Pre/Power type rig?

[René_Julien]

Hi - I don't currently know a lot about separate pre/power rigs. I would appreciate some replies and comments related to the following basic questions about this style of setup. Bassybill has said if the information collected is going to be useful to lots of people he will put a link to this thread in the FAQ sticky.

What are the main pros and cons of a pre/power rig compared to a typical head?

What should I be looking for in tech specs for a poweramp?

Can pretty much any PA type poweramp be used in a pre/power bass rig?

How would your choice of power amp influence cabinet choice?

Does anyone here use a pre/power rig for just practice?

Does anyone here use multiple power amps working together in their rig?

How do you hook up a pre/power rig (cables, inputs and outputs, et cetera)?

Anybody got any troubleshooting stories with their pre/power setup?

Any links to manufacturers or other useful info?



...
Okay, I consulted bassybill before I posted this thread. He helped to make a list of these general questions and issues.
We (as in we all, especially newbies) need a good link in the FAQ regarding poweramps.
I spent several time in the amp forum, using the search function, spending a lot of time browsing and reading to know what I needed to know. (And I still don't know if I should go the poweramp rout myself. )
All the information is out there, but I had to piece it all toghether.
So let's focus all the general info in this thread.
There are a lot of experts and experienced people that hang out in the amp forum.

So please, give us your insights. (Tackle one of the above questions, or tackle them all. Your choice.)
Thank you in advance to everyone who contributes.

 

[Chad Michael]

Last live gig I played:

Used my Eden WT600 as a preamp, with a Crest CA6 power amp (thru a Goliath 4x10).

Advantage: The Crest drove that cabinet with so much more authority than the Eden alone. Even with the Eden bridged (@ 600 "Eden" watts), it was no match for one channel of the Crest (400 "Crest" watts) in terms of just good, healthy beefy tone. Night and day difference.

Disadvantage: Most modern-day bassists are wildly obsessive with the weight of everything, adding the Crest to my rig adds an honest 44 pounds....

Playing the Eden head alone was like towing an 8,000 pound trailer with a 350 Chevy. Sounds good, gets the job done.... but - using the power of the Crest was like towing the same load with a Cummins diesel. (grunt grunt - "I move heavy stuff" grunt grunt)

 

[slyjoe]

What are the main pros and cons of a pre/power rig compared to a typical head?

Pros are you have flexibility and generally more power available. Also, a little more reliable - if one of the power amps goes down you may have the other side you can use (if you are running one side only - most are stereo). Cons - most are solid state, so you don't have the tube "sound" of power amp tubes. Pre/Power setups CAN take up more room/weight than integrated head.

What should I be looking for in tech specs for a poweramp?

Sensitivity that matches or is close to your preamp. Enough power for your needs, but be careful - some power specs are marketing hype. I also look for weight and in some cases depth.

Can pretty much any PA type poweramp be used in a pre/power bass rig?

Pretty much.

How would your choice of power amp influence cabinet choice?

It doesn't, at least for me. The cabinet and preamp will create your sound - most power amps are pretty transparent.

Does anyone here use a pre/power rig for just practice?

Well, I have a second rig at home for practice, but I generally just use the LMII for bedroom practice.

Does anyone here use multiple power amps working together in their rig?

No, unless you consider that my power amp is stereo, so there are two amps in there.

How do you hook up a pre/power rig (cables, inputs and outputs, et cetera)?

Now here it can get complicated. I biamp, which means I have two outputs from my preamp (hi, low); one goes to each side of a stereo power amp. Each side drives its own cabinet. There are other ways to hook it up
1. only using one side of the power amp
2. drive both sides of the power amp, with a Y from the preamp
3. single output from preamp to what is known as a "bridged" stereo amp - one output of the power amp feeds the other. I personally wouldn't recommend, but some do it.

You can find owners manuals (e.g., QSC) online that show various hookup details.

Anybody got any troubleshooting stories with their pre/power setup?

I've been using it so long I forget - initial setup took some learning, but I can't remember the pre or power ever going down.

