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Old 17th November 2013, 01:04 PM   #221
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Quote:
Originally Posted by 6L6 View Post
A bit of advice - the pot will take the place of R2 on the PCB, input to the junction of R1/R2, output to the Jfet Gates and then connect the pot to ground. A little surgery or creative thinking will be needed for those connections. Nelson has suggested keeping R1, as it's there to stop parasitic oscillation.
Just this part. Its OK, but I don't get it. . I tried to visualize it, but without cutting traces or removing R1 and R2 and connecting them off PCB, I don't think it will work.
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Old 17th November 2013, 01:11 PM   #222
6L6 is offline 6L6  United States
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You are right. That's not gong to work as described. I think the easiest will be to place R1 on the pot or input jack and wire the pot into the R2 pads as best one can.
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Old 22nd November 2013, 02:41 AM   #223
6L6 is offline 6L6  United States
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A little progress today. The most important thing was getting to my buddy's shop and using his mill to cut the hole for the IEC connector. The back panel needs only to be wired.

The transformer is a 120VA 20+20V Shielded Antek. Because of this I will use a LM317/337 regulator from TubeCad. Also the rotary AC switch and selector are from TubeCad. Very, very nice pieces. There are a number of good 'building blocks' available there. both low- and high-voltage.

The Attenuator is a series stepped Goldpoint with Dale RN60 resistors.

I have yet to make the final order to Mouser for components, that is why the preamp PCB is not currently installed.

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Old 22nd November 2013, 05:21 PM   #224
6L6 is offline 6L6  United States
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A bit more wiring today.

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Old 22nd November 2013, 05:51 PM   #225
Neville is offline Neville  United States
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Looking good Jim, that chassis is from the store right? which one is it?
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Old 22nd November 2013, 05:56 PM   #226
Zen Mod is offline Zen Mod  Serbia
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I believe - nothing wrong with placing selector and attenuator all the way back , with extending shafts to front ?
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Old 22nd November 2013, 06:22 PM   #227
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6L6, you decide how you are going to connect the attenuator? My setup is a lot like yours.
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Old 22nd November 2013, 08:50 PM   #228
6L6 is offline 6L6  United States
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Neville -- Galaxy 388 (3mm Front) - Compact with Quasi Heatsinks - Chassis

Vince - I'm going to try placing the R1 resistor in the output of the pot (attenuator). Probably right at the PCB. It's a gatestopper shared by both input Jfets, so hopefully should work. I will have photos when I wire it.

Choky - I don't have the necessary hardware for the shaft extension and internal switch/potentiometer mounts and such. I do like the idea, however.

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Old 22nd November 2013, 09:13 PM   #229
Hikari1 is offline Hikari1  United States
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Good place for extension shafts, volume knobs, etc:

Audio Catalog

That's what I am using. Shipping was pretty quick to the US (they are in HK) and the prices are great.
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Old 22nd November 2013, 09:38 PM   #230
Zen Mod is offline Zen Mod  Serbia
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shaft - plain M6 screw rods - any hardware store

mounting element for att and selector to bottom plate - piece of Al angle

wanked pots for shaft sleeves

plastic or rubber hose for joining extending rods to pot and selector
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