The schematic i have posted is wrong
Also the PNP driver has colector inverted related the emitter.
regards,
Carlos
Also the PNP driver has colector inverted related the emitter.
regards,
Carlos
One thing here is that when your father bought the Rotel, pretty much all of the major manufacturers were expected to meet certain standards. Here in the USA they were established by the FTC. If I remember correctly from what I have read, this spec. required that the amp was able to supply full rated power, at the rated distortion spec, from both channels at the same time, for one hour minimum. Thus if you look at the back of that amp, it probably shows a consumption of over 100 watts in for a total of 25 watts out per channel, or 50 watts. Now look at a modern multi-channel surround receiver and try to figure out how they get 100 watts a channel to 5 channels, but only consume 280 watts, as an example. Any ideas why your old Rotel can rock so well. And the size of that heatsink for the power rating doesn't hurt either.
Peace,
Dave
Peace,
Dave
Impossible.... we cannot create energy... and our friend knows that.
he just decided not to accuse people as liers.
With 99 percent of efficiency, these 280 watts would be divided by 5 channels, or 56 watts rms each channel.
But the traditional Class AB, with 50 percent average of efficiency (maximum of 65) cannot produce much more than 28 watts rms each channel.
Maybe you will have more using only two channels, but usually you connect an AC voltimeter and the unit will measure 14 to 15 volts having sinus sinal entering the power amplifier, frequency of 50 or 60 hertz, exaclty the way multimeters are precise...so, real RMS volts...this means 25 to 30 watts aproximatelly.
All channels added, when the 5 channels uses class AB analog amplifier, will not reach 150 watts, unless the power consumption is also a "wrong" number.
So, your amplifier has almost the same power to each channel compared to the modern ones.
Well, this is not good, but worse is the PMPO (Peak musical power output) used in some countries (in Brasil we are not using this anymore) when the power is measured when the amplifier is 10 percent distorted, then they add rigth and left channels, the result they multiply by 10, and i could see units multiplied by 20.
This makes a 5 watt per channel amplifier, with 16 watts of power consumption, be advertised as 320 watts amplifier.
During the sixties the measurement was not decent too, the IHF old rules used a burst of audio, many times bigger than the maximum level an amplifier can hold, one channel was measured, so the supply was not really loaded, and they do not bother about distortion...numbers were enormous too...i remember a Fisher 75 watts i had, maximum undistorted power was 15 watts per channel, and could not operate with 4 ohms.
People use tricks, now a days people observe square wave in the frequency of 10 kilohertz instead of 20 kilohertz, and they use 1 watt or 10 watt, when the same square wave, full power, is much worse...so, they measure lower frequency and lower power to "make" the square wave be better when observed into the Oscilloscope.
regards,
Carlos
he just decided not to accuse people as liers.
With 99 percent of efficiency, these 280 watts would be divided by 5 channels, or 56 watts rms each channel.
But the traditional Class AB, with 50 percent average of efficiency (maximum of 65) cannot produce much more than 28 watts rms each channel.
Maybe you will have more using only two channels, but usually you connect an AC voltimeter and the unit will measure 14 to 15 volts having sinus sinal entering the power amplifier, frequency of 50 or 60 hertz, exaclty the way multimeters are precise...so, real RMS volts...this means 25 to 30 watts aproximatelly.
All channels added, when the 5 channels uses class AB analog amplifier, will not reach 150 watts, unless the power consumption is also a "wrong" number.
So, your amplifier has almost the same power to each channel compared to the modern ones.
Well, this is not good, but worse is the PMPO (Peak musical power output) used in some countries (in Brasil we are not using this anymore) when the power is measured when the amplifier is 10 percent distorted, then they add rigth and left channels, the result they multiply by 10, and i could see units multiplied by 20.
This makes a 5 watt per channel amplifier, with 16 watts of power consumption, be advertised as 320 watts amplifier.
During the sixties the measurement was not decent too, the IHF old rules used a burst of audio, many times bigger than the maximum level an amplifier can hold, one channel was measured, so the supply was not really loaded, and they do not bother about distortion...numbers were enormous too...i remember a Fisher 75 watts i had, maximum undistorted power was 15 watts per channel, and could not operate with 4 ohms.
