Strange intonation problems on a Drop Db tuned bass

[markus]

Hi everyone,

I know it's a bit off topic for the forum here, but with that many masters of the trade present I though I'd give it a shot... hope you don't mind.

Our bass player recently started experiencing strange intonation problems on his 4-string bass. It's probably worth mentioning that we play in Drop Db tuning and that the intonation was set by a guitar tech accordingly. He never had a problem... until a few months ago.

Basically the problem we're seeing is that when he tunes the open Eb string down to Db and then plays a fretted note on the first four frets, it's sharp by 15-20 cents. The intonation is fine when he tunes the string back to the normal Eb, so I guess it must have something to do with tuning the string down to Db. We're kinda at a loss trying to explain why it only started to happen recently though.

I have all my Andersons tuned to Drop Db and I never had any problem at all.

Any idea what might be going on?

Thanks,
Markus

[tom]

when you de tune, the tension goes way down on the string, so fretted notes go sharp. there's not an easy way to try this, but the nut needs to be closer to the first fret like with the bfts. then it needs to be intonated "wrong" from standard. i don't have a number, but it will want to be sharper than normal.
when i drop d tune, which i do a lot, i tune my D just a little flat to help make the first few frets sound more in tune.

[markus]

Thanks for the quick reply, Tom.
Now that you mention it, I realize that I do exactly the same - tune the open Db string just a little flat. So, maybe that will do the trick for our bass player also. In case it doesn't, do you know if a bass can be retrofitted with the bfts?

Thanks,
Markus

[tom]

yes there are offsets for bass, and i would think they may have to be altered a bit to allow for the extra low tension of the de tuned string.
bruce here is a retrofitter. he should be in later today and i'll quiz him about it.

[bruce]

What will also REALLY help is bumping up on the string gauge when de-tuning.. then of course having a fresh set up with the new string gauge... this is a must. The BFTS will help, but this will help much more I think... I've experimented with this same thing on guitars this whole summer on tour... upping the gauge from .010 to .011 was the fix on even a half step down tuning for me.

[markus]

Thanks Bruce! We'll definitely give the heavier string gauge a try then.
As for the same problems on guitars - I play two of my Andersons in Drop Db tuning with .010 without any problems. The low Db string is a bit floppy with .010, but I kinda like it that way. I never had any intonation problems though...

Anyway, thanks for your reply and thanks to Tom also.

Cheers,
Markus