Anyone using a power amp with a Shuttle? (Shuttle as a pre?)

**mikeddd** · #1 04-19-2010, 04:00 AM

I'm considering racking my Shuttle 6.0 and using it as a pre along with a QSC GX5 (which I already own). In a two, 8-ohm cab situation I'd have almost double the power (1Kw vs. 600w). Arguably, the type of power amp would/could make a diff as well; Class D for the Shuttle vs. Class H for the GX5. The power amp might also have better control over the cab too. All hypothetical/guessing on my part, obviously.

I'm curious about what differences I'd hear and feel as far as "bite/oomph/thump" go. It's difficult for me to test at home b/c I live in an apartment...no cranking anything up at home, unfortunately.

There's at least one user here I know of, but can't remember his name, that does something similar. He's got a Shuttlemax and a PLX3602 *drool*. Anyone else? I'm really interested in hearing your experiences and thoughts. If the GB folks would like to chime in, I'd love to hear from you too.

**Ukiah Bass** · #2 04-19-2010, 08:04 AM

Your solution will work great. I use this one:

**mikeddd** · #3 04-19-2010, 10:16 AM

Yep, that was you I mentioned in my OP, Ukiah Bass.

I just couldn't remember your username. I always drool when I see that pic. So simple, yet so versatile and powerful. *drool* Thanks for posting a pic of the back of the rack. Quick question: The output of your Shuttle into the input on the amp, that's an unbalanced connection, correct? Which output on the Shuttle are you using?

ERIC31 · #4 04-19-2010, 03:43 PM

Thank you for posting pictures. I'm about to add a power amp to my setup (SWR Workingmans 160 head, QSC GX3 power amp) and I was wondering how that works. I'm only running a 1x15 and a 2x10 at 4 ohms so 500 watts will do great for me.

Does it matter if the power amp is on top or bottom? Do you control the volume with the two knobs on the power amp?

**mikeddd** · #5 04-19-2010, 03:54 PM

The position of the power amp in the rack matters based on it's air intake and exhaust patterns. QSC amps suck in air from the back and blow it out the front. Other amps are the reverse. Basically, as long as the power amp can intake cool air and exhaust hot air where it won't get sucked in or bake other things in the rack, you're good.

AFA controlling the volume goes, you really should set the knobs on the power amp and never touch them again. The best way to set gain controls is with a DMM and the owner's manual for all your gear. A little math is involved, of course. But for Ye'Olde Average Working Man, I'd set the gains on the amp at 3/4 full up for a start and use the preamp's gain/output to control volume.

**Ukiah Bass** · #6 04-19-2010, 05:05 PM

I used the ShuttleMAX's "Master Send Preamp Out" jack to send the signal to the QSC power amp. The cable has balanced 1/4" connectors.

Since the ShuttleMAX is used only as a preamp, I do not use its master volume knob. I do set the FET and tube preamps Gain and Volume levels, as they directly affect the amount of signal fed into the QSC power amp. For example, if I want to add just a touch of tube, I set that preamp's Gain and Volume knobs to a lower setting. If I want no tube or no FET, I turn that preamp off. Depressing the High Gain buttons on either preamp provides a significant boost in volume to the QSC. Output volume for the rig is controlled with the QSC's volume attenuators.

The ShuttleMAX is on the bottom because it's four rubber feet prevented topside placement. I did not want to remove the feet, so the simple solution was to reverse the tradtional placement of each component. The result sounds the same.

I saved a few pounds by replacing each component's stock power cord with short ones. I also inserted a surge protector power strip in back. Much lighter than a traditional "power conditioner," and MUCH less expensive. Also gives me extra power sockets to use for my field recorder and guitarist's amp.

ERIC31 · #7 04-19-2010, 05:13 PM

Thanks for the advice guys. Much appreciated. I don't want to blow my stuff up!

There's a send jack on the rear of my head which I'll use to send the signal to the power amp.

