Author Topic: Directly driving a power amp? (Read 538 times)

Bradley Young · « **on:** August 18, 2009, 08:52:18 AM »

I'm in the process of setting up a home rig (my other setup is semi-permanently installed at church).

I am currently building the cabinet, a fEarful 12/6. I'm thinking of pairing this with a DSP enabled power amp (and bi-amping; then I won't have to deal with building/buying a passive crossover).

Here's the question for the electronics masterminds here: can I run my Series II directly into the power amp? How might I discern if this is a good fit? I would be running from a DS-5.

I know that running a pre-amp is considered necessary, but heard hints from JimmyJ that he sometimes runs direct to a power amp (maybe through a DI?). I know that there is a potential issue with impedance matching, but I don't actually know how to suss out whether things will be compatible.

If you have any ideas on how compatible this might be, and what the potential results might look like (f'rinstance, I might be willing to live with somewhat lower output), I'd be much obliged.

811952 · « **Reply #1 on:** August 18, 2009, 10:15:30 AM »

I did that for more than a decade. Works just fine.

John

JimmyJ · « **Reply #2 on:** August 18, 2009, 10:45:19 AM »

Bradley,

You bet you can! The results will be the cleanest, biggest and most dynamic sound you have ever heard.

Having said that, this signal path is obviously not for everybody. You are essentially limited to the tone controls on the instrument and whatever you can vary on the speaker's or amplifier's crossover. If you want EQ or effects of any kind you've got to start looking into line-level gear.

You may need to crank up the output trim pots on the bass to drive the amp with enough level. One of the great things about our basses is that these output levels and the master volume control can be run at any setting without changing the TONE. Although my basses are all set to put out a line level (even through my DI boxes) I have a mark where the output would be considered normal level and if the situation doesn't allow for a line level I just dial it back to that mark.

I have been running like this for quite a while. If I play a club with decent monitor wedges I ask where the power amp is and try to run a cable directly to that input. Unless the cabinet is particularly weird sounding or has some odd active processing, the results are usually great. A powered monitor wedge is even easier. And if there is only a bass amp available then I will first connect directly to the effects return jack (usually a direct power amp input) to see how that works.

I also have a normal DI in the path (of my 5-pin cable) which puts out regular mic level through an xlr for the PA input. Because I'm dealing with several different ground points I sometimes need an isolation transformer in the line running to the monitor amp. But I can usually find the combination that makes everything quiet.

In your case, for a home rig this should work great. If you really want to spoil your ears you can build two cabinets and run the bass in stereo. But i must warn you that it is best to have a mediocre sounding home rig and the greatest sounding work rig. Much more fun to be blown away by the tone on the gig!

Best of luck, have fun!
Jimmy J

chalie_holmes · « **Reply #3 on:** August 18, 2009, 01:13:14 PM »

Hmmmmm....This sounds interesting.
How do I hook my rig up to do that.
I own 2 QSC 2450's and 2 FX's, and I have 2 Bag End 2x10's. I'm performing on a Distillate Series I short scale too.
What do I connect to what to be in stereo mode and do I need special Male cables Y comming from the bass to the power amps? Please give me the details on the connection process. Thanks Man!
Chalie Holmes

terryc · « **Reply #4 on:** August 18, 2009, 02:37:23 PM »

This is a coincidence, I am seriously thinking of 'building' a 400W RMS power amp from modules I can obtain from reputable companies, They have smoothed toroidal transformers.
It is the same thinking as chalie, the specs on the data sheets of these modules is that a volume control can be placed on the amp to adjust final output.
In conjunction I am going to build a balanced ported cab using Thiele & Small charts and hoping to use one of those lighter neodymium speakers.
I have a Boss ME50B which has an array of EQ controls with a mid frequency selector..this could be my 'pre amp'
The reason I am considering this is because 90% of the time I run my Roland with all the EQ flat.
Comments on idea jimmyj???

