I have one set of buffers in a separate case, with a separate +/-15v PSU. I'm sure that I don't need to show anybody how that would be wired up! 
If you want to put a pot in the same box, simply wire it in between the RCA input sockets and the buffers.
The buffers in the DAC are turning out a bit more tricky as I have some hum that is proving difficult to get rid of!
If you want to put a pot in the same box, simply wire it in between the RCA input sockets and the buffers.
The buffers in the DAC are turning out a bit more tricky as I have some hum that is proving difficult to get rid of!
Hi all,
It seems to me, though of course I'm probably wrong, that what is wanted from the PR buffer is the LPF filter i.e. the 75R + the 47n.
Would it be possible to insert these two into the input of a IGC or NIGC after the Potentiometer but before the input resistor, as in the DecDun schematic here: Building a buffered Gainclone chip amp. ?
Jim
It seems to me, though of course I'm probably wrong, that what is wanted from the PR buffer is the LPF filter i.e. the 75R + the 47n.
Would it be possible to insert these two into the input of a IGC or NIGC after the Potentiometer but before the input resistor, as in the DecDun schematic here: Building a buffered Gainclone chip amp. ?
Jim
In my view you are mixing up different concepts.
A power amplifier needs filters at it's input. I prefer both low pass and high pass to allow the amplifier to properly work with wide band audio signal.
A source needs adequate current capability to drive the load. The load seen by the source is a combination of the cable impedance, the filters before the power amp and the Power Amp input impedance.
If a buffer is needed to enhance the sources ability to drive current then the buffer needs to be at the source end of the cable, not in front of the power amplifier.
If the source has adequate current capability then a source buffer is not required and still it holds true that the power amplifier will not benefit from an added buffer stage in front of it.
A power amplifier needs filters at it's input. I prefer both low pass and high pass to allow the amplifier to properly work with wide band audio signal.
A source needs adequate current capability to drive the load. The load seen by the source is a combination of the cable impedance, the filters before the power amp and the Power Amp input impedance.
If a buffer is needed to enhance the sources ability to drive current then the buffer needs to be at the source end of the cable, not in front of the power amplifier.
If the source has adequate current capability then a source buffer is not required and still it holds true that the power amplifier will not benefit from an added buffer stage in front of it.
Last edited:
Dear Andrew,
Alas your obfuscations do not answer the question I asked.
But it seems to me from your answer there needs to be a length of cable between the buffer and the GC, would a couple of inches be OK [if they were in the same box] or would 2 feet [600mm] be more like it?
Jim
A simple yes or no would have been quite sufficient
Alas your obfuscations do not answer the question I asked.
But it seems to me from your answer there needs to be a length of cable between the buffer and the GC, would a couple of inches be OK [if they were in the same box] or would 2 feet [600mm] be more like it?
Jim
A simple yes or no would have been quite sufficient
Last edited:
R,
thanks for listening, others don't.
I will explain further.
A Power Amplifier using a chipamp in inverting topology has a lowish input impedance.
Power Amplifiers of this type can rarely be driven by Domestic Sources.
If the Domestic Source (or any Source) cannot drive the cable//the input filters//the inverting input impedance, then there are at least two solutions.
Sort the Source or sort the Power Amplifier.
Cordell's balanced adapter to hang on the front of the Power Amplifier is typical case where one of these solutions has been adopted.
He choose to increase the input impedance of the inverting input (-IN) to a more normal input impedance that can be driven by most Sources and at the same time incorporates circuit trimming to ensure that the balanced impedances seen by the balanced source are actually balanced (equal in value).
thanks for listening, others don't.
I will explain further.
A Power Amplifier using a chipamp in inverting topology has a lowish input impedance.
Power Amplifiers of this type can rarely be driven by Domestic Sources.
If the Domestic Source (or any Source) cannot drive the cable//the input filters//the inverting input impedance, then there are at least two solutions.
Sort the Source or sort the Power Amplifier.
Cordell's balanced adapter to hang on the front of the Power Amplifier is typical case where one of these solutions has been adopted.
He choose to increase the input impedance of the inverting input (-IN) to a more normal input impedance that can be driven by most Sources and at the same time incorporates circuit trimming to ensure that the balanced impedances seen by the balanced source are actually balanced (equal in value).
Last edited:
Hi Andrew
I always wondered if we should place a buffer on the input of the amp or at the output of the source.... You cleared that perfectly... The buffer also takes care of the cable´s resistance and inductance.
So Cordell´s balanced adaptor works like a buffer that he places in front of the low inpedance imput amp right ?
I always wondered if we should place a buffer on the input of the amp or at the output of the source.... You cleared that perfectly... The buffer also takes care of the cable´s resistance and inductance.
So Cordell´s balanced adaptor works like a buffer that he places in front of the low inpedance imput amp right ?
The + - 15v PSU is ready, the case already has the rca´s, the ELMA switch and the ALPS pot.
Looking carefully at Justblair´s PCB, I see there is no connection between the PSU GND and the In/Out GND.
Should I connect both GND to the case earth or should I leave the PSU "floating" ?
I suspect that if I do not connect the Input / Output GND to the PSU GND, I might have no sound at all.
What are your experiences ?
Looking carefully at Justblair´s PCB, I see there is no connection between the PSU GND and the In/Out GND.
Should I connect both GND to the case earth or should I leave the PSU "floating" ?
I suspect that if I do not connect the Input / Output GND to the PSU GND, I might have no sound at all.
What are your experiences ?
I figured out the GND connections and...... It´s alive.
To power the buffers, I used a double winding TX, double rectifier bridges, double smoothers and two positive SSLV1.
The switch is by ELMA and the pot is a 50k ALPS.
Now connected between an AIWA tape deck and a B&O amplifier.... Incredible clarity.
I will now build a DCB1 to compare
To power the buffers, I used a double winding TX, double rectifier bridges, double smoothers and two positive SSLV1.
The switch is by ELMA and the pot is a 50k ALPS.
Now connected between an AIWA tape deck and a B&O amplifier.... Incredible clarity.
I will now build a DCB1 to compare
Pedja's buffer combined with a NIGC is a realy good combo. In fact he has a few special tricks to get ecvery ounce of quality out of it.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.