VLSI,
Tell me about your PCB. Is it DIY or did you have some made at a PCB shop? Is it the one from the app notes? Has anyone done a circuit/PCB with integrated DC and short protection? Which output configurations have proven themselves with this chip?
I'm not sure I could figure out how to configure an output section to fit this chassis, but if I were to reconfigure the amp as 4 x 125 watt amps, it would be much easier to use off-the-shelf output sections.
..Todd
Tell me about your PCB. Is it DIY or did you have some made at a PCB shop? Is it the one from the app notes? Has anyone done a circuit/PCB with integrated DC and short protection? Which output configurations have proven themselves with this chip?
I'm not sure I could figure out how to configure an output section to fit this chassis, but if I were to reconfigure the amp as 4 x 125 watt amps, it would be much easier to use off-the-shelf output sections.
..Todd
Why not just refab some new circuit boards. those were great amps!
Hell i would LOVE to find some old beat up 4B's! I would put one in my bass rig and use one for a subwoofer. these things were great for bass.
I would rebuild those amps in a heatbeat. If it were me, i would simply have new PCB's made and rebuild them to new.
I hunt ebay everyday for gold just like this! and even broken they sell for more then i can afford!
Seriously, if you dont see there value, sell them to someone else that does, then use that money to buy some new chassis and build whatever you want.
Heck Trade then to someone fo some custom chassis. i bet you could find that in a heartbeat!
Oh man im going to be just sick.
If your company comes across anymore, i will buy them!
Zc
Hell i would LOVE to find some old beat up 4B's! I would put one in my bass rig and use one for a subwoofer. these things were great for bass.
I would rebuild those amps in a heatbeat. If it were me, i would simply have new PCB's made and rebuild them to new.
I hunt ebay everyday for gold just like this! and even broken they sell for more then i can afford!
Seriously, if you dont see there value, sell them to someone else that does, then use that money to buy some new chassis and build whatever you want.
Heck Trade then to someone fo some custom chassis. i bet you could find that in a heartbeat!
Oh man im going to be just sick.
If your company comes across anymore, i will buy them!
Zc
new thread needed for LM4702 ?
Ok, Taj ... after looking at the photos, I agree. The chassis and some of the parts are all that is useful and worth saving.
The transformer should either be heavily shielded or scrapped = not torridal.
The heat sinks can be used two ways: with the (renovated) chassis as is (= an amp that won't be stolen 'cause it looks like junk =
) ... or repainted and repaired as needed and used with a new chassis. (FYI: these old heat sinks are available from http://www.halted.com/ ... in their Rohnert Park, Ca. store, not online, I've seen 'em).
...
VLSI: I'm tempted to start a thread for the LM4702(x), probably the B version. This chip amp's a neat little trick and would do very well as a b-amp speaker driver or straight ahead power amp.
http://www.national.com/pf/LM/LM4702.html & http://www.national.com/images/pf/LM4702/20158319.pdf & http://www.national.com/images/pf/LM4702/20158308.pdf & http://www.national.com/an/AN/AN-1490.pdf
Are there "eval" boards available or should we roll our own? (I might want balanced inputs and solid recommendations for the Darlington push/pull output transistors.)
Yes, this would be a very interesting project for Taj's broken 4B chassis = he could install as many as four of these for a THX 8-channel amp !
Ok, Taj ... after looking at the photos, I agree. The chassis and some of the parts are all that is useful and worth saving.
The transformer should either be heavily shielded or scrapped = not torridal.
The heat sinks can be used two ways: with the (renovated) chassis as is (= an amp that won't be stolen 'cause it looks like junk =
) ... or repainted and repaired as needed and used with a new chassis. (FYI: these old heat sinks are available from http://www.halted.com/ ... in their Rohnert Park, Ca. store, not online, I've seen 'em)....
VLSI: I'm tempted to start a thread for the LM4702(x), probably the B version. This chip amp's a neat little trick and would do very well as a b-amp speaker driver or straight ahead power amp.
http://www.national.com/pf/LM/LM4702.html & http://www.national.com/images/pf/LM4702/20158319.pdf & http://www.national.com/images/pf/LM4702/20158308.pdf & http://www.national.com/an/AN/AN-1490.pdf
Are there "eval" boards available or should we roll our own? (I might want balanced inputs and solid recommendations for the Darlington push/pull output transistors.)
Yes, this would be a very interesting project for Taj's broken 4B chassis = he could install as many as four of these for a THX 8-channel amp !
ZeroCool,
You're going to have to get over this. You have them over-valued in your mind. Original 4B's are not exactly revered in audio circles, especially here.
Contact a bunch of concert sound companies. I'll bet you'll find plenty of old original 4B's in their graveyard pile if they haven't already been dumped. They are considered boat anchors now and are often used to keep the trucks from rolling back down the hill or to provide extra heat in the hotel room. But like mine, they won't be pretty.
If you want to make me an offer for these, do so, but please don't make me out to be an amp murderer over this.
..Todd
Hi Everyone
I tried to get some more interest in the LM4702 on the chip amp thread but must have been looking in the wrong place.
