400uF in series with the loudspeaker????
That's going to have TERRIBLE bass performance.
I dunno why the cap is there: besides that part, the circuit is cloned 100% from National's application note.
And it's not going to give 300W/Ch on a 30/0/30 transformer - more like 120-150W/ch.
That's going to have TERRIBLE bass performance.
I dunno why the cap is there: besides that part, the circuit is cloned 100% from National's application note.
And it's not going to give 300W/Ch on a 30/0/30 transformer - more like 120-150W/ch.
30-0-30 will give something like 70W into 8 ohms 🙂
That circuit has a lot of problems... Looks like the designer had no idea what (s)he was doing.
2N3055 for vbe multiplier??? That's insane!
That circuit has a lot of problems... Looks like the designer had no idea what (s)he was doing.
2N3055 for vbe multiplier??? That's insane!
ok ok
my point of view also ....
i think that its a joke .... but let us for a minute try to see some other prospect ....
lets suppose that we increase rails ....how much will be possible ....
and then add a proper vbe multiplier ( complete circuit )
and then borrow the qsc idea ( all transitors mounted to ground and speaker lead comes from CT and psu caps and so on and on
are we getting somewhere ????
my point of view also ....
i think that its a joke .... but let us for a minute try to see some other prospect ....
lets suppose that we increase rails ....how much will be possible ....
and then add a proper vbe multiplier ( complete circuit )
and then borrow the qsc idea ( all transitors mounted to ground and speaker lead comes from CT and psu caps and so on and on
are we getting somewhere ????
I was playing with those chips those days
You can see into Youtube many things published showing strange behavior.... noises.... off set fluctuations....movies showing this are there.
They are very sensitive, also unstable and hard to built without face unstabilities... board is critical, distances must be very small...parts position critical too.
They sound good... depending the audio source, the music style and speaker they sound very good but not safe, not reliable, not stable in my point of view.
So..the better could be the circuit surrounding them..knowing those LM4702 represents two LM4701 inside same case, they are not something safe to be used.
The output condenser is small and the power amplifier biasing is not very good.... they are not kidding, just they are trying to offer something plays loud...very loud!....maybe audiophile quality is not the main focus...main target.
About LM4701 (same circuit inside LM4702) here into youtube:
http://www.youtube.com/watch?v=F5tr4gHsNkU
regards,
Carlos
You can see into Youtube many things published showing strange behavior.... noises.... off set fluctuations....movies showing this are there.
They are very sensitive, also unstable and hard to built without face unstabilities... board is critical, distances must be very small...parts position critical too.
They sound good... depending the audio source, the music style and speaker they sound very good but not safe, not reliable, not stable in my point of view.
So..the better could be the circuit surrounding them..knowing those LM4702 represents two LM4701 inside same case, they are not something safe to be used.
The output condenser is small and the power amplifier biasing is not very good.... they are not kidding, just they are trying to offer something plays loud...very loud!....maybe audiophile quality is not the main focus...main target.
About LM4701 (same circuit inside LM4702) here into youtube:
http://www.youtube.com/watch?v=F5tr4gHsNkU
regards,
Carlos
I think it's definitely someone who doesnt know wtf they are doing! That chip has been tried by various people in the Chip Amp forum and they've had great success with it, though.
Can you be more precise about the one does not know
what was doing.
Mr. Jaycee.
As you have perceived this...why don't you do it better?.... say... in the case of bad made design, do it better and offer to us the corrections needed.
If not well tested, them produce better testing to us...be positive, do something can be usefull.... criticisms may be interesting, but has lack of result...do not help us ..will not make the designer better or the evaluator better.
Teach us how to do it better...or to evaluate it better... help us to leave the ignorance behind... give us a chance to evolute!
As you may know things we do not know... why not to share with us?
regards,
Carlos
what was doing.
Mr. Jaycee.
As you have perceived this...why don't you do it better?.... say... in the case of bad made design, do it better and offer to us the corrections needed.
If not well tested, them produce better testing to us...be positive, do something can be usefull.... criticisms may be interesting, but has lack of result...do not help us ..will not make the designer better or the evaluator better.
Teach us how to do it better...or to evaluate it better... help us to leave the ignorance behind... give us a chance to evolute!
As you may know things we do not know... why not to share with us?
regards,
Carlos
THANKS
UNCLE "VALVOULA" CHARLY .....
i licked very much this xpression ha ha ha
yes this is the idea about
as many times said by me and probably others this might be a simple cheap approach with qualities similar expected ....
mercedes is a car but also hyundai is a car ....
may be after all should exist some permenet thread about simple to make cheap with related quality audio
since quality amps exist more than many in this forum
i recall in one post was mentioned one amp that psu and circuit was calculated in this way so in case of output shortcircuit not enough current was ther to cause outs to short ......very weird approach ....but yet was done by a relativelly good designer
UNCLE "VALVOULA" CHARLY .....
i licked very much this xpression ha ha ha
yes this is the idea about
as many times said by me and probably others this might be a simple cheap approach with qualities similar expected ....
mercedes is a car but also hyundai is a car ....
