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I would like to have a real discussion of the different amplifiers on the market, the engineering that went into them, the "behind the scenes" on the amplifier, it's designer, his true design goals, the real world specs, performance, reliability, and everything else that could even be thought of on this whole subject. I dont want to get into the different classes of amps, we've covered that. I think that some of our more technical posters should have no problem with this post, and I really think it could help some of the new posters in making decisions in the future on amplifier purchases, and just for general knowledge. Now, I also dont want someone to just cut and paste the specs for the amplifiers either. Any and all makes/models welcome, any output, anything, even experimental and home brew amps are welcomed. Just trying to stir up a little activity, the forum has been a morgue since long before spring break. Have at it! And PLEASE be as technical as you know how!
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STILL waiting to hear a GOOD pair of HLCD's!!
Use your ears to judge components, NOT your wallet! K.I.S.S.
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In my view the best complete line Amp manufactuer is Zapco great reliability performance per buck ratio on the AG line, excellent warranty awesome sq amps and now a BIG effiecient Sub amp cabable of 2000 watts, also great customer service. Just my view 1.Zapco 2.XTANT 3.MTX 4.Rockford 5.US AMPS (TOO Expensive)
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I've been impressed with USAmps since about 1992 when one of the designers came to a shop near me with a truck with 8 Volcano subs. I talked to the designer for a couple minutes and that is what really got me into electronics. I don't remember too much about talking with him except for the fact the had an amp that would do around 3000 watts and was four foot long. Building a big class AB amp is more than adding more parts and getting a bigger heatsink, so when companies build them I am pretty impressed. Class D amps don't really impress me since they are pretty simple past the controller chip, but gettin a good frequency response and SQ is a different story. There are companies that have 1000 watt class D amps the are 3" square. They don't have power supplies and output filters but depending on the application they might not be needed. As far as homebrew and experimental, I'll let you know in a couple months.
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I think everyone knows my favorite is RF. They have always been reliable, a good value/watt, and rugged. Plus they have many design features I find superior: Cast heatsinks - the mass and porosity compared to extrusions really does mean more efficient cooling which keeps their footprint small; MEHSA - superior cooling for better reliability; Direct Surface Mount parts - zero tolerance parts and maximum accuracy during manufacturing. Other companies employ some of these technologies as well but RF always seems to push the envelope on their amp design, whether to make a circuit simpler, or to eek out more power per cubic inch. Plus, I have to respect a company that shares technology with Hafler - arguably the best studio equipment on the planet. Essentially: The sh1t goes loud and don't blow up!
------------------ Blow your mind - PORT your box!
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class "T"..this technology has been around since the mid '90's...but i would suspect to see these type of amps as the next "BIG" thing to audio....these type of amp designs are intresting to say the least.
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Posts: 122 | From: St.Louis, MO | Registered: Feb 2000
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Dukk, let's try to get more detail on the actual workings of MESHA, and whatever other technologies are out there! I myself have always looked at RF amps and drooled over they're DSM's... Class T is already in use, but, if we're going to talk about it, let's hear all you know about it! How it differ's from class D? I know it's a variation of the class D topology, but that's about all I know. A2000 hasn't done ANY testing of a class T amp, so I'm out in the dark totally!
DrFosgate, Let's hear more of your opinion, not just a list of manufacturers, but why, and what technologies they employ in they're circuit design!
JC2, I KNOW you can get way in deeper on circuit design! I want to know, in your opinions, why things were done the way they were done! Oh, I met the owner of US amps once, although his name fails to come to mind now... at a shop I worked at in Granite City Il. Nice guy, explained a bunch to me of why his amps could run ANY load.
ShadowStar??? Your contributions are NEEDED!!! Along with TECH MAN!!!! Light the bat light!!!!
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STILL waiting to hear a GOOD pair of HLCD's!!
Use your ears to judge components, NOT your wallet! K.I.S.S.
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Thanks Audiophyle for trying to dig a little deeper. The thing is with me is that I'm familar with system design but I do ask alot of questions that can only be answered by experience...That why I look to guys like yourself and Dukk. Anyways I'd to understand more about the technology that goes in to these amps. Here a question for you guys...Is there an advantage to circuit layout? For example if you look at pictures of the PPI amps you'll find that they're somewhat symetrical while other amps like Xtants)
------------------ Knobs Rule! Keep it simple, clean, and loud!
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Well the reason I didn't get to technical is because I don't have too much in depth knowledge of amps other than RF and my broken down SS ref 700sx which still baffles me. So without know how the circuit is designed I can't offer too much insight on what I think of them. I will offer some thoughts on the circuit layout question. For audio frequencies circuit board layout isn't as critical as for RF frequencies so the layout whether it be symetrical or not is probably for looks or to simplify the layout. Taking your two examples, the PPI is laid out end to end, the power connections on one side and the speakers on the other. So it makes sense to lay out the parts for the right side channel on the right side heatsink, and the left on the left. Because the big output transistors are going to have to be on the outside this lends itself to having a symetrical mirror image layout. The Xtants on the other hand have all the connections on one side. And in this case the output transistors are along the cooling tunnel. So the layout really cannot be symetrical. If you look at most amps the output sections are designed and layed out the same, for example on my broken down SS ref 700sx the output sections are identically layed out but they aren't symetrical.
