of the headphone amp at various resistive load values, I notice the thd could be fine tuned if the load was the same as the headphone used... But, why not adjust for lowest thd with the actual headphone plugged in instead of a resistor value? Sometimes, the complex Z of the real headphone (or speaker) is more difficult than a pure resistance and raised THd of the amp.

Well, the thd is different when an actual headphone was used. So I retuned it with one of my favorite headphones attached -- The load is a HiFiMan HD500. Still well below -100dB harmonics (the test gen/Audio-Precision is at -120dB). I can get the 2H lower but just balanced it with the 3H. [it can be inyeresting to learn what such harmonic manipulations sound like with music].

HPA with HD500 load.jpg


If you have the equipment, you can use your own headphone when adjusting or balancing the amp

THx-RNMarsh

Last edited by RNMarsh; 1st October 2013 at 07:29 PM.
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Old 25th October 2013, 08:35 PM   #694
RNMarsh is offline RNMarsh  United States
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Here is the HD including the signal generator source overlaid on the same graph. If the source distortion was zero, the amps 2H and 3H would be closer to -120dB.
[still using an external gen]


-Richard Marsh


DSC01149 B.jpg

Last edited by RNMarsh; 25th October 2013 at 08:38 PM.
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Old 6th January 2014, 07:44 PM   #695
RNMarsh is offline RNMarsh  United States
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I am wondering if anyone would like to comment on the sound quality with their headphones.

Thx-RNMarsh
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Old 8th January 2014, 01:41 AM   #696
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Default i'm in for four (4) PCB's

Put me down for four (4) PCB's. Take care.
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Old 8th January 2014, 01:59 AM   #697
mlloyd1 is offline mlloyd1  United States
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I'm not a reviewer (caveat), but I'm loving mine. My headphones are the Sennheiser HD595 low impedance model. For many years, I used a OPA627 + EL2008 buffer to drive my BeyerDynamic DT990 headphones (the old version). For ME, that was a great combination. My Beyers were damaged and I never repaired or replaced them. The HD595 was a Christmas present from my wife. I never got around to making anything that really makes them "sing" to me the way the Beyers did, but paired up with this amp, I'm a happy camper again. My tastes vary widely so equipment that is "tuned" for a particular genre is not preferred. When listening through cans, I like a clean, airy but authoritative sound when the music calls for it and this combo delivers in SPADES! I've retired my other headphone amps.

Thx Richard!

mlloyd1
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Old 16th January 2014, 01:58 AM   #698
RNMarsh is offline RNMarsh  United States
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Default Happy camper once again --

Hi Mlloyd1 --- Its a good day when I get feedback on the sound... I try to make them as neutral as possible... no 'tuning' for me either.
BTW - what did you use for a power supply?

Thx-Richard Marsh

PS sorry for the late reply.


HPA - AP2722.jpg

Higher resolution data. ^

Last edited by RNMarsh; 16th January 2014 at 02:08 AM.
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Old 21st January 2014, 04:06 AM   #699
mlloyd1 is offline mlloyd1  United States
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sorry for the late response; just saw your message.
i have some sulzer-borbely regulator boards built up in the past as "utility" supplies when i need a psu quick. it's powered by an avel-linberg toroid and soft-recovery rectifiers. No extra line filters, no common mode choke, no snubbing for either the transformer secondary or the rectifiers.
yeah, i know, i know, i'm being lazy.
just enjoying listening at the moment
even good with audiobooks
:-)
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Old 21st January 2014, 05:33 PM   #700
RNMarsh is offline RNMarsh  United States
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That is fine and maybe better than i use. Enjoy the music !

Thank you,
Richard Marsh
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