Dear All,
To make a very compact and easy design I want to use the LME49810 driver with STN03N/P darlington output devices. These have integrated temperature compensation diodes for biasing. So no need for a VBE multiplier. How to do that with the LME49810 which has dedicated bias pins. Let them unconnected?
With kind regards,
Bas
To make a very compact and easy design I want to use the LME49810 driver with STN03N/P darlington output devices. These have integrated temperature compensation diodes for biasing. So no need for a VBE multiplier. How to do that with the LME49810 which has dedicated bias pins. Let them unconnected?
With kind regards,
Bas
Dear,
Thanks for the responses. I did read your very interesting article about your PAX amplifier Janneman. In fact it was your article which inspire me to go with the STD03 devices. The point is, this design have to be extremely compact, nearby the dimensions of a class D amplifier. that is why the choice for a all in one driver chip, and darlingtons with integrated diodes. This way I safe a discrete driver stage. With using Darlingtons I safe space for driver transistors after the LME49819.
But I still wondering how to implement the LME49810. How to use the bias pins? Since biasing is doing direct at the didoes of the STD03 with a resistor (variable pot in this case)
Should i short the bias pins so maximum current is flowing? There must be a way to include the internal diodes of the STD03 in the bias pins circuit as replacement for the VBE multiplier.
I keep you informed, but 'm still not out of this.
With kind regards,
Bas
Thanks for the responses. I did read your very interesting article about your PAX amplifier Janneman. In fact it was your article which inspire me to go with the STD03 devices. The point is, this design have to be extremely compact, nearby the dimensions of a class D amplifier. that is why the choice for a all in one driver chip, and darlingtons with integrated diodes. This way I safe a discrete driver stage. With using Darlingtons I safe space for driver transistors after the LME49819.
But I still wondering how to implement the LME49810. How to use the bias pins? Since biasing is doing direct at the didoes of the STD03 with a resistor (variable pot in this case)
Should i short the bias pins so maximum current is flowing? There must be a way to include the internal diodes of the STD03 in the bias pins circuit as replacement for the VBE multiplier.
I keep you informed, but 'm still not out of this.
With kind regards,
Bas
Dear,
I wanted to post some results about my experiments with the LME49810 chip and the Sanken STD03 darlingtons.
I end up with shorting the BIAS pins of the LME49810, and that gives a forward current flowing of +/- 2,8mA over the diodes in the STD03 die. I'm experimenting with the idle current bias settings. Unlike the older SAP devices the new STD darlingtons don't have the built in emitter resistor anymore (with the risk of blow them) so now it is possible to experiment with higher biasing (In the older SAP devices this higher current will blow up the internal emitter resistor). I found the amplifier sound better with idle current of 50mA.
The sound of this combination is incredible!! It is the most compact amplifier I ever designed and the PCB dimensions can equal an B&O ICE 250A class D module. No longer is class D the only alternative if the circuit have to be very compact.
Hence... The output power is less then a class D design but more then sufficient for the target I design it for. The STD03 devices are very powerful though.
With an idle biasing of 60mA the amplifiers sounds extremely transparent, fast and musical. I could not believe such a simple and compact design can sound so smooth, musical and powerful. the LME chip have some smoothness and classy sound I truly like.
I only use one pair of STD03's.
I will experiment with two pairs in parallel like Jan Didden's PAX design. I know the SAP papers advice a variable resistor per pair when u use more then one pair of darlingtons. But it should be possible to combine the diodes and use only one variable resistor. I know Arcam and Musical Fidelity do it that way also. (this for ease of manufacture process, only one adjusting point)
I will keep u informed and post schematics once the circuit is finalized. I think this is the perfect compromise between the LM3886 chip amps and total discrete. This approach gives just a little bit more freedom in design then the LM3886 chips. Especially in biasing techniques and the freedom to bias the output stage further in class A (what I prefer judging by my ears)
With kind regards,
Bas
I wanted to post some results about my experiments with the LME49810 chip and the Sanken STD03 darlingtons.
