Why?
1 - Anaview module has differential inputs and low input impedance.
2 - Anaview modules are located behind my speakers. Short speaker cables.
3 - When I built my preamp with PGA2320 volume control & output buffer it was just as easy to use DRV134 as it would have been to use a single ended output buffer and professional balanced interconnects are cheap.
I have used ALC0300 modules (200W into 8 ohms) and they are the best sounding amps I have owned. With no buffers.
I now have AMS0100 modules in BTL mode and they do not sound as good.
Lack of bass. I was hoping a buffer would improve things by raising the input impedance.
I was going to move the original ALC amps into my hobby room but currently they are reinstated in my lounge.
Mooly;
Yes, I thought of shorting one of the inputs to ground (making it single ended). Didn't know if the DRV134 would tolerate a short on one output. Looking at the data sheet this is the correct way of making it single ended output so an easy poke with a screwdriver test. Or messing with resistor values - I have the circuit reproduced on breadboard so easy to play around.
1 - Anaview module has differential inputs and low input impedance.
2 - Anaview modules are located behind my speakers. Short speaker cables.
3 - When I built my preamp with PGA2320 volume control & output buffer it was just as easy to use DRV134 as it would have been to use a single ended output buffer and professional balanced interconnects are cheap.
I have used ALC0300 modules (200W into 8 ohms) and they are the best sounding amps I have owned. With no buffers.
I now have AMS0100 modules in BTL mode and they do not sound as good.
Lack of bass. I was hoping a buffer would improve things by raising the input impedance.
I was going to move the original ALC amps into my hobby room but currently they are reinstated in my lounge.
Mooly;
Yes, I thought of shorting one of the inputs to ground (making it single ended). Didn't know if the DRV134 would tolerate a short on one output. Looking at the data sheet this is the correct way of making it single ended output so an easy poke with a screwdriver test. Or messing with resistor values - I have the circuit reproduced on breadboard so easy to play around.
That's what I don't understand, I would have thought the DRV134 would have driven the Anaview module with ease. What's the input impedance?
Left -12K5 & 1K4
Right 1K4 & 12K5.
So connecting both together for BTL I reckon 1K2.
Yes I'd have thought it would also.
DRV134 data sheet claims good for 250ft cables into 600 ohms but then says for best results drive a high impedance (9.1 in application notes).
TBH I was surprised to hear any difference between the amps. That.s why I thought I'd try a buffer.
My original ALC amps are not BTL therefore an unequal 12K5 & 1K4 input impedance.
Right 1K4 & 12K5.
So connecting both together for BTL I reckon 1K2.
Yes I'd have thought it would also.
DRV134 data sheet claims good for 250ft cables into 600 ohms but then says for best results drive a high impedance (9.1 in application notes).
TBH I was surprised to hear any difference between the amps. That.s why I thought I'd try a buffer.
My original ALC amps are not BTL therefore an unequal 12K5 & 1K4 input impedance.
Russc, the buffers shown in your previous posts are not equivalent as the non inverting buffer will have a gain of 2. the inverting one will have a gain of 10.
if you use a 47k input resistor on the inverting one, they will almost match gain.
if you use a 47k input resistor on the inverting one, they will almost match gain.
If you just want to buffer your outputs and do not need any gain or gain reduction then you do not need any circuit components except the 5532 and a cap directly across the PS supply pins to it. The schematic is input to the non inverting input, and feedback directly from the output to the input. Since this is exactly unity gain, you simple use the dual-amplifier 5532 to implement one of these buffers on each of the (+) and (-) signal lines separately.
Used in this "follower" configuration, the 5532 is very good. You could add a 10k resistor from the inverting input to ground if the network leading up to it does not have any grounded connection.
Hi Charles.
Yes, I can and probably will implement a non-inverting buffer - I have already breadboarded it.
We are puzzling over why the inverting buffer does not work in differential/balanced mode.
Yes, I can and probably will implement a non-inverting buffer - I have already breadboarded it.
We are puzzling over why the inverting buffer does not work in differential/balanced mode.
