Benb thanks for your reply.
Over the past 25 years I have built several solid state power amplifiers, both bi-polar and
power mosfet types.
On all of them I used a 220uF low ESR electrolytic capacitor for feedback decoupling.
I found that using a 220uF capacitor improved bass response compared to a lower value as often shown on many circuit diagrams.
Also I leave out the input DC blocking capacitor and DC couple the power amplifier to my OP27GN pre-amplifier.
Also my pre-amplifier has no input DC blocking capacitor.
This brought about a huge increase in sound quality across the whole of the audio spectrum.
I realised that DC blocking capacitors aren't required as I always incorporate DC offset loudspeaker protection.
I have also carried out these simple modifications on two MXF900 commercial mosfet power amplifiers which has brought about an enormous improvement in sound quality.
Over the past 25 years I have built several solid state power amplifiers, both bi-polar and
power mosfet types.
On all of them I used a 220uF low ESR electrolytic capacitor for feedback decoupling.
I found that using a 220uF capacitor improved bass response compared to a lower value as often shown on many circuit diagrams.
Also I leave out the input DC blocking capacitor and DC couple the power amplifier to my OP27GN pre-amplifier.
Also my pre-amplifier has no input DC blocking capacitor.
This brought about a huge increase in sound quality across the whole of the audio spectrum.
I realised that DC blocking capacitors aren't required as I always incorporate DC offset loudspeaker protection.
I have also carried out these simple modifications on two MXF900 commercial mosfet power amplifiers which has brought about an enormous improvement in sound quality.
Yes, claiming a "a huge increase in sound quality across the whole of the audio spectrum" by omitting an input coupling capacitor is not a technical contribution; it is wishful thinking. How about saying 'a tiny change in bass response' instead?
This is all well and good, though knowing the resistance/impedance associated with each capacitor helps determine the exact effect. For the feedback cap, the R in series (such as R2 in post #214) along with the capacitance value determines the low frequency cutoff.
I understand what you are saying regarding the input capacitor.
However, a very short piece of copper wire must surely be better than a capacitor. The copper wire doesn't have a frequency dependant reactance across the audio spectrum and doesn't introduce any phase shift either.
My comment regarding the sound quality does produce a considerable improvement in bass extension. However, to my ears and the ears of my friends there is a good improvement in the mid and treble clarity.
These improvements are based upon listening tests not wishful thinking.
For my listening tests I'm using a pair of Tannoy Canterbury GR speakers.
Maybe you think the Tannoy's aren't good enough to show up the difference in which case perhaps you could recommend speakers that are good enough.
Ten years ago I designed and published an improved crossover circuit for the
3828 Tannoy Dual Concentric speakers.
My improved crossover has been copied by many people who are very pleased with the performance compared to the original Tannoy crossover.
Now if that's not technical enough for you then please explain what is.
You could get more phase shift by moving your head a few cm. "A considerable improvement in bass extension", if real, means that the original capacitor was the wrong value.Chiefmegawatty said:
Jan was commenting on your contribution to this thread. As you are new here none of us have any idea about your previous contributions elsewhere. The fact that something in audio has been copied by others means nothing; there are sections of the audio world where daft ideas are more popular than sensible ideas, and we have no way of knowing which yours was without extensive reverse engineering or carefully controlled blind listening tests.
Maybe we have a language problem here. I don't see anything technical here, unless it is the point that you designed a crossover?
In that case, I can claim this is a technical post because I am using a keyboard which I installed on my computer.
In my book, a technical post is a post with technical content as opposed to 'I build this and it sounds great and my wife agrees'.
Jan
People who are conversant in perception issues and related factors tend to realize that these are often one and the same.
Jan
There's my last post in Blowtorth about Feynman's Cargo Cult Science and the oil drop experiment. The people who did those measurements were Real Scientists!
There are several approaches to get better results:
1) go to post #58 and 60 #under
myths and facts on electrolytic capacitors in audio circuits
2) Bypass of a foil capacitor
3) Bypass of a diode
4) without the NFB cap and offset servo.
I prefer the approach of number 1) - unfortunately only to use with jFET-LTP as input stage.
In case of an unbalanced power supply this issue don't exist, because GND and neg. rail are the same potential.
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