Soft clip limiter

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Soft clip limiter

Postby playingdead » Fri Apr 10, 2009 2:39 pm

With the speculation that part of Jerry's tone came from driving the MC2300 so hard, I was interested to find this in the owners manual of the bass head I just bought -- a little GenzBenz Shuttle 6.0 -- 600 watts Class D power into 4 ohms with a tube front end ... 3.5 pounds. Sounds terrific into the 2X10 cab designed for it. And will be a good backup power amp for my guitar rig. Although this thing is so potent I don't think I could ever turn it up that loud, it's pretty damn deafening at about 3 on the master volume.

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OUTPUT LIMITER – The SHUTTLE 6.0® contains an internal power amplifier “Soft Clip” Limiter. This Limiter allows
simulation of the output stage saturation as the amplifier nears it maximum power. The limiter is a compound
multistage analog circuit, is quite graceful in nature and is particularly musical sounding, even when driven hard.
The output “CLIP/LIMIT” LED shows limiting action for the first 6dB above the maximum power threshold and then
indicates power amplifier clipping as the power amplifier gradually transitions into gentle clipping.

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Re: Soft clip limiter

Postby tigerstrat » Fri Apr 10, 2009 3:25 pm

They make great stuff.

3 1/2 pounds!!

That (and my aching back and shoulders), makes me feel like giving my my 60 lb. Yorkville power amp one last heave- into a steel scrap shredder.
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What are you using for reverb again?
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Re: Soft clip limiter

Postby tigerstrat » Fri Apr 10, 2009 3:39 pm

Your typical wah-wah pedal weighs more than that amp.
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Re: Soft clip limiter

Postby playingdead » Fri Apr 10, 2009 4:36 pm

I am serious ... it sounds GOOD.

"POWER AMPLIFIER – The SHUTTLE 6.0® uses a state of the art, class D power amplifier design and a high frequency switch-mode power supply to achieve unprecedented high performance and lightweight packaging. Switch-mode power supplies convert the AC line directly to high voltage DC, then the precision PWM inverter creates a new AC power signal at a frequency approximately 2000 times higher than the original wall frequency of 50/60Hz. This new high voltage, high frequency power signal is then fed into a custom high frequency transformer that steps the voltage down, a high frequency rectifier and high ESR filter capacitors finish the process off by converting the high frequency AC signal back to the DC voltages that the amplifier’s internal circuitry uses. One advantage of this conversion process is that the DC power supply rails are refreshed 1000 times more often than in traditional linear supplies, thus reducing annoying hum in the audio signal. The high frequency switching is used to reduce the size and weight of the magnetic and filter components while increasing the performance by recharging the power supply rails more often. The class D amplifier uses digital PWM (pulse width modulation) techniques similar to those in more familiar digital to analog converters to reduce the size and weight by a factor of 10 times that of a comparably rated conventional class AB amplifier. Essentially, a class D amplifier converts the analog signal into a logic level PWM digital signal with a digital to analog converter, level shifts this PWM signal up to a higher voltage and current and then reconstructs the analog signal by passing it through what is essentially a power digital to analog converter. Additionally, we developed our own, proprietary limiting and signal processing techniques to give a distinctly analog feel and sound to the class D platform. This system provides exceptional performance even for low frequency applications such as bass guitar."
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Re: Soft clip limiter

Postby SarnoMusicSolutions » Fri Apr 10, 2009 6:09 pm

I think the problem most of us face with the MC2300 besides the weight and bulk and price is that the limiter only kicks in at very loud levels. Many power amps have a built in protection circuit to help limit peak power levels. Often times these peak limiters don't sound pretty, but they do protect. I had a talk with Steve Kimock about this, and he said that Jerry told him he was always pegging the McIntosh, maxed out, needle pegged to the right. So it's interesting here that Genz Benz has included a soft-clip peak limiter to protect maximum power. The problem I see there is that 600 watts is just too loud to use that limiter in a musical way. It's been told that Jerry went thru different phases, sometimes using the Mc2300 bridged to mono and placing a 2.7 ohm load (3 JBL's) on the 2-ohm taps. Other times Jerry supposedly only used one side of the Mc2300. So this gives 2 scenarios. The bridged mono setup would have the Mc2300 peak limiter active at around 450 watts. If using just one side of the amp then this would be happening at 225 or so watts. There were periods with 4 JBL's and in that case we would have seen full power from the Mc2300. So the extreme case would have been 600 watts, but I'm suspecting that much of what we heard for a long stretch of time with the 3-JBL's was the 225 watt scenario with the peak limiter squashing the transients and adding a bit of dirt or hair to the sound since the peak limiter is kind of a super-fast and crude type.

So it seems to me that it would be nice to find a peak limiter that maybe has a bit of clipping along with a very high ratio hard and fast limiting action so that it would only catch the peak transients, but not affect the bulk of the dynamic range. Kind of like power tubes, but a bit cleaner sounding. I'm going to be working on some approaches at this kind of circuit, but if anyone finds a limiter that behaves this way, please share it with us. Hardly any of us can realistically play at Jerry loudness levels and not get fired or kicked out of the venue. I'm thinking that if we could put a limit on the level in the 80 to 180 watt range that would be cool. And if the limiter is a bit nasty and not too clean, that would be cool. But it scares me to think of these guitar players out there using 600+ watt amps with no peak limiting or protection. That can be a brutal and thin sound when playing totally clean, and it a sure path to a nasty case of tinnitus and hearing loss if all that power gets used.

