I'm running a bias test on the LM4702 and Sanken STD03N STD03P:
The LM4702 itself chews up about 23mA.
Here's a chart of idle current vs time:
An externally hosted image should be here but it was not working when we last tested it.
The LM4702 itself chews up about 23mA.
Here's a chart of idle current vs time:
An externally hosted image should be here but it was not working when we last tested it.
yildiray said:
SAP15N/P are obsolete -- new devices are STD03N/P -- the only difference seems to be the omission of connection to the emitter degeneration resistor in the older devices. You can get the Sankens from Profusion PLC.
I don't know whether Janneman used matched devices in his PAX amplifier (now also seen in August 2009 AudioXpress) -- Sanken suggests using a separate potentiometer between each of the diode strings in the p an n-channel devices.
LM4702 Boards
Hi Spasticteapot
Have a look at the P-4702H and P-4702I boards from CP Design (www.chip-pcb.cn) $8.00 and $10.00 USD.
I have built 5 amplifiers with earlier boards from them, mostly using the now obsolete SAP16 Darlington's and find them very good.
I like to keep the input impedance to 10k with no input or feedback capacitors, (dc protection circuit a must) bias 40-60ma range, Gain about 30 (10k/330R) DC +/- 50v is good for around 100w 8ohm with a single pair of Darlington's.
No pre-amp, input is direct from a Audio-gd "Reference One" DAC or a passively equalized LME49710HA phono pre-amp via a 5k stepped attenuator.
Tested on heaps of speakers but mostly Scan speak Revelatory designs from Zaph Audio and Troels Gravesen, The sound is magic.
I have had (on loan) a number of hi-end monster amps including Krell, Classe, and McCormack to compare with this little amp and apart from the lack of bass authority it hold its own in the mid and top.
Try and use the LM4702B, keep B+/- and speaker wires short and the same length, and if you can, try and make both channels as symmetrical as possible, experiment with your PS filtering capacitors and bypass them with good grade polypropylenes, also I use a separate shunt regulated PS just for the LM4702.
All the LM4702/SAP's amps I have built have a similar characteristic sound, despite very different power supplies and layouts.
Next amp is a 4702 with 6 pairs of BJT devices to see how this affects the bottom end.
As fun as it is to use crazy expensive parts the law of diminishing returns kicks in to hard and the money could be spent on say another power amp module.
One amp built with a good friend used the same chassis and PS but we built 3 LM4702 boards, one each with FET, BJT, and Sanken darlington outputs so we could quickly compare (btw the SAP Darlington's sounded best)
Good luck with your amp, look forward to seeing the finished product.
Kind Regards
Hi Spasticteapot
Have a look at the P-4702H and P-4702I boards from CP Design (www.chip-pcb.cn) $8.00 and $10.00 USD.
I have built 5 amplifiers with earlier boards from them, mostly using the now obsolete SAP16 Darlington's and find them very good.
I like to keep the input impedance to 10k with no input or feedback capacitors, (dc protection circuit a must) bias 40-60ma range, Gain about 30 (10k/330R) DC +/- 50v is good for around 100w 8ohm with a single pair of Darlington's.
No pre-amp, input is direct from a Audio-gd "Reference One" DAC or a passively equalized LME49710HA phono pre-amp via a 5k stepped attenuator.
Tested on heaps of speakers but mostly Scan speak Revelatory designs from Zaph Audio and Troels Gravesen, The sound is magic.
I have had (on loan) a number of hi-end monster amps including Krell, Classe, and McCormack to compare with this little amp and apart from the lack of bass authority it hold its own in the mid and top.
Try and use the LM4702B, keep B+/- and speaker wires short and the same length, and if you can, try and make both channels as symmetrical as possible, experiment with your PS filtering capacitors and bypass them with good grade polypropylenes, also I use a separate shunt regulated PS just for the LM4702.
All the LM4702/SAP's amps I have built have a similar characteristic sound, despite very different power supplies and layouts.
