Double Bass New GK

[Ric Vice]

I had GK 112MBE, sold it after I tried and bought an old
GK 200MB (discontinued, but with better voicing for URB than 112MBE) plus new GK MBX112 extension cab. This setup works great for my both: electric and upright with Underwood pickup. Nice,warm sound and enough volume even for big bands .I usually let my two boxes on the floor, changing their direction - first one for my ears, second for the brass section, or else...

I belive the reason for that may be that the earlier GK's ( Micro Bass Series I and II, 200, 400, and 800 RB series) were traditional analog amplifier designs. F Deck can help us out here. I owned two of them. The power supply wasn't digital, it was a tranformer bolted to the bottom of the speaker cabinet.

 

[robgrow]

I belive the reason for that may be that the earlier GK's ( Micro Bass Series I and II, 200, 400, and 800 RB series) were traditional analog amplifier designs. F Deck can help us out here. I owned two of them. The power supply wasn't digital, it was a tranformer bolted to the bottom of the speaker cabinet.

The latest GK MB150 design still utilizes a linear power supply with a toroidal power transformer (that is bolted to the top of the amp). Basically, a power supply is either a linear type, or a switching type (AKA switch mode). The terms analog and digital don't really apply here.

Incidentally, the current GK MB150 amps use what is described as a Class H power amplifier design. This is done to improve efficiency over a typical class AB design although it is still not as efficient as a class D amp which can have an efficiency of 90% or better. There is an article on Wikipedia that explains audio power amplifier class designations (class A, AB, etc.): http://en.wikipedia.org/wiki/Electronic_amplifier I'd recommend it as good reading for anyone interested in what all those letters mean.

 

[Ric Vice]

The latest GK MB150 design still utilizes a linear power supply with a toroidal power transformer (that is bolted to the top of the amp). Basically, a power supply is either a linear type, or a switching type (AKA switch mode). The terms analog and digital don't really apply here.

Incidentally, the current GK MB150 amps use what is described as a Class H power amplifier design. This is done to improve efficiency over a typical class AB design although it is still not as efficient as a class D amp which can have an efficiency of 90% or better. There is an article on Wikipedia that explains audio power amplifier class designations (class A, AB, etc.): http://en.wikipedia.org/wiki/Electronic_amplifier I'd recommend it as good reading for anyone interested in what all those letters mean.

Rob,
Thanks for clearing that up. I was unaware that the newer GK's had a torodial power supply. So thanks for that information. That sheds a whole new light on the subject. I guess this is one of the many reasons that I still prefer the sound of a Walter Woods over the GK.

Ric

 

[TheSuzie]

Rob,
Thanks for clearing that up. I was unaware that the newer GK's had a torodial power supply. So thanks for that information. That sheds a whole new light on the subject. I guess this is one of the many reasons that I still prefer the sound of a Walter Woods over the GK.

Ric

Could you please explain why a linear power supply designed with a toroidal transformer would be significantly different from a linear power supply designed with a laminated transformer of similar specification? Once the output of the transformer has been rectified, filtered, (possibly) regulated and filtered again - I just don't see two similar transformers of different construction but with similar specs creating an audible difference.

I am not trying to be sarcastic at all here. I really want to know the difference besides size/form factor because there may be something I am not aware of. I happen to be the owner of a couple of classic hi-fi amps and one uses toroids and the other laminated, so I do have a genuine interest in this aspect of amp design.

If anyone has comments and doesn't want to derail here - please shoot me a PM

Thanks,
S

 

[robgrow]

Could you please explain why a linear power supply designed with a toroidal transformer would be significantly different from a linear power supply designed with a laminated transformer of similar specification? Once the output of the transformer has been rectified, filtered, (possibly) regulated and filtered again - I just don't see two similar transformers of different construction but with similar specs creating an audible difference...

You are right on here. As you mentioned, there are basically two types of power transformers commonly used in amplifiers: conventional iron core, and toroidal. They both do exactly the same thing which is step up or down an AC electrical voltage and provide isolation. Toroidal power transformers typically are lighter and more compact than a comparable iron-core PT, which is their main advantage. However toroidal power transformers tend to be more expensive than an iron core unit, so their use is sometimes limited by cost considerations. That is why toroidal power transformers are usually found in higher end amps.