Although “veteran” has posted a PCB for the LM4702 somewhat based on the NS App. note.
It would be great to have feedback on this part from others in the DIY community, I myself are very excited about it’s potential as an easy solution to high power and Hi-fidelity.
In my old age I mover cautiously so my first project was to pull all the guts out of a KODA A-260 amp (A2760 from DSE in Australia) and fit one LM4702. (I also change the output transistors for Darlingtons as used by NS in their applications note)
The improvement if sound quality was obvious, Next on the same amp I introduced a separate PS just for the chip (but unregulated) 5v above the output stage. Also at the same time I fitted 4x 4.7uf polypropylene capacitors from the collector’s of each output transistor to the star ground and one or both of these modifications also made a big improvement to the sound.
Next I upgraded 2x Luxman 5L15 Amplifiers (very east to do as the layout was perfect and they already have a +/- 60v regulated PS I could use for the chip.
I have almost completed an amplifier from scratch based again on the NS app note (only +/- 45v) If this sounds as good or better than the modified KODA I will scale it up to 3 pairs of output transistors at +/- 80v
Maybe one day move up to the mil-spec LM4702A (gold TO-3) @ AU-$300.00ea maybe?
The maximum length I have used from the chip source/sink output to the bases of the drivers is 150-200mm and the same length for the output to the negative feedback (this was on the 5L15 and it is as stable as a rock) although the distortion my be compromised?
The PCB is home made single sided just for the chip, It has provision for capacitors but in all 3 amps I am using it DC coupled as this sounds best and the 5L15 where DC coupled anyway.
At a gain of 30 DC offset is –5mv one chan. and a bit high at +25mv the other. All amps are the same so maybe it is the batch of chips I have?
Please ask any question as I have made lots of notes.
I tried to get some more interest in the LM4702 on the chip amp thread but must have been looking in the wrong place.
Although “veteran” has posted a PCB for the LM4702 somewhat based on the NS App. note.
It would be great to have feedback on this part from others in the DIY community, I myself are very excited about it’s potential as an easy solution to high power and Hi-fidelity.
In my old age I mover cautiously so my first project was to pull all the guts out of a KODA A-260 amp (A2760 from DSE in Australia) and fit one LM4702. (I also change the output transistors for Darlingtons as used by NS in their applications note)
The improvement if sound quality was obvious, Next on the same amp I introduced a separate PS just for the chip (but unregulated) 5v above the output stage. Also at the same time I fitted 4x 4.7uf polypropylene capacitors from the collector’s of each output transistor to the star ground and one or both of these modifications also made a big improvement to the sound.
Next I upgraded 2x Luxman 5L15 Amplifiers (very east to do as the layout was perfect and they already have a +/- 60v regulated PS I could use for the chip.
I have almost completed an amplifier from scratch based again on the NS app note (only +/- 45v) If this sounds as good or better than the modified KODA I will scale it up to 3 pairs of output transistors at +/- 80v
Maybe one day move up to the mil-spec LM4702A (gold TO-3) @ AU-$300.00ea maybe?
The maximum length I have used from the chip source/sink output to the bases of the drivers is 150-200mm and the same length for the output to the negative feedback (this was on the 5L15 and it is as stable as a rock) although the distortion my be compromised?
The PCB is home made single sided just for the chip, It has provision for capacitors but in all 3 amps I am using it DC coupled as this sounds best and the 5L15 where DC coupled anyway.
At a gain of 30 DC offset is –5mv one chan. and a bit high at +25mv the other. All amps are the same so maybe it is the batch of chips I have?
Please ask any question as I have made lots of notes.
I want two !
VLSI:
Did you use the basic NS application note circuit: http://www.national.com/pf/LM/LM4702.html ...??
" ... mil-spec LM4702A (gold TO-3) @ AU-$300.00ea ..." I'll bet this price will come way down if NS can get the volume up ... maybe they have a few laying around in their engineering department
I guess the next step is to get your "as built" diagrams and possibly some pictures ... how are the chances of this?
Then I suppose we should get one of the DIYAudio monitors to start another thread ... or do we do that ourselves?
I would like to build some of these for insertion into several projects. I still think it would make a good bi-amp for my main speakers. I would also like to have balanced XLR inputs ( but better than this = http://www.dplay.com/dv/balance/fig5.gif )
VLSI:
Did you use the basic NS application note circuit: http://www.national.com/pf/LM/LM4702.html ...??
" ... mil-spec LM4702A (gold TO-3) @ AU-$300.00ea ..." I'll bet this price will come way down if NS can get the volume up ... maybe they have a few laying around in their engineering department
I guess the next step is to get your "as built" diagrams and possibly some pictures ... how are the chances of this?
Then I suppose we should get one of the DIYAudio monitors to start another thread ... or do we do that ourselves?
I would like to build some of these for insertion into several projects. I still think it would make a good bi-amp for my main speakers. I would also like to have balanced XLR inputs ( but better than this = http://www.dplay.com/dv/balance/fig5.gif )
" ... I tried to get some more interest in the LM4702 on the chip amp thread but must have been looking in the wrong place. ..."