David Houck · « **Reply #5 on:** August 18, 2009, 03:36:17 PM »

Chalie; to do what Jimmy is talking about, you would go from one side of the DS-5 to one QSC, and from the other side of the DS-5 to the other QSC. You would leave out the F-1Xs.

lembic76450 · « **Reply #6 on:** August 18, 2009, 05:18:56 PM »

Dave,
Do I remember something about you can only do this with Series basses?

David Houck · « **Reply #7 on:** August 18, 2009, 05:47:13 PM »

Kenn; I think you are right. If I recall correctly, the non-Series electronics packages don't put out as much signal as the Series electronics.

JimmyJ · « **Reply #8 on:** August 18, 2009, 06:58:38 PM »

Chalie, as Dave said, use the two separate outputs from the DS-5 directly into two separate amp/speaker channels if you want to check out the stereo thing. If your series I has the older style stereo 1/4 jack then you could do this with a stereo splitter cable - but for full level output (and not eating the batteries) I would recommend using the power supply. The master volume on your instrument is all you need to adjust the volume - just be careful plugging and unplugging things when it is all fired up.

Terry, yeah that power amp into that cabinet would probably sound great. But what I'm talking about is using the bass as a preamp and just skipping that step altogether. If you like what your ME50B does then I don't think you can use it this way because the specs say it is built to operate at -10dBu in and out. This unit may choke if you try to insert it into a line level signal.

But you see where this is leading? If you like the direct sound but still need some color, EQ, compression or maybe delay, you could start looking at audio gear which is meant to run at line level. This excludes a lot of guitar pedals but includes a ton of Pro Audio gear. It opens up a whole 'nother can of worms. Ha!!

Jimmy J

Bradley Young · « **Reply #9 on:** August 18, 2009, 06:59:20 PM »

Jimmy and John,

Thanks for the feedback, and the confirmation. I'm putting this on the list of potential options.

The home rig keeps getting more and more expensive-- who would have thought? Oh well, I should be under $1000 for a pretty serious hi-fi rig.

Bradley

Bradley Young · « **Reply #10 on:** August 18, 2009, 07:06:42 PM »

Jimmy,

As of the last couple of years, the Series instruments have a mono/stereo switch on the 1/4 jack. Mine does.

Bradley

sonicus · « **Reply #11 on:** August 18, 2009, 07:36:19 PM »

Let's talk specs ______Line level audio signal level specs ; Consumer =10dBv
Pro =4dBu
What is the audio signal level spec of Non-Series electronics?
What is the audio signal level spec of SERIES I /II ?

I think the answers may be in the specs _____

(Message edited by sonicus on August 18, 2009)

JimmyJ · « **Reply #12 on:** August 18, 2009, 10:13:26 PM »

Wolf,

Pardon my ignorance regarding consumer line level vs pro. Balanced vs unbalanced also complicates the issue of level and leaves me with that questioning look on my face... Instead of actually learning what these numbers mean (I could use a few years of electrical engineering school) my tendency is to just plug it all in and see what happens.

I am also curious to know if there is a spec for the output level of the different electronics packages. All I know is that I have been driving power amps directly off the Series basses for quite some time and I enjoy the sound.

Jimmy J

sonicus · « **Reply #13 on:** August 19, 2009, 02:38:48 AM »

Hi Jimmy ,
By no means was I implying any ignorance on yours or any one else's part, I think that your posts are always most informative and brilliant, We are fortunate to have your input and I always enjoy what you write.I apologize if I appear arrogant. You have more knowledge of Alembic electronics then I do ! I am however VERY interested in finding out what the output level specs of our onboard Alembic electronics are for non-series and for Series I/ II? What are the I/O specs for the SF-2? What are the I/O specs for the F2B?
When I go into troubleshoot mode I ask lots of questions out loud .

Wolf

mario_farufyno · « **Reply #14 on:** August 19, 2009, 04:54:29 AM »

I'd like to now the output levels, too...