Brad
Last edited by SarnoMusicSolutions on Sat Apr 11, 2009 10:29 am, edited 1 time in total.
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Re: Soft clip limiter

Postby playingdead » Fri Apr 10, 2009 6:35 pm

Jeez, I think you would bleed from the ears at that point! I have never turned up the master on these amps past four, even at an outdoor gig. And four is just stupid loud. The power amount is total overkill, as these are amps designed for bass reinforcement where that power is getting used, but there is also a lot of built-in headroom. You have to be smart about it.

The load is an interesting part of the equation; this new head I have is rated 375 watts into eight ohms. It will not push a 2-ohm load, although my Focus 2R head will (I am using only the power amp section on these little heads for guitar applications). I wonder if wiring the speakers series instead of parallel would reduce the power output and enable the clipping. I don't know if that would damage anything, though. I had a chance to buy a couple of 16-ohm NOS E-120s a while back.

GenzBenz also makes a 300-watt version of the Shuttle, which is 175 watts into eight ohms. It lacks the tube preamp -- it has an FET circuit instead -- but it does sound nice, as well. Presumably the power section is the same and includes the limiter. That would probably be easier to push to its limits at a small venue. Playing a bass through that 300 watt combo at the store, with an single 10" speaker in an 8-ohm load, it could be pushed very hard without being extremely loud, although it was fairly potent.

I bought this amp primarily as a studio/rehearsal tool for bass -- I got the head, which sells for $699, with its matching 2X10 bass cabinet for just $950 total as a B-stock item -- but I am planning on carrying the head to gigs as a backup amp to my Focus 2R. Playing the Tiger guitar straight into the tube preamp on it and into the E-120s was a pretty decent tone, actually,albeit with the treble control wide open. Well, actually, that's pretty much what Jerry did, come to think of it.

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Pretty amazing, with the Focus and the Shuttle, that's a total of 10 pounds of amps, yielding 1400 watts into four ohms. Now, if someone could make a light speaker that sounded as good as those E-120s ...
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Re: Soft clip limiter

Postby SarnoMusicSolutions » Sat Apr 11, 2009 8:09 am

These speakers may interest you:


http://taweber.powweb.com/weber/neo12.htm




Brad
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Re: Soft clip limiter

Postby strumminsix » Mon Apr 13, 2009 6:02 am

How does it compared to a Crate a Powerblock?


SarnoMusicSolutions wrote:These speakers may interest you:


http://taweber.powweb.com/weber/neo12.htm

Brad


Brad, I've got a 2x12 with them, a 1x15 with the 15" equiv & my custom amp from Ben Fargen has one of the 12"ers.

HIGHLY RECOMMEND!
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Re: Soft clip limiter

Postby playingdead » Mon Apr 13, 2009 6:38 am

I have a Crate Powerblock as well, the Shuttle blows it right out of the water, although the Crate will do some (limited) higher gain tone.

The Powerblock was my "oh s---" backup head. When my former Twin head went down at a gig, I grabbed the Powerblock. It couldn't run the 2 E-120's -- wasn't designed for a 4-ohm load. The protection circuit was cutting it in and out at crucial moments. Two songs later, I kicked the Twin head a couple of times and it came back to life.

So, if you're runing a pair of 12s, don't count on the Powerblock as a backup, you'll need to just run one 12 with it.

My Focus head is rated for 2 ohms (1000 watts!) and the Shuttle can handle 4 ohms (600 watts). The Crate was only 150 watts.
Last edited by playingdead on Mon Apr 13, 2009 7:50 am, edited 1 time in total.
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Re: Soft clip limiter

Postby strumminsix » Mon Apr 13, 2009 7:20 am

Interesting.... I've had my PB at good volumes at 4 ohms mono and then 4o and 8o stereo. No issues.
HOWEVER, this was for maybe an hour max and not at unmic'd gig level volumes.
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Re: Soft clip limiter

Postby playingdead » Mon Apr 13, 2009 7:49 am

We were at a 350 seat club in Boston ... I had to turn it up loud on that stage. It was pretty much dimed. We even got it on video ... about 3:55 into the opener (Aiko) I turned up the volume on the guitar, went to play a lead ... nothing. I'm fumbling with the guitar controls, etc. Did the same thing during Stranger. That's when I got the Twin working.

http://playingdead.net/032108aiko.html

It really disliked the envelope filter.

http://playingdead.net/032108stranger.html

Actually, the tone playing through the E120s wasn't bad. But not at that level for long.

I called the Crate guys up, they told me pushing it under 4 ohms was guaranteed to trip the protection circuit. That's four ohms out of the one jack, bridged. It's okay to push two 4-ohm speakers, out of the left and right jacks, but my cabinet is not wired that way. And 75 watts wasn't going to do it that night anyway.

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Re: Soft clip limiter

Postby strumminsix » Mon Apr 13, 2009 8:22 am

Thanks for the good info! What about running just the L or R channel unbridged? Is that okay for a 4ohm cab? I know for your application that is very small volume but just asking.
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Re: Soft clip limiter

Postby playingdead » Mon Apr 13, 2009 8:34 am

That would be okay, according to the Crate guys ...
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Re: Soft clip limiter

Postby Rusty the Scoob » Tue Apr 14, 2009 9:31 am

Nice amp, Vic! Genz-Benz is on my short list of things to look at when/if something happens to my Redhead. The Shuttle in particular gets great reviews on all the bass forums.
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