People use tricks, now a days people observe square wave in the frequency of 10 kilohertz instead of 20 kilohertz, and they use 1 watt or 10 watt, when the same square wave, full power, is much worse...so, they measure lower frequency and lower power to "make" the square wave be better when observed into the Oscilloscope.
regards,
Carlos
Hello nad, as destroyer x described, the marketing is deceptive at best. Since based upon the laws of physics you can't get more out than you put in, the most you could ever get out of the theoretical amp I described is 280 watts, assuming 100% efficiency. As destroyer x also described (Obrigado Carlos) the best that a conventional class AB amp can do is 50-65%, so no way you will get 100 watts out of all five channels at once. The way that the companies get away with that sort of claim in their marketing is that they don't expect the amps to ever need to drive all five channels to full power at once. Seems deceptive to me.
Now if you look at your amp, it claims only 25 wpc, but that is continuous power, both channels driven, for one hour minimum, at the rated distortion. Seems to me that it's a much more honest definition of power output. It also has the tendency of creating a pretty good buffer of reliability into the amp. That's why your little powerhouse kept going!🙂 Nice isn't it?! However all things age, at some point some of the components will start to show their age, so it might be advisable to start thinking about either checking things yourself, if you are qualified, or having it looked at by a good repair tech. If this is done then, that little Rotel should have another 20+ years of happy service.😎
Peace,
Dave
P.S. destroyer x, I missed your mention of not being able to create energy. Please accept my apologies!
Now if you look at your amp, it claims only 25 wpc, but that is continuous power, both channels driven, for one hour minimum, at the rated distortion. Seems to me that it's a much more honest definition of power output. It also has the tendency of creating a pretty good buffer of reliability into the amp. That's why your little powerhouse kept going!🙂 Nice isn't it?! However all things age, at some point some of the components will start to show their age, so it might be advisable to start thinking about either checking things yourself, if you are qualified, or having it looked at by a good repair tech. If this is done then, that little Rotel should have another 20+ years of happy service.😎
Peace,
Dave
P.S. destroyer x, I missed your mention of not being able to create energy. Please accept my apologies!
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You see folks, they have their "style" to make amplifiers, a topologie
This is another model, also the same type of circuit.
I have searched and HIFI engine has several Rotel manuals, i will study all them.
Target is to understand/learn the reasons these units use to be reliable...this is not the first time people tell me good things about the brand.
regards,
Carlos
This is another model, also the same type of circuit.
I have searched and HIFI engine has several Rotel manuals, i will study all them.
Target is to understand/learn the reasons these units use to be reliable...this is not the first time people tell me good things about the brand.
regards,
Carlos
Attachments
Well, they have tried other topologies too...so, they have not their style the way
i was thinking about, so, as i believe topologie sounds, this means to me they have not their "sonic signature", and this reduces their importance to me.
Rotel research is closed to me...a mutant style.... from unit to unit you gonna have different sound.
regards,
Carlos
i was thinking about, so, as i believe topologie sounds, this means to me they have not their "sonic signature", and this reduces their importance to me.
Rotel research is closed to me...a mutant style.... from unit to unit you gonna have different sound.
regards,
Carlos
Attachments
yo will notice that in the three schematics you published,
they use a shunt compensation on the vas collector ,
and no classic cdom..
regards,
wahab
Though I havent driven a full on techno party, I have used my old Rotel amp for DJing with (small Chill music type setup that could fit in my boot) and rehearsed my techno band through it (using Wharfedale speakers) and used it to power my Alesis studio monitors for a while.. It was the first bit of "real hifi" gear I got and got me hooked on this stuff.. though the amp was good enough that I didn't feel the need to upgrade it for years and years. Mine was one of the slim black ones with no tone controls.
Sold it to a mate who is still making good use of it, though I think its time to give it some new capacitors.
Sold it to a mate who is still making good use of it, though I think its time to give it some new capacitors.
reliabilty on these amplifiers uncle charly has absolutelly nothing to do with the schematic
sound qualities and sonics versus ammount of power is scehmatic depenting
durabilty / last long years /reliability is mostly parts depenting
for example japanese made amplifiers noticed how to install pots so these will take years before dirt or corosion ( not all of them but many of them )
then again the rest of it is about parts the problem is that the "costumer" or the "user" can inform u if the machine is playing or not but how well is playing that is a totaly diferent story
it is the same with a 1985 car ...it may be still on the street and running but top speed of 250 klm is out of the question / consuming numbers like 6.5 liters /100klm is also ut of the question / and finally if need to brake then braking distance is too big for todays standards and of course much too biger compaired with the same car when bought new
other than the above the car is till on the street and the ROTEL still produces sound ...
