Author Topic: Mars Octal Phono  (Read 1109 times)

Offline Mars

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Mars Octal Phono
« on: October 13, 2016, 10:48:49 AM »
I've completed the design of the octal phono preamp and took photos of the build:



Power transformer and filter caps



Top view:



Power supply inside:



View of two phono stages:













Outputs to RCA:



Cathode follower resistors:



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Offline iondb

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Re: Mars Octal Phono
« Reply #1 on: October 13, 2016, 11:01:56 AM »
Looking really good there Mr Mars!!!!

Offline Qualityten

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Re: Mars Octal Phono
« Reply #2 on: October 15, 2016, 12:59:27 PM »
Such beautiful work, thanks for posting.  Does locating the power transformer and filter caps above with a metal cover protect the circuit from hum?

Offline King_Julian_S

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Re: Mars Octal Phono
« Reply #3 on: October 15, 2016, 02:35:03 PM »
+1 Karel 👏🏾


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Offline vinyljan

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Re: Mars Octal Phono
« Reply #4 on: October 15, 2016, 06:12:51 PM »
Very nice Karel :thumbs:, can you please post a schematic?
In a maximum bank turn in a normal category airplane, like a typical Cessna, everything is fine until you turn across your own wake

Offline Mars

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Re: Mars Octal Phono
« Reply #5 on: October 19, 2016, 09:24:56 PM »
Such beautiful work, thanks for posting.  Does locating the power transformer and filter caps above with a metal cover protect the circuit from hum?

Yes, your power transformer needs to be boxed in. If it is mounted below, you'll need to enclose it in a tin housing, otherwise hum problems will arise.
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Offline Mars67

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Re: Mars Octal Phono
« Reply #6 on: October 21, 2016, 06:50:15 AM »
Wow what a build!!!

Offline El Sid

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Re: Mars Octal Phono
« Reply #7 on: October 21, 2016, 03:12:09 PM »
Nice! Will this hit the market at some point?

Offline Mars

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Re: Mars Octal Phono
« Reply #8 on: October 24, 2016, 08:42:05 AM »
Thanks for the comments :mates:

Yes, this preamp is being developed for the market. We hope to have a finished, marketable product before the end of the year.
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Offline TriodeFan

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Re: Mars Octal Phono
« Reply #9 on: October 25, 2016, 05:46:23 PM »
Hey Mr Mars ... that look really good! ... I wish you every success with it ... I recently added a 6SL7 based mono phono to the system here, which I built and m very happy with!

Offline Qualityten

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Re: Mars Octal Phono
« Reply #10 on: October 26, 2016, 10:49:10 PM »
Yes, your power transformer needs to be boxed in. If it is mounted below, you'll need to enclose it in a tin housing, otherwise hum problems will arise.

Thanks for the confirmation.  Valve phono stages make such a difference to enjoying vinyl.  I wish you every success.

Offline Ampdog

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Re: Mars Octal Phono
« Reply #11 on: October 27, 2016, 01:17:48 AM »
Also from me, Karel,

Kudos to your always explanatory and well-taken photographs accompanying your work!

(As the matter regarding power transformer influence was raised, I wanted to add something on transformer placement, but thought it better to rather leave a few hints under the 'DIY' section, for general knowledge.)
Creativity requires the courage to let go of certainties.  (Erich Fromm)

Offline movershaker

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Re: Mars Octal Phono
« Reply #12 on: November 30, 2016, 11:24:42 AM »
And there I was, living in Paarl for 8 years en never knew I was surrounded by Audiophiles en Valve Masters. Now I live in Pretoria, but this time I know a bit more...
I've been too long too far away from music....