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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

6V6 line preamp

I have the breadboard somewhere. Still with PSU and pot mounted if I remember correct. Think CF confed atm but easily rebuildable. Dual SSHV. Building my workbench now. A lot of work. Mostly playing with speaker filters. Just got some new resistors, my favvo in speaker filters Isabellenhutte PHB, most transparent I have found in that app.

I will dig the breadboard up and re-mode it this weekend and we'll see after that.
 

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Easy to set up a ding test for microphony since pin compatible. A true triode without fb and preferably some doze of second order distorsion (equalising normal room echoes etc) is what I think most ppl prefer in an amp. Naturally it has to do with the rest of the stuff and the room itself. I dont care much for distorsion as long its not odd numbers and not far out. Microphony is even Numbers dist byw. Maybe desirable. As in a TT.
 
Mm. But for me that is two different things that I desire. A triodes (differs ofc by tube and config) second order distorsion is desireable to an amount. The direct feeling of a DHT is something else. I guess it has to do with free flowing electrons in vacuum heated rather then indirectly. And further electrons flowing thru semiconducting material.
 
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Tonight I have this funny experiment to do. I got a fiftyeleventh scope just because I like its low tec exterior. The lunie sent it to me in a regular move box without shock damping so the trigger buttons was all pushed in and stuck. Now i think I have fixed that but in the apart taking I found a loose interconnect. Theres like 50 plus seatings for it so either it burns tonight or I find the spot. Lets find out:)
 

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diyAudio Chief Moderator
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Tonight I have this funny experiment to do. I got a fiftyeleventh scope just because I like its low tec exterior. The lunie sent it to me in a regular move box without shock damping so the trigger buttons was all pushed in and stuck. Now i think I have fixed that but in the apart taking I found a loose interconnect. Theres like 50 plus seatings for it so either it burns tonight or I find the spot. Lets find out:)

Ask help in the equipment section since we have some members familiar with classic scopes
 
I guess a correct experiment would be: put a speaker right near the tubes and the line+power amps speaker in the other room. Rig XTZ Room Analyzer Pro II output in separate amp to the speaker near toobz and the microphone in the cone in the speaker in the next room. Run a 20-20k sweep in the toob amp speaker and record from the speaker in the other room. And then roll the tubes. Did I do that? No but I had a metaxa and a beer at the local greec. Close enough:)
 
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Ok. Came home and mounted a pair of Ruby with the common round mica with little star points to the glass. Full volume on the 6v6 common cathode and also on the 2 v in sensitive el84pp as before (overdriven). Clapping near the tubes and I can almost drive it up to self running feedback. Big difference from the Philips with long running mica only touching glass in each end. Now I need a new metaxa.
 

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Ok. Since you're clapping so much, a surprice. A pair of JAN metal envelopes. Needed some filament CCS adjust. Can barely hear loud and frenzy clapping near tubes. After some heat up dings very stable. Sound? Most stable so far controlled to the edge of boring. Wasnt that a surprice?
 

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Some russkies to wrap up the octal race. I do have plenty more, Ferranti, more Philips (also dutch), RCA, Sylvania and some more. But I think its obvoius now, you really cant tell so easy what will sound good. As little as I can tell you what you like. The russkies then? Well the warm up dinging hardly never stops. The CCS filament setting from former 6,1 setting ended up on over 7 v on those. Easy driven heaters. Microphony duff, very mild lower hz. Sound: absolutely top class. Controlled but not dull.
 

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