It happend 30 years ago...

gladiator335

gladiator335

MRTI
In a galaxy far far away... Well, actually it was 30 years ago in long gone now Soviet Union. I was an engineer supporting mainframe. That day I was working second shift and all bosses were long gone. Nobody except operators. I had absolutely nothing to do (I was on tech support and amazingly everything worked fine that day) so I decided to tweak my power amplifier which I built but haven't tested yet. Hooked up huge 8 ohm resistor to one channel, unplugged second channel from a power supply and connected signal generator and oscilloscope. All set!
Output sine wave seemed perfect and I decided to push a gas a little bit to see when amp clips. Suddenly I felt smell of something burning. Crap! Moving on pure instinct I yanked out power plug and started looking for a damage. Hmm... Nothing wrong inside an amp: no burned parts, no smoke. WTF? And then it dawned on me: it was a burning wood smell! And there it was: dummy load got so hot that it burned a wood on a desktop! I was lucky my boss wasn't there. FYI: the last reading before "fire alarm" went off was 260 WPC @ 8 OHm. And output signal was perfect! No clipping.
I never figured out what was this amp's limit. I used it for 6 years after that, blew pair of 60 watt speakers (after turning the whole thing on with volume up about 60%), bought a pair of 150 watt Soviet-made speakers (which looked similar to Yamaha NS-1000) and actually were capable of much more than 150 watts, cracked a glass in my room's window when new speakers were tested (room was very small) and finally gave it to my friend. I guess it's still working...
 
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33 years ago

When I was in Engineering School, one of my electronics instructors gave us an assignment to build a useful device. Buying a standard "kit" and assembling it would not qualify, but if you modified a standard design with a significant improvement, that was acceptable.

I was running a Pioneer SA-9100 integrated in my stereo and pushing JBL L-100s. My best friend and lab partner was a Navy vet and was attending on the G.I. Bill. He wanted to build a power amp.

We agreed that he would pay for all parts, he would keep the completed unit and we were approved by the instructor that we would both receive credit for the project.

We selected a kit sold by G.A.S. (Great American Sound) to build an Ampzilla power amplifier. The kit came with most of the components but you supplied your own power supply components and housing.

There was a place of business that sold U.S. Navy surplus and salvage gear in town and had a big selection since at that time, the U.S. Navy Sixth Naval District was located in the same town.

We purchased transformers, diodes and rectifiers as well as a double-drawer rack for pennies on the dollar.

After we got it all put together, it sounded pretty good! We decided to test the power output much as the previous post did, but our 8 ohm wirewound resistors were very heavy duty and were submerged in an oil bath.

We tested it with a signal generator and monitored the input and output signals via a dual-trace oscilloscope (Remember, we were using the school lab equipment).

I don't remember the actual numbers, but within the THD limits that we had determined to be relevant, probably 0.5 %, we maxxed out around 300 watts RMS per channel into 8 ohms, 20-20,000 hz. :rockon:

The kit stated that it should do about 125 wpch. Remember that this was when 100 wpch was big power!

We contacted G.A.S. to ask about the discrepancy between their specs and our results. They asked about our power supply and after we explained what we had constructed our unit with, G.A.S. said that their internal tests had indicated that with the right power supply, their unit would hit over 400 wpc!

We asked them why they didn't build and market the unit at that power and they said that the cost to build a power supply to achieve that level of performance would be prohibitive. :nono:

The components that we bought at the surplus/salvage store were from a phased array radar system and counting the 2-drawer rack, we spent about $100. :yes:

He kept the unit and used it with some older Wharfedales at home until we graduated. After that, he moved back home to Connecticut. A year or so later, I went to Connecticut to attend his wedding. He still had it, but his future wife didn't like its looks and would not let him run it in their new apartment.

Anyone here have (or had) an Ampzilla?

BTW, we got an "A" on our project. :thmbsp:
 
Gladiator, I know that the Russians and China used many American designs in their everyday lives ( so I understand from an American education). Did they use the Williamson Design or similar topologies with different improvements? Also, did they design a completely different design than the Western World that was a breakthrough in amplifier design in the former Soviet Union? Just curious about their topologies.
 
Back in the late 70s and early 80s, building a 'home' computer was expensive and memory chips were the most expensive items after the power supply costs.