Audiophyle, I love talking technical but I can't think of anything to just come out and say about any particular product. If you guys ask questions I will answer them as well as I can.
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I reflect JC2s feelings. I could go into detail about the different RF technologies I like (MEHSA, INDIGO, TRANSANA, DIABLE, TOPAZ, etc) but it's on their site and I don't feel like typing all that
Also, ditto on the layout thing. One thing I cant understand is a company like Alpine that puts the inputs on the same end as the speaker outs. This means they have to run skywires back across the board. Sure, it doesn't hurt anything, but it looks cheesy.
Finally, I think that as long as any amp is used within it's ranges it will sound identical to any other amp, regardless of brand. What makes the difference is how far you can push those ranges and what happens when they are exceeded!!!!
------------------ Blow your mind - PORT your box!
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I'll be a more "respond to inquiries" kind of guy. I like it when the circuit is laid out in a logical order with the finals set well on the other side of the case so as to reduce in induction of current from the toroid (a very large source of noise) to any of the preamp or output circuitry. In other words I like power connectors on one side and output connections on the other. Next I like regulated power supplies for their efficiency. When I build an amp nowadays it is exclusively a regulated design. Next I have a irritation with any designer that doesn't put enough cap on the primary side of their power supply. It's a no brainer way to further stabilize a power supply and keep noise out of the rest of the system. Most all decent amps nowadays have plenty of cap in the power supply. The guilty parties are the cheap amps and those cheasy power inverters. Anyone notice that those suckers can make noise galore on the radio? I'm a fan of A/B and quasi class A design for SQ. Easy to build and tinker with and not hard to chase distortion out of. I don't like people who use a couple of 1 watt resistors and 1 watt zener diodes for their preamp regulation. I feel to not spring for a set of IC's like the LM317 and Lm 337 or the LM7815 and LM7915 is overly cheap skate of them. Oh and I could go on........ hehehhehe
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Along the lines of Tech's comments I have a couple things the I don't like on amps. First why can't everybody put separate gain controls on their amps. I mean it will add less than a buck of cost to the company. There are some high end manufacturers using a single control. It wouldn't be a problem if the two channels tracked each other closely but most don't. I also agree with the comments on regulated power supplies, why design something whose performance varies depending on something like battery voltage that will always vary. I understand for SPL amps but for everyday and SQ amps it doesn't make sense to me. Also if you are designing an amp that will do 200 watts per channel at 14.4 volts why not regulate the power supply and get 200 out of it at 12 volts. I know some of that is marketing, but I'm an engineer so I don't understand. Using zeners in a power supply is simply stupid, you save 75 cents per amp, I haven't seen that many amps that do this but I have heard some of the SS amps did. I was thinking about all the amps I used to drool over and what I liked about them. The Audison HR-100, a dual mono amp that was gorgeous, but had cheesy ribbon cable running through it, something I had seen on a Cadence amp but wouldn't want to see it on an amp costing 6000 dollars. Adcom had an amp that I can't remember the name of, that had separate chassis for the power supply and output section. The power supply was probably 80% caps. That enough for you Tech?
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Tech Man refered to components in the amp...What do you look for in a quality amp? Are there certain ICs or a specific circuits that set one amp to another...
------------------ Knobs Rule! Keep it simple, clean, and loud!
posted
Specific components, let's see... For power supply controllers everybody uses either 3524 or TL494/594. I would say the choice of controller isn't a determining factor on how well the power supply is built. For power supply switches everybody uses MosFETs because in this type of duty they are superior to BJT's. I would rather see a smaller number of devices with higher current ratings that a larger number with smaller ratings. Once again the choice of MosFET probably isn't a determining factor in quality. Common devices are IRF40,44 NDP7060, BUZ11 those are the ones I can think of right now. For the power supply to the op-amps, there should be either the 78/79 voltage regulators or the 317/337 regulators. For the op-amps I would like to see Burr-Brown, Analog Devices, something along those lines. But any op-amp designed for low distortion at audio frequencies is a good sign. LM837, TL074 are two good quality op-amps you will see pretty often. For output devices There is the choice between MosFET and BJT devices. There are excellent examples of each, and there are crappy examples of each. I can't think of specific devices for FET outputs, but for BJT tip102/tip107 are a very common pair. That is what my beloved BROKEN Soundstream amp uses.
One thing I would like to see discussed here is a "voodoo" topic, NFB.
NFB is negative feedback, whereby output and input differences are fed back through the amplifier to kill output differences, DRASTICALLY increasing linearity (distortion performance).
Many people argue that NFB can be heard in the output by such things as smearing of vocals and improper placement of source material, however, my take on it is that, if an amplifier follows the input to within .001 % deviation, the human ear is not sensitive enough to pick up any difference.. No smearing, no blearing..
