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In Reply to: RE: Cathode Follower Line Stage posted by Triode_Kingdom on May 15, 2017 at 19:10:47
If you don't need the gain, why not just build a board with multiple pairs of input jacks and a selector switch and go directly into the amp from one set of output jacks? Might also want to include a volume pot.
I have run my cd player directly into my amp and it sounds pretty good.
Edits: 05/16/17 05/16/17Follow Ups:
Most of my future amplifier builds won't have volume controls. So, I need a control amp that can adjust the volume and also perform an impedance transformation. Otherwise, I would have a 100K or 500K volume control driving a length of cable. That's no good.
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Buy Chinese. Bury freedom.
I'm curious. What would happen if you put a volume control with each set of input jacks? Also why no volume control on the amps? I like the extra fine tuning you get with dual controls.
Edits: 05/16/17
Vinnie, there are several reasons not to cascade volume controls in the way you suggest. For one thing, every stereo volume control exhibits errors in channel-to-channel tracking. Then there's the noise of wipers and carbon tracks, as well as the effect a variable input resistance has on frequency response due to Miller effect. These issues can be significant, even with only one volume control, and they're cumulative when the controls are connected in series in the audio chain.
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Buy Chinese. Bury freedom.
The output impedance of a 100k pot adjusted to the -6db point will be 25k.
25k driving the Miller capacitance of the first stage will likely cause a loss of high frequencies in the audio band.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
If it above 12khz I probably can't hear it anyway. One of the joys of being 70!
"Otherwise, I would have a 100K or 500K volume control driving a length of cable. That's no good."
100% correct! A buffered control center is an excellent, practical, solution. Passive control centers require VERY low capacitance cabling between them and the power amplification. Equate VERY low to short and unshielded, which creates its own set of problems. TANSTAAFL will, forever, be with us.
Eli D.
Or use an autoformer based volume control. I've been using one for years. The new modules from Intact Audio are really nice.
High sensitivity, wide dynamic range, low distortion, and smooth frequency response. Pwk
http://www.itishifi.com
.
Have Fun and Enjoy the Music
"Still Working the Problem"
Most of them seem to cost more for a pair than I spend on the rest of the parts for an amp!
vishay cermet Oring sealed trimmers. they are the little black knobs with one white spot on and are very good for level setting used with a fake law resister. they are affordable and can be relied on to stay stable over large periods with out turning them.(years) I think they may be out of production as some popular values are increasing in price and newer conductive plastic versions of dubious quality are being added to the farnel catalog. The original cermet version are so clean and are comparable to a fixed resister in sound quality imho.
IME, no matter what is behind it, if I were going to go and get nutty I'd start with one of Dave's autoformers and a good 2-gang switch. Then I'd put something that can amplify and buffer behind it. A core of Supermalloy, with a small gap is likely ideal...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
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Have Fun and Enjoy the Music
"Still Working the Problem"
nt
High sensitivity, wide dynamic range, low distortion, and smooth frequency response. Pwk
http://www.itishifi.com
You are missing my point. If I was spending $4k on the rest of the amp parts it would make sense, but if I am building an amp for $500 and using say alps pots, they are unlikely to be the item that would most affect the sound. The money would be better spent on better opts or beefing up the psu.
Edits: 05/17/17
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