I had just arrived at Hewlett-Packard as a computer repair guy as they were updating a lot of customer equipment with the latest memory boards. Naturally, being a hobbyist, I wanted some of the chips and devised a way to remove them quickly:

- Take a small propane torch (like you use to sweat copper pipes)
- Then, with someone on the opposite side of the board held upright in a vise, quickly pull the memory chips out as I would run the torch across the soldered backside of the board.

Well, it seemed like a good idea until the smoke detectors in the office building HP leased went off. Turns out that the fiberglass board material was emitting all sorts of gasses. Never tried that one again........

Cheers,

David
 
Very cool thread... I wish I had the knowledge to DIY a pre-amp and power amp... looks like there are a lot of cool DIY projects out there!
 
70salesguy said:
When I was in Engineering School, one of my electronics instructors gave us an assignment to build a useful device. Buying a standard "kit" and assembling it would not qualify, but if you modified a standard design with a significant improvement, that was acceptable.

I was running a Pioneer SA-9100 integrated in my stereo and pushing JBL L-100s. My best friend and lab partner was a Navy vet and was attending on the G.I. Bill. He wanted to build a power amp.

We agreed that he would pay for all parts, he would keep the completed unit and we were approved by the instructor that we would both receive credit for the project.

We selected a kit sold by G.A.S. (Great American Sound) to build an Ampzilla power amplifier. The kit came with most of the components but you supplied your own power supply components and housing.

There was a place of business that sold U.S. Navy surplus and salvage gear in town and had a big selection since at that time, the U.S. Navy Sixth Naval District was located in the same town.

We purchased transformers, diodes and rectifiers as well as a double-drawer rack for pennies on the dollar.

After we got it all put together, it sounded pretty good! We decided to test the power output much as the previous post did, but our 8 ohm wirewound resistors were very heavy duty and were submerged in an oil bath.

We tested it with a signal generator and monitored the input and output signals via a dual-trace oscilloscope (Remember, we were using the school lab equipment).

I don't remember the actual numbers, but within the THD limits that we had determined to be relevant, probably 0.5 %, we maxxed out around 300 watts RMS per channel into 8 ohms, 20-20,000 hz. :rockon:

The kit stated that it should do about 125 wpch. Remember that this was when 100 wpch was big power!

We contacted G.A.S. to ask about the discrepancy between their specs and our results. They asked about our power supply and after we explained what we had constructed our unit with, G.A.S. said that their internal tests had indicated that with the right power supply, their unit would hit over 400 wpc!

We asked them why they didn't build and market the unit at that power and they said that the cost to build a power supply to achieve that level of performance would be prohibitive. :nono:

The components that we bought at the surplus/salvage store were from a phased array radar system and counting the 2-drawer rack, we spent about $100. :yes:

He kept the unit and used it with some older Wharfedales at home until we graduated. After that, he moved back home to Connecticut. A year or so later, I went to Connecticut to attend his wedding. He still had it, but his future wife didn't like its looks and would not let him run it in their new apartment.

Anyone here have (or had) an Ampzilla?

BTW, we got an "A" on our project. :thmbsp:
Click to expand...

That's a great story!! You know, I've always wanted to build a power amp, just for the experience and fun. I've played with simple transistor circuits, all low voltage stuff. Does anyone sell a kit that is reasonably priced, and doable without too much fuss? Just wondering.
 
gladiator335 said:
In a galaxy far far away... Well, actually it was 30 years ago in long gone now Soviet Union. I was an engineer supporting mainframe. That day I was working second shift and all bosses were long gone. Nobody except operators. I had absolutely nothing to do (I was on tech support and amazingly everything worked fine that day) so I decided to tweak my power amplifier which I built but haven't tested yet. Hooked up huge 8 ohm resistor to one channel, unplugged second channel from a power supply and connected signal generator and oscilloscope. All set!
Output sine wave seemed perfect and I decided to push a gas a little bit to see when amp clips. Suddenly I felt smell of something burning. Crap! Moving on pure instinct I yanked out power plug and started looking for a damage. Hmm... Nothing wrong inside an amp: no burned parts, no smoke. WTF? And then it dawned on me: it was a burning wood smell! And there it was: dummy load got so hot that it burned a wood on a desktop! I was lucky my boss wasn't there. FYI: the last reading before "fire alarm" went off was 260 WPC @ 8 OHm. And output signal was perfect! No clipping.
I never figured out what was this amp's limit. I used it for 6 years after that, blew pair of 60 watt speakers (after turning the whole thing on with volume up about 60%), bought a pair of 150 watt Soviet-made speakers (which looked similar to Yamaha NS-1000) and actually were capable of much more than 150 watts, cracked a glass in my room's window when new speakers were tested (room was very small) and finally gave it to my friend. I guess it's still working...
Click to expand...

