Double Bass GK question

[Chris Fitzgerald]

You are overdriving the front end of the amp. You've learned
how to get the sound out of the bass, you just haven't learned how to get the sound out of the amp.

Many people leave this end of the equation out, and the result can be almost as bad as overlooking the first part of the equation (natural acoustic sound). Why go to all the trouble of getting a great acoustic sound and then **** it all up with lousy amplification?

The idea is to go from the preamp out, to the effects return jack on the back of the amp. This way you bypass the GK preamp so you don't have a preamp going into another preamp. Only the
master volume will work on the GK at that point. Do a little experimenting with this. You might like the sound much more,
or not depending on the bass, pickup, amp match up.

And even if you don't want to do the whole "into the effects return" thing, you can still use the regular input if you stop thinking of the preamp as simply a line amplifier, but think of it rather as an impedance buffer and EQ circuit. I know that Wil and I have gotten into several little tangents about "gain staging" (which will probably have BESAME NOT MUCHO rolling his or her eyes even further), but on my old bass, by the time I got through setting the EQ on my preamp for the most natural possible sound, the signal was often actually quieter than plugging the pickup straight into the amp input would have been - the difference being that it sounded a hell of a lot better. The way to use a preamp in this way are simple:

1) Never boost any EQ band; filter out the "bad" frequencies rather than boosting the "good" ones.

2) make sure the level coming out of the preamp is appropriate for where the signal is going. If you are going into a regular amp input, there's no need to boost the signal on the preamp that far - a preamp that is being pushed towards its headroom ceiling starts to produce a more "compressed" sounding signal than one that is in its comfort zone headroom-wise.

3) If your amp's internal preamp is clean (like on an EA iAmp, WW, or Clarus), there's no real reason to bypass it unless you feel that the effects return sounds better (I don't on the EA and AI heads). If your amps internal pre is colored and you don't like the color, then use the effects return as an input.

 

[bassfiddlesteve]

I've priced some of the alternative amplifiers suggested on this thread and they are all more expensive than the GK MB150S which cost me less than $700. The closest was the AI Contra which sells for $919 and some of the head cabinet combinations are well over $1K. If I decide to return the GK after this weekend's gigs I guess I'll just stick with the SWR WM12 as my main acoustic bass rig as I can't really spend more than $700 on an amp, and to be honest I feel I shouldn't have to to get a decent sound for the the low-to-moderate volume gigs I play. I also can't see spending major bread on an amp only to bypass the preamp section. When I plugged my Fishman Pro-EQ into the effects return of my SWR and Roland amps I was less than impressed with the results. Of course, this was with the Underwood pickup which I was never completely happy with to begin with. Speaking of happy, I was just listening to some newly released live Jimmie Blanton on the Duke Ellington Centennial Collection CD and boy did he sound awesome. Gut string and no amp. Ah

-Steve

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[TroyK]

I care about my tone and have been using an older GK 150MB for about a year now, almost exclusively. My teacher who is arguably my town's first call guy uses an even older one.

Honestly, it's tough to find fault in it. There are a few odd situations when I feel like I'm challanging the head room, but I've got an extension cab for those circumstances. I find that, as you all know, every room sounds different. I start with the EQ flat and then tweek it a little if need be. There are gigs where I love my sound and gigs where I fight it all night, but I've had that same experience with every rig I've ever used.

I've played a gig and a jam session with an AI Contra and have found the same issues with it. If I was new amp shopping and price was no object, I would probably buy something different, but I paid less than $500 used for my GK and have never, ever, for a second, regretted it. I keep telling myself that someday I'll get a Walter Woods head or something and probably will when I fall into a deal, but I doubt that I'll ever part with my little GK. True, the size is the draw, but most of the time I don't find a problem with the sound either.

Before you assume that I just don't care about my tone, I have a 100+ year old carved bass and obsess about just the right combination of strings...which I think I may have solved.

Use what works for you.

-tk

 

[Eric Jackson]

I've tried the preamp-into-effects-return approach after reading about it on this site. Once again, it sounded slightly different, not necessarily better.
I'm sure a better, more expensive preamp would sound better, used in this way.
I'm also sure a better, more expensive head/cab combo would sound better.
But the cost-benefit analysis just dunt work fer me. I'm 80% pleased with my current bass/pickup/preamp voicing/power amp setup. I get compliments on my sound from the players around me, some of them bassists. I can't justify spending 400% more on gear chasing a 19% improvement in sound. (We're never 100% satisfied, are we?)
I'm a part time player with kids in university. Like keykendrick, if an affordable deal falls in my lap, I'll upgrade. Till then, I'll stick with the GK.

 

[bassfiddlesteve]

Well, I used the GK MB150S on two gigs, one with a quartet in a fairly large community center and the other with a drumerless trio in a small restaraunt. The GK sounded good in both of the venues and I got compliments from the other musicians. The GK put out more than adequate low end and the Hi Boost was helpful in adding some attack to the inherently dark sounding Realist. It's also seems a little "tighter" sounding than the SWR WM12. Today is the outdoor concert so we'll see how that goes.