Next amp is a 4702 with 6 pairs of BJT devices to see how this affects the bottom end.
As fun as it is to use crazy expensive parts the law of diminishing returns kicks in to hard and the money could be spent on say another power amp module.
One amp built with a good friend used the same chassis and PS but we built 3 LM4702 boards, one each with FET, BJT, and Sanken darlington outputs so we could quickly compare (btw the SAP Darlington's sounded best)
Good luck with your amp, look forward to seeing the finished product.
Kind Regards
setting bias
Hi, I have built a 2ch amp based on LM4702 and SAP15's
To set the bias I can measure current in one supply rail but how much do I contribute to the LM4702 and can I assume the two SAP pairs draw the same current each ?
Another thought is if the built in resistors are accurate I could measure the voltage between two emitters to calculate bias ? I tried measuring them and my meter wasn't really that accurate ( same resistor gave varying readings ).
Pete
Hi, I have built a 2ch amp based on LM4702 and SAP15's
To set the bias I can measure current in one supply rail but how much do I contribute to the LM4702 and can I assume the two SAP pairs draw the same current each ?
Another thought is if the built in resistors are accurate I could measure the voltage between two emitters to calculate bias ? I tried measuring them and my meter wasn't really that accurate ( same resistor gave varying readings ).
Pete
If you like lateral MOSFET's you can use mine -- here's one fitted into my Pioneer SX-838:
An externally hosted image should be here but it was not working when we last tested it.
I have my LM4702 amp up and running after several hurdles. I would really like to thank jackinnj for all his wonderful help. This is using the AN4442 transformer and 58/60 lateral mosfet configuration. It has 4 analog single ended inputs, ipod dock, remote, front panel lcd that displays input and volume via AtMega128. The sound is amazing. I have it running two Polk Audio RTIA3 bookshelf speakers and couldn't be happier with the sound quality.
Attachments
OT posts moved to:
Hello
My hand s of the IC are the following.
3 pieces LM4702CTA
5 pieces LME49810BTA
5 pieces LME49811BTA
In addition, these transistors are also 5 other units.
MJL21193G
MJL21194G
NJW1302G
NJW3281G
NJW21193G
NJW21194G
NJL0281DG
NJL0302DG
NJL4302DG
NJL4281DG
MJL4281AG
MJL4302AG
MJE15030G
MJE15031G
MJE15032G
Especially liked and has been applied to the circuit drawings made with LM4702CTA Can you share?
Hi all,
Good thread about the LM4702. Still working through the pages. Curious if anyone has used this pre-assembled module for a DIY audio-quality grade amplifier though. I'm looking to build an amp based on this module and was wondering what success anyone has had with this guy. Pictures would be nice too.
Also, what PSU have you used with this module? Thots?
Good thread about the LM4702. Still working through the pages. Curious if anyone has used this pre-assembled module for a DIY audio-quality grade amplifier though. I'm looking to build an amp based on this module and was wondering what success anyone has had with this guy. Pictures would be nice too.
Also, what PSU have you used with this module? Thots?
I remember that National semi has issued newer version of LM4702,they are LM49830 and LM49811.The 830 designed to drive MOSFETs out up to 500 watts,and the 811 designed to drive Bipolar.
Unlike some well known componets as OPA1612,LM4562....,the LM498xx and LM4702 was designed for extreme circuit,but I didn't find any Hi-End "Big block" amplifiers put them in.It's weird.
Unlike some well known componets as OPA1612,LM4562....,the LM498xx and LM4702 was designed for extreme circuit,but I didn't find any Hi-End "Big block" amplifiers put them in.It's weird.
So, you're saying that they have an industrial quality to them - perhaps more than is needed for a typical home audio amp DIY setup? If I were to go with one of these modules, should I use a toroid, or R-core xformer? What secondary voltage should I be looking at for maximum output and to get +-60v rails?
Looking for comments from anyone that has built an amp around this particular module and what xformer and PSU board you may have used. Thx.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.