From mark.longo@highmarkdesign.com Mon Apr 30 10:47:58 2001
Subject:Re: Electro Harmonix 6550's


Hi Folks,

As promised, here's a quick note on the my live gig experience
with the new Electro Harmonix 6550's this past weekend. These tubes
are exellent. As I mentioned in my previous note, they take a little
bit of the edge off the highs produced by a clone, rounding out the
tone a little. I wondered if that might cause them to not cut
through the mix as well as the Svets or others I've used. I'm
pleased to report that that was no problem at all. I found that they
delivered a firm and full-bodied tone that carved out a nice niche in
the mix with no problem. The tone is firm and has good presence and
even tone throughout the keyboard range. The volume levels they
deliver are good, the same as I've had with new Svetlanas and also
NOS GE's I've used, which are pretty loud. So this is good; another
source for decent 6550's is welcome with the Svetlanas no longer
available.

> Hi there Mark,
> Could you kindly advise the price for a duet matched 6550's
> and from whence cometh these items.

Since Electro Harmoinix is not a no-name brand, I assume you can
find them at large music stores. I got mine via mail order from BT
Productions (Tony LaBrasca, 630.773.9211) for $60 USD/pair.

> I think that I am probably going to have to replace my
> ageing set of valves, date installed unknown, but aparently
> using spider-web and dust technology.
> I am getting a small amount of distortion from my 145 at volumes
> which I suspect are somewhat below normal tube distortion levels.
> This disappears when I back off the volume.

Reduced volume and distortion at low volume are normal if the
6550's are worn out. Replace those.

> I have replaced the pre-
> amp valve with a Groove Tube from the Orient (it came with a bag of
> noodles to go) which has not improved the situation.

Beware of tubes from the orient, especially the Chinese 6550's.
In the past some Chinese 6550's have been reported to fail
catastophically (total failure) without warning. This is very
dangerous to your Leslie amp. The 6550's in your Leslie work in
concert and both tubes MUST be working. If one fails completely and
the other remains intact this can destroy your amp and even cause a
fire in your flamable wooden Leslie.

Also, the 12AU7 preamp tubes have a pretty long life in the
Leslie amp. The 6550's should be the first tubes you suspect because
their useful life is much shorter (of course, they're the most
expensive Leslie tubes!).

> Could you also advise the volume setting of the Leslie which
> is the maximum before tube distortion tend to kick in?

I normally run my 145 amp with the volume on 8. I feed it a
pretty hot signal. At this volume I get clearly audible distortion
on 4 note chords with the volume pedal all the way down on a draw bar
setting of say, 888625203 for example. If I add a low bass note I
get the distortion a little sooner. But this is VERY subjective
depending on how hot the signal you send to the Leslie is, what type
of driver/speaker you're using etc. Your mileage will probably vary.

Mark Longo