Revolutionary Power Amps (Historical)

[agedhorse]

This thread is intended to highlight some historic milestones in audio power amps and the products/companies/designers that made them.

 

The first one I want to mention is the Crown DC-150 and DC-300. They were based on early power op-amp technology, were direct coupled and had a bandwidth that went down to CD as they were used as servo amps in industrial applications as well.

 

The second one is the Phase Linear 400 and 700, both were early and moderately successful attempts an very high power, high voltage designs. While they were used somewhat in the pro audiio market, they were really Hi-Fi amps that were ruggedized by a few companies for live use. The topology was what many pro audio amps that followed were loosely based on.

 

The third one is QSC, the legacy stuff with the aluminum faceplates and screened vents (can't remember the model numbers but something like 4.2) which led to their interpretation of the grounded bridge in the original series 1 (1400, 1700 etc) was stiff competition to Crown and their grounded bridge designs.

 

The fourth is Crest, with amps like the P2501, 3501 and even earlier models. These were from the original Kelsey and Dallas Music Industries guys, and went after the heavy duty rock market. The early amps were pretty unreliable but they soon got things figured out and the rest is history. They were one of the early ones along with BGW to use an integrated op-amp as the differential front end.

 

Anybody remember BGW and SAE?

[oldschooler]

Have you heard of Great American Sound Company? I had one of their Ampzillas a long time ago. It was heavy as a rock but sounded fine. I think it was 250x2@ 8 ohms. I toss it in the trash a few years ago only to find out they had a collectors following.

[guitarharv52]

I don't remember BGW oe SAE but In the 70's we used a DC150 for our tops and DC300 for subs on our "stacks".Some friends had a combo of Crest and Crown DC's.

[gonzobassman]

I think from a historical point the Peavey CS 800 deserves a mention.Bands that couldn't afford those Crowns generally had those.

[W. M. Hellinger]

 

The third one is QSC, the legacy stuff with the aluminum faceplates and screened vents (can't remember the model numbers but something like 4.2)

 

From some old cut-sheets I had in a file cabinet:

A-3.7: 90W

A-4.2: 40W

A-5.1: 80W

 

I don't remember these above listed amps... maybe they were install versions?

 

A-21, A-22: 80W

A-31, A-32: 125W

A-41, A-42: 200W

 

I believe the difference between the "1's" and "2's", is that the 1's were the base models, and the 2's had LED's in the front and a limiting circuit.

[Dogoth]

Have you heard of Great American Sound Company? I had one of their Ampzillas a long time ago. It was heavy as a rock but sounded fine. I think it was 250x2@ 8 ohms. I toss it in the trash a few years ago only to find out they had a collectors following.

 

I remember using Ampzillas (70s?).

 

for BGW, SAE & the Peavey CS series. All legacy amps from the early days of high power amplifiers. Haffler is another company of note. JBL/UREI took a stab at making amplifiers. They sounded great but weren't very roadable. I think you'll find some of the steel from these amps in the unibody chassis of your korean car (I think about 1 16ru amp rack = 1 car :>).

 

 

FWIW I'm listening to a modded Crown DC300A (the silver face ones) right now (Estephan I believe). It drives my legacy JBL4312s in my studio (no noisy fans :>).

[RoadRanger]

I think from a historical point the Peavey CS 800 deserves a mention.Bands that couldn't afford those Crowns generally had those.

The pre-DDT CS800 was certainly a revolution as it was the first robust amp that was a dollar a watt. Peavey's DDT was another revolution in itself - I don't know if any other amps had integral clip limiting before that but I do believe it was the first mass produced adaptive limiter to use the full rail to rail voltage available .

[Gomer Pyle]

The output stages of the early CS 800 is very similar to the original Phase Linear 400

[Bobby1Note]

 

Anybody remember SAE?

 

 

I sure do. SAE = Scientific Audio Engineering, out of California if I remember correctly.

