Lm4702

[SpittinLLama]

It will work just fine. Take Jack's suggestion on the cap across the Source/Sink pins. You might want to try different values like a small pF range cap and then maybe a larger value (uF). Different combinations and values will allow you to get good results.

For sure go for a potentiometer for the bias resistor, 500 - 1K ohms will be plenty. These devices only need about 1V across them to get around 100mA of bias current. You might also want the gate resistors to be 500ohm pots you can adjust.

Have some small silve mica caps for the compensation capacitor (C3, C4). You won't be able to get great slew rates driving the FETs directly so you may want to reduce these capacitors to as low as 10pF.

The whole design is pretty sensitive to layout so be careful about routing power and GNDs. I would plan some places for supply decoupling capacitors on each output device.

Tell us how it goes.
-SL

 

[monkey29]

MOSFET can use simplified circuit

When using MOSFET output level, the "G" of the MOSFET not need for gate current,
so can the use of OP amplifier output with MOSFET drivers directly.

But input capacitance , MOSFET than Bipolar transistors much, and so should be provided by the OP amplifier capacitance transient charge and discharge currents. Therefore, OP amplifier directly with MOSFET drivers, worried about its stability and high frequency characteristics.

 

[space]

PS: On output you see 10E resistors. However theyre coils not resistors. [/B]

Are you sure that it isn't both. Often the output use a 10ohm resistor with a coil wraped around it.

space

 

[Dxvideo]

Dear friends,

I am not experienced on transistor or MOS designs. So I copied that circuit from a friend.

First; I dont know what C3/C4 are for? Theyre a kind of stabilisator and to prevent high frequency oscillations? If they are, then if I use larger values that causes reducing the frequency response. Is it?

And L1 on outputs. Yes theyre not only coil. Theyre coil around on a 10R resistor.

 

[jackinnj]

Re: MOSFET can use simplified circuit

When using MOSFET output level, the "G" of the MOSFET not need for gate current,
so can the use of OP amplifier output with MOSFET drivers directly.

But input capacitance , MOSFET than Bipolar transistors much, and so should be provided by the OP amplifier capacitance transient charge and discharge currents. Therefore, OP amplifier directly with MOSFET drivers, worried about its stability and high frequency characteristics.

To optimize slew rate with stability some compensation of the feedback loop is necessary when using MOSFETs.

 

[ttan98]

jackinnj,

I have bought LM4780 boards from you before, I am looking at LM4702 driver board, my query to you is would this driver better partner with mosfet or transister esp. the Sanken. Is there any big differences in sound quality or just perferences, ie individual tastes. Even with different o/p devices does the LM4702 has similar sound character or signature to the LM3886 or Lm4780.

Would be able to summarise the advantages and disadvantages of each type? I am interested.

Thanks

 

[lonewolf]

power darlington

hello...what would be a good combination to make a power darlington using the 2sc5200 as the second transistor....would anything be better than a mpsa42 for the first one if I want high voltage capabilities?

 

[AndrewT]

Hi Lonewolf,
you got it just right

anything be better than a mpsa42

 

[tryonziess]

small devices

soldering the dip. i have found that stripping out the lead on a thermocouple which is hollow and inserting and soldering the ic to it makes a good junction and it will stay on the legs while you solder. the thermocouple leads come in very small diameters.

 

[monkey29]

new LM4702 + SAP15

new LM4702 + SAP15

 

[jackinnj]

Re: new LM4702 + SAP15

new LM4702 + SAP15

I've been trying to get the replacement for the SAP15 which is rendered obsolete by the manufacturer.

 

[ttan98]

jackinnj ,

any difference in sound quality between mosfet and sanken, sap(I presume)? or just for individual taste?

I ask you this question in my last email, so far no response from you.

thanks

 

[jackinnj]

I was at a graduation in Pittsburgh -- I don't know how you can describe it in words as I am not a reviewer for Stereophile -- the MOSFET version is really excellent -- I stopped working with the SAP devices when they were discontinued -- and I haven't been able to source samples in the U.S. If and when I get some samples I will do more work with the Sanken products.

I've been playing around with a totem driver for the less expensive IRF-Vishay HexFETS -- works as a prototype so I had some burned.

 

[monkey29]

Re: Re: new LM4702 + SAP15

I've been trying to get the replacement for the SAP15 which is rendered obsolete by the manufacturer.

Different output stage and have different voice colors, Different people have different interpretations.

 

[ttan98]

monkey59,

I agree with, maybe someone write a summary on the comparison. It would be interesting.

 

[monkey29]

Seeking common ground while reserving differences

Different voice characteristics, composition of the wonderful world of voice.
I understand that this is a DIY audio spirit. Thanks.

 

[SpittinLLama]

Looks like this appeared on the 28th but I just noticed it today:

http://www.national.com/pf/LM/LME49810.html

LME49830, mono driver, same 200V ability but with 60mA output current, a Baker clamp and a clip indicator. I'm not sure what exactly a Baker clamp is (besides reading a wiki). Clip indicator might be nice for DIY or I guess you could use it for some sort of control. Wonder how this sounds compared to the LM4702.

Also found a new LM4702 app note (May 24th): Found it here:

http://www.national.com/apnotes/AudioDrivers_150V__v1.html

Since some are using are trying to use FETs with the LM4702 it might be of interest.

-SL

 

[jackinnj]

These two articles are well worth reading...will anxiously await the forthcoming article on compensating the LM4702.

...and again, I don't want the LM4702 heatsinked on the same piece of aluminum as the output devices.

 

[Nordic]

Can't wait to test one of these...

General Description

--------------------------------------------------------------------------------

The LME49810 is a high fidelity audio power amplifier driver designed for demanding consumer and pro-audio applications. Amplifier output power may be scaled by changing the supply voltage and number of power transistors. The LME49810¡¯s minimum output current is 50mA. When using a discrete output stage the LME49810 is capable of delivering in excess of 300 watts into a single-ended 8§Ù load.

Unique to the LME49810 is an internal Baker Clamp. This clamp insures that the amplifier output does not saturate when over driven. The resultant ¡°soft clipping¡± of high level audio signals suppresses undesirable audio artifacts generated when conventional solid state amplifiers are driven hard into clipping.

The LME49810 includes thermal shutdown circuitry that activates when the die temperature exceeds 150¡ÆC. The LME49810¡¯s mute function, when activated, mutes the input drive signal and forces the amplifier output to a quiescent state.

 

[glennb]

New thread for LME49810

Looks like this appeared on the 28th but I just noticed it today:
http://www.national.com/pf/LM/LME49810.html

(sic) LME49830, mono driver, same 200V ability but with 60mA output current, a Baker clamp and a clip indicator. I'm not sure what exactly a Baker clamp is (besides reading a wiki). Clip indicator might be nice for DIY or I guess you could use it for some sort of control. Wonder how this sounds compared to the LM4702.
-SL

I started a new thread on the LME49810 at http://www.diyaudio.com/forums/showthread.php?s=&threadid=102973