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Old 20th December 2002, 09:29 PM   #61
MJ is offline MJ
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Actually I think you're correct, and as an added elegance, because the second stage is a ladder the impedance is constant and so can be factored in, negating the requirement for the buffer stage. Only one thing to add to the given design the OdB setting on the -1.25dB stage has a different impedance, I would add a resistor to make sure the impedace is constant what ever the setting of the stages.

Thanks and well spotted. Very usefull. and I think I might be able to take the priciple even further!?! eventually the whole deign may be reduced to a direct binary count and be able rid the design of the 74HC238s and reduce the relay and component count down even further. Just thinking aloud - will get back to you on that one.
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Old 16th January 2003, 12:08 AM   #62
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Default Attenuator

Hey, you should check LcAudios sidewinder preamp and the http://www.lcaudio.dk/sidewind.pdf on page 20 or so there are schematics for a relay based attenuator with precise db steps... You need to recalculate the resistor values because as i remember they use steps of 1,5dbs...
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Old 16th January 2003, 12:26 AM   #63
BrianGT is offline BrianGT  United States
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Default Re: Attenuator

Quote:
Originally posted by Kongen
Hey, you should check LcAudios sidewinder preamp and the http://www.lcaudio.dk/sidewind.pdf on page 20 or so there are schematics for a relay based attenuator with precise db steps... You need to recalculate the resistor values because as i remember they use steps of 1,5dbs...
You need to capitalize PDF. Here is a working link:
http://www.lcaudio.dk/sidewind.PDF

Also, it is kind of hard to read (page 21 on pdf), is there a better version of this schematic available?

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Brian
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Old 16th January 2003, 01:04 AM   #64
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Default LcAudio

Sorry about the non-capital pdf - should have picked up on that... On page 10 of the pdf there is a schematic of the amplifier priciples or maybe try to contact lcaudio...
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Old 20th January 2003, 10:02 PM   #65
dorkus is offline dorkus  United States
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Default MSB preamp (again)

i've had the MSB MVC Gold preamp ($1699) in my system for a while now and i can't say enough good things about it. this is a really great piece - transparent, musical, with lots of slam. despite being a very IC-heavy design it doesn't suffer from many of the ills of IC preamps i've heard in the past - the glazing, grain, hard upper midrange, congestion, etc. makes me wonder if ruling out ICs entirely is pig-headed on my part... i'm starting to feel more and more that it matters more how you do it than what you use. of course you can't make a silk purse out of a sow's ear to repeat that cliche, but i don't think we should assume a preamp is doomed because it uses ICs, even when we are talking the highest levels of transparency here. compared to even a passive preamp the MSB aquits itself very well in the areas of reproduction that most active designs fall short - and terms of dynamics and slam it'll trounce most passives. i'll eventually get around to opening up the unit to see what's inside... right now i'm enjoying some Ella & Louis so the last thing i want to do is unplug it from my system!

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dorkus
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Old 19th April 2003, 10:09 PM   #66
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I would like to draw your attention to the Apox work going on here http://www.diyaudio.com/forums/showt...331#post163331

You could end up with a 6 channel relay based attenuator unit with front panel display and remote (without attenuation resistors) for about $350. The input switching scheme is quite costly if you are going to go full monty with all channels - I don't need input switching given that I am using digital source switching and digital crossover.

Petter
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