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In Reply to: RE: To split hairs... posted by AbeCollins on June 02, 2016 at 15:07:36
I don't think anything I said contradicts their description. A cathode-follower IS the output driver stage.Sure it is. Output stage, exactly! ARC's wording doesn't involve "driver" in describing the implementation with the LS25. Did you follow my embedded link to their description? That phrasing is different from your original assessment:
In this regard, it is my opinion that most of the sonic character of this linestage should be "solid-state" and slightly smoothed out (and potentially a bit rolled off) by the 6H30 buffer.
A buffer is a buffer (matching impedance with unity gain) and an output stage provides additional gain.
Do you know of any output stages that don't?
And in every gain stage I've ever encountered, there lies the ability to determine character. The tubes aren't there for show as they are with "tube buffer" products.
Edits: 06/02/16Follow Ups:
Abe is correct. I looked at the schematic, and as you would expect the output stage is a cathode follower.
Cathode followers (a.k.a. "buffers") have a voltage gain of less than 1. In other words - no gain, in fact they attenuate the signal slightly. But they do have a much lower output impedance which is useful for a preamp.
So listen to what Abe is saying - he's got it right.
I sit corrected.How did the original version use its 6922 tubes vs the 6H30s of the MKII? Schematics on the original are easy to find, but I have not been able to find one on the MKII version. Where did you locate that?
Were two of them for gain and the other two used as cathode followers?
I seem to recall that Victor Khomenko used to say that one 6H30 could replace two 6922s hence the moniker "super tube".
edit: Abe - I got the text of your deleted post. I have found myself mistaken a number of times, especially when empirical data was unavailable. Search for "mistaken" and "corrected" and you will find numerous hits where it applied to me. You were right. I have no trouble admitting that I am wrong (now and again) :)
Edits: 06/02/16 06/02/16 06/02/16
...it's not like I've never been wrong.
The schematic is on the ARCDB site (link below). Scroll down that page and the Mk II schema is there.
.
Interesting. It looks like the LS25 is "all tubes" except for a FET that appears to be a constant current source and the other two I'm not sure. For biasing?
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