Which power amp for bass?

[Bob Lee (QSC)]

Many amps allow the user to switch in and manipulate a high-pass filter. That's useful for protecting loudspeakers against overexcursion, for example. It's a good feature to have.

 

[Jim C]

I'll go with ""I am a huckster and shyster, preying on the ignorant and gullible". That best explains my career.

Got to love an honest answer!
20 years ago the tech staff at a twin 24 track challenged the enigneers to an amp listening shootout

Amps were Bryston, Crown DC300, QSC RMX, and an ancient, beat to deathy Peavey CS800 amp that had been left by a client and was used as a foot rest in the shop

Speakers were Urei Time Alligns and a 2tk tape was the source material

The big 3 all sounded great and we could not accurately tell one from another although the Bryston was the mathematical winner; could have easily been dumb luck

Amazingly the Peavey did not sound all that bad and could have worked in a pinch

IMO, all the major manufacturers make high quality amps that are dependable within similar price ranges, and, you would never be able to tell the difference for bass use in a band situation; pick the one that suits your budget and weight requirements that has good factory support (and a decent waranty if you buy new)

BTW, last time I checked the Bryston & QSC were still working fine and have not ever had a problem; the Peavey is in a basement PA application and also continues to work fine; not sure where the Crown is but would bet money that it's going strong as well

 

[Sickneedhelp]

..."The big 3 all sounded great and we could not accurately tell one from another....."
"Amazingly the Peavey did not sound all that bad" ....

Aren't those two statements in conflict?

So,..... you couldn't tell the difference between a pair of high feedback, quasi-comp slow output device (2N2773 based) amplifiers, with a slow speed high gain IC inside the feedback loop, versus a high speed, low feedback, local feedback, discrete front end, complimentary output amp? All those thousands of amplifier designers who spent years improving circuitry to improve the sound of amplifiers could have just stopped with early 70's Jack Sondermeyer and RCA design handbook quasi-comp circuits. Why did they bother improving circuitry, inventing various ways to do error correction, etc., when the results would be so futile?

I'll bet when you conducted your test, you had a mixer or equalizer, or some other electronics between the source and the amplifier. You were probably listening to the interface electronics and swamped out the amplifier differences. It only takes one or two stages.

I spent 12 years in MI retail (most of it in Austin during the 70's) selling amplifiers by handing the customer the A/B switch. Our track record spoke for itself. During my 11 years at Crest (pre Peavey), we built a pretty darn good reputation based on amplifier sound quality. For modern day amp differences, I find this link by one of the forum gurus interesting:

Invalid Link Removed

It supports your claim that bass amps sound alike, which I agree with unless you do some creative servo tuning such as what the CA6 & CA9 have. As for the rest of the frequency range, it's a pretty obvious improvement. We sure do get a lot of customer feedback about how good the new generation amps sound. I have a problem accepting all those customers are full of BS.

 

[Bob Lee (QSC)]

I find that those who can hear differences often didn't do a very rigorous test.

 

[Bob Lee (QSC)]

20 years ago the tech staff at a twin 24 track challenged the enigneers to an amp listening shootout

Amps were Bryston, Crown DC300, QSC RMX

The RMX must've been delivered by time machine.

 

[Sickneedhelp]

I find that those who can hear differences often didn't do a very rigorous test.

Do you mean like until you are so burned out that they do sound alike?

BTW, that 20 year old PLX design has certainly also withstood the test of time? Kudos to Pat.

 

[Bob Lee (QSC)]

No, I said those who can hear differences tend to not do rigorous listening tests. Yeah, everyone "hears" a difference in sighted tests, in random-set gain tests, in half-blind tests, etc. The real test is in a double-blind test, when you have to rely on sound alone to identify what you're listening to. Hand the customer an ABX switch instead of an AB and see what happens.

And if two amps sound different (assuming they're gain-matched for the comparison), at least one of them is doing something to the signal beyond simply amplifying it. Comparing the output signal with the input signal would be a good way to investigate what's happening inside the box.

 

[Sickneedhelp]

...... And if two amps sound different (assuming they're gain-matched for the comparison), at least one of them is doing something to the signal beyond simply amplifying it.....

Yep, I agree completely.... mostly. I contend most amplifiers are still doing something to the signal beyond amplifying it. Many engineers will continue the quest to minimize imperfections based on the presumption that there is still room for improvement. With most of us knee deep in class D, we pretty much start over.

 

[Bob Lee (QSC)]

They all do something to the signal. How significant is that something? I contend that any artifacts significant enough to be audible would be, by today's technological standards, unacceptably sloppy. (Of course, those artifacts might happen to sound good. ) Amplifier performance is asymptotic and not open-ended.

 

[Sickneedhelp]

They all do something to the signal. How significant is that something? I contend that any artifacts significant enough to be audible would be, by today's technological standards, unacceptably sloppy. (Of course, those artifacts might happen to sound good. ) Amplifier performance is asymptotic and not open-ended.