Any links to manufacturers or other useful info?

I hear the internet is on computers now. Try google for Crest, QSC, Crown power amps. Also, you can probably find on Musician's Friend or other online store a listing of what they carry, and go from there.

Hope this helps. This is all my opinion, and YMMV. Good luck.

 

[René_Julien]

Thanks bimplizkit and slyjoe for your comments.

Okay some personal questions that might also apply to others.
What I want is a rig that I can use as a halfstack around 500w with a 4x10 cab (home practice, rehearsal, small gigs) which I can expand with another 4x10 cab for bigger rigs.

My local store carries Crown poweramps.
In stock:
XLS 202 D, 2x300w @ 4ohm
XLS 402 D, 2x450w @ 4ohm
XLS 602 D, 2x600w @ 4ohm
XLS 802 D, 2x800w @ 4ohm

So let me compare this to the power section of an Ashdown MAG 600 head:
MAG 600: 575w @ 4ohm.
So to get these same specs I can use the XLS 202 D in bridged mode. <- edit: this is wrong, XLS 202 D is 600w @ 8ohm (?)
Or with an XLS 602 D I would get actually two time the power section from the Ashdown MAG 600. Give or take a few watts.


Am I getting this right? edit: not really
The XLS 202 D in bridge mode plus the preamp of my choice is comparable with a MAG 600.

But when looking at the specs on the Crown website I notice that XLS 202 D in bridge mode has a minimum impedance of 8 ohm. (I think.)
So I can only hook up one 8 ohm cab to this poweramp getting 600w while on the MAG I can hook up two 2 8ohm cabs getting 575w or 1 8ohm cab getting about half the power of that.
(I am talking about 410 cabs with 400-600w power handling.)

So the XLS602D (with preamp) is a better choice. I can hook up 1 cab to get the same power as the MAG with that same cab. Or two cabs to one side of the poweramp to get the same power as two cabs hooked up on the MAG.
And then I also have the option of hooking up another 2 cabs to the other side of the poweramp.
4 cabs hooked up like this to this poweramp would be like having two MAG 600 fullstacks.

Are my conclusion all correct?

(note: I only used these two brands and types of poweramp and amp head for comparison on the power section. It has nothing to do with quality or reputation of the mentioned products.)



Oh and by the way, please keep adding your knowledge, insights and experiences on the questions and issues in my OP.
Thank you.

(I think I am getting the hang of this poweramp business now. Unless my conclusions in this post are wrong.)

 

[groove pump]

Since making the switch to a pre/pwr layout from an SWR SM-400, I haven't missed the head one bit. My sound is better, even without a semi-parametric eq for my mids, I can power any or all of the cabs I've got, and I've had zero issues with reliability. In a pinch, I could even use half of my power amp to run a portion of a PA.

My pre is an Ampeg BSP with two channels that can be blended or played separately, so I can patch my Q-Tron into the overdrive channel's effect loop without the gain on that channel cranked beyond 3 or 4. That actually lets me set the level of the effect and mix it with my clean sound. I have enough power that I only use one side of my QSC to run a pair of 2x10's and even though there's a little less portability with the modular setup, I'm already hauling a car full of gear to my shows.

I recently found a crazy cheap older Genz-Benz M-Line 12" combo for taking to rehearsals. Very healthy sound output for band practice and I'm getting to like it for noodling at home, too. Even though my big rig is also up in my room, I'm liking the low volume sound that I get out of the combo - good find for me because it even makes great sound from the keyboard that I sometimes play with.

Can't answer any questions concerning sensitivity, etc. I found both my pre and pwr amps second hand for very low prices and every time I see a rather powerful head at a shop or in an ad somewhere, I don't even stop to check them out anymore. For what they typically go for, there's no comparison for me. Modular rigs can deliver amazing bang for the buck. I may look into a really good compact rig like the G-B Shuttle line or something down the road, but the only thing I really need for my sound these days is better technique!

