Author Topic: Mars Mullard 3-3 ST  (Read 719 times)

Online Mars

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Mars Mullard 3-3 ST
« on: February 07, 2017, 10:53:35 AM »
We have a Single Ended EL84 kit with tube rectifier in production. It is a stereo version of the Mullard 3-3 without the tone controls.

I took some photos of the kit before delivery:

SE84 by Karel Mars, on Flickr

SE84 by Karel Mars, on Flickr

SE84 by Karel Mars, on Flickr

SE84 by Karel Mars, on Flickr

SE84 by Karel Mars, on Flickr

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Offline King_Julian_S

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Re: Mars Mullard 3-3 ST
« Reply #1 on: February 07, 2017, 11:29:25 AM »
Awesome Karel
What will the pricing be and output ratings etc ...
will there be options for tone controls and phono stage etc ...
Non audiophile music lover...

Offline iondb

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Re: Mars Mullard 3-3 ST
« Reply #2 on: February 08, 2017, 09:38:11 AM »
Looking good Mr Mars!!

Online Mars

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Re: Mars Mullard 3-3 ST
« Reply #3 on: February 09, 2017, 11:47:52 AM »
Thanks for the encouragement   :dop:

Hi King Julian, the price is R6900 for the kit, or R9900 for complete, ready to play, amplifier.

Iondb,  We are building a version with tone controls, and plan to offer it as an option.
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Online Mars

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Re: Mars Mullard 3-3 ST
« Reply #4 on: February 25, 2017, 11:54:49 AM »
Thursday we powered up the Mars Mullard 3-3 ST for the first time.

We started off with the negative feedback loop disconnected.

First we checked the power supply, and voltages were on target. Next we monitored the voltage across the EL84 cathode resistor as we turned up the variac. One resistor went over the 28V target. We checked the circuit. Next we moved the two tubes from the functioning channel to the over heating side. Problem disappeared. One EF86 turned out to be broken. After replacing the EF86, all was well.

Next we used crocodile clips to check the NFB loop. Once we confirmed that the NFB phasing was correct, we soldered the NFB loop in place.

The sound: What a great sounding circuit! Absolutely no hum. This seldom happens from a DIY build, but there it was. I can recommend this circuit, in spite of its apparent complexity. It seems to be immune from power supply ripple, much less so than regular SE circuits.

The sound is very clear and the bass was impressive. One happy amplifier owner went home.

There is another build of the kit about to be tested. I will report the outcome later.

 :dop:
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