Well I'll admidt it certainly is more difficult to pick out the differences at age 62 than during my 20's...... or the designs are improving. Surely it's the latter.

Good sounding artifacts count don't they? They do exist and they certainly can make one amp sound better to a customer than the other amp. Someone posted a quote somewhere that says "If it sounds good, it is good."

Hope I didn't turn this into a chat room.

 

[Bob Lee (QSC)]

Artifacts that sound good in one context won't necessarily sound appealing in every other. IMHO, such "effects" should be controllable and defeatable by the user, not added arbitrarily to everything that passes through.

 

[higgi]

Hi Sickneedhelp,
I just bought your IPR1600, can't wait till it arrives. I was wondering if it had any highpass filter (like 30Hz)?

I bought it over the Crown XLS1000 because of the lower input volt requirements. (.7 Vrms vs. 1.4 Vrms) I think all my floor type preamps are capable of .7 Vrms. I also thought the extra power would be handy.

I plan on running this amp bridged, if that matters. I need about 500W at 8ohm. Bridged is over kill but I thought it might run cooler and last longer that way. Can I put this in a SKB 2U shallow rack case, will the side vents get enough air flow?

 

[Jim C]

Aren't those two statements in conflict?

So,..... you couldn't tell the difference between a pair of high feedback, quasi-comp slow output device (2N2773 based) amplifiers, with a slow speed high gain IC inside the feedback loop, versus a high speed, low feedback, local feedback, discrete front end, complimentary output amp? All those thousands of amplifier designers who spent years improving circuitry to improve the sound of amplifiers could have just stopped with early 70's Jack Sondermeyer and RCA design handbook quasi-comp circuits. Why did they bother improving circuitry, inventing various ways to do error correction, etc., when the results would be so futile?

I'll bet when you conducted your test, you had a mixer or equalizer, or some other electronics between the source and the amplifier. You were probably listening to the interface electronics and swamped out the amplifier differences. It only takes one or two stages.

I spent 12 years in MI retail (most of it in Austin during the 70's) selling amplifiers by handing the customer the A/B switch. Our track record spoke for itself. During my 11 years at Crest (pre Peavey), we built a pretty darn good reputation based on amplifier sound quality. For modern day amp differences, I find this link by one of the forum gurus interesting:

Invalid Link Removed

It supports your claim that bass amps sound alike, which I agree with unless you do some creative servo tuning such as what the CA6 & CA9 have. As for the rest of the frequency range, it's a pretty obvious improvement. We sure do get a lot of customer feedback about how good the new generation amps sound. I have a problem accepting all those customers are full of BS.

Why are you attacking my statement; this is what we observed.

We used a mic pre's from a Sony console to boost gain with no EQ and we did not spend a lot of time matching gain although all amps were listened to at a variety of volume levels. We did not have an A/B switch and had a few minutes break between amps for re-cabling.

Great marketing efforts on your part; I compliment a low end piece of gear that your company built and you want to fight?

Bob, it was a QSC amp and I must have incorrrect model numbers; we did not have a time machine although I'd be interested in one if you have a connection...

 

[Sickneedhelp]

Why are you attacking my statement; this is what we observed.

We used a mic pre's from a Sony console to boost gain with no EQ and we did not spend a lot of time matching gain although all amps were listened to at a variety of volume levels. We did not have an A/B switch and had a few minutes break between amps for re-cabling............

Hi Jim. Obviously I took your first sentence the wrong way on your prior post. My apologies.

The Sony you passed signal through explains your results to me. At Crest I demonstrated that even a module of a Jim Gamble console rendered us incapable of hearing the difference between a known bad amplifier versus a good. Both consoles are examples of excellent design, but there is lots of stuff between input and output. Had you patched more directly, you would have noted that the DC300 and the CS800 sounded close to the same. The Bryston would have been easily identified as different from the other two. Fortunately for the HiFi & AV industry, those differences allow a market for the ultra-esoteric products. I went up against some of them a few times thinking my design was good enough for that market and had my clock cleaned. Only now is that starting to change, but it's been a long strange trip en route. I should have used that time machine.

Again, my apologies.

 

[Sickneedhelp]

Hi Sickneedhelp,
I just bought your IPR1600, can't wait till it arrives. I was wondering if it had any highpass filter (like 30Hz)?

I bought it over the Crown XLS1000 because of the lower input volt requirements. (.7 Vrms vs. 1.4 Vrms) I think all my floor type preamps are capable of .7 Vrms. I also thought the extra power would be handy.

I plan on running this amp bridged, if that matters. I need about 500W at 8ohm. Bridged is over kill but I thought it might run cooler and last longer that way. Can I put this in a SKB 2U shallow rack case, will the side vents get enough air flow?

Higgi, thanks for buying the IPR. Hartley appreciates it also.