 

[Rick Auricchio]

Usually, bridging requires double the impedance; thus, an amp that can drive 2 ohms per side bridges into 4 ohms. If it drives 4 per side, it bridges into 8.


I have an Eden WTX-260 for small gigs, a WT550 for larger gigs, and now a Stewart World 1.6 power amp for bigger things.

Specs (wattage approx):

WTX260: ----@2, 260@4, 130@8
WT550B: 750@2, 550@4, 300@8
World 1.6: 700@2, 550@4, 300@8
World 1.6: ----@2, 1400@4, 1100@8 bridged

By coincidence, it's easy to remember that the power output is very close to that of the WT550.

For a really large power requirement, I can patch the Stewart from either head. I can also use the WT550 for one cabinet and patch its FX send to one or both sides of the Stewart. Lots of flexibility.

The Stewart amp takes 2 rack spaces, weighs 16lbs (7.25kg), and it is designed as two independent mono amps in one box. There are two independent power supplies; they share the power cord and fan. It requires 120v/60Hz.

 

[brisonic]

I prefer the pre power setup immensely. A crown power base 1 years ago got me hooked. You do need to pay attention to the rms power rating, this is typically the most trustworthy wattage rating. Some amps can influence cab choices, there are qsc amps with a 100hz iirc crossover, so you could sub one cab and then run the rest on the other channel. Some amps support 2 ohms, though typically at a higher distortion rating, I wont do this. The tonal flexibility you get is the big plus. I have an 8u rack. I plug bass into an epifani pre. This has a tuner out I plug into a boss tuner pedal. It has an effects loop I run through a compressor and a sonic maximizer, then back to the pre. I then run an out to my qsc rmx 1450 amp. My rmx supports bridging the inputs, so I just plug a signal into 1 channel, then it feeds both separate amps. Each channel of the amp has its own subsonic frequency filter, so I can protect my non sub cabs (until I get a 1x18) from frequencies below either 30Hz (my avatar 2x12), 50Hz (my triad), or not at all. It is so much louder. One channel of this amp at 400 watts is so much louder than the swr 350 watt it replaced into the same swr triad. I am somewhat of an audio snob, loud sucky tone doesnt work for me.

 

[pbass6811]

I pretty much agree with Slyjoe on his assessment of the pre/power setup, but I'll add my $.02 anyway...


What are the main pros and cons of a pre/power rig compared to a typical head?

The main pros in my opinion would be flexibility. You can have as much or as little power as you require and your not locked into any "sound". If the preamp isn't cutting it, dump it! If the power amp is too weak, get a bigger one! I also believe it would be more reliable. If you have a head and the pre section goes...so goes the rest of your amp!

The main cons would be more weight...although most manufacturers are trying to make lighter power amps these days. Then there's the added expense of a rack to put it all in and the cables to hook it all up...still worth it in my opinion!

What should I be looking for in tech specs for a poweramp?
Something that matches your cabinets capabilities! If you have two 8 ohm cabs, pretty much any amp will run a 4 ohm load bridged or 8 ohms per side. Be aware that if you have two 4 ohm cabs, you probably WON'T be able to run a bridged mono setup as almost no amp will run a 2 ohm load in bridged mono(although most WILL run 2ohms in stereo!)! So if you have two 4 ohm cabs or a 4 and an 8 ohm, you'll almost assuredly have to run a stereo or dual mono setup.
Can pretty much any PA type poweramp be used in a pre/power bass rig?
I'd say yup!

How would your choice of power amp influence cabinet choice?
It doesn't. Probably more the other way around if anything...

Does anyone here use a pre/power rig for just practice?
I suppose if it's all you have. I'd look into getting a small combo amp for just practicing...
Does anyone here use multiple power amps working together in their rig?
Unless your on the "Bleeding Ears" tour, or your band is stupid loud, I really can't imagine why you would need more than 1 power amp? 1 amp, capable of a 2 ohm load per side, should, theoretically, power up to eight 8 ohm cabs(4 per side).

