I need alittle help.

Hey guys,

I have this old sony amplifier receiver and it has 8 transistor inside of it. They are fairly old transistors and they only put out about 50w each. I was wondering if i can upgrade those transistors to 8 2n3055 transistors to get more power? If so will i need to change anything else in the receiver to make it work properly? Do i need to get a higher powered transformer to power those higher powered transistors?
 

Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
It's a good question, but very naive. While it may make some sort of sense that the transistors are limiting the power of the Sony, it's actually the power supply voltage that is the limitation. That's very important to know. Look up Ohm's law, find a calculator and do the math. You'll quickly understand the problem and will have learned something rather useful. Knowing Ohm's law will help you in all sorts of electrical problems.

Try the calculations, spend some time with them. You'll be happy that you did. :up:
 
The heat sinks, fans (none) and transformer current are also limiters.
Buy a blown up PA amp and repair it. That is what I did, and learned a lot. Peavey, QSC, Crown, Yamaha are known for putting out the watts (into 4 ohms) mentioned in the name for hours and hours. Other brands IMHO are 4 hour or 8 hour rated. E bay amps are 3 second rated, in general.
Or buy a class T amps. You have to find a grounded box to put them in, and put capacitors on the inputs and chokes on the outputs to keep them from howling into every thing else audio, but they are cheap. See STEVAL-CCA003V1 - STMICROELECTRONICS - TS4984, STEREO AUDIO POWER AMPLIFIER, EVALUATION BOARD | Newark element14
STEVAL-CCA003V1 - STMICROELECTRONICS - TS4984, STEREO AUDIO POWER AMPLIFIER, EVALUATION BOARD | Newark element14
TPA2006D1EVM - TEXAS INSTRUMENTS - TPA2006D1, AUDIO POWER AMPLIFIER, EVALUATION MODULE | Newark element14
Read the details to see which are stereo and which mono, there are 84 other power amplifier kits at that vendor.
For these you'll also need a +-50v transformer with suitable current for the power rating, some rectifiers, some electrolytic capacitors, some rca jacks and binder posts. Read power supply thread about buildiing one, or buy the diyaudio supply kit in the selector strip above. Some may require +-15 also for input section, the vendor in New Jersey sells transformers with all four windings. Or use your receiver as a preamp to drive the power section.
 
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This is like asking whether your car will go any faster if you put on tires rated for higher speed. Which obviously isn't the case unless you put some work into the engine and transmission departments first and possibly swap out some underrated parts along the way.

Same thing with a power amp. Higher-rated finals by themselves won't gain you anything, in fact you might get oscillation instead. The power supply and rest of the circuit have to be adapted, which ultimately may require as much knowledge as building the circuit from scratch.

It still is a long way from Ohm's Law to being able to properly rescale a power amplifier...
 
The heat sinks, fans (none) and transformer current are also limiters.
Buy a blown up PA amp and repair it. That is what I did, and learned a lot. Peavey, QSC, Crown, Yamaha are known for putting out the watts (into 4 ohms) mentioned in the name for hours and hours. Other brands IMHO are 4 hour or 8 hour rated. E bay amps are 3 second rated, in general.
Or buy a class T amps. You have to find a grounded box to put them in, and put capacitors on the inputs and chokes on the outputs to keep them from howling into every thing else audio, but they are cheap. See STEVAL-CCA003V1 - STMICROELECTRONICS - TS4984, STEREO AUDIO POWER AMPLIFIER, EVALUATION BOARD | Newark element14
STEVAL-CCA003V1 - STMICROELECTRONICS - TS4984, STEREO AUDIO POWER AMPLIFIER, EVALUATION BOARD | Newark element14
TPA2006D1EVM - TEXAS INSTRUMENTS - TPA2006D1, AUDIO POWER AMPLIFIER, EVALUATION MODULE | Newark element14
Read the details to see which are stereo and which mono, there are 84 other power amplifier kits at that vendor.
For these you'll also need a +-50v transformer with suitable current for the power rating, some rectifiers, some electrolytic capacitors, some rca jacks and binder posts. Read power supply thread about buildiing one, or buy the diyaudio supply kit in the selector strip above. Some may require +-15 also for input section, the vendor in New Jersey sells transformers with all four windings. Or use your receiver as a preamp to drive the power section.

Hi sir, what places or websites do you recommend i check out to get a broken PA amplifier?
 
In the USA, craigslist.com is online king, music instruments or electronics for sale section. That is where I found my $55 PV-1.3k. Put 127 parts in it, most salvage, but 20 new output transistors and mica washers were installed at $4.50 each.
In Canada, kiji is onine
In the UK, gumtree is online
Other places, no knowledge.
Repairmen here state defective 800 to 1500 watt PA amps containing transformers are used as door stops at repair shops. Bar bands don't want to carry the weight around. The PV-1.3k is 55 pounds; I brought it home in a backpack on the city bus. Check around for CS800 a,b,c,d,x suffix, PV-8 PV-1.3k pa amps with transformers. I had to pay about $150 for my switcher supply CS800s with 2 problems - blown input resistors, and power supply that trips the breaker unless turned on a number of times. He did that right before I got there to test it, I am sure. He also had the music going in the output plugs which worked but was a kluge. The resistors were $.02 each and the mains electrolytic caps not installed yet, about $16. Peavey schematics are mostly on line which is cool, and the transistor substitution list for private label transistors is also on line.
 
And another note for you, if you want more power, I am expecting what you really want is louder. Power is not loudness, not directly. If you somehow doubled the output power, the system would only be 3 decibels louder. Not twice as loud, just 3db. 3db is just about enough to tell the difference, side by side. it is not night and day at all.
 
That is why I didn't suggest a PV-4C, Allen S100 or Rodgers S100. All that work to repair them, they would only be double or 3 times the power into 8 ohms . That is only 3 or 5 db volume increase. (yeah, the 4c would put out 200 w in 4 ohm, but a 1970 or 1980 speaker will be probbably be 8 ohms) A CS800 would fill up the room with 260 w/ch, and maybe make one want to buy some more capable speakers.
Really obsolete amps like the Armstrong 621, the leak delta 70 and the dynaco ST120 can have as much gain as a cs800, ie they are just as loud, with post 1980 output transistors because those 1966 transistors had gain of 5 and those amps had 80 v power supplies. Mj15003 and later have gain of 20. Just those old amps won't play house music (constant volume) that loud for hours, the heat sinks won't take it. I melted the solder in the dynaco ST120 trying to do PA work in a church Christmas cantata. These old 1964-70 amps are the one case of where replacing output transistors really ups the (classical music) volume. What is cool, they are only about $50 used on e-bay when they do come up.
 
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