 

I have a bunch of that stuff in my family room. The T-101 tuner, E-101 equalizer (parametric), P-101 pre-amp, and the A-501 power-amp (250wrms/ch @ 8 Ohms). I probably bought that system around 1980, after my old Marantz components were stolen. (break-in). The Marantz equipment was purchased somewhere around 1970 as I recall.

 

If I remember correctly, SAE also had a power-amp called the A-1001, which was 500wrms/ch/ 8 Ohms.

 

I rarely use that SAE system these days, and a few years ago, I took it in for servicing/ re-conditioning. The guy who owned that shop was very happy to see that amplifier, and said "Now,, THAT'S an amplifier", with a big grin on his face.

 

Bob

[madjack]

I remember and used to use a couple of BGW amps - 4 rack spaces, ~70lbs, ~200w/channel. I still have an SAE amp. Again, 4 rack spaces, etc. I used a pre-DDT rack of Peaveys in the late 70s; CS800 for lows, CS400 for mids, CS200 for highs, all crossed over with a Crown VFX2 crossover. First decent power amp I used was a Southwest Technical Products Universal Tiger kit amp. We had two of them used together for FOH. Never had any problems with them at all.

[agedhorse]

 

The output stages of the early CS 800 is very similar to the original Phase Linear 400

 

 

About the only thing they have in common is TO-3 NPN output transistors, which just about everything else of that era had as well since PNP's were very expensive.

 

The PL-400 was a double-darlington, had a slowed down low frequency network on the VI limiter, diode compensated transistor VBE mult, Baker clamp protected input diff pair, etc.

 

The early CS-800 used a triple NPN darlington, fast VI limiter, diode string bias network, op-amp front end, compression based on loss of feedback detection, and a triac crowbar output protection.

[agedhorse]

 

From some old cut-sheets I had in a file cabinet: A-3.7: 90W A-4.2: 40W A-5.1: 80W I don't remember these above listed amps... maybe they were install versions? A-21, A-22: 80W A-31, A-32: 125W A-41, A-42: 200W I believe the difference between the "1's" and "2's", is that the 1's were the base models, and the 2's had LED's in the front and a limiting circuit.

 

 

All of those from that era was the beginings of high powered reliable amplification.

[agedhorse]

I worked with an ex-SAE engineer for a summer on another amp company project (1981?), an interesting experience that I learned a lot from. Sharp guy. The SAE stuff was only moderately reliable.

 

BGW was a great company, solid amps that were easy to repair. Used a power op-amp tpopology with an on-amp front end. Very reliable.

 

Peavey does deserve mention for being the first caompany to put higher power in the hands of relative idiots. DDT was essential in perventing a flurry of HF driver failures.

 

Tigers... one interesting product from SWTPC. I built a few Tigersarus 250's in my day. In hindsight a horrible amp but was an early high powered kit amp along the lines of Dynaco and Heath.

[jabney]

BGW 500 - a speaker-killer if you weren't careful, but the sound. Yeah. I'd take one over their 750 if I had to choose. No scientifically tested reason, just my ears.

 

I hope the Dallas Music Industries amps aren't too unreliable. I'm liking listening to one now - and it's fan-less.

 

What about the Kelmar 150 plus? Another fan-less wonder. And it seems to like 2 ohm loads. A movie theater amp (made by Ashly, perhaps?).

 

Maybe the greatest (big) tube amp of all: the McIntosh MI-200. An output of 200 watts from one pair of triodes. Scary good. With the emphasis on the scary (950 volts on the plate - the exposed top terminal plate).

 

The QSC PL (single digit) series - e.g. PL 4, PL 6, etc.

 

The Crown MA 2400. Big iron, usually sounds right wherever it's used.

 

And the Crest CA series - last of the big iron?

 

best,

 

john

[Shaster]

I remember fondly the BGW amps and the Phase Linear 400.

 

My first power amps were BGW. I had two not very powerful (by today's standards) that were powering a three way 4560(as low)/mid/horn, PA - all Altec drivers I believe. Sounded pretty good back in the late 70's.

