| ??? 06/16/06 13:44 Read: times |
#118412 - People who can hear caps... Responding to: ???'s previous message |
Peter said:
The usual supply for this kind of electronics is +9V which means I will have to use a virtual ground (input of the opamp on ½ VCC) and use input and output capacitors. This can influence the sound of the guitar. What sound? There's no sound of guitar, you must form it by the amplifier, by adding lots of distortion, compression and filtering. So, there's no sound that can be badly influenced by a simple cap. That's ridiculous! Peter said:
(not my opinion and certainly not my goal to discuss this…) Refuse to work for this idiot. If he can "hear" these caps, then you can never statisfy him. Believe me, I know these "famous guitar players". Peter said:
I read in another thread (http://www.8052.com/forum/read.phtml?id=104410) on this forum that with good pi filters these converters can be used to power sensitive circuits like audio amplifiers / buffers. I have searched for example circuits of the converter / filter combination but I couldn’t find it. Was from me. And an example was given also. When I remember correctly, then I was assuming a much higher switching frequency. Peter said:
I also thought about placing an 78L12 and 79L12 behind the DC/DC converter but I think that’s a little overdone. Not at all. They provide a ripple rejection of about 35dB at 100kHz. Not bad... Peter said:
Can anyone help me with an example of these filters? Take a 33µH small bobbin core and two 100µF/25V aluminium eletrolytics, each paralleled by 100nF/X7R. Choke should have a minimum series resistance of 1Ohm to avoid ringing. This pi-filter should give you again more than 30dB ripple rejection. At power supply pins of OPamp use a RC-filter of 22Ohm plus 100µF/25V, paralleled by 100n/X7R, again providing a ripple rejection of more than 30dB. So, finally you get about 95dB of ripple rejection. Enough? Peter said:
I’m also a bit worried about the radiated emision (hope I’m using the correct term) of the DC/DC converter. Can this influence the signals?
The converter will sit aprox. 1.5 inch from the opamp. I would not worry about the OPamp, but the coils of guitar. A single coil is more sensible than a humbucker, though. Peter, it's not at all a good idea to use a switcher only because your "famous guitar player" can "hear" a few caps in the signal chain. Tell him, that when his famous solo is being recorded in a professional studio, his guitar signal will have to pass hundreds of such caps finally... Kai |
| Topic | Author | Date |
| DC/DC converter for audio application | 01/01/70 00:00 | |
| It can be done | 01/01/70 00:00 | |
| Murata filter | 01/01/70 00:00 | |
| is there a thing called a "Murata filter | 01/01/70 00:00 | |
| Murata | 01/01/70 00:00 | |
| People who can hear caps... | 01/01/70 00:00 | |
| Caps, guitarplayers and DC/DC converters | 01/01/70 00:00 | |
| Some hints... | 01/01/70 00:00 | |
| Re : some hints | 01/01/70 00:00 | |
| 78L12, 79L12 | 01/01/70 00:00 | |
| LM317L and LM337L | 01/01/70 00:00 | |
| He could add a choke... | 01/01/70 00:00 | |
| LDOs | 01/01/70 00:00 | |
| Re:LDOs | 01/01/70 00:00 | |
| Very helpful, though | 01/01/70 00:00 | |
| Re : Very helpful, though | 01/01/70 00:00 | |
| Pop-eliminator | 01/01/70 00:00 | |
| Re : Pop-eliminator | 01/01/70 00:00 | |
| Caps charging | 01/01/70 00:00 | |
| 9v batteries | 01/01/70 00:00 | |