I end up with shorting the BIAS pins of the LME49810, and that gives a forward current flowing of +/- 2,8mA over the diodes in the STD03 die. I'm experimenting with the idle current bias settings. Unlike the older SAP devices the new STD darlingtons don't have the built in emitter resistor anymore (with the risk of blow them) so now it is possible to experiment with higher biasing (In the older SAP devices this higher current will blow up the internal emitter resistor). I found the amplifier sound better with idle current of 50mA.
The sound of this combination is incredible!! It is the most compact amplifier I ever designed and the PCB dimensions can equal an B&O ICE 250A class D module. No longer is class D the only alternative if the circuit have to be very compact.
Hence... The output power is less then a class D design but more then sufficient for the target I design it for. The STD03 devices are very powerful though.
With an idle biasing of 60mA the amplifiers sounds extremely transparent, fast and musical. I could not believe such a simple and compact design can sound so smooth, musical and powerful. the LME chip have some smoothness and classy sound I truly like.
I only use one pair of STD03's.
I will experiment with two pairs in parallel like Jan Didden's PAX design. I know the SAP papers advice a variable resistor per pair when u use more then one pair of darlingtons. But it should be possible to combine the diodes and use only one variable resistor. I know Arcam and Musical Fidelity do it that way also. (this for ease of manufacture process, only one adjusting point)
I will keep u informed and post schematics once the circuit is finalized. I think this is the perfect compromise between the LM3886 chip amps and total discrete. This approach gives just a little bit more freedom in design then the LM3886 chips. Especially in biasing techniques and the freedom to bias the output stage further in class A (what I prefer judging by my ears)
With kind regards,
Bas
Hello Bas,
My experience with the Sankens is exactly the same - just about 50-60mA bias per pair sounds best. That's a bit more than the 40mA recommended for zero tempco, but I have never had any problems with thermal runaway anyway.
I am a bit sceptic about 'combining the diodes for a single bias pot', unless you match the output pairs wrt Vbias. You can set the bias that way for two pairs to 120mA, but it will most probably not divide evenly between the two.
But maybe I'm wrong, I haven't tried it yet.
Jan Didden
My experience with the Sankens is exactly the same - just about 50-60mA bias per pair sounds best. That's a bit more than the 40mA recommended for zero tempco, but I have never had any problems with thermal runaway anyway.
I am a bit sceptic about 'combining the diodes for a single bias pot', unless you match the output pairs wrt Vbias. You can set the bias that way for two pairs to 120mA, but it will most probably not divide evenly between the two.
But maybe I'm wrong, I haven't tried it yet.
Jan Didden
Dear Jan,
In first instance I also though it would be impossible (and I didn't tried it myself yet) but then I saw it happened in the Arcam FLM monoblocks and almost al former Musical Fidelity stuff. If you want to I have the scmematics of the Arcam FJM P1 who use the same Sanken Darlingtons. They do something very neat with a opamp configured in a current feedback loop with using the V+ and V- pins.
With kind regards,
Bas
In first instance I also though it would be impossible (and I didn't tried it myself yet) but then I saw it happened in the Arcam FLM monoblocks and almost al former Musical Fidelity stuff. If you want to I have the scmematics of the Arcam FJM P1 who use the same Sanken Darlingtons. They do something very neat with a opamp configured in a current feedback loop with using the V+ and V- pins.
With kind regards,
Bas
Dear,
Today some new experiments. I raise the bias level even more. As an matter of fact. I made a relais switch between the diodes with an extra bypass resistor. This way I can switch between high idle bias and low idle bias. The high bias sounds much better. I'm much higher then advised with around a current 70mA, but it sounds incredible smooth and with so much ambiance and depth.