Try the two buffers separately. Balanced inputs and outputs are fine but You should still get sound if You connect one of the outputs to ground.
Sorry, You should not short the output of any of the buffers of course. What I meant was that You could connect one of the inputs to following stage to ground.
My guess is that it is a wiring mistake.
Sorry, You should not short the output of any of the buffers of course. What I meant was that You could connect one of the inputs to following stage to ground.
My guess is that it is a wiring mistake.
Last edited:
I thought I ought to update this post.
I built input buffers on stripboard - 1 dual op-amp per channel, non-inverting, differential buffer.
I built one channel first - checked for shorts + to -. Didn't check for shorts supply to ground. Blew onboard supply fuse. Luckily, no damage apart from SMD fuse. Sorted short, all worked & sound good. De-cased the circuit so I could copy for second channel. Found supply wires had been burning - probably melted pvc when soldering. Cleaned off the soot, rebuilt first buffer and built the second. Added sockets for connections - M/F for in/out so I have the possibility of easily comparing with/without buffer. With both channels running the amps sound great. One day I'd like to do a frequency test to compare with /without buffer to prove I'm not imagining the difference.
I built input buffers on stripboard - 1 dual op-amp per channel, non-inverting, differential buffer.
I built one channel first - checked for shorts + to -. Didn't check for shorts supply to ground. Blew onboard supply fuse. Luckily, no damage apart from SMD fuse. Sorted short, all worked & sound good. De-cased the circuit so I could copy for second channel. Found supply wires had been burning - probably melted pvc when soldering. Cleaned off the soot, rebuilt first buffer and built the second. Added sockets for connections - M/F for in/out so I have the possibility of easily comparing with/without buffer. With both channels running the amps sound great. One day I'd like to do a frequency test to compare with /without buffer to prove I'm not imagining the difference.
Great to hear you have it all working 
It is always good to test projects objectively, even simple ones.
It is always good to test projects objectively, even simple ones.I need a unity buffer for Anaview ams0100 as well. Nice to know its working well for you.
What is the purpose of the 100pf cap across the 100k as suggested in the anaview datasheet. Not really important?
Anyway my main question is regarding psu bypass caps. Did you use any on your buffer?
Lots of suggestion on NE5532 requiring supply bypass caps, including the datasheet.
Not sure if the anaview aux psu doesn't need bypass caps any less than others, but not very likely.
What is the purpose of the 100pf cap across the 100k as suggested in the anaview datasheet. Not really important?
Anyway my main question is regarding psu bypass caps. Did you use any on your buffer?
Lots of suggestion on NE5532 requiring supply bypass caps, including the datasheet.
Not sure if the anaview aux psu doesn't need bypass caps any less than others, but not very likely.
If you mean the 100pF as shown in the diagram in post #2 then it could actually be very important. Its purpose is to roll off and prevent unwanted high frequencies entering the input of the chip.
Rightly or wrongly I put 10uF from +ve to 0v & -ve to ov.
I put 0.1uF ceramic between + & - pins of op-amp on reverse of pcb.
I put 0.1uF ceramic between + & - pins of op-amp on reverse of pcb.
Thanks Mooly, I intend to keep the 100pF.
Russc, thanks for sharing.
Ti datasheet for NE5532 recommends 0.1uF low ESR ceramic +V to Gnd and -V to Gnd.
10uF seems good too as it is often used in this.
Maybe it is overkill to add the 0.1uF cap across the power supply pins, but don't think it required to be removed once in place.
Russc, thanks for sharing.
Ti datasheet for NE5532 recommends 0.1uF low ESR ceramic +V to Gnd and -V to Gnd.
10uF seems good too as it is often used in this.
Maybe it is overkill to add the 0.1uF cap across the power supply pins, but don't think it required to be removed once in place.
think of the decoupling as the sole charge to power the chip for a few microseconds.
The two HF decoupling capacitors are connected together.
The outers are connected to the power pins.
This +power pin > cap > cap > -power pin route must be very short to minimise inductance.