However, many companies produce amplifiers that don't use NFB, or much of it, like Eclipse.. However, if you compare the actual distortion specs of an eclipse amplifier to that of say, a Crossfire amp which uses a great deal of global NFB, you will find the crossfire amp will more than likely be the cleaner of the two, even though it possibly has other issues.
? What say ye?
ShadowStar
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Posts: 2579 | From: Somewhere In the Northeast | Registered: May 1999
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posted
From what I've seen after playing with a few different amps (adcom/ads/orion/PG/kenwood/RF) I'm with JC2, why don't we see an sq amp with some burr brown op amps?? RF uses lm837's.. good but... and ads and orion use JRC op amps.. I don't know much about it, just that in a x-reference table of parts.. the JRC ALWAYS comes in a few times cheaper than anything else.. (don't know if it's lesser quality.. but price has to mean something) Orion/ADS do use motorola mosfets etc.. (good choice there) I also have a kenwood PS-150.. this is supposed to be their performance line for a few years back.. I'll give them points on origionality, if you get a chance, pull one apart they're very unique. (circuit layout and parts etc) but my favorite amp is the Adcom 4404 this is a 4 channel 40x4 amp 24" long, very well layed out, logical and symetrical. I got one of these non working a short time ago, it has LED's for each power supply and amp channel and the protection circitry.. well by looking at these LED's and no other knowledge of the amp I tracked down the problem and fixed it in under 5 mins. The adcom is the first amp I've seen to use all discrete components (no op amps here) and it seems to work because the adcom is one of the best sounding amps I've had the chance to play with. On the other hand I've heard amazing things about Linear Power.. their T0-3 series basically uses op amps all the way as the T03 devices in the output stage (instead of mosfets or bjt's) are big power op amps. So from what I can see with the experience I have, it's not ONLY what you put in the amp it's more how you use it. (but bad parts won't make a good amp, where good parts might make a bad amp) but until I make my own amp from scratch I won't see many of the problems that have to be overcome or may be easily overlooked.. (I have a small regulated class A in the works.. just have to see what the "real world" can throw at my design) (if anybody wants I could probably take some pictures of the board of the amps I have around right now, just let me know.. Adcom 4404, Orion hcca 225, PG xs2500, Kenwood PS150, ADS power plate 240)
------------------ Digital Designs 9515 Mmats d300hc (2) (soon) Pioneer source MB Quart fronts ADS power plate RW Audio processors
Posts: 736 | From: Calgary AB | Registered: Oct 1999
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posted
The tip102 and 107 are darlingtons. I have a dislike of all amps who use darlington transistors but the soundstream amps do sound good. There was a ss model with just a couple of zener diodes and power resistors. Coustic is also bad about using darlingtons along with a few others. Oh and the 3525 and 3526 are popular pwm ic's too. I prefer the 494 and 594 but they aren't superior or anything, just personal preference.
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I have heard only one car audio amp that you could switch off the NFB, and it sounded horrible without the feedback. When you add feedback your linearity increases and your distortion goes down (good way to reduce crossover distortion) but the overall gain of the amp will go down. When you take away the negative feedback the gain goes up so in most cases the distortion is more audible. I have heard some great home amplifiers that don't use any negative feedback but the Sony amps that you can switch off the feedback sound bad IMO. RWAudio the JRC op-amps don't seem to be all that bad according to their specs. I am considering doing some upgrades on my EQ's that have the JRC opamps. A couple models have specs that aren't to far off from the OPA134's, one particular model is quite a ways off though. I thought LP used regular devices in their outputs not power op-amps, I know MMATS uses the LM12 80 watt op-amps in their design. Dukk, I knew somebody would say that. But not every company works that way.
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oops.. my mistake JC.. I was lookin at a few diff sites when I thought that.. the one that uses the T03 op amps wasn't LP... they use TO3 transistors, but yes mmats does use the LM12 haven't heard one yet though. so what does US Amps use for for their BIG amps for mosfets/output devices? and how many?
------------------ Digital Designs 9515 Mmats d300hc (2) (soon) Pioneer source MB Quart fronts ADS power plate RW Audio processors
Posts: 736 | From: Calgary AB | Registered: Oct 1999
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RW quit creaming over my babys brother (4404) ur making mine jelous lol. i'd have 2 say out of the amps i've pulled apart the Adcom 4404 is the nicest of all, very clean design, big bulky power full and clean. I was dissapointed with the old Rockford Series 1 amps, thats the most bunk stuff i have ever seen in my life.
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The last few US amps that I've seen inside of and the old monster I have use Tip35 and Tip36's that are so popular in many amps of the last several years. Regular Bipolar transistors. TO-3P cases. They have mosfets in the power supply on all the newer stuff.
'Where there's a will there's a wall' 'Would you like a little SQ with your SPL?'
Posts: 926 | From: Sugarland, Tx | Registered: May 1999
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Tech, can you explain more about disliking the darlington BJT's. Is it the darlington configuration itself, or just the devices that have a darlington configuration. To be honest I don't know as much about output design as I would like to, especially since I am starting to design an amp. I was planning on using Bipolar outputs simply because I have more experience with them.
Does anyone here have a picture of the inside of a Linear Power amp? They are one of the few amps I haven't seen the inside of.
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