Probably you were in the right place. Sometimes there are so many projects ongoing, that folks don't recognize a great new trick when they see it. We could try again.
Probably you were in the right place. Sometimes there are so many projects ongoing, that folks don't recognize a great new trick when they see it. We could try again.
I see the photo's you posted earlier. I used to have this same model that came from the Toronto Skydome. i restored it and my Buddy is using it now and he loves it. It was a little harsh on the top end but the bass was unreal! It added an entire octave to the bottom end of my speakers VS. the amp i had been using at that time.
Yes i would seriously like to make you an offer/trade whatever. I will rebuild those babies!
Zc
Yes i would seriously like to make you an offer/trade whatever. I will rebuild those babies!
Zc
VLSI et al:
Looks like someone beat us to it: http://www.chip-pcb.cn/7300/4702e.htm
Needed to add (apparently) is transformer, hookup leads, I/O binding posts & connectors and of course a case or chassis.
I would still want to make mine have balanced inputs ...
Looks like someone beat us to it: http://www.chip-pcb.cn/7300/4702e.htm
Needed to add (apparently) is transformer, hookup leads, I/O binding posts & connectors and of course a case or chassis.
I would still want to make mine have balanced inputs ...
FastEddy
Thanks for the link.
My good old friend Tony has ordered a set of amplifier & PS boards, I will let you know what they are like when they arrive.
2 pairs of SAP15 transistors should be good for more than the 35v AC specified, That would be about 100w 8ohm and 150-180w 4ohm
If reading the NS applications note is any guide PCB layout is very important and it will be interesting to see how good these amps sound.
Have you used the ON Thermaltrak transistors?
I am still mystified as to why amplifiers sound so different even when they have much the same specifications.
Do you think we should start a new thread or move to the old LM4702 thread?
Greg
Thanks for the link.
My good old friend Tony has ordered a set of amplifier & PS boards, I will let you know what they are like when they arrive.
2 pairs of SAP15 transistors should be good for more than the 35v AC specified, That would be about 100w 8ohm and 150-180w 4ohm
If reading the NS applications note is any guide PCB layout is very important and it will be interesting to see how good these amps sound.
Have you used the ON Thermaltrak transistors?
I am still mystified as to why amplifiers sound so different even when they have much the same specifications.
Do you think we should start a new thread or move to the old LM4702 thread?
Greg
VLSI: Looks like your headed in the right direction. See: http://www.diyaudio.com/forums/showthread.php?postid=1080368#post1080368
I plan to order at least two myself in January (too many projects this month).
FYI from the factory in China ..."
Q: Is the above in Hong Kong dollars or US$ funds??
A: Product marked price for US dollar.
Q: Is this the correct amount for two complete amplifiers shipped to the USA ??
A: Yes. (US$42 + US$15 + US$16 + shipping, each amp module set [time 2 for me])
Q: Do I need to order the heat sinks separately??
A: Does not need. In the module including heat sinks.
Q: What is the SAP15 ??
A: The SAP15P and SAP15N is Darlington Transistor For Audio Amplifier With Temperature Compensation.
Please visit http://www.sanken-ele.co.jp/en/prod/semicon/ptr/ptr_u/ptr_01e.htm
Q: I have transformers and cases and mounting hardware, do I need any of the other parts / modules ??
A: Does not need.
These replies, hoped may solve your question.
Best Regards,
Servicee-CP
servicee@chip-pcb.cn
2006-12-13
..."
Their ordering page indicates two different power supply boards are required for each amp mudule for rated output ...
I plan to order at least two myself in January (too many projects this month).
FYI from the factory in China ..."
Q: Is the above in Hong Kong dollars or US$ funds??
A: Product marked price for US dollar.
Q: Is this the correct amount for two complete amplifiers shipped to the USA ??
A: Yes. (US$42 + US$15 + US$16 + shipping, each amp module set [time 2 for me])
Q: Do I need to order the heat sinks separately??
A: Does not need. In the module including heat sinks.
Q: What is the SAP15 ??
A: The SAP15P and SAP15N is Darlington Transistor For Audio Amplifier With Temperature Compensation.
Please visit http://www.sanken-ele.co.jp/en/prod/semicon/ptr/ptr_u/ptr_01e.htm
Q: I have transformers and cases and mounting hardware, do I need any of the other parts / modules ??
A: Does not need.
These replies, hoped may solve your question.
Best Regards,
Servicee-CP
servicee@chip-pcb.cn
2006-12-13
..."
Their ordering page indicates two different power supply boards are required for each amp mudule for rated output ...
Another option I'm considering is maybe to try the LM4702 in front of the Bryston's output section (4 pairs of TO-3 devices per channel at 72 volt rails). This way, I could try a new amp design without butchering the 4B completely beyond restoration.
Worst case option, I could replace the circuitry and keep the Bryston PCBs in case I ever want to restore it later.
But then if CoolZero makes me an offer I can't refuse, they're all his to do with as he pleases.
...Todd
Worst case option, I could replace the circuitry and keep the Bryston PCBs in case I ever want to restore it later.
But then if CoolZero makes me an offer I can't refuse, they're all his to do with as he pleases.
...Todd
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