How do you hook up a pre/power rig (cables, inputs and outputs, et cetera)?
Are you running a mono pre? a dual mono pre? Are you bi-amping? Are you running the output through a compressor or a crossover? You're gettin' the point here, right? Without know the specs of the rig, it's almost a moot point to talk about hook ups. Again Slyjoe's setup is a good starting point
Anybody got any troubleshooting stories with their pre/power setup?
Lemme tell you about the time my power amp caused a rift in the time space continuum...

Any links to manufacturers or other useful info?
There are a TON of great preamps and power amps out there and almost every manufacturer has a website of some kind with all the info you wanted to know but were afraid to ask...Have fun and good luck on your bass tone journey!!

 

[Implosion]

If the OP is still reading the topic, he should really read the quote below. It's from another topic, but it has got some useful information about the Crown XLS.

Contrary to Crown documentation the XLS series amps actually can be run bridged to 4 Ohm; I do run my Ampeg SVPCL/XLS202 into two 8 Ohm cabs.

I was confused by this last summer when I bought the amp as all German online retailers seemed to list a rating of 660W briged @ 4 Ohm for the 202 so I emailed Crown customer service and received the following reply:

Jouni,
The XLS amplifiers are safe to run at 4 ohm bridge mono. The confusion is because the higher power models are being revaluated by the regulatory agencies as to what size power cord is needed. Until this is resolved, the 2 ohm stereo and 4 ohm bridge-mono numbers are not fully published.

 

[René_Julien]

If the OP is still reading the topic, he should really read the quote below. It's from another topic, but it has got some useful information about the Crown XLS.

Thank you for that.

It's going to be the XLS 602 or 606, I'll have to weigh the pros and cons of those two myself.

And thank you all for keep commenting.

Thanks to all the explanations I decide I know enough to go the poweramp way.
I still need to learn a lot about power and ohms and hooking up...
But I guess I learn that if I actually do own a poweramp.

Now that I know more about poweramps it seems so simple.
But to someone who isn't technical minded at all this can seem like a rubiks cube.

Pros for me to going to poweramp way:

- I still am strong enough to carry heavy stuff and I have a large van (from my business).

- Flexibility, I can switch preamp tones of my choice. (Right now I am enjoying a Line 6 POD X3 as preamp, but I can always get another preamp in the future.)

- Also is going to be my practice rig, I have the luxury to have the place and to practice as loud as I want to.

- POWERRRRRRR!!!!


About cabs I don't know yet. I understand the I can use any cab I want.
But that doesn't help me decide what exactly I am going to buy.
My local store owner is recommending me an Ashdown ABM 4x10" (mainly because that's the only one he has in stocke. )

I don't know, Hartke 4.5 XL seems a cab I might consider.

 

[René_Julien]

How would your choice of power amp influence cabinet choice?
It doesn't. Probably more the other way around if anything...

Yes, I have a different view on this then I had a few weeks ago.

So most of the pre/poweramp rig users have a favourite cab(s) of their choice. I assume.
Again: flexibility I guess, you can like cabs from one brand while not liking the heads of that brand, or vice versa.

So, my cabinet choice will effect the choice of how powerful my poweramp should be. That's what pbass6811 means. (Right?)

So a practical issue from my own ponderings:

My cabinets of choice: Hartke 410TP (used) for now, and in the future maybe new Harkte 410XL cabs.

The 410TP is 300w@8ohm...
The 410XL is 400w@8ohm...
I'm planning to go with two cabinets at one channel of the poweramp. (Other channel in the future maybe for biamping, perhaps.)

Most likely I will get a Crown XLS series head.
So if I want to fully utilize the potential of two Hartke 410XL heads, which one should I get?
XLS 202 300w@4ohm enough?
XLS 402 450w@4ohm better?
Or go even more powerful with the XLS 602 or 802 if I maybe get cabs with more power handling in the future?

Any thoughts, which Crown XLS would you get for two Hartke 410XL cabs (at one channel) ?



Oh, and please keep sharing your wisdom and experience regarding pre/power rigs. Thanks.