FarkusSWR · #8 04-19-2010, 07:50 PM

If I may, where did you get those short power cords?

tallboybass · #9 04-19-2010, 09:19 PM

Yes, it works great! Sounds more solid on the low-end too, not to mention louder. You're right, come out the 'effects send' into the power amp. Since I'm using a PLX1804, it fits in a shallow effects rack and weighs about 20 lbs. total. I'll bet you dig it!

**Ukiah Bass** · #10 04-20-2010, 08:11 AM

Quote:

Originally Posted by FarkusSWR

If I may, where did you get those short power cords?

Package of four 12-inch cables for $31.

http://www.proaudio.com/product_info...oducts_id=7253

jnewmark · #11 04-20-2010, 08:36 AM

It's getting to the point where you can use these lightweight heads as preamps in a rack with a power amp or other rack mountable bass head. In some cases, they are even lighter than some bass preamps. Lotta options!

**Ukiah Bass** · #12 04-20-2010, 09:13 AM

Quote:

Originally Posted by jnewmark

It's getting to the point where you can use these lightweight heads as preamps in a rack with a power amp or other rack mountable bass head. In some cases, they are even lighter than some bass preamps. Lotta options!

Yeah, I love the tonal options of the ShuttleMAX but my 8-ohm cabs needs LOTS of power to express their potential, and I typically use them one at a time. I'll ditch the power amp if Genz comes out with a new MAX line with more power for 8ohm configurations, but for now this combo works best for me. Total flexibility. Always sounds great on gigs and recordings. I'm finally at a point where my focus is on technique, not gear.

Burlington · #13 04-20-2010, 09:20 AM

Quote:

Originally Posted by Ukiah Bass

Package of four 12-inch cables for $31.

http://www.proaudio.com/product_info...oducts_id=7253

Thanks for the link- I'm totally picking some of those up.

agedhorse · #14 04-20-2010, 10:14 AM

Let me clarify and correct a few things for accuracy here...

1. The effects send and preamp output on the Shuttles/Max's are unbalanced, 1/4" TS and using a balanced cable does not make the signal balanced. A 1/4" TS (unbalanced) cable is identically electrically as the ring and sleeve are conected internally. This is true of all manufacturer's bass amps on the market that I am aware of. One thingto note, using a TRS cable on some products can result in NO signal if the ring floats on the preamp out. I have seen some other products do this.

2. Be careful using surge protectors and power conditioners with power amps, and don't turn on and off all the units in the rack with the master poower switch. While it's ok with some products (specifically the PLX and the Shuttles) due to inrush current limiting management, other products do not have this feature and can destroy the master power switch on the strip since they do not (generally) contain inductive load switching protection. This is especially true of older "lead sled" style power supplies. The typical symptom is a power switch that won't turn off because the contacts got welded together from arc-over.

3. The feet are easily removed and reinstalled on the Shuttle line by popping out the center blind rivet and pulling the foot off. To reinstall, push the foot mount back into the hole and reinsert the blind rivit by pushing down on it. It's a 10 second process (if you are slow).

**mikeddd** · #15 04-20-2010, 10:29 AM

Nice looking rig, tallboybass! I just ordered the rackmount kit for my Shuttle 6.0 yesterday. It looks mighty fine all racked up.

@Agedhorse: Thanks for clarifying several points. In fact, I emailed QSC yesterday about the best way to use a QSC GX5 with my Shuttle. They recommended a matching transformer for max S/N ratio, etc. I'm planning on using this: http://www.mcmelectronics.com/produc...0HC385-/35-595 My big question is: Will the matching t-former affect the tone coming out of the amp? I don't want it to sound thin or sterile.

tallboybass · #16 04-20-2010, 12:17 PM

Quote:

Originally Posted by jnewmark

It's getting to the point where you can use these lightweight heads as preamps in a rack with a power amp or other rack mountable bass head. In some cases, they are even lighter than some bass preamps. Lotta options!