regards sakis
sound qualities and sonics versus ammount of power is scehmatic depenting
durabilty / last long years /reliability is mostly parts depenting
for example japanese made amplifiers noticed how to install pots so these will take years before dirt or corosion ( not all of them but many of them )
then again the rest of it is about parts the problem is that the "costumer" or the "user" can inform u if the machine is playing or not but how well is playing that is a totaly diferent story
it is the same with a 1985 car ...it may be still on the street and running but top speed of 250 klm is out of the question / consuming numbers like 6.5 liters /100klm is also ut of the question / and finally if need to brake then braking distance is too big for todays standards and of course much too biger compaired with the same car when bought new
other than the above the car is till on the street and the ROTEL still produces sound ...
regards sakis
right, and they tried to keep the same "sonic signature" , in
carlos s words...
the first two schematics are classical LIN topologies, i.e, simple differential,
and the third is a symetrical differential...
not only they use a shunted vas collector compensation,
they also reduce the open loop gain of the vas with 33k
resistors from collectors to ground, and this, in the
three schematics again..
But I think I could get that 80s Rotel amp to near showroom condition by replacing some capacitors and perhaps the volume potentiometer, and maybe a good clean.
Yes, there are some "designer" characteristics, and this happens in all schematics
some personal touch from the designer...i love that.
You can recognize Aksa schematics very fast if you have watched at least one of them...there's some signature, some details that you will find in all them.
Thanks to diodes he used (in the past, do not know now a days) i have not lost transistors because i have inverted polarity...heheheh..i use to do that, and very often.
Since Hugh perceived me as a "borning designer" then he closed the informations to me...good that, this means he respect me...good that..i am becoming a real designer, so, he is keeping hidden things from competition.
I'm a competition man!...this makes me very proud!.... the respect from Hugh Dean is alike a Nobel prize to me..because he is a hell good!, the amplifier's God in my personnal point of view..i have jumped from 4 to 7 inches tall related know how since i have met Hugh.
All brands and designers have their own "personnal touch", and i feel that lovely, it is alike a painter and their art product.
I personally do not like mutant designs, we can see that, now a days, with Marantz.. "because sound matters", but style does not matters anymore.
regards,
Carlos
some personal touch from the designer...i love that.
You can recognize Aksa schematics very fast if you have watched at least one of them...there's some signature, some details that you will find in all them.
Thanks to diodes he used (in the past, do not know now a days) i have not lost transistors because i have inverted polarity...heheheh..i use to do that, and very often.
Since Hugh perceived me as a "borning designer" then he closed the informations to me...good that, this means he respect me...good that..i am becoming a real designer, so, he is keeping hidden things from competition.
I'm a competition man!...this makes me very proud!.... the respect from Hugh Dean is alike a Nobel prize to me..because he is a hell good!, the amplifier's God in my personnal point of view..i have jumped from 4 to 7 inches tall related know how since i have met Hugh.
All brands and designers have their own "personnal touch", and i feel that lovely, it is alike a painter and their art product.
I personally do not like mutant designs, we can see that, now a days, with Marantz.. "because sound matters", but style does not matters anymore.
regards,
Carlos
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Yes that is very correct
apply a package like
--- replace all small electro's
--- by the way some of them can be beefed up
--- by the way at some points beyond decoupling bypass is better
--- replace all ceramics with better quality
--- by the way look also some resistors for high tollerance
--- replace trimers with multiturns and retune
--- good cleaning everywere
--- may be a more audiophile wiring
--- relocation of zobel circuits
--- seperated return to star ground for that
and then yes you will have not only showroom condition but also high end almost performance
please notice that all these may be cost 20 usd but for sure is very time consuming and especially for anyone that never done this before
apply a package like
--- replace all small electro's
--- by the way some of them can be beefed up
--- by the way at some points beyond decoupling bypass is better
--- replace all ceramics with better quality
--- by the way look also some resistors for high tollerance
--- replace trimers with multiturns and retune
--- good cleaning everywere
--- may be a more audiophile wiring
--- relocation of zobel circuits
--- seperated return to star ground for that
and then yes you will have not only showroom condition but also high end almost performance
please notice that all these may be cost 20 usd but for sure is very time consuming and especially for anyone that never done this before
Sakis use to do that, years long, he knows what to do
I strongly suggest people to listen Sakis, as he is doing these things daily.