 

I seem to remember thinking the Phase Linears were very warm sounding, especially with the old Soundcraft boards.

 

And those Peavey 800's were everywhere too.

 

I think Bi-Amp made power amps for a while - I know they made boards that were pretty good for back then.

[twostone]

AB International amps

[agedhorse]

Which DMI amp do you have... photos and schematics? If it's what I am thinking of, it's an on-amp based front end, full complimentary. I did a lot of work for DMI on the west coast in the early 80's.

 

Kelmar was an older cinema amp, sold as a package generally with their processing and automations.

 

QSC was one of the early adopters of the SMPS power supply, and they did an excellent job of keeping reliability high with no sonic issues.

[agedhorse]

AB International amps

 

Of course, they were on of the earliest folks to introduce class G/H product, with QSC close behind MX/EX series. The 900A/1100A/1200 were solid amps.

 

There was also Soundcraftsman, one of the earliest adpotees of class G/H but suffered from tragic reliability problems.

 

Note that these are USA companies, there were international companies that trached along these lines too, MC-squared out of the UK was one that seemingly has been re-born.

[gearhead1972]

McIntosh MC 2300

89 of them powered The Grateful Dead's "Wall of sound" in 1974

[SoundMan]

"Peavey does deserve mention for being the first caompany to put higher power in the hands of relative idiots."

 

I'm not sure if that's a compliment, or not.

 

Also remember, we were doing class D in the 80's. Maybe not the best, but we were doing it.

 

The IPR doesn't have a track record yet, but I do think it's changing the landscape of the power amp industry.

[jabney]

 

Which DMI amp do you have... photos and schematics? If it's what I am thinking of, it's an on-amp based front end, full complimentary. I did a lot of work for DMI on the west coast in the early 80's.

 

 

It's an SMF Stereo 150 with a diagonally divided US/UK flag on the front. Sorry, no schematic, and no photos (but if I can locate a couple of charged AA cells, I will try to take a picture or two).

 

It's supposed to be class B, right?

 

best,

 

john

[agedhorse]

 

"Peavey does deserve mention for being the first caompany to put higher power in the hands of relative idiots." I'm not sure if that's a compliment, or not. Also remember, we were doing class D in the 80's. Maybe not the best, but we were doing it. The IPR doesn't have a track record yet, but I do think it's changing the landscape of the power amp industry.

 

 

It is a compliment and it really highlighted many Peavy users who had a heck of a struggle making a soiund system work without blowing things up. Without DDT, I'm sure the failure rates would have been a lot higher and the amp would have been known as a speaker killer due to lack of operator knowledge.

 

It's also true that the DPC stuff was revolutionary, and unfortunately for Peavey it was pretty unreliable. When it did fail, it did so quite impressively too.

 

The IPR has every reason to be successful, provided Peavey doesn't do some goofy marketing program highlighting their lack of understanding of the pro audio business. That's one area where they seem to have a heck of a challenge.

[dboomer]

 

. Anybody remember BGW and SAE?

 

 

Yes. Some of the BGW guys started Crest so Brian Wachner's designs pre-dated the Crest products. The Peavey CS800s also borrowed heavily from the BGW designs.

 

How about Carl Countryman and the first switch-mode power amp? As I remember he was getting about 2000W from a single power amp in the very early 70s.

[agedhorse]

 

It's an SMF Stereo 150 with a diagonally divided US/UK flag on the front. Sorry, no schematic, and no photos (but if I can locate a couple of charged AA cells, I will try to take a picture or two). It's supposed to be class B, right? best, john

 

 

Should be either class B or AB, don't know for sure. I would love to find a schematic of this.

 

It's a big 'ol pig of an amp!

[RoadRanger]

The IPR has every reason to be successful, provided Peavey doesn't do some goofy marketing program highlighting their lack of understanding of the pro audio business.

You mean like loading it up with lots of blazing blue DJ bling lights?