What diodes are bolted onto the Sanken outputs there? Like a MUR860 or something?
After scouring this thread for a while I have my LME boards and the 2 pair output boards on order with Panson.
Now I need to decide do I go with Thermal Track outputs(Sanken) or BJT(most likely the Sanken 2SA1295/2SC3264)
I am leaning towards the LME49811.
I have an 800W +/- 60V SMPS that needs a home
Ample heatsink chassis
Speakers are 4 ohm 2-way bookshelves at about 90dB
Casual low to medium volume listening
Any other considerations?
Now I need to decide do I go with Thermal Track outputs(Sanken) or BJT(most likely the Sanken 2SA1295/2SC3264)
I am leaning towards the LME49811.
I have an 800W +/- 60V SMPS that needs a home
Ample heatsink chassis
Speakers are 4 ohm 2-way bookshelves at about 90dB
Casual low to medium volume listening
Any other considerations?
+-60Vdc and 4ohms speaker is a lot of power.
Expect a maximum output from a +-60Vdc supply to be around 45Vpk to 50Vpk
Those are equivalent to 253W into 4ohms and 312W into 4ohms.
What is the recommended maximum power input for your speaker?
BTW,
I got ~310W into 4r0 with a +-58.5Vdc supply (from a 40-040Vac transformer)
Expect a maximum output from a +-60Vdc supply to be around 45Vpk to 50Vpk
Those are equivalent to 253W into 4ohms and 312W into 4ohms.
What is the recommended maximum power input for your speaker?
BTW,
I got ~310W into 4r0 with a +-58.5Vdc supply (from a 40-040Vac transformer)
WOW, yes I figured it would be quite a bit. I cant find the paperwork on the tweeters but the woofers are rated for 120W max.
I know I will need to be careful.
I would prefer to get the amp up and running with the components I have and then optimize later. I dont really have any other use for that SMPS and it wasnt cheap.
I know I will need to be careful.
I would prefer to get the amp up and running with the components I have and then optimize later. I dont really have any other use for that SMPS and it wasnt cheap.
was reading all the 545 replies and just finished it. I have few questions as I have built the LME49810 I have used it in the following way..
PCB 2 Layer
https://dl.dropboxusercontent.com/u/7421969/pcb2L.jpg
points considered
1. Decoupling caps being close to pins
2. Star ground
3. Near symmetrical output stage
1. used two R core trafos for the psu with Driver psu being 55V and Output stage at 50V
2. I have no ground loops observed even without the ground being connected to the chassis.
3. I have some hiss coming from the tweeter when I get close enough to 10cm and its perceivable. I am thinking that it might be coming from the Psu ( The psu has 4 100nF bypasses for the bridge and a 2k2 5W wire wound bleeder and one 1ohm wirewound with 100nF as snubber. Is that the reason for the hiss? Its not perceived at the listening position of 7ft but when you go closer we can clearly observe it.
4. Do we need to isolate the two ground points of the driver and the output? As its powered with two transformers.
5. Do we need to use a choke for the ground connection between the signal ground and the power ground? Is it ok if we completely isolate the both grounds? or we have to have them connected? Right now its used as first all the signal grounds and driver power grounds are connected and then both together is connected to the output stage power ground.
6. Now I am planning to move to 4 layer pcb as its said that the Noise floor is much better in that case it said that one single unbroken ground plane is used in common for both. Is it recommended that we split it into two and use in the above way
like output stage power ground on left side of the above pcb and signal ground with driver power ground on the right side of the pcb and then connect using a choke or may be just short it with a 2mm pcb trace.
what do you recommend. I feel Mr Sebastiaan or even Andrew Audioman54 Panson all you are quite experienced in LME chips please guide me how to deal with the 4 layer grounding aspect.
Eliminating the Hiss is becoming one challenge I admit that one will have some hiss in any amp but it should be audible only when we come very close as much as 3 to 5 cm to tweeter.
