Proximity of reverb tank to amp/tubes?

[jar240]

I'm going to be installing an amp with reverb tank into a custom-built head-style cabinet. Is there a rule of thumb in terms of keeping the reverb tank a certain distance/orientation with respect to the amp chassis?

Thanks,
Chris

[EWBrown]

The main things are: don't put it too close to the power transformer and choke, in order to prevent magnetically induced hum pickup; and don't locate it over the tubes, to avoid excessive heat buildup.

If your amp chassis in mounted from the top of the cab, with the tubes hanging down (as was common practice), then just mount the reverb tank on the inside bottom of the cab. The usual practice is to connect with shielded cables, so length isn't a real issue here, leave yourself some cable slack.

Before you permanently mount it, it would be a good idea to leave it "loose" and try various positionings and orientations, in order to see what gives the minimum hum pickup.

/ed B in NH

[erichayes]

For additional isolation and physical protection, get a "bag" for the tank. AES has them for around $11.00.

[Gingertube]

If one end of the tank has to be close to trannies make sure its the drive end Tank input) The drive end is low impedance and high signal level and therefore fairly tolerant of stray magnetic fields etc.

Its the output end (tank out) thats very low level, higher in impedance and has a fair amount of amplification attached to it that is really sensitive to stray fields.

Cheers,
Ian

[nyazzip]

hey, this thread enlightened me, in that, for 10 years i had a marshall jcm800 head- it came designed with a reverb tank (in the head-very close to the transformers), but the previous owner had taken it out. i ended up adding one myself, but it was very hummy/noisy, so i didn't use it. but now i think i know why. would have been fun playing around with long wires and using an external box or something.....oh well, i just finally traded it
guess thats why most heads don't have reverb huh.....

[EWBrown]

If the solid state "bucket brigade delay line" form of reverb is used, then the EMI hum issue is rendered moot... But, then, he sound just isn't the same, the old "boingy" long springs have a unique sound of their own.

The BBDL technology does allow for some interesting effects, like phasing / flanging, if one is into such sounds

A bit of rock'n'roll music trivia:

This technique First used in Timi Yuro's "The Big Hurt", back in the early 1950s. It was done by using two R2R tape recorders and by dragging a finger on one or the other's feeder reel's flange to introduce a slight (on the order of milliseconds) delay.

It can also be done with two turntables, which are "mixed" together, I often fooled around with this, during a few fill-in sessions of (then WLTI) at Lowell Tech's FM station in Mass, back around late 1972-early 1973.

One sone that worked out very well with "flanging" was "White Bird" on the LP ambum called "Marrying Maiden", by It's a Beautiful Day.

Funny thing, 20-30 years later, Art Bell did this very same thing to the very same song onhis "Coast to Coast AM" radio program. What goes around comes around (literally, in this case).

/ed B in NH