The junction between the two caps is the Power Ground.
All output current from the chip must return to this Power Ground and into the capacitor which was the current source.
The above considers the capacitor as the source of current and that current MUST RETURN to the capacitor.
One capacitor (of the pair) sources the +ve half-wave output current. The other capacitor source the -ve half-wave output current.
That HF decoupling handles the ultra short duration current transients.
Repeat the process for the MF decoupling using higher capacitance and allowing slightly longer circuit routes. The junction between the MF decoupling capacitors needs to be connected to the junction between the HF decoupling capacitors.
The amplifier now has a low impedance "point" for the HF transients and a low impedance "point" for the MF transients.
All the chip output current has to return to this low impedance "point".
So we have two HF capacitors and two MF capacitors and the output return lead all meeting at this point.
There are two more connections. The amplifier output Zobel only operates at high frequencies and needs to connect to this low impedance point.
Finally we have the PSU Zero Volts feed to make up the seventh connection.
I think of a power amplifier on the same lines. The amp/opamp outputs a current and that current MUST RETURN to it's Source.
The two HF decoupling capacitors are connected together.
The outers are connected to the power pins.
This +power pin > cap > cap > -power pin route must be very short to minimise inductance.
The junction between the two caps is the Power Ground.
All output current from the chip must return to this Power Ground and into the capacitor which was the current source.
The above considers the capacitor as the source of current and that current MUST RETURN to the capacitor.
One capacitor (of the pair) sources the +ve half-wave output current. The other capacitor source the -ve half-wave output current.
That HF decoupling handles the ultra short duration current transients.
Repeat the process for the MF decoupling using higher capacitance and allowing slightly longer circuit routes. The junction between the MF decoupling capacitors needs to be connected to the junction between the HF decoupling capacitors.
The amplifier now has a low impedance "point" for the HF transients and a low impedance "point" for the MF transients.
All the chip output current has to return to this low impedance "point".
So we have two HF capacitors and two MF capacitors and the output return lead all meeting at this point.
There are two more connections. The amplifier output Zobel only operates at high frequencies and needs to connect to this low impedance point.
Finally we have the PSU Zero Volts feed to make up the seventh connection.
I think of a power amplifier on the same lines. The amp/opamp outputs a current and that current MUST RETURN to it's Source.
Last edited:
Andrew T,
Thanks for your sharing.
For the purpose in hand, ie NE5532 unity buffer, what value would you recommend for the HF and MF decoupling capacitors.
And is a zobel network really required in this application?
Thanks for your sharing.
For the purpose in hand, ie NE5532 unity buffer, what value would you recommend for the HF and MF decoupling capacitors.
And is a zobel network really required in this application?
The recommended HF and MF decoupling is usually in the manufacturer's datasheet.
It is unusual to need an Output Zobel for opamps.
Discrete opamps may well require an Output Zobel.
It is unusual to need an Output Zobel for opamps.
Discrete opamps may well require an Output Zobel.
I'm quite surprised that this thread has garnered 77 posts for a NE5532 op-amp based buffer that in the end will only sound "fair" at best.
Simply amazing...
Simply amazing...
I'm quite surprised that this thread has garnered 77 posts for a NE5532 op-amp based buffer that in the end will only sound "fair" at best.
Simply amazing...
Perhaps your pockets are deeper than mine then......
If you've nothing to add in a positive way then maybe you should refrain from passive aggressive posts.....
Other posters are genuinely trying to help... pay attention and you could learn something from them...
Last edited:
What about Nichicon VR P.E.T. (Polyethylene) that look like electrolytic cans? (What exactly is the construction? They are polar, look like electrolytic cans but are marked P.E.T.)
I have probably 50 of those caps on the video board of a defunct receiver that I recycled as a case for a project amplifier. I assume they are used in the video section due to good high frequency characteristics?
I was thinking of using those as coupling caps in two preamps I am working. (One is NE5532 like the MBL6010 and the other is a diamond buffer like HDAM SA3. I wanted to compare the two side by side.)