With kind regards,
Bas
Today some new experiments. I raise the bias level even more. As an matter of fact. I made a relais switch between the diodes with an extra bypass resistor. This way I can switch between high idle bias and low idle bias. The high bias sounds much better. I'm much higher then advised with around a current 70mA, but it sounds incredible smooth and with so much ambiance and depth.
With kind regards,
Bas
Dear All,
Long time no see in this topic. In finished my prototype with the LME49810 and the STD03B/P's. A lot of experiments went into the biasing and the perfect combination of the LME49810 and the STD03's. To little bias in the LME49810's make no bias current flow at all, to much raise the bias to high. It is the trick to find the ideal pre bias current just enough to drive the STD03's diodes and then further bias between the diodes of the STD03's. I will post parts of the schematics tomorrow.
Now the most important part. Biased in class A the sound is really really good. In direct comparison to a 6 parallel/serial LM3886's this combination has a more floating smooth and 3D image. The LME3886's sound flatter and less relaxed (more squeezed) in the mid-highs. I love the LME49810/STD03 sound very much if the biasing is done all right.
Will be continued
With kind regards,
Bas
Long time no see in this topic. In finished my prototype with the LME49810 and the STD03B/P's. A lot of experiments went into the biasing and the perfect combination of the LME49810 and the STD03's. To little bias in the LME49810's make no bias current flow at all, to much raise the bias to high. It is the trick to find the ideal pre bias current just enough to drive the STD03's diodes and then further bias between the diodes of the STD03's. I will post parts of the schematics tomorrow.
Now the most important part. Biased in class A the sound is really really good. In direct comparison to a 6 parallel/serial LM3886's this combination has a more floating smooth and 3D image. The LME3886's sound flatter and less relaxed (more squeezed) in the mid-highs. I love the LME49810/STD03 sound very much if the biasing is done all right.
Will be continued
With kind regards,
Bas
gianxdiy said:
Dear Gianni,
Well the ON-SEMI's have a big benefit that you can actually use the on die diodes in the bias generator since you have access to both sides of the diodes. With the Sankens they are tied internal to the base.
I was very stubborn and ignored the Sanken application note. Namely Bias the system so that you have 2,5mA total through the diodes and 40mA trough the emitter resistors. I attempt to bias the STD03's 10 watt in class A which sounded and measured great! But with such a high bias currents through the diodes the system suffered huge thermal run away and I blow up the output stage. I don't give up on high class A biasing since the sound was so promising. I hope to accomplish this by using an ordinary VBE multiplier in the STD49810 bias circuit to avoid the huge thermal run away. Then bias the sanken's in class A with a potentiometer between the diodes.
I really love the sound of the STED49810 and the sanken STD03's
Keep you informed.
With kind regards,
Bas
homemodder said:
Dear Alex,
http://www.profusionplc.com/pro/gex/prodGen.html?prdtyp=power darlington
Here you go
With best regards,
Bas
homemodder said:
Dear.
I think it depends. They use the TL072 not as a normal voltage opamp but rather as current opamp by using it's supply pins as current outputs. I love the Arcam design in it's capacitorless design and because of the Sanken darlingtons which I simply love in sound quality.
I also find Arcam a very approachable company since they where happy to provide me the schematics. I like their explanation in the first pages about their circuit and I can taste the passion in it. A very well respected company by me
With kind regards,
Bas
Dear,
One question for Jan Didden,
In your PAX article I read about the biasing of the STD03's. You advice a voltage drop of 24mV. over the emitter resistor. In your design you use 0,22 Ohm emitter resistors.
Gives me I=0,024/0,22=0,109 109mA bias idle current. More then twice as much as specified by Sanken. You don't have any problems with Thermal run away?
When I biased as high as 0,6A (don't laugh!) I had HUGE thermal run away and the biasing become very dangerous and rised over 1,2A after heat up But with this high bias the amp sounded really better and THD and IMD dropped on the Audio Precision ATS-1
One last question. How do you measure the voltage drop over the diode string in order to adjust for exact 2,5mA diode forward current? I guess it got wrong there in my experiment.