PCB 2 Layer
https://dl.dropboxusercontent.com/u/7421969/pcb2L.jpg
An externally hosted image should be here but it was not working when we last tested it.
points considered
1. Decoupling caps being close to pins
2. Star ground
3. Near symmetrical output stage
1. used two R core trafos for the psu with Driver psu being 55V and Output stage at 50V
2. I have no ground loops observed even without the ground being connected to the chassis.
3. I have some hiss coming from the tweeter when I get close enough to 10cm and its perceivable. I am thinking that it might be coming from the Psu ( The psu has 4 100nF bypasses for the bridge and a 2k2 5W wire wound bleeder and one 1ohm wirewound with 100nF as snubber. Is that the reason for the hiss? Its not perceived at the listening position of 7ft but when you go closer we can clearly observe it.
4. Do we need to isolate the two ground points of the driver and the output? As its powered with two transformers.
5. Do we need to use a choke for the ground connection between the signal ground and the power ground? Is it ok if we completely isolate the both grounds? or we have to have them connected? Right now its used as first all the signal grounds and driver power grounds are connected and then both together is connected to the output stage power ground.
6. Now I am planning to move to 4 layer pcb as its said that the Noise floor is much better in that case it said that one single unbroken ground plane is used in common for both. Is it recommended that we split it into two and use in the above way
like output stage power ground on left side of the above pcb and signal ground with driver power ground on the right side of the pcb and then connect using a choke or may be just short it with a 2mm pcb trace.
what do you recommend. I feel Mr Sebastiaan or even Andrew Audioman54 Panson all you are quite experienced in LME chips please guide me how to deal with the 4 layer grounding aspect.
Eliminating the Hiss is becoming one challenge I admit that one will have some hiss in any amp but it should be audible only when we come very close as much as 3 to 5 cm to tweeter.
possibly due to oscillation and or ringing on the DC supply.
Remove the capacitors and if you need add a snubber (NOT capacitors).
The excess noise could be due to inappropriate resistor values, or inappropriate nose gain or simply a mistake on your part.
Have you measured the noise+hum on the output?
Have you measured the output offset?
Did you do these BEFORE attaching a speaker?
Last edited:
The amp is perfectly stable without any oscillation.
There is absolutely no hum on the output.
The output offset is 2mV
Initially the amp is tested for it generic stability and then set the bias to 60ma with inputs being shorted and the output being connected to a very cheap speaker and once the bias was stable then connected to a highend speaker.
All stable playing everything very good.
Its not excess hiss its there but not audible at listening position.
Why to forget the 4 layer pcb? why not Bas has built it with 4702 resulting very good performance.. I get my pcbs done by professionals who do alot of RF PCBs.
Last edited:
You actually can use a ground-plane with excellent results. I finally bite the bullet and went for ground-plane topology, after being told many times ground-planes are no good for amplifiersBruno Putzeys from Hypex finally convinced me, and thought us how to do it.
If you take very good care about placement of components, (start with a empty piece of paper and draw out the ground loops out). Another point, my amplifiers are all feed balanced, so the negative input reference to the output of the driver opamp instead of the ground-plane. That can be the biggest reason why I don't have any ground-loop related hum.
I used the LM4702 in a multichannel amplifier application, with one unbroken total ground-plane, and the THD measurements are below the limits of what I am able to measure (0.0005%). I never achieved this results with star grounding. Noise floor is inaudible low.
Second benefit, I can put my cellphone in front of the circuit and no "buzz" anymore over the speakers.
A ground-plane design does sound different then a star-ground design. The same circuit with ground-plane sound more analytical, and a more airy in the high-end. and it seems subjectively speaking, more resolving details. Most strange was that the bass seemed a factor 10 tighter with the ground-plane. Can't really explain why in technical terms, but it was very noticeable in a listening panel of people.
One other note though, my design is a 4 layer board, and all high current supply lines and loudspeaker lines are all stacked on top of each other and are kept away from the LM4702 and other low current stages. Magnetic influences are minimized.
My opinion is, with careful design and routing, one can make superior results with ground-plane topology, and the LM/LME driver chips can work perfectly with ground-planes.
There is a understandable "fear" fro ground-planes, but we should overwin those, learn from RF experts and papers and give it a try.
