Help me tune up my Two Rock Ruby please.

[mojo]

I haven't posted here in quite a while - life gets in the way a lot. I also am a little intimidated to post here as I know just enough about messing around with amps to get the simple stuff done. When I play lately my antique Ampegs have been getting most of the action. Anyway, I recently blew the dust off of my Two Rock Ruby and fired it up. After playing with it a little I'm thinking I may need some help tuning it up. It is of course loud as all heck, so I really can't play it without the attenuator. It also has a pretty biting, piercing treble, pretty harsh sounding, as well as having a bit of a static sound when I roll up my volume at around 7 or 8 that I don't notice with my other amps. Its pretty gained out at around 4 on the gain knob. I've tried putting a 12AU7 in V2, which helps slightly, and putting a 12AY7 in V1, which tames it quite a bit, but loses some of the 'Wreckish character. I'm hoping someone here has messed around with one of these (I know some here probably got the "kits" from TR) and can give me some suggestions on how to get it sounding more like the 'Wreck it was apparently copied from. Thanks in advance.

[mojo]

I just realized that there are a number of helpful tips in the "Assembly Instructions" in the files section. I'm gonna mess with those awhile and hopefully post some good reports here soon.

[mojo]

I recently got a chance to A/B my Ruby with a real 'Wreck. The Ruby didn't sound quite as good, but it was close. The Ruby was a tad gainier, less smooth, and slightly less complex/musical, but again, just barely. I'd like to tune it the right direction.



Looking at the schematics I've seen, the most obvious difference is the tail resistor of the long tail pair is higher value on the Ruby - its 22 as opposed to the 10 of the 'Wreck. I can see that making a difference, but I'd think that would make the Ruby smoother and more stable, rather than the opposite.



I've also seen some suggestion that a lot of the distortion comes from the third triode stage being biased into functioning as a "clipper" to some degree. If that's the case, I've mulled over decreasing the cathode resistor on the third triode stage, maybe just slightly, to maybe 8K.



Anybody with any "Ruby tuning advice" for me? What do you think of the alterations I mentioned above? Thanks!

[M Fowler]

There would be more gain with 10k tail then 22k.

[matt h]

(deleted)

[mojo]

Hmmm. Me likey tubey magic.

The 'Wreck I compared the Ruby to definitely had a tad more tubey stuff goin on.

Maybe I'll try dropping the tail to 10K and the 3rd gain stage cathode resistor slightly, maybe to 8 or 9K and see what I get. What I'm hoping for is slightly more complexity and musicality, a little less aggression and edge, along with the distortion coming on a little later on the gain knob.

Apparently some 'Wrecks had 22K at the tail, maybe tuned for a slightly different sound, since some of the schematics had that and the Ruby was apparently copied from one. The 'Wreck I compared to was "Amanda Lynn", and who knows which circuit it has.

Anybody have any idea which 'Wreck the Ruby was based on?

[mojo]

I just found a post on the "Huge Racks" forum - an ad for a Ruby that claims the Ruby was blueprinted from a 'Wreck named "Amanda Lynn"! How wild is that - I may have been A/Bing my Ruby with the exact 'Wreck it was cloned from! If that's true, they must have missed something, 'cause the Ruby definitely sounds gainier, more aggressive, and to my ear somewhat less musical. Of course the 'Wreck is likely much more played in, and in the cool hardwood cab, and some component selection differences, but still, if its a direct detailed clone of the exact circuit of that amp I'd have expected the difference to be a bit smaller.

[M Fowler]

http://ax84.com/drums/bbs/dm.php?thread=79606

[matt h]

(deleted)

[mojo]

Thanks for the help so far.

Mark - that thread does give a couple of thoughts that are relevant, thanks.

Matt - I did put each amp through the same speaker cab, but didn't change tubes out. The 'Wreck seemed to have new, mostly JJ I think, tubes, while mine had an old Mullard in V1, a USA old stock in V2 and a Sovtek LPS in V3 (I think).

I'm not really wanting to make major changes in the the amp - its really close as is. I just want to fine tune a little in the direction I mentioned - slightly cleaner and slightly more complex, maybe a little less edge.

[gingertube]

mojo,
2 things come to mind for you to consider.

A "bright tamer" cap can be added to the 3rd gain stage. Try a 330pF or 470 pF across the 100K anode load resistor (or better from anode to 0V). I run a 300pF Silver Mica in my amp. I've seen guys use up to 1000pF (1nF) here.

The other is a caution - one of the Expresses I built sounded quite nasty when turned beyond about 12 O'clock on the volume knob. This turned out to be the Phase Inverter breaking into ultrasonic oscillation when driven above a certain level. 22K grid stop resistors on both PI triode sections fixed this.

This was not the usual full output swing oscillation but bursts of very high frequency just after the signal peak, as the signal swung downward again.

Cheers,
Ian

[matt h]

(deleted)

[gingertube]

matt h's post reminded me

- the OTHER thing I had a problem with was a long plate 12AX7 for V1. I was using a Philips NOS from my special stash. Had bad buzzes and farts from microphonics.

Ended up with a modern production Eletroharmonix in there.

Cheers,
Ian

[Jackie Treehorn]

Harsh top can also be a sign of instability in these types of amps. Can you dime all the controls without audible oscillation?

[mojo]

Nope, squeals with all controls 3/4 way up. I'm rechecking lead dress now. Thanks!