- Steve

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[fdeck]

I have had a GK MB150E combo for upwards of 6 or 7 years. Originally it had the problem with the effects send / return jacks, which I simply bypassed. The footswitch jack similarly flaked out.

Growing more and more frustrated with my tone, I finally measured the frequency response curve and have persuaded myself that the preamp is malfunctioning. Meanwhile, I had already switched to a homemade preamp.

Now the worst thing... it started buzzing. I can only work on this problem when everybody's out of the house, and hopefully my latest fix will be the winner.

The portability is addictive, and the tone of the power amp plus speaker is good. I can't say if the preamp sounds good, because I don't know if it has ever worked properly. So I have to reserve judgement.

For all of us fussy URB players who are going to use our own preamps anyway, GK should come out with a "powered speaker" version of this combo.

I have the schematics, and am pretty knowledgeable about electronics. It is a fairly generic design, and also fairly old. But with a power amp, if it works, then it works. Now that Peavey's patent is expired, any power amp without a self adjusting compressor limiter is outdated. I added this feature to my MB150E, not a task for the faint of heart.

 

[fdeck]

I applaud you for tweakage above and beyond the call.

I want no compression -- just the sound of the bass, thanks. Any power-amp with a built-in compressor-limiter is useless for me (and will make me sound like I'm playing through a Peavey). To each their own.

Agreed. Perhaps "limiter" would have been a better term for what I am doing. The Peavey circuit is completely inactive until you reach the clipping threshold of the power amp, then it kicks in with a hard knee. Thus, it only compresses when the alternative would be clipping distortion.

With that said, a lot of good amps have a switch to disable the compressor.

As for using a compressor as an effect, I also prefer the sound of the bass itself. The MB150E "limiter" has a soft knee, so I don't use it.

I have noticed that I seldom activate my compressor when playing upright bass. Indeed, it would probably take enough volume to drive me into the feedback zone, even with a magnetic pickup. But the compressor lets me get away with a relatively small amp on electric bass gigs.

 

[Marty Forrer]

I always use my 150E on top of a little 12" sealed cab, regardless of how small the venue is. The difference in tone over just the 150 on its own is amazing. I have tried preamps of different types, both in front, and in the return loop, and prefer the sound straight from bass to amp. I tried a Clarus and hated it. I tried a David, and was unimpressed. For jazz, my GK and its ext cab cant be beat. I kinda like my Barbera and Lenzner guts too! LOL!

 

[Giacomo]

I have been thinking of getting a little extension cab to go with my 150E, and Marty's comment about the difference in tone has made up my mind. I chose the 150E for portability...bad back + 26lb. = less pain. It seems to make sense to me that the GK Microbass Series 112MBX extension cab would be a no brainer. "Housed in specially designed aluminum cabinets, they are a little over a foot high and wide, weigh only 12lbs......[Invalid or Expired Link Removed] they are tone monsters!

A search of the DB forums comes up with very little, and none of it from anyone who has actually had any experience with the cab. There was a comment that it produces 100W at 80 ohms and may not be loud enough because it is a sealed unit(?) That's beyond my technical knowledge, which is virtually nil.

I have surfed the Ampeg Portabass Series, PB112H, 23 lbs. and a telescoping handle (didn't say wheels!) but the comments on Ampeg's Message Board were a bit discouraging. i.e., the handle was an option and if you put it on, it voided the warranty...sounds crazy to me too. I'm guessing that that has been rectified and their website corrected. Also, someone mentioned that the 93dB sensitivity could be an issue. (Again, beyond my comprehension.)

A search of the DB Forums finds mostly positve comments on the Ampeg.

So...has anyone had any experience with the GK 112MBX cab, with the GK 150E? or without?

 

[fdeck]

So...has anyone had any experience with the GK 112MBX cab, with the GK 150E? or without?

No experience, just some observations based on surfing the GK site. It looks very much like the cab is identical in design to the speaker in the combo. In fact, it would not make sense for them to maintain two different designs.

I have gotten good results with an extension cab consisting of a Eminence 121895 ($55 from Madisound) in a little homemade box not much bigger than the GK. The Eminence Delta-12-LFA for $99 from US Speaker also looks like a good choice.

A friend of mine who uses a MB150 combo with a 15 inch extension commented to me that he can move the extension away from his bass and get more "music to feedback ratio" from his rig.

 

[winston]

Just a couple of weeks ago I shared a gig with a bass player who used an MB150/112MBX setup.

My band played first. We were playing Django-style Gypsy jazz in a large wooden pub with high ceilings. I played my Messenger EUB through an Eden WT-400 into a Bergantino HT-112 raised a foot off the floor. I went as far away from the amp as my cord would allow (about 12-15 feet) to check my tone and make adjustments. I ended up with a clear, full, punchy sound that blended well with the other instruments (amplified Selmer-style acoustic gtr. and drum kit).

