Use a good film type for the input coupling cap. Do not omit this part.
Bass response can be affected by other things also. You have to look at the entire unit, not just the amp section. Then there is the amp design.
As Japanese amps go, Denon isn't that bad for it's market position. You wil be able to bring it to a point, and that's about it before the unit is totally redesigned and in a new case. Get my point?
-Chris
Bass response can be affected by other things also. You have to look at the entire unit, not just the amp section. Then there is the amp design.
As Japanese amps go, Denon isn't that bad for it's market position. You wil be able to bring it to a point, and that's about it before the unit is totally redesigned and in a new case. Get my point?
-Chris
Hi Craig,
Yes I read that post. I happen not to agree with it. Having been involved with audio service my entire working life I know not to tempt fate. Even if you have a source that puts out 0 uVDC it may fail some day. Could be the output, muting "part" or supply. Whatever it is you stand the risk of blown outputs, drivers or for the very trusting, fire (speakers).
The cap at the input is the least expensive to spec a quality part for. Most film types will sound very close to each other.
-Chris
Yes I read that post. I happen not to agree with it. Having been involved with audio service my entire working life I know not to tempt fate. Even if you have a source that puts out 0 uVDC it may fail some day. Could be the output, muting "part" or supply. Whatever it is you stand the risk of blown outputs, drivers or for the very trusting, fire (speakers).
The cap at the input is the least expensive to spec a quality part for. Most film types will sound very close to each other.
-Chris
Why bypass the input cap? Couldn't you just replace it with a larger value. Same with the feedback cap.
I would think 10uf or 22uf for the input would do. Maybe at least 100uf for the feedback cap, maybe even a 220 or larger. Being that it can take a couple seconds for larger caps to charge with low currents, I would imagine that would take bass response to near 0hz but still be DC coupled.
Here's an example:
I just built a subwoofer amp, and I used 10uf for my input cap, instead of the standard 2.2 or 4.7 uf, because my input impedance is high (63K ohm). Also used a 100uf feedback cap, and a 470uf bootstrap as well. When powering on, it takes a second or so to reach 0 offset because the caps take long to charge. When playing really low notes below 20 hz from bass test CD tracks, the speaker will visibly move back and forth at notes way too low to hear or reproduce. Seems to go plenty low enough for me.
I know DC coupling may seem like the best option, but if the amp is already built with caps, I wouldn't chance bypassing them because of a potential offset voltage at the output if the wrong thing is connected to the input
I would think 10uf or 22uf for the input would do. Maybe at least 100uf for the feedback cap, maybe even a 220 or larger. Being that it can take a couple seconds for larger caps to charge with low currents, I would imagine that would take bass response to near 0hz but still be DC coupled.
Here's an example:
I just built a subwoofer amp, and I used 10uf for my input cap, instead of the standard 2.2 or 4.7 uf, because my input impedance is high (63K ohm). Also used a 100uf feedback cap, and a 470uf bootstrap as well. When powering on, it takes a second or so to reach 0 offset because the caps take long to charge. When playing really low notes below 20 hz from bass test CD tracks, the speaker will visibly move back and forth at notes way too low to hear or reproduce. Seems to go plenty low enough for me.
I know DC coupling may seem like the best option, but if the amp is already built with caps, I wouldn't chance bypassing them because of a potential offset voltage at the output if the wrong thing is connected to the input
anatech said:
Hi Chris,
Use to do service as well for a little while. Do other things now.
Sure, there can always be a fault condition and a coupling cap is good protection.
Using this criteria and drawn to a logical conclusion however then the best place to put the coupling caps would be at the speaker o/p of the amp. There may be fault conditions that the amp may not be able to protect or the protection circuitry may fail to protect. Cap coupling for the speakers will take care of that condition. An input coupling cap wont.
I like to use the criteria of ultimate audio reproduction. Part of that includes the elimination of signal coupling caps wherever possible.
rgds, cb
Hi EWorkshop1708,
Actually, I was suggesting to replace the input coupling cap, not to bypass it. Oversizing the cap gets you into other troubles sometimes. As the cap gets larger in value, the physical size increases. It may not fit properly and also , because it's closer to other parts, start to couple to other parts of the circuit. I have seen this. The other thing is that leagages and inductance will increase depending on the cap. So too large a value can be a problem in itself.
Hi Craig,
Yup, I work in the Telecom field now although I still do service. As I mentioned above, the larger caps become less "ideal". An output coupling cap becomes far more expensive and a problem for damping factor at subsonic frequencies. The high current tends to vaporize foil over time. So the lowest impact will be coupling at the input. That and you don't want the DC impedance to change on the input. This will cause pops as the DC input bias currents change when , say, unmuting. The onus for speaker protection is on the amp designer. Bettcha a relay affects the sound less than an output coupling cap. Assuming both are in similar condition.
-Chris
Actually, I was suggesting to replace the input coupling cap, not to bypass it. Oversizing the cap gets you into other troubles sometimes. As the cap gets larger in value, the physical size increases. It may not fit properly and also , because it's closer to other parts, start to couple to other parts of the circuit. I have seen this. The other thing is that leagages and inductance will increase depending on the cap. So too large a value can be a problem in itself.
Hi Craig,
Yup, I work in the Telecom field now although I still do service. As I mentioned above, the larger caps become less "ideal". An output coupling cap becomes far more expensive and a problem for damping factor at subsonic frequencies. The high current tends to vaporize foil over time. So the lowest impact will be coupling at the input. That and you don't want the DC impedance to change on the input. This will cause pops as the DC input bias currents change when , say, unmuting. The onus for speaker protection is on the amp designer. Bettcha a relay affects the sound less than an output coupling cap. Assuming both are in similar condition.
-Chris
Yes Chris, your right about a relay over cap coupling. I wouldn't dream of using a relay either though. Although I do have a relay protection circuit which I have developed which is not in series with the signal o/p and is not a crowbar.
I'll put myself in the no cap coupling and extra protection camp.
I'll put myself in the no cap coupling and extra protection camp.
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