With kind regards,
Bas
Bas can you please share the pcb view of the 4 layer ones ? that gives a good idea how to use the ground plane.
Have you tried connecting the signal negative pin to the ground instead of balanced input?
If you are using a balanced input your input capacitors will be very high value not so easy to get in film caps like polypropylene so have you used electrolytic at the intput of the driver?
You asked.
Read what I posted.
I referred to oscillation on the DC supply.
I suggested you remove the capacitors that could be causing this oscillation.
Instead you come back with some other statement.
snubber is already there. Which capacitors to be removed if so?
http://www.ti.com/lit/an/snaa057b/snaa057b.pdf
I have used the same pow supply design but removed the automatic muting when power is turned of to eliminate the strange PSU caps discharging noise while discharging when power is turned off.
http://www.ti.com/lit/an/snaa057b/snaa057b.pdf
I have used the same pow supply design but removed the automatic muting when power is turned of to eliminate the strange PSU caps discharging noise while discharging when power is turned off.
Last edited:
A snubber is a resistor. It loads the supply/circuit and damps the oscillation.
A capacitor does not snub.
I quote your section3 in my reply, post547.
It shows you have added capacitors. Remove them, all of them.
A capacitor does not snub.
I quote your section3 in my reply, post547.
It shows you have added capacitors. Remove them, all of them.
1r0+100nF is probably too low a resistance. Is it attached to the transformer lead outs?
is excess noise. Measure it.
Last edited:
Measurement Numbers pls, not what your ear hear.
Suggest to use Quasimodo to determine the optimum snubber components for the specific transformer.
I believe AndrewT has a LME49830 design using OPC wireamp, what is its noise measurement?
Assumption is to compare similar test setups using ANSI "A" noise weighting filter, shorted input. See if they match the device spec's?
As a reference, the Elektor Qwatt has
• Signal to noise ratio: > 94 dB (linear, B = 22 Hz to 22 kHz)
(reference 1 W / 8 Ω) > 97 dBA
It uses a LME49811 and 15K/390 as feedback values and a 15K input R.
Happy new Year everyone!!
Suggest to use Quasimodo to determine the optimum snubber components for the specific transformer.
I believe AndrewT has a LME49830 design using OPC wireamp, what is its noise measurement?
Assumption is to compare similar test setups using ANSI "A" noise weighting filter, shorted input. See if they match the device spec's?
As a reference, the Elektor Qwatt has
• Signal to noise ratio: > 94 dB (linear, B = 22 Hz to 22 kHz)
(reference 1 W / 8 Ω) > 97 dBA
It uses a LME49811 and 15K/390 as feedback values and a 15K input R.
Happy new Year everyone!!
Last edited:
This is something to be considered? like take to 2.5ma of output current where it will be in class A if im not wrong and then switches to class B.
So if this is driving a driver consider 2sc5171 with beta being worst at 50 then the output of the drive will be 0.125A and with output transistors with beta even consider 50 avg so it will be 6.25A wouldnt that be sufficient?
Yes when you crank beyond 100W yes I believe it will switch to class B but yes even I would prefer atleast 8ma.
Lets see what experienced say about this putting Rsb to 680 ohm. Yes consider the heatsink is large enough. But adding just a heatsink wouldnt be sufficient when the mode of operation is in class b after 2.5ma.
I am more curious how to get the drivers 2sc5171 to be driven in class A.
Any possibility?
Hi panson where is C8 placed in the circuit I cant see any of your circuit posted here.
Is this the same C8 in this circuit?
what should be the voltage ratings of C8 cap in the circuit?
http://www.pansonaudio.com/Docs/Kits/Initial Power Amp/Initial_DriverBoard_rev1p4.pdf
Last edited:
Yes, it is. A good quality film cap of 50V is fine. The voltage across this cap (pin BIAS_P and BIAS_M) is not high.
Do you have a copy of LTspcie? You can run simulation to figure out how much idle current is needed for the driver stage. If the driver (assumed EF) emitters are not connected to output, driver will never turn off.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.