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Old 18th April 2007, 04:54 AM   #1
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Default Digital potentiometer corrupt tube amps

I am looking at the possibility of a tube based 5.1 preamp. So far I have found no reasonably priced 6 channel attenuators/pots. I also considered various methods of mechanical coupling of normal stereo pots bu it is beginning to look like digital pots may be the only viable option. What is not clear to me is what effect these devices would have on the sound.

I am not particularly overjoyed with putting any solid state in the signal path. Do these devices use semiconductor based resistances or metal film or something else? Does the signal pass through the actual switching circuits or only across benign resistances?

Other suggested approches? What would you do?

mike
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Old 18th April 2007, 05:30 AM   #2
Tim__x is offline Tim__x  Canada
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They are switched, and they are solid state.
You should consider the fact that you will not find a single 5.1 recording that has not gone through solidstate equipment, infact I'd be very suprised if you found any 5.1 material that's been through less than ten opamps, a DAC, and subsequently an ADC, plus a couple more opamps in the ADC.
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Old 18th April 2007, 05:58 AM   #3
bibster is offline bibster  France
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Mashaffer,
You could have a look here: Lightspeed Attenuator a new passive preamp
Sounds feasible to make 5.1 version

Paul
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Old 18th April 2007, 08:52 AM   #4
EC8010 is offline EC8010  United Kingdom
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How about a bank of uniselectors form an old Strowger mechanical telephone exchange as the switches in your switched attenuator? "Dialing in the volume" could take on a whole new meaning...
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Old 18th April 2007, 08:56 AM   #5
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Quote:
Originally posted by EC8010
How about a bank of uniselectors form an old Strowger mechanical telephone exchange as the switches in your switched attenuator? "Dialing in the volume" could take on a whole new meaning...

... and the Strowger switches would give you 100 levels of attenuation! Up ten and across ten.
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Old 18th April 2007, 09:12 AM   #6
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'click and bang' volume control- Brilliant. Where can I get one?

James
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Old 18th April 2007, 09:41 AM   #7
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and how would you mute the audio ...... hang up?
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Old 18th April 2007, 02:25 PM   #8
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Thanks Tim. I am not so much concerned with the 5.1 sources for the reasons that you mentioned. The main concern is phonograph and tape sources.

Bibster, thanks for the link. That looks interesting but will take some time to study it. It is possible that some type of shunt control would have less of an effect on sonics. Eventually I do want to make the whole thing remote controlled.

I have an old ADC Sound Shaper II 12 band stereo equalizer with bad switches that I may be able to use for an interim manually controlled unit. I had thought about repairing it but I haven't really needed an eq for years. It is however a nice box with two meters and 24 50K faders. What I am not sure of is whether they are linear or log. If they are log I think I could gang 6 of them together and use another 6 to adjust the relative levels of each channel. That way I could get to work on the tube stages while my brother works on the digital decoding stuff.

mike
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