Mezmerize DCB1 Building Thread - Page 68 - diyAudio
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Old 18th January 2013, 02:14 AM   #671
rokoko is offline rokoko  United States
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Just one more thought: for item (2), would this be even better to use a cap before relay. Like JFETs middle point goes to existing 220 Ohm resistor and cap in-series with it, from the right side of the cap: to 1M resistor to GND and to center (flying) relay contact, other relay contact goes to power amp input and through 1M resistor to GND (or even no this last 1M resistor at all relay contact straight to power amp?. Would this be more logical?
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Old 18th January 2013, 08:15 AM   #672
Salas is online now Salas  Greece
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It will be equivalent to having the cap in series with the existing DC coupled output on the PCB. Save hacking the board. Use 2 parallel RCA outputs, one direct, the other with the 6.8uF to 10uF output capacitor, so to have both DC coupled and AC coupled outlets. Depending on what you drive (AC/DC input coupled amps or DC input coupled amp with output DC fault protection relays) it will be a flexible configuration.
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Old 22nd January 2013, 03:25 PM   #673
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Quote:
Originally Posted by ramallo View Post
Finally I did the hot-rod first stage and I'm very impressed, the bass are incredible, as well the sound stage are wider and deeper.

I'm using two 16 Ohm resistors in parallel, the DCB1 are now close to 200m to 210mA (The voltage across the resistor drops a bit) (The DCB1 is cold).

A photos of the "near to finish" Mezmerize:

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Thanks Salas!
Hi all,

I'm looking for ideas for mounting the volume and source selectors on a thick front plate (the one from the store). It looks like I'll need to mount them similar to the one above but I can't see it in the photo. Any help would be appreciated!

Mark
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Old 22nd January 2013, 04:05 PM   #674
Renron is offline Renron  United States
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Mark,
Could you be more specific please?
Are you referring to the shaft extension on the volume?
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Old 22nd January 2013, 04:14 PM   #675
Marra is online now Marra  United Kingdom
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It looks like the input switch is mounted on a piece of L shaped alluminium.
Extension brackets like this are available but where in the USA I don't know.

Extension kit Hifi Collective
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Old 22nd January 2013, 06:20 PM   #676
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Quote:
Originally Posted by Renron View Post
Mark,
Could you be more specific please?
Are you referring to the shaft extension on the volume?
Sorry, I'm looking for ideas for a mounting bracket, and for an extension for the alps volume pot. The source switch already has an extended shaft.
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Old 22nd January 2013, 06:30 PM   #677
rokoko is offline rokoko  United States
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What is the wise target of Idss for matched 2SK170BL in order to get the lowest THD?
Do they have to be matched with +/- 0.05mA, or 0.1-0.15mA range would be adequate?
Just want to understand what numbers to get to Spencer ordering JFETs.
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Old 22nd January 2013, 06:38 PM   #678
Renron is offline Renron  United States
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An easy, easy extension shaft for the pot is a short piece of rubber tubing (automotive, vacuum or gas line) slipped over the pot shaft with another metal shaft on the other end. You can use a grommet or plastic tube (straw) where it penetrates the faceplate so it's not metal on metal. The knob will hide the penetration grommet. Hobby shops, and hardware stores have all different sizes of metal tubing. Doesn't have to be solid. Set screws on the knob will hold just fine.

[]--==----

pot >shaft>tubing>shaft

These ascii drawings don't usually work out well, but I tried.
Ron
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Old 22nd January 2013, 06:42 PM   #679
Salas is online now Salas  Greece
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Quote:
Originally Posted by rokoko View Post
What is the wise target of Idss for matched 2SK170BL in order to get the lowest THD?
Do they have to be matched with +/- 0.05mA, or 0.1-0.15mA range would be adequate?
Just want to understand what numbers to get to Spencer ordering JFETs.
Its primarily about offset. THD here has to do with transconductance and signal level mainly. Try to get the best but 0.1mA deviation is no party stopper.
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Old 23rd January 2013, 03:45 PM   #680
rokoko is offline rokoko  United States
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Salas, can you please clarify:
Quote:
but an Obbligato MKP oiler, the one in black can with flying leads should be economical and effective since you need some uF.
It is a radial type of can, both flying leads on the same side (end), not the axial type of cap?
About the potentiometer-mutistep switch: what DIY-selfers use the most as a good aesthetitac approach and most nice rotation feeling, is it a Alps type 20kOhm potentiometer or DACT, GOLDPOINT Stepped Attenuator?
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