Bridged into eight will give you over 1kW. Cooling won't be a factor until you get down to two ohms per channel or four bridged. Thermal performance is just adequate to pass UL requirements for a two ohm rating.

Each channel has a 100Hz crossover. Sorry, it's not tuneable, so no go with the 30Hz high pass. The -3dB point is 6Hz. There is no bridge switch, so you will have to patch externally. That part is done differently from normal and is a bit confusing. If you would like, PM me with your contact info and I'll go through it with you, or just call Customer Service and have them transfer you through.

Regards
jd

 

[Bob Lee (QSC)]

With most of us knee deep in class D, we pretty much start over.

True, in class D we're revisiting a lot of the dragons that had been slain (or at least forced into retreat) in classes AB, G, and H long ago.

 

[Jim C]

Hi Jim. Obviously I took your first sentence the wrong way on your prior post. My apologies.

The Sony you passed signal through explains your results to me. At Crest I demonstrated that even a module of a Jim Gamble console rendered us incapable of hearing the difference between a known bad amplifier versus a good. Both consoles are examples of excellent design, but there is lots of stuff between input and output. Had you patched more directly, you would have noted that the DC300 and the CS800 sounded close to the same. The Bryston would have been easily identified as different from the other two. Fortunately for the HiFi & AV industry, those differences allow a market for the ultra-esoteric products. I went up against some of them a few times thinking my design was good enough for that market and had my clock cleaned. Only now is that starting to change, but it's been a long strange trip en route. I should have used that time machine.

Again, my apologies.

No worries and thanks for the clarification.
I thought the sentence in question was a great way to difuse a difference of opinion.

As an amp designer, what is a better way to go from say a 2tk source to an amp for such a test?

I have always assumed that a channel strip with EQ off was about as transparent a piece of gear that one would find in a studio.
Ironicaly, I have found that the Sony consoles from that era were much less colored than the Neve console that I spent years using and have not spent enough time on some of the new SSL or Neve desks to be able to accurately form an opinion of new vs. old (other than quieter and MUCH better automation).

Also of interest is how projects get mastered.
I've done a few records with Jack Skinner over at Sterling Sound 25 years ago. Back in the day his mastering room was loaded with many different speakers and amps. Always told him that he knew his room better than I and I was there because I liked the way his records sounded.
He preferred Canton home stereo speakers (as opposed to some high end B&W's, JBL's, Tanoy's, etc) and some old tube amp (instead of Bryston, Revox, Crest, etc) as he liked the sound better and trusted that rig for consistent mastering as he was so used to it.

Maybe not transparent but his mastering was solid; go figure.

 

[higgi]

Higgi, thanks for buying the IPR. Hartley appreciates it also.

Bridged into eight will give you over 1kW. Cooling won't be a factor until you get down to two ohms per channel or four bridged. Thermal performance is just adequate to pass UL requirements for a two ohm rating.

Each channel has a 100Hz crossover. Sorry, it's not tuneable, so no go with the 30Hz high pass. The -3dB point is 6Hz. There is no bridge switch, so you will have to patch externally. That part is done differently from normal and is a bit confusing. If you would like, PM me with your contact info and I'll go through it with you, or just call Customer Service and have them transfer you through.

Regards
jd

The -3dB point is 6Hz. Wow!!

I got the bridge mode stuff from another peavey guy on here. I may send you a pm if I get lost. It's just parrellel input and 180 out of phase out put. Hook the + from 1 and the - from channel two and it's bridged, right? I plan on haveing a 4 ohm load now and then but that should be a 1000watts max.

The programmable filter almost made me buy the xls1000. But I didn't want to run it near it's max at all times. Plus I have had nothing but good experiences with Peavey products. I love the company basses!

 

[Sickneedhelp]

The -3dB point is 6Hz. Wow!!

I got the bridge mode stuff from another peavey guy on here. I may send you a pm if I get lost. It's just parrellel input and 180 out of phase out put. Hook the + from 1 and the - from channel two and it's bridged, right? I plan on haveing a 4 ohm load now and then but that should be a 1000watts max.

The programmable filter almost made me buy the xls1000. But I didn't want to run it near it's max at all times. Plus I have had nothing but good experiences with Peavey products. I love the company basses!

Higgi, four ohms bridged is the same as two ohms per channel. Your wattage into four bridged is 1600 using a 0.1% @ 1kHz spec. If you use a 1% spec as many manufacturers do for the two ohm rating, your wattage is 1800. Music power gets you around 2200. Keep the amp out of clip.

For bridge, patch the inputs together in parallel as you said. The output is ChA 1+ and ChB 1-.

Again, feel free to call.

 

[Bob Lee (QSC)]

Bob, it was a QSC amp and I must have incorrrect model numbers; we did not have a time machine although I'd be interested in one if you have a connection...

Twenty years ago, it was probably an MX, possibly an EX.