GREAT story...but you dont end it right...

should say:
Then i hooked it up to a couple of Altec Theater speakers , pointed it at the Berlin Wall , cranked it up and the wall crumbled and turned to dust! And thats how i ended the cold war...:king:

.....your welcome!
 
How I ended the cold war

OhioEric said:
GREAT story...but you dont end it right...

should say:
Then i hooked it up to a couple of Altec Theater speakers , pointed it at the Berlin Wall , cranked it up and the wall crumbled and turned to dust! And thats how i ended the cold war...:king:

.....your welcome!
Click to expand...

:D:D

At that time the following was available to me: DIY amplifier, Berlin Wall.
The following wasn't available (and even heard of):Altec Theater speakers.
 
By the way this is not the whole story yet. So the amp by itself worked. But I had to put it in some sort of case. Because company I worked for built huge trucks we had every imaginable mechanical facility. So all I had to do is to make a drawing with all dimensions, specify materials and provide couple bottles of vodka (yeah, right! It was a universal currency if you want to get something) to one of my buddies in manufacturing. A week later I had all the parts and assembled the whole thing. To be more specific: top cover was made of 1 mm steel, side panels were made from 8 mm thik titanium (that's right: titanium. It was the only 8 mm material available and my "design" required thick side panels. I just didn't care...), front panel was cut and drilled out of 2.5 inch thick aluminum, all knobs and buttons were manufactured from solid aluminum as well.
Now you can understand why all the references to silver Pioneers "built like a tank" make me laugh out loud! You guys have no idea what "built like a tank" really means!
Volume knob alone was 3 inch in diameter solid aluminum!
I guess my amp could survive direct hit from AK-47.
At the end it tipped the scale a bit over 80 lbs. And all it cost me was 1 liter of vodka and...that's it. All the parts I got from scrapped mainframe peripherals (we had tons of them), circuit board was designed and built from scratch, and probably around 10 bucks (roubles that is) for some switches and wires. Oh, and the look on my friend's faces when they saw it: PRICELESS!
 
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You doity, doity bestidge !! Shame on you for Stealing from The People's Collective like that !! You prolly got the director of that factory sent to Siberia because then they were unable to meet their production quota of Glorious Soviet Tractors for that year !! (grin)
 
I would love to build my entire amplification stage sometime....Pre and Power...

WONDERFUL STORIES on this thread.
 
gladiator335 said:
By the way this is not the whole story yet. So the amp by itself worked. But I had to put it in some sort of case. Because company I worked for built huge trucks we had every imaginable mechanical facility. So all I had to do is to make a drawing with all dimensions, specify materials and provide couple bottles of vodka (yeah, right! It was a universal currency if you want to get something) to one of my buddies in manufacturing. A week later I had all the parts and assembled the whole thing. To be more specific: top cover was made of 1 mm steel, side panels were made from 8 mm thik titanium (that's right: titanium. It was the only 8 mm material available and my "design" required thick side panels. I just didn't care...), front panel was cut and drilled out of 2.5 inch thick aluminum, all knobs and buttons were manufactured from solid aluminum as well.
Now you can understand why all the references to silver Pioneers "built like a tank" make me laugh out loud! You guys have no idea what "built like a tank" really means!
Volume knob alone was 3 inch in diameter solid aluminum!
I guess my amp could survive direct hit from AK-47.
At the end it tipped the scale a bit over 80 lbs. And all it cost me was 1 liter of vodka and...that's it. All the parts I got from scrapped mainframe peripherals (we had tons of them), circuit board was designed and built from scratch, and probably around 10 bucks (roubles that is) for some switches and wires. Oh, and the look on my friend's faces when they saw it: PRICELESS!
Click to expand...

I would LOVE to see a photo of that!!!!!! :drool:
 
70salesguy said:
We selected a kit sold by G.A.S. (Great American Sound) to build an Ampzilla power amplifier.
Anyone here have (or had) an Ampzilla?
Click to expand...

The guy that I bought my Crown DC-300A from locally has a whole house full of Ampzillas. Next time I see him, I'll ask if he is an AK'er. He had several in use and many, many more in various stages of disassembly. He said he collects them and sells them only if someone is willing to pay the price. :scratch2: He said most are not willing.
 
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