 

[Implosion]

Yes, I have a different view on this then I had a few weeks ago.

So most of the pre/poweramp rig users have a favourite cab(s) of their choice. I assume.
Again: flexibility I guess, you can like cabs from one brand while not liking the heads of that brand, or vice versa.

So, my cabinet choice will effect the choice of how powerful my poweramp should be. That's what pbass6811means. (Right?)

So a practical issue from my own ponderings:

My cabinets of choice: Hartke 410TP (used) for now, and in the future maybe new Harkte 410XL cabs.

The 410TP is 300w@8ohm...
The 410XL is 400w@8ohm...
I'm planning to go with two cabinets at one channel of the poweramp. (Other channel in the future maybe for biamping, perhaps.)

Most likely I will get a Crown XLS series head.
So if I want to fully utilize the potential of two Hartke 410XL heads, which one should I get?
XLS 202 300w@4ohm enough?
XLS 402 450w@4ohm better?
Or go even more powerful with the XLS 602 or 802 if I maybe get cabs with more power handling in the future?

Any thoughts, which Crown XLS would you get for two Hartke 410XL cabs (at one channel) ?



Oh, and please keep sharing your wisdom and experience regarding pre/power rigs. Thanks.

Why wouldn't you use both channels or bridge mode with two cabs? There's no reason to leave the other channel useless IMO. Some say that it won't put so much strain on your amp, because it doesn't have to work as hard with only one channel running. But my philsophy is that you buy the gear to be used, not to be spared.

Choose the biggest power amp your budget allows. You can turn down an amp that's too loud, but you can't turn up too small of an amp if your allready max'd.

And choose the XL instead of TP, it seems to be getting a better rep.

 

[René_Julien]

Why wouldn't you use both channels or bridge mode with two cabs? There's no reason to leave the other channel useless IMO. Some say that it won't put so much strain on your amp, because it doesn't have to work as hard with only one channel running. But my philsophy is that you buy the gear to be used, not to be spared.

Choose the biggest power amp your budget allows. You can turn down an amp that's too loud, but you can't turn up too small of an amp if your allready max'd.

And choose the XL instead of TP, it seems to be getting a better rep.

I would use the other channel for maybe biamping in the future. (Maybe a channel for clean sound and another channel for effects.)
Plus, to use it in stereo I better use 4ohm cabs.
Maybe bridging is something to consider, but on the XLS serie I'm not sure if that's a good idea to go bridged at 4ohms.

I can get a Hartke 410TP used for a good price. I'm not sure if I'm going to buy that one or get a new XL cab.
Advantage of the TP is that it is lighter.
But the TP is disontinued I think.
I still have to think about that.

 

[Rando McNally]

One of the best parts of the pre/power amp route is flexibility. I can swap out power amps, I can vary configurations with speakers, impedances, etc. It's a much more flexible setup.

If something goes wrong at a gig there's more flexibility to come up with a quick solution, vs. a head blowing up and being dead for the night. I haven't had this happen at a gig, but it's happened at practice before. A fuse blew in my preamp.

I have a boss gt6b and a tech 21 sansamp in my signal path, so a few quick cable swaps and my sansamp took over as preamp (instead of stomp box) and we only missed about 30 seconds. You can't do this on most heads because most lack a "pre out" and "main in."

I have a pair of power amps (one big and one huge), and I sometimes use both!

Your power amp should not be a determining which cabinet you get, your cabinet should determine which power amp you get.

I've always been of the opinion that you build your rig (home theater, stereo system, etc) from your ears backwards. Get the best speakers you can find. They will make the most difference. Then work backwards.

I've seen kids with $400 pedal boards playing through bottom of the barrel crate amps, or some ragged out old blown up gear. Don't do this.

That being said, heads are easier. If you have one you like (I mean REALLY like) you might want to hang onto it until you make the full transition.