Likewise, a switch mode power supply ultimately does the same thing as a linear power supply, which is to provide DC to operate the amplifier. Switch mode power supplies can be made to be more compact and lighter in weight than a comparable linear power supply. Disadvantages of the switching power supply are more complexity and higher cost.

 

[fdeck]

But Ric was talking about a Walter Woods, which I believe contains a switching power supply.

My older MB combo has the conventional tranny inside the speaker box. The schematics show a switching power supply for the head version. I don't know the status of the series III head. Switching to a toroid and Class-H power amp would be a logical design evolution, without great impact on the sound. Designers like to avoid re-inventing the wheel, and it is quite possible that the MB150 uses the power amp circuit from one of its bigger brethren, albeit running on lower power supply voltages.

Making the series III a bit more efficient is a boon. The old MB combo does get rather hot on top. I played one gig outdoors in the sun, and the MB combo was hot enough to fry an egg before I even turned it on. Fortunately I had an extension cab, so I hid the combo in the shade and played through the cab.

 

[TheSuzie]

But Ric was talking about a Walter Woods, which I believe contains a switching power supply.

OK, now that particular possibility did slip by me. I do know that there does seem to be some bias both for and against switchers. For me it is usually more about the quality of the design and implementation than the type of circuit. In any case it is hard to argue with WW.

Peace,
S

 

[fdeck]

One notable thing about WW is that his amps are said to be voiced, meaning that they don't have a flat response when the EQ knobs are centered. I don't know if that is truth or folklore. If it is truth, that is where I would expect to find the root cause for the favored tone of his amps.

 

[robgrow]

But Ric was talking about a Walter Woods, which I believe contains a switching power supply.

My older MB combo has the conventional tranny inside the speaker box. The schematics show a switching power supply for the head version. I don't know the status of the series III head. Switching to a toroid and Class-H power amp would be a logical design evolution, without great impact on the sound. Designers like to avoid re-inventing the wheel, and it is quite possible that the MB150 uses the power amp circuit from one of its bigger brethren, albeit running on lower power supply voltages.

Making the series III a bit more efficient is a boon. The old MB combo does get rather hot on top. I played one gig outdoors in the sun, and the MB combo was hot enough to fry an egg before I even turned it on. Fortunately I had an extension cab, so I hid the combo in the shade and played through the cab.

I am under the impression that it's just a type of linear supply with hi and low rails for the class H amp circuit, but I am by no means an expert.

...For me it is usually more about the quality of the design and implementation than the type of circuit...

I couldn't agree more.

 

[carved czech]

But guys, I was originally talking about differencies in sound of older and newer GK Microcombos. I owned both in the same time, compared them, and old MB200 definitely won! For me THAT was the reason to sell MBE112. I am not sophisticated in electronic,so I can not tell why it is so, but have my ears to hear what is better (warmer) sounding. BTW a lot of bassmen here have the same opinion and would prefer to have the old MB200(discontinued) if it is available...

 

[Ric Vice]

But guys, I was originally talking about differencies in sound of older and newer GK Microcombos. I owned both in the same time, compared them, and old MB200 definitely won! For me THAT was the reason to sell MBE112. I am not sophisticated in electronic,so I can not tell why it is so, but have my ears to hear what is better (warmer) sounding. BTW a lot of bassmen here have the same opinion and would prefer to have the old MB200(discontinued) if it is available...

Carved Czek.
Based on Rob's info about the newer GK's power amplifiers and power supplies, the sound of the older Amps would now have to be pretty dependent on the way they voiced the older preamplifiers. I owned all the versions of the Microbass amplifier and they sound very different to my ears as well. IMHO the pre MBS-MBE amplifiers had a warmer midrange timbre for Contrabass. When they added that 2 band parametric midrange eq they they gained an edge for the Electric Bass that didn't favor the Acoustic. As I remember ( I could be wrong) not to long after the MBE's were introduced GK started producing the MBS models to address this problem. All I really know is the Upper Midrange sounds pinched on the MBE's, with my bass and that tonal characteristic remains no matter how you set the midrandge controls on the MBE.
The 200, 400, 800's and Series I and II microbass amplifiers midrange eq produced a different equalization color. At least to my ears. That said the MBS and MBE are the certianly one of the most affordable compact amplifiers and combos for bass.

Ric

PS I found the eq points for the older 200 series Micro Bass amplifiers
they were 60,250,1K,4K.