may be after all should exist some permenet thread about simple to make cheap with related quality audio
since quality amps exist more than many in this forum
i recall in one post was mentioned one amp that psu and circuit was calculated in this way so in case of output shortcircuit not enough current was ther to cause outs to short ......very weird approach ....but yet was done by a relativelly good designer
destroyer x, i did not mean any design with this chip that you have done, i meant the design of whoever did the electronics-lab.com thing - sorry for the confusion 🙂
I've read and seen the problems you had with the chip. If you don't mind me asking, what transistors did you use at the output? I'm just curious now as I did think about building an amp based around one, but had difficulty sourcing them and also didnt like the idea of not being able to replace them if/when it blew up in 5 years time or so. Instead I'll probably make something not to dissimilar from your own DX Precision amp 🙂
I've read and seen the problems you had with the chip. If you don't mind me asking, what transistors did you use at the output? I'm just curious now as I did think about building an amp based around one, but had difficulty sourcing them and also didnt like the idea of not being able to replace them if/when it blew up in 5 years time or so. Instead I'll probably make something not to dissimilar from your own DX Precision amp 🙂
All rigth Jaycee.... i do not read english very well
sometimes there are misunderstandings...my native language is portuguese.
The chip amplifier i have built was LM4701T... and i have burned many units till i have discovered how critical they were to be built...i have used P2P wiring and have not worked fine...only one survived, and it is still working here, but unstable, sometimes turns hot and i do not know why... stand by current is normal and not oscilating (I hope).
The constructions was made following datasheet....i found it too much sensitive and i have decided to tweak the gain... resulted better with lower gain...but needed those condensers into the board... and they have to be at least 1000uf to stabilize a little...well... there are many recordings about my adventure or tragedy.
I will receive some more chips and will try once again... i like the sound they produce..using those cheap speaker we have in brazil they sound good.... sadly i found them unstable and could not discover my mistakes and errors building them.
Of course they were insulated from the heatsink, voltage was correct, parts were good... problem was not obvious to me.... datasheet was followed with care.....but have not resulted stable...i do not know what happened, i felt the unit not stable...but maybe my mistake somewere...why not?... i am human, not a computer!
If i discover something will inform folks, will produce video into youtube and will erase (delete) all videos that produces some criticisms about this chip...no problem to correct and to tell folks what was the problem i had.
No transistors were used... schematic from National Semiconductor Datasheet was used, all pages readed, all values respected...short connections made into them.
bye
Carlos
sometimes there are misunderstandings...my native language is portuguese.
The chip amplifier i have built was LM4701T... and i have burned many units till i have discovered how critical they were to be built...i have used P2P wiring and have not worked fine...only one survived, and it is still working here, but unstable, sometimes turns hot and i do not know why... stand by current is normal and not oscilating (I hope).
The constructions was made following datasheet....i found it too much sensitive and i have decided to tweak the gain... resulted better with lower gain...but needed those condensers into the board... and they have to be at least 1000uf to stabilize a little...well... there are many recordings about my adventure or tragedy.
I will receive some more chips and will try once again... i like the sound they produce..using those cheap speaker we have in brazil they sound good.... sadly i found them unstable and could not discover my mistakes and errors building them.
Of course they were insulated from the heatsink, voltage was correct, parts were good... problem was not obvious to me.... datasheet was followed with care.....but have not resulted stable...i do not know what happened, i felt the unit not stable...but maybe my mistake somewere...why not?... i am human, not a computer!
If i discover something will inform folks, will produce video into youtube and will erase (delete) all videos that produces some criticisms about this chip...no problem to correct and to tell folks what was the problem i had.
No transistors were used... schematic from National Semiconductor Datasheet was used, all pages readed, all values respected...short connections made into them.
bye
Carlos
Ahh, now I see. I had thought LM4701 and LM4702 were similar. The 4702 is just the "front end" of a power amplifier, and then you add VBE multiplier + output transistors, so not a complete amp as the LM4701 is.
I did build a 2xLM3886 based amp, works well and stable, but that chip is rated 68W and I use it only for 30W in 8 ohms (25v supplies). I did not build like a "Gainclone", but nearer to discrete power amp.. good decoupling right next to the chip, 330uF + 100nF, and 2x4700uF capacitors per rail on a seperate pcb for power supply. You are welcome to my PCB layout if you want to try it 🙂
It is good, but I am sure a full discrete amp will sound better. I mainly built this amp because I got the chips very cheap, I had all other parts, and at the time I could not afford to spend much money.
For LM4701 They seem to have taken LM3886 design, moved the pins around, made it lower power and added "standby". Pretty useless in my opinion!
There is also LME49810, which is similar to LM4702, ie a "front end" stage only, but this time only 1 channel. It looks nice, good for manufacturers for sure... again, hard to get !
I did build a 2xLM3886 based amp, works well and stable, but that chip is rated 68W and I use it only for 30W in 8 ohms (25v supplies). I did not build like a "Gainclone", but nearer to discrete power amp.. good decoupling right next to the chip, 330uF + 100nF, and 2x4700uF capacitors per rail on a seperate pcb for power supply. You are welcome to my PCB layout if you want to try it 🙂
It is good, but I am sure a full discrete amp will sound better. I mainly built this amp because I got the chips very cheap, I had all other parts, and at the time I could not afford to spend much money.
For LM4701 They seem to have taken LM3886 design, moved the pins around, made it lower power and added "standby". Pretty useless in my opinion!
There is also LME49810, which is similar to LM4702, ie a "front end" stage only, but this time only 1 channel. It looks nice, good for manufacturers for sure... again, hard to get !
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