 

[NickyBass]

I recently switched over to a pre/power rig. I found that, while I liked the pre sections on alot of the new heads, I don't always dig the lightweight digital power section. I've found that, by combining a modern preamp with a lead sled power amp, I can get closer to the tone in my head. The downside is the weight and size.

Though the seperates route will offer much more flexibility, I'm not too interested in that. I know it is a huge plus for some, but I'd rather stick to one setup that covers all styles. The only sound that this rig is missing is the all tube tone. But, I have my tube heads for that.

 

[Blues Bass 2]

One thing to keep in mind is that it is cheaper to change your tone if you don't like the sound of your Pre/Poweramp rig. Poweramps don't have an inherent sound,they pretty much all sound close to the same so when you want to change your tone you only have to change the preamp and they are much cheaper than a whole new bass head with the same power as your Pre/Poweramp. A couple good preamps for not too much money are the SansAmp RBI and RPM and the BBE Max preamps. Used ones come onto the classifieds on Talkbass from time to time for around $200 to $250.

Another thing is that your setup doesn't have to weigh a ton. My rig I just got rid of had a Crown XTI 1000 that's 17 pounds and QSC has a PLX 1804 that only weighs 13 pounds and both will power a big rig to loud volumes. My rack with an RBI preamp and the XTI 1000 only weighed 32 pounds and had 1400 watts to fool with.

 

[svtb15]

People often say that " power amps dont have an inherent sound".. That is very misleading.. Theoretically on paper perhaps but in real life it isnt so,,
There are many threads about that particula topic already...

Especially in AB tests..
We can go around and around with that... But with bass guitar Crown does not sound like BGW or Yamaha Pro or the QSC Powerlights.. they all sound different... Maybe less inherent with Program material such as a CD that has been mastered and compressed.. but with Bass instrument there is a huge difference in the delivery and punch of different power amps///
There is a difference between the Crown PSA2 or DC300 to my old BGW.. as well as the Crest CA6 to my Carvin DCM1500..

In fact even brand to brand dont sound the same... My friend works for a large sound company that uses the newer Crown I-Tech amps in their systems.. The head engineer says although they sound great, they dont sound like the Macro techs... this guy has numerous major stadium and arena tour mix jobs under his belt ove rthe past 20 years... I trust his word , experience and ears..

 

[Rando McNally]

Every bass player should have a sansamp bass driver of some kind. It's a HUGE tool in the arsenal. It can be a preamp, DI, or distortion box. It can save your tone in a board mix.

Remember, FOH should be waaay up in your consideration. Your stage mix is really just for you and your bandmates. We spend all this time obsessing about our stage rig, but the crowd hears our board mix, not our stage mix. I know this is a thread about rigs, but I feel compelled to bring that up. Sorry.

 

[dave_kts]

I'm running an el cheapo behringer ep1500 bridged into a single 8ohm 410 pro cab for three years now and i couldn't be more happy. It has the subsonic filters to protect the drivers, limiters, at practice ill even run a kick drum mic thru a mixer into the 2nd input and it works great, can handle both my bass and the kick seamlessly.
i paid 200 bucks for my behringer used, suprisingly it has been just fine. I wouldn't count on it pushing the claimed 700 watts into 8 ohms bridged, but has far more headroom than just about any head ive tried. except for an all tuber...
I chose the pre/power setup for a couple reasons. flexability obviously, i can swap out a pre when i get the money for something better, and i wanted to go with rackmount tuner, compressor and so on cause i hate pedals. too buch garbage to hook up for gigs, too many connections/power supplies to go wrong.
I also think it has a more professional look than a bunch of pretty colored pedals strewn across the floor...

 

[Blues Bass 2]

I guess I'm wrong about the poweramps sound. I used the power section of my old Carvin R 1000,basically a DCM1000,and then a Crown CE 1000 and then a Crown XTI1000 with the same RBI preamp and basses. They all sounded about the same to me but with different gain on the front ends. I guess I'm part tone deaf but I couldn't tell much difference,I was still getting my tone with the same preamp settings.

Regardless once you do get a poweramp you like the preamp will be what you want to change to get your different tone.