The bass player using the GK setup is one of Sacramento's very busiest (and best) players. I've heard him in many other situations with other amps, and he's always had a warm, full, clear tone. His tone with this rig (placed on the floor) had precisely 0% fatness or balls, even with an old P-Bass. I was sitting only a few feet away from the spot where I checked out my own tone.

I'm not kidding--the guitar player had an itty-bitty PolyTone combo with an 8" speaker on a chair, and was projecting more bottom end.

I love GK equipment--my default rig is an '87 400RB into an EA Wizzy 112. IMO this setup smokes the MB150/112MBX for volume, tone and punch; only weighs about 5 pounds more; and is much cheaper. I used to have a 200MB (predecessor of the MB150)--it was fine for low-volume practice, but totally got lost in a band setting (even with ext. speaker) with no PA support.

 

[Marty Forrer]

To clarify; my ext cab is homemade, is sealed, marginally bigger than the MB150, and houses a Bag End 12" 250watt 8 ohm speaker. As I do not really like the sound of the GK on its own, I cant imagine the GK ext cab being any improvement, seeing as its the same design as the amp. I have also used the MB150 with my SWR 4x8", which is a component of my rockabilly rig (WT400, 4x8, 1x15), and that sounded wonderful. A bit over the top for jazz gigs though.

 

[fdeck]

Marty, did Bag End sell you a raw driver?

My MB150E is fixed -- a piece of bicycle inner tube rolled up and stuffed between the power transformer and bridge rectifier seems to eliminate the buzz. Don't try this at home unless you are an experienced technician, since there are high voltages in there.

So I am back to being happy with this amp. The Series III looks like it has some welcome improvements.

 

[fdeck]

I applaud you for tweakage above and beyond the call.

I want no compression -- just the sound of the bass, thanks. Any power-amp with a built-in compressor-limiter is useless for me (and will make me sound like I'm playing through a Peavey). To each their own.

After a couple gigs with the new rig, I realized that the main thing I was getting from the compressor was the little indicator light. The compressor is history, and the MB150E is restored to factory stock condition.

Live and learn.

 

[Giacomo]

Thanks to all of you who gave feedback on my GK112MBX ext. cab query a while ago, especially Winston who was live on the scene! I've been out of commission for a while and just getting back in the swing.

Based on the feedback, the GK cab has been scratched off the list. It seems like the Ampeg Portabass PB112H is the route for me, so I better start shopping. Thanks.

 

[bassfiddlesteve]

Just for the record, I am still happy with my Gallien-Krueger 150MBS. It is my amp of choice for the upright bass (with a Realist or Bass Max pickup) and I've come to prefer it's warm, punchy sound over the "hi-fi" SWR Workingman's 12 for my Fender Jazz Bass as well. I purchased the padded bag with shouler strap for added portability and protecion and I happily remain in the "one trip from the car" club

- Steve

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[Christopher]

I have the MB150E. It's primary value to me is as a portable practice amp and stage monitor for low- to medium-volume gigs. A drumkit played with sticks can definitely overpower it, and it gets nasal and unpleasant sounding the more it's cranked.

That said, my complaints about its mediocre sound disappear once it's plugged into a bigger, nonsealed, bass-friendly enclosure (of course, this largely defeats its portability advantage). I don't think GK put any thought into "designing" the cab, which is a shame, because the preamp is more versatile than the built-in speaker will let you hear.

Like Marty, I don't see the point in buying the matching GK extension cab, since it seems to repeat the design mistakes/compromises of the combo.

BTW, mine buzzes too, unless I engage the ground lift. Then it's dead silent.

 

[Irishbass]

As a very late addition to this thread, I have a 12 year old GK150 microbass combo that I have played thousands of gigs with and it has been extremely reliable in that time, just having one repair job done when a limiter circuit gave some trouble. I bought the MBX112 ext cab for it about 4 years back and I found the following to be the case. If you put the 150 combo right on top of the 112 ext cab like a mini stack, the resulting tone is simply terrible..way too thin with absolutely no balls, no warmth and definately no grunt! It actually made my combo sound like half the amp it usually is. I know this sounds very strange and doesnt make sense but its quite true. However.....move the extension cab way from the combo a few feet with a decent lenght of speaker cable and low and behold, tons of extra volume and punch. I have even played at weddings with both my NS CR4M EUB and various electric basses where this tiny set up has proven to be capable of keeping up with a fairly loud band playing all the usual pop/rock/jazz classics with only a tiny touch of bass feeding into our very small PA system. I'm no expert on electronics or the physics of why this is the case with the GK's, full power is achieved with the addition of an extra 8 ohm cab, but in the case of the MBX112 it needs to be placed at least 6 ft away from the combo...then its great!!

 

[fdeck]

Irishbass, this sounds like a phase problem. But rather than dissecting the speaker, try reversing the phase on an old speaker cable that you don't care about. I think it's worth a try.