VERY true! I bought a GK 2001RBP, and it definitely weighs more than the 6.0 + rackmount!

tallboybass · #17 04-20-2010, 12:57 PM

Quote:

Originally Posted by mikeddd

Nice looking rig, tallboybass! I just ordered the rackmount kit for my Shuttle 6.0 yesterday. It looks mighty fine all racked up.

@Agedhorse: Thanks for clarifying several points. In fact, I emailed QSC yesterday about the best way to use a QSC GX5 with my Shuttle. They recommended a matching transformer for max S/N ratio, etc. I'm planning on using this: http://www.mcmelectronics.com/produc...0HC385-/35-595 My big question is: Will the matching t-former affect the tone coming out of the amp? I don't want it to sound thin or sterile.

Thanks man!

I'd wait for 'agedhorse' to weigh in on the need for a transformer. I just used a 1/4" TS cord from effects send to power amp in and it works great!

**mikeddd** · #18 04-20-2010, 01:12 PM

When I emailed QSC asking if using an unbalanced connection would work, here's the (detailed and professional

) reply I received. I really love QSC's customer service!

Quote:

In short, the answer is YES. Keep in mind that if you feed a signal into the 1/4 input with an UNbalanced cable, you are potentially losing about 6 dB (about 1/2) of the potential level. You probably will not even notice it, however, since your preamp has PLENTY of drive signal to compensate.

If it were me, I would use a 1/4 unbalanced to XLR balanced MATCHING TRANSFORMER -- this will ensure you have max signal to the amp, so you can turn down the knobs and still drive the amp to full power. Turning down the knobs means less noise from your bass or preamp gets amplified. Use the balanced TRS jumper cable to parallel-feed the 2nd channel. This will give you the most optimum setup. You shouldn't notice any tonal differences. MAYBE a slight volume difference. Try it with/without the transformer -- for around $10 or so you can afford to experiment a bit!

He then linked me to the transformer I showed, above.

I just ordered a couple from MCM; they're nice to have around anyway for the PA. I'll try it both ways just for grins. My biggest worry is that the transformer will change the tone. We'll see what Agedhorse has to say.

tallboybass · #19 04-20-2010, 01:20 PM

Cool, forgot to mention you can compare balanced and unbalanced by coming out of the DI post EQ and line level with a mic cable.

agedhorse · #20 04-20-2010, 01:20 PM

Quote:

Originally Posted by mikeddd

Nice looking rig, tallboybass! I just ordered the rackmount kit for my Shuttle 6.0 yesterday. It looks mighty fine all racked up.

@Agedhorse: Thanks for clarifying several points. In fact, I emailed QSC yesterday about the best way to use a QSC GX5 with my Shuttle. They recommended a matching transformer for max S/N ratio, etc. I'm planning on using this: http://www.mcmelectronics.com/produc...0HC385-/35-595 My big question is: Will the matching t-former affect the tone coming out of the amp? I don't want it to sound thin or sterile.

There is absolutely no need for a matching transformer, has nothing to do with S/N ratio or level matching or anything of the like. Take the 1/4" TS output of the effects send/pre out which is already nominal +4dBu, the channel volume control rather than the master volume will be what you use as a "master volume". The amp senistivity control(s) should be turned all the way up, this gives roughly a +4dBu input sensitivity.

Regarding the matching transformer that you posted, this is the wrong tool for the job regardless. It's XLR output is a 100:1 impedance transform, meaning that the signal will undergo a voltage drop of say 12-16dB, maybe more depending on it's construction. This will result in a horrible mismatch of levels and you will not be able to adequately drive the GX power amp to anywhere near full output. Also, this transformer will saturate and exhibit terrible distortion characteristics at low line level frequencies.

The only time where a transformer is necessary is for isolation, and for that a special 1:1 line level device is indicated. This would be to isolate incompatable grounding topologies, not all that often encountered for applications like this. I do sometimes build up 1:1 isolation transformers custom for touring customers where we know they are likely to encounter very odd, unusual situations and circumsances. I've done a couple for some TB folks.

Would you PM me with the QSC contact that you delt with so that I can be sure they don't give other folks the same incorrect information. This is the second time I have encountered this.