With kind regards,
Bas
One question for Jan Didden,
In your PAX article I read about the biasing of the STD03's. You advice a voltage drop of 24mV. over the emitter resistor. In your design you use 0,22 Ohm emitter resistors.
Gives me I=0,024/0,22=0,109 109mA bias idle current. More then twice as much as specified by Sanken. You don't have any problems with Thermal run away?
When I biased as high as 0,6A (don't laugh!
) I had HUGE thermal run away and the biasing become very dangerous and rised over 1,2A after heat up But with this high bias the amp sounded really better and THD and IMD dropped on the Audio Precision ATS-1One last question. How do you measure the voltage drop over the diode string in order to adjust for exact 2,5mA diode forward current? I guess it got wrong there in my experiment.
With kind regards,
Bas
Dear All,
As promised here the schematics of my try out with the LME49810 and the STD03 Darlington’s.
My new design philosophy is less is more, and I want to use as less as possible components.
The amp turned out to be stable on most speakers without any filter or zobel on the outputs. I couldn’t measure any oscillation. For extra security I added a Zobel filter. I prefer not to use the typical resistor and inductor in series with the output. Listening experiments turned out that I lost my super tight low end with addition of this filter.
I experiment with many power supplies, and the current one with total 30x 1000uF Panasonic FC elco’s gives a significant tighter low end. (To tight for some taste)
I am still surprised about the sound quality results. We compare this simple amp with many expensive respected amplifiers, and in most cases the LME49810/STD03 amp wins hands down in terms of 3D image speed and bass control. Just with a singe pair of transistors it has an awesome control like the bass is constant in a “rails”
Despite the specified 40mA current through the Re’s I added a relays switch which allow me to switch between a lower and a higher bias setting
With PSU of +/-35VDC and 300V/A transformer I measure 50 watt @ 8 Ohm and 100 watt @4Ohm.
I prefer this setup day and night over the LM3886 chip amp designs, which I also build and compared. The air and 3D spatial imaging in the highs is just better then the LM3886, which the later sounded more “compressed” and flat in comparison.
Never change a winning team the say… But in the next experiment I want to try out to add a pair or two pair of STD03’s and add a separate regulated PSU for the LME49810.
The LME49810 is gold in my opinion!
I keep you informed.
With best regards,
Bas
As promised here the schematics of my try out with the LME49810 and the STD03 Darlington’s.
My new design philosophy is less is more, and I want to use as less as possible components.
The amp turned out to be stable on most speakers without any filter or zobel on the outputs. I couldn’t measure any oscillation. For extra security I added a Zobel filter. I prefer not to use the typical resistor and inductor in series with the output. Listening experiments turned out that I lost my super tight low end with addition of this filter.
I experiment with many power supplies, and the current one with total 30x 1000uF Panasonic FC elco’s gives a significant tighter low end. (To tight for some taste)
I am still surprised about the sound quality results. We compare this simple amp with many expensive respected amplifiers, and in most cases the LME49810/STD03 amp wins hands down in terms of 3D image speed and bass control. Just with a singe pair of transistors it has an awesome control like the bass is constant in a “rails”
Despite the specified 40mA current through the Re’s I added a relays switch which allow me to switch between a lower and a higher bias setting
With PSU of +/-35VDC and 300V/A transformer I measure 50 watt @ 8 Ohm and 100 watt @4Ohm.
I prefer this setup day and night over the LM3886 chip amp designs, which I also build and compared. The air and 3D spatial imaging in the highs is just better then the LM3886, which the later sounded more “compressed” and flat in comparison.
Never change a winning team the say… But in the next experiment I want to try out to add a pair or two pair of STD03’s and add a separate regulated PSU for the LME49810.
The LME49810 is gold in my opinion!
I keep you informed.
With best regards,
Bas
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