We ALL have a very good idea related what to do, and some related "HOW" to do, there are tips and tricks Sakis can tell us.
- The trick to insert new condenser lead into the hole not to destroy or lift copper island, the way to dessolder fast and clean copper islands using WD40 and hard brush (hair brush to wipe melted solder out from the board), the trick to paint in the board the polarity not to mess with polarities, the value indication, the trick to do one by one, the insulating voltage tips and tricks, how to measure and evaluate condensers using analog voltimeter, to assemble diodes distant from the board, well..the one do this job daily know much more than we can imagine.
You see...the cleaning chapter:
- Clean using what?
- how to clean, submerge the board?, what to remove first?, use brush, air jet, water jet?
- What product to clean, what produce to lubricate, how to dry?... hot air. cold air?, sunlight?
Potentiometers and trimpots:
- How to clean then
- the product used
- How to proceed?, is it only turning and moving the potentiometer several times?... are there mechanical adjustment to be made with plyers?.... what to use, can we use WD40?.. why not?
So, there are hundreds of pages someone skilled can write to us, if they have time and will to do that.
regards,
Carlos
I strongly suggest people to listen Sakis, as he is doing these things daily.
We ALL have a very good idea related what to do, and some related "HOW" to do, there are tips and tricks Sakis can tell us.
- The trick to insert new condenser lead into the hole not to destroy or lift copper island, the way to dessolder fast and clean copper islands using WD40 and hard brush (hair brush to wipe melted solder out from the board), the trick to paint in the board the polarity not to mess with polarities, the value indication, the trick to do one by one, the insulating voltage tips and tricks, how to measure and evaluate condensers using analog voltimeter, to assemble diodes distant from the board, well..the one do this job daily know much more than we can imagine.
You see...the cleaning chapter:
- Clean using what?
- how to clean, submerge the board?, what to remove first?, use brush, air jet, water jet?
- What product to clean, what produce to lubricate, how to dry?... hot air. cold air?, sunlight?
Potentiometers and trimpots:
- How to clean then
- the product used
- How to proceed?, is it only turning and moving the potentiometer several times?... are there mechanical adjustment to be made with plyers?.... what to use, can we use WD40?.. why not?
So, there are hundreds of pages someone skilled can write to us, if they have time and will to do that.
regards,
Carlos
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I have simulated , and result was good
0.015% at 20 watts (THD)....fourier analisis fine too...standard and very common results....nothing extraordinary and nothing bad too.
0.03% at 30 watts.
About the sound....welll, only listening the unit or building.
Building always result better than the original, because you will not have pre amplifier, switches and tone controls.
I have downloaded several service manuals, different models, and the amplifier seems to be excellent.
regards,
Carlos
0.015% at 20 watts (THD)....fourier analisis fine too...standard and very common results....nothing extraordinary and nothing bad too.
0.03% at 30 watts.
About the sound....welll, only listening the unit or building.
Building always result better than the original, because you will not have pre amplifier, switches and tone controls.
I have downloaded several service manuals, different models, and the amplifier seems to be excellent.
regards,
Carlos
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Just had a look at the back, it quotes 200w consumption so I wonder how efficiant it really is and at what percentage of distortion the rated 25wpc lays at?
The output is actually pretty good, although a little laid back but with plenty of bass and drive for a little amp. The pots are all fine too, no scratchyness.
I've decided not to touch it and leave it how it came out of the factory some 30 years ago, shame to start ripping it to bits.
Hello nad, from the power consumption you quoted, compared to the power output per channel, it sounds like Rotel keeps the amp in Class A mode for a little longer before crossing over to Class B. That usually does good things for the sound quality.😎
The thing you need watch out for with older electronics is primarily the Electrolytic Capacitors. They wear out as they get older. Some may last for 40 or more years, others may go bad in a few years. This is the main thing I would suggest getting checked. Otherwise, enjoy what you have!
Peace,
Dave
The thing you need watch out for with older electronics is primarily the Electrolytic Capacitors. They wear out as they get older. Some may last for 40 or more years, others may go bad in a few years. This is the main thing I would suggest getting checked. Otherwise, enjoy what you have!
Peace,
Dave
no way Jose !!!! if its a Rotel and claims 200 W in the back that is exactly equal to : 200W mains power devided by 2 channels is 100W per chanel devided by the efficency factor 50% ( which is low ) means exactly 50W per chanel
that is no more than fair for a rotel of that age
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