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In Reply to: RE: Tube Buffers ? posted by mark.korda@myfairpoint.net on July 17, 2021 at 12:32:06
Everything below the line is Nelson Pass explaing, among other things, buffers, with regard to his B1 buffered preamp. Link to the full article at the bottom.
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"Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control.
This suggests the possibility of using a high quality buffer in conjunction with a volume control. A buffer is still an active circuit using tubes or transistors, but it has no voltage gain - it only interposes itself to make a low impedance into a high impedance, or vice versa.
If you put a buffer in front of a volume control, the control's low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower. You can put buffers before and after a volume control if you want.
The thing here is to try to make a buffer that is very neutral. Given the simple task, it's pretty easy to construct simple buffers with very low distortion and noise and very wide bandwidth, all without negative feedback."
Follow Ups:
Viridian and Shovel, thanks, that was just what I was looking for. That Nelson Pass article was easy to understand too...Mark K.
Hi Viridian, thanks for that site on the FX01! If the first guy liked it better than the Bottlehead I might not be going insane.I got the better tubes right off and they were 20 bucks.As good as it sounds,and I read about the new power supply mod, the tubes glow a MacIntosh aqua blue and the power supply or adapter projects a planetarium light effect when playing in the dark.My best test cd is Sammy Davis Live at the Coconut Grove.He says right on the concert that their recording this with some new techniques described on the cd case or album cover.I've used this again and again testing which preamp sounds best.At the start of the cd you can hear Sammy trying to clear up a frog in his throat.You can hear him sipping whiskey and his throat continually improving and it's full of great songs and impersonations all while president Kennedy was still alive.I gave up for a while my turntable restoration projects when I heard this.Thanks Viridian.....Mark Korda......You too Shovel!
I don't think Sammy, or any of the other Rat Pack, sipped whiskey during a show. There are plenty of interviews with both Dean Martin (who's trademark was a drink in hand) and Frank Sinatra that debunked those claims (much later in their careers). Both have said that it would be impossible to sing while drinking. Although it was amazing to see Dean puff away on a cigarette and sing. Ahhh, those were great days!
I'm sure that after the show was a different story.
Sorry about the spelling. Dean Martin did drink apple juice, claiming it was Jack. He often was out early the next morning, that morning(?), for a round of golf. Per one of his Bios, Frank, on the other hand, drank 3 dozen glasses of Jack daily. A full day to Frank was a movie scene in the AM, a recording session in the afternoon, a gig at night, followed by an occasional late night fist fight. Gordy Howe had nothing on Frank.
Hi Airtime,
I heard the same thing about the rat pack.Sammy starts out with For Once in a Lifetime and he struggles with the notes.That's where I mentioned a frog in his voice.I don't know what he did to recover lest put his hand over the mike and hack his guts into some sort of spittoon.That's why I thought a little nip of whiskey might have loosened his vocals, not being drunk...yet.Like you said probably after the show. He was a heavy smoker and I know all about that.His voice keeps getting sharper and sharper thru the recording.
I've been on the wagon for 7 years but vividly remember a shot of Jack cleansing the old gizzard for a rendition of One for my Baby down at the Eagles in front of 4 people on Kareoke night.It loosens up your vocal chords....Mark Korda
Already have some nice JAN tubes, NOS, and a linear power supply that would fit right in.
Enjoy! All the best, Marty.
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