Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hesamadman on January 02, 2014, 06:16:59 am
-
I have an old Gretsch 6150T in my shop. Re-tubing. Couple little small things. I think I'm going to clone this thing just for the hell of it. Its small and incredibly simple. I just had a question. I don't think I need the Tremolo. But I'm not sure how to cut it out. Is the whole 12ax7 being used by the tremolo or do we have some additional tone shaping going on in this 12ax7 unrelated to tremolo.
Thanks everyone!
(http://i89.photobucket.com/albums/k205/fratbasher/gretsch.jpg) (http://s89.photobucket.com/user/fratbasher/media/gretsch.jpg.html)
-
You should be able to eliminate everything highlighted in green. Since you have the amp in hand, just pull V2 to check it out. Pulling V2 will simulate removing everything that is highlighted.
-
hi; you could always just use this schemo bcuz it's the same amp without the trem. I have built several of these and they sound great.
http://www.el34world.com/charts/Schematics/files/gretsch/gretsch6150.pdf (http://www.el34world.com/charts/Schematics/files/gretsch/gretsch6150.pdf)
:icon_biggrin:
-
you could always just use this schemo bcuz it's the same amp without the trem.
They are similar but still quite different even when the tremolo is removed.
-
Maybe I'm experiencing a form of cognitive blindness, but I can't find an output from the LFO that goes anywhere useful. Unless it's just making B+ sag for V1. What am I missing?
Chris
-
I had to look, too. Sneaky. The left hook "C" coming off pin 3, 2nd K of the LFO, goes back to a cathode on the preamp, pin 3 of V1.
-
I had to look, too. Sneaky. The left hook "C" coming off pin 3, 2nd K of the LFO, goes back to a cathode on the preamp, pin 3 of V1.
Ah, see it now. Thanks. Agree with other posters that eliding everything in green should do the trick.
Chris
-
I have a feeling the trem buffer leaks DC current through path "C" into V1a, and is a part of V1A's bias. Rough guess is that the "1.5K" under V1a could be changed to 2.2K or 2.7K for a better copy. If you have a working amp in hand, note V1a voltages (including the B+ node, since relative ratios are more important than exact voltages) and fiddle the clone for similar bias.
Ah, and the trem tube loads the 15K in the B+ filter, so without it the 15K might better be 22K or so.
But I don't think it will make-or-break the clone to use the 1.5K/15K values.
-
Looks like Classictone started making the original 3.2 ohm OT again. http://www.classictone.net/40-18052.html (http://www.classictone.net/40-18052.html)
-
Looks like Classictone started making the original 3.2 ohm OT again. http://www.classictone.net/40-18052.html (http://www.classictone.net/40-18052.html)
Sure, but who has a 3.2 ohm speaker?
Chris
-
Sure, but who has a 3.2 ohm speaker?
:laugh:
Fit a 2x12 cab with one 4 ohm and one 16 ohm in parallel and you'll be spot on. No worries! (Or just figure a 4 ohm speaker isn't going to be too different a load to begin with, but that's too easy.)
-
I have used the Classic Tone OT that runs 3.2 ohms. Mag. Components in Chicago has all the original winding drawings and specs archived and they build the new ones from those specs. That is a faithful reproduction of the OT that Valco used for the single ended amps they built. They sound terrific into 4 or 8 ohms. I've run them all day into 4 or 8. They are also making a repro of the infamous Valco Thunderbolt OT. I haven't tried one of those but I sure would like to.
:icon_biggrin: