Amplifier Testing

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i wonder how many of these amps shown in this forum ....to begin with as schematics ever managed to make what destroyer x says real life :smash: and also let us for a minute define real life...... cause if real life means carefull listening ...(after scopes and simulation of course) of nice music with very good speakers .....its simply not enough :bawling: ....at least for me ....

PA use or even better abuse should be the real thing working for 5-6 hours to a 100% or may be more .....overdriving ....bi amp... hotsuap of plugs ...distorted signals and goes on

Thats real life to me ..... and of course its not importand if amp is 45 or 600w abuse is abuse in any way you look at it .... and even if the use is PA i dont find any no reason why the sound should be also very nice there

i wonder what simulators have to say about that ..... also reminds me how many B&W speakers come in to my shop for repair after just a simple kids party ..... also amps ..... outputs shorted or even transformes burned to hell .....

still i belive that info existing in the forum is so critical and also the amazing will of people to do and share audio from scratch !!!!!!

happy easter to diyaudio !!!! all the best !!!!
 
Have you made that "abuse" test with your amplifier Sakis?

Can you inform more things for us, please.

What amplifier was abused?

Can you please post schematic?

Was this abuse over resistive loads or speakers?

Can you, please, post some pictures?

Have you adjusted Bora amplifier to your needs?

What modifications have you done?

I will be happy to know.

good to see you here Mr. Petropoulos

Carlos
 
i work in a pro audio shop, and yes, these amps get abused. usually they are run for several hours at a time, at or near 100% power, with inadequate cooling and squirrelly loads (half of which also have blown drivers).
then about half way through the evening when everybody's ears have become numb from 120+db sound levels, they try to push the amp even harder........ quite often letting out the magic smoke :redhot: .....:confused: :redhot: :eek: :bawling:


tom holman used to say that running a class AB amp at between 50 and 75% power was actually harder on the output devices, because they dissipated much more heat per output watt than they did at full power.
 
about 150pcs of IERFP250

the original problem was when tryied to operate boras amp legend 4 with voltage 60-66vdc per rail ......

it all end up to almost 150 very expensive mosfets send to outer space while testing and trying to make it work ......:hot:

input was to sensitive to anything like a hot suap of plugs or just a litle bit of overdrive

bora of course recomended to add 0.18R 5W to the out of every mosfet as first change

and then a 33-56 pf miller styroflex capacitor between b and c on the MJE 340 vas amplifier to improove some ocilation was there

schematic is also available ......

still didnt work

destroyer x a very nice guy from brasil his original name is Carlos Eugênio Mergulhão - Destroyer x and me worked out some mods and in real life this all seems to work no matter if used or abused ha ha ha ....

the new schematic is also available
 

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personally i would use a dc servo instead of the offset cap. i don't like reactive components in the feedback loop...... offset caps launch the amp to the rails when they go bad. a dc servo uses caps, but with a much lower voltage rating and capacitance, and early warning signs of failure, such as high ESR are more easily troubleshot, since it tends to reduce the low freq gain of the amp first, rather than the first sign of trouble being the amp latching to the rail.
 
theory aproach

well thank you for posting in any way .....

all this is too much theory to me that i canot really understand ....you see i am a constructor ...a screwdriver guy i cannot come in so deep in theory ...i dont run simulators .....but i do construct .... often from scratch ....

so if you like to post a schematic with your opinion that will be very nice for me and carlos that bother with this story also .....

for anything that worths the amp as is now seems to be running like hell supplied with 66+66 vdc per rail .... and four of them worked in party ....abused like hell ... biamped......personaly take care of pushing them to the limit with out any problems ...even with models that had ..lets say not enough cooling the performance was nice and the temprature was very ok meaning that they got warm but not hot .....

since i dont run simulators ...to my ears sound was just perfect but on the other hand could i ever tell diference with some small changes on feedback ???? really dont know ....

any help is so welcome
 
unclejed613 said:
i work in a pro audio shop, and yes, these amps get abused. usually they are run for several hours at a time, at or near 100% power, with inadequate cooling and squirrelly loads (half of which also have blown drivers).
then about half way through the evening when everybody's ears have become numb from 120+db sound levels, they try to push the amp even harder........ quite often letting out the magic smoke :redhot: .....:confused: :redhot: :eek: :bawling:


tom holman used to say that running a class AB amp at between 50 and 75% power was actually harder on the output devices, because they dissipated much more heat per output watt than they did at full power.


IMHO, the adjective 'pro' seems to be synonymous with 'loud'. Of course if you make it loud enough, then the sensitivity of peoples' ears will react to the sound pressure and they won't hear the distortion coming from the over-driven amp anyway. :clown: :smash:
 
there are real pro's out there that can run a system at far above 120db, but nobody will notice it, until they try to talk to somebody next to them. they run the system so clean that it doesn't sound "loud" at all. then there are the "pro's" that can't seem to get more than 100db out of a system, but it sounds "loud" (so severely overdriven that it sounds like exploding dog doo), and they're the ones that blow up amps and speakers on a regular basis
 
You can check if it is saturating your ear drum listening outside the shop

50 meters distance will be enougth to perceive the quality and to reduce saturation to a good level.

Other objects may be ressonating because enormous sonic pressure..outside shop your evaluation will be better....also deep bass will be better perceived distant, because of sound wave length.

regards,

Carlos
 
Hi,
the gain has gone from 21times to 27times. An increase of 1.9db. that increases the gain margin by the same 1.9db, not much of a change but in the right direction. The Miller comp cap could probably have been omitted if the two stage feedback cap had been increased from the 20pF to 27 or 33pF.

What component values are fitted for the input filters?
Are they 1uF & 10k + 9k & 990pF? changed to 470nF & 10k.
 
The input filters are a bit close to narrow band, but if this is the only way to make the amp reliable then so be it.

Low pass 47mS ~F-3db @ 3.4Hz. For good fidelity I suggest going a full octave lower and preferably 1.5octaves lower.
High pass 3.3uS ~F-3db @ 50kHz. Again one to three octaves higher would let through most (all?) of the audio signal.

For a cheap and cheerful amp doing cheap and cheerful PA duty it is probably good enough (much like many of the poor quality discos I've heard).
 
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Joined 2002
unclejed613 said:
there are real pro's out there that can run a system at far above 120db, but nobody will notice it, until they try to talk to somebody next to them. they run the system so clean that it doesn't sound "loud" at all. then there are the "pro's" that can't seem to get more than 100db out of a system, but it sounds "loud" (so severely overdriven that it sounds like exploding dog doo), and they're the ones that blow up amps and speakers on a regular basis

Indeed. On bigger tours, there is a "rack man" who's job is to set up and monitor the system properly, so the FOH engineer has only his kit to worry about.
 
Sakis. himself will be the rackman Pink.

The guy has a company, a business, related Audiovisual productions, he use to rent audiovisual material and he loves to construct amplifiers.

His last units were made to help an Institution that take care of children..those ones have not daddy and mum to take care of them... work made for free...just to give him a fair presentation to all our friends...another precious stone we have in our forum.

Just to inform forum personnel, about Sakis "quality" as a man with special character...the nice behavior that move himself to spend a lot of money to help Institutions dedicated to aid poor lonely young kids.

Sakis Petropoulos...ancient heritage related his ascendence...millenium family...he may be proud of it.

I have enormous respect related those folks.

regards,

Carlos
 
thank u andrew t

all these info is very usefull to us thank you andrew t ......


and just for general info ....Pa for me is to manage to reproduce high quality signals to higer levels ...... if you go to hilevels and you loose on quality ...then whats the point of it ????

thank you again andrew ....also for starts i wnated to have one amplifier to produce "related" quality but some stabiliy in any kind of abuse also ....

working ...... i am fine with this performance so far ....
 
real life legend 4 stereo

there is a picture of real life legend 4 stereo constructed in a inter m 2300 old existing

this is capable of almost 165 w rms @8R with 66+66 vdc psu also tested in real life in a party actually pushed to the limit for more than 5 hours ...working as second way in bi amp system (2way high )

all went just fine as about sound to my ears was way to good ....
 

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real life f** up

this is a picture of the construction of a board legend 8 schematic and pcb was given for free from bora to me

the only thing i did was to use a heatsink on vas amplifier MJE340 and also attach it with a screw to the board in allready existing mark of a hole ....

the existance of the screw there eventhough didnt touch anything created some capacitance and so much ocilation enough to give you 50 volts dc in the output with no signal or load in the input ......

thats some ..... of real life construction and how much problems you may run to....
 

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Hi Sakis,
adding a heatsink created capacitance and oscillation, or adding the through board screw created the capacitance and oscillation.
Which?

Either way, it seems to indicate that there is little phase margin in this amplifier, no wonder you are concerned about reliability.

Why 50Vdc on the output when it oscillates?

BTW,
my recently tested Leach clone (3pr) does 170W into 8r0 from +-58.5Vdc supply rails. It does not need +-66Vdc rails.
 
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