Which cables to use with preamp and DI?

buckminster · #1 06-19-2008, 12:41 PM

I just picked up an Aguilar DB924 pre and a DB900 DI box.

This will be my signal chain...

Bass -> db924 (pre) -> db900 (DI) -> power amp -> speaker

What type of cables should I be using between the pre, the DI, and the power amp?

Thanks from a technically-challenged fellow TBer...

superkicky · #2 06-19-2008, 01:05 PM

normal 1/4" cables will do fine, but i'm wondering if the 924 has enough output to drive the power amp...

bongomania · #3 06-19-2008, 01:22 PM

I almost guarantee the 924 cannot drive a power amp by itself, with only 18dB gain and an unbalanced output. You would have to feed a pretty hot signal into it to get a hot-enough signal out of it, as well as using a power amp with a low number (like .7V) for the input sensitivity rating. The 900 has unity gain through its 1/4" out, so it does not amplify the signal at all.

If your bass signal is already quite hot, and if your power amp has a low sensitivity rating, and if it can accept an unbalanced input, then this may work. In that case you would use a standard instrument cable (1/4" mono plugs on both ends) between each piece.

buckminster · #4 06-19-2008, 03:06 PM

How can I tell if my amp will accept an unbalanced input? It say it will take XLR (that's right out), and TRS connections. Also, I think the input sensitivity is 1.0V...

bongomania · #5 06-19-2008, 05:12 PM

TRS connections are typically balanced, but some are what they call "servo balanced" and are able to act as unbalanced connectors if an unbalanced plug is inserted. Read the manual or ask the manufacturer.

buckminster · #6 06-20-2008, 10:25 AM

Thanks Bongomania,

The TRS connection is "designed to receive either balanced or unbalanced input signals" according to the manual. So looks like I'm O.K. there if I wanted to use either standard TS or TRS cables.

Is there any reason why I couldn't use the XLR out on the DB900? Wouldn't this send a cleaner signal to the amp than the TRS cable?

Also, the manual claims that "because this (the XLR input) is a balanced input, the gain will be 6 dB higher than using the 1/4” input jack with non balanced lines." Is this true?

bongomania · #7 06-20-2008, 01:52 PM

Quote:

Originally Posted by buckminster

Is there any reason why I couldn't use the XLR out on the DB900?

You'll need that for sending the DI signal to the PA. Also its output is at nominal "mic level", which is typically a lot lower than the "line level" that could drive a power amp.

Quote:

Originally Posted by buckminster

Wouldn't this send a cleaner signal to the amp than the TRS cable?

No, it will be at a different level, but not cleaner.

Quote:

Originally Posted by buckminster

Also, the manual claims that "because this (the XLR input) is a balanced input, the gain will be 6 dB higher than using the 1/4” input jack with non balanced lines." Is this true?

Yes, that is true. Not all amps are designed that way, but many are, it's common.

buckminster · #8 06-20-2008, 02:03 PM

So even though the XLR cable input is 6dB hotter, I'll be losing gain because the DI output of the DB900 is so much lower?

And if I'm using a TRS cable from the DB900 to the power amp, is this considered a balanced connection?

And final question...really...

If the TRS cable makes a balanced connection, am I getting that "extra" 6dB?

Thanks again for your patience and responses...

bongomania · #9 06-20-2008, 02:09 PM

Quote:

Originally Posted by buckminster

So even though the XLR cable input is 6dB hotter, I'll be losing gain because the DI output of the DB900 is so much lower?

Yep.

Quote:

Originally Posted by buckminster

And if I'm using a TRS cable from the DB900 to the power amp, is this considered a balanced connection?

Nope, as the 900's 1/4" output is unbalanced only, no matter what you plug into it.

Quote:

Originally Posted by buckminster

If the TRS cable makes a balanced connection, am I getting that "extra" 6dB?

If it weren't for that pesky unbalanced 1/4" from both Aggie units, the answer woud be 'yes'. If you buy a different pre that does have a balanced output at line level, then you would benefit from the extra 6 dB gain.

If you are not in a hurry, the Aggie Tone Hammer is supposed to be able to drive a power amp. Unfortunately it's had some delays in production, may not be available for at least another few weeks, maybe months, who knows.

buckminster · #10 06-20-2008, 02:23 PM

Well, I'm not in a hurry, but I've never had a problem when plugging my bass (9V active electronics) straight into my power amp. Now maybe I'm not getting all the juice out of it that I can, but it works and is pretty freakin' loud.

Am I wrong in assuming that I'll get the same amount of gain / level, etc. if I put the Aggie units in the signal chain?

I am planning on getting a Tone Hammer. I've got to give my local dealer a call. He was supposed to get back to me with a price and an ETA...

bongomania · #11 06-20-2008, 06:12 PM

Hey, if your bass drives your power amp to your satisfaction, then the Aggie pre will be even better, up to 18 dB better. The technical/cautionary stuff I was describing is for optimal usage of the gear, but whatever works for you, works.

Jim Carr · #12 06-20-2008, 07:03 PM

http://www.bgra.net/2004/review.php?id=34&type=preamp

It seems it might have been done before. Might.

buckminster · #13 06-21-2008, 08:18 AM

Quote:

Originally Posted by Jim Carr

http://www.bgra.net/2004/review.php?id=34&type=preamp

It seems it might have been done before. Might.

Thanks Jim. I read that BGRA review. I've read almost every online review I could find on both products before buying.

Anyway, I eventually will be getting a Tone Hammer, and if that is sufficient to drive a power amp, then sweet. But for now, I'm using what I've got.

Thanks for all the technical help guys.