 

[Ric Vice]

One notable thing about WW is that his amps are said to be voiced, meaning that they don't have a flat response when the EQ knobs are centered. I don't know if that is truth or folklore. If it is truth, that is where I would expect to find the root cause for the favored tone of his amps.

They do sound different to my ears, because the midrange is very even
and present, without that (for the lack of a better description) nasal quality that the newer GK MBE's have.

 

[carved czech]

IMHO the pre MBS-MBE amplifiers had a warmer midrange timbre for Contrabass. When they added that 2 band parametric midrange eq they they gained an edge for the Electric Bass that didn't favor the Acoustic.

Thank you Ric.
That´s it! That´s why I bought older GK 200MB and got rid off MBE112. I don´t need any preamp now (I was using Fishman preamp with MBE112) plus my sound is more ´natural´.
CC

 

[fdeck]

I posted the preamp voicing graphs on the Distortion / Gain Staging thread by mistake. But you can see them there.

 

[62bass]

I used the exact same combination for years. I used to put the G-K on a stand, slightly tilted, and aimed backwards at the wall behind me. This got around the laser beam effect you sometimes get when aiming the amp straight forward. As good as that pickup/amp combination was, I'm even happier with the custom K & K Bob (All hail) Gollihur had made for me with an AI Contra. If it's a small, no-fuss, get in-get out gig, I'll bring the G-K.

Don Thompson and other jazz bassists in Toronto use this same technique. Thompson, for a long time used a Roland Cube. I don't know if he still does.

 

[snowdan]

I just got a MB150E about a month ago. Although I have not done an upright gig with it yet it was recommended to me by the sound guy at the medium size club I'll occasionally play upright at. "All the jazz cats use 'em" was his sentiment. Where I have used it is at loud electric jams. This thing is amazing for electric. It has the tonal qualitys of my big rig, tower of power, Ampeg solid-state, 350 watt with 4/10s and 1/15 and Sansamp bass driver! It has that same punchy big feel. Not as loud 'course but LOUD. I am blown away by this little amp and at $599.99 I could actually afford it! I would like to buy a cover for it and not 150 bucks if anyone has any suggestions.

what's the drug called?

well jokes aside, my observation is different. may have to do with the bass used. with my boutique 6 the GK sounds like poo. colored, boxy, muffled. it's nice though with my G&L and flats on it, then it has a nice woody bark and punch.

anyway, it't is still a great unit. but limited in terms of modern sounds.

 

[Ric Vice]

Don Thompson and other jazz bassists in Toronto use this same technique. Thompson, for a long time used a Roland Cube. I don't know if he still does.

I actually owned one. Incidentally, they were "bright orange". For the time it was a nice little combo. As long as you didn't push them they
had a good sound. I don't think they would hold up agianst the newer Acoustic Images, GK MBS, or even the newer SWR Working Pro's.
Don Thompson is such an amazing player one would have to think that he would sound incredible playing a cardboard box. He's that good. The Jim Hall live album on AM Horizon tells it all.

Ric

 

[Murf]

Do you care to open up the amp? Of course you have to do it safely. Two problems are possible. First is that stress on the input jack has cracked the solder connections between the jack and the printed circuit board. Simply re-melting those connections would have you back in business. Don't just heat the connection with a soldering iron, but flow in some new solder to benefit from the flux.

Second, the jack may be worn out, in which case you would have to replace it. Desoldering those jacks is not 100% straightforward, but not impossible. I think the jack is a standard Neutrik part available from catalogs. I believe the actual quality of those jacks has been improved by some design changes over the years. As you can damage the circuit board by improper de-soldering, you might not want this to be the first de-soldering job you ever attempt.

Third, stress on the jack could actually crack the circuit board. This can sometimes be revealed by shining a bright light through the board from the other side. The typical repair is to solder solid wire over the cracked traces.

Rule of thumb, 90% or more of amp problems are "mechanical" in nature. The mechanical bits are mainly the connectors and pots. Those are the culprit in most repairs that I have done.

Apologies for resurrecting this thread..but I have a similar problem with my GK 700 Rb..and this fix seems perfect, thanks for the input fdeck much appreciated...you rock dude



Murf

 

[fdeck]

Apologies for resurrecting this thread..but I have a similar problem with my GK 700 Rb..and this fix seems perfect, thanks for the input fdeck much appreciated...you rock dude

Murf

Thanks for the kind words, and I am glad it worked! One question: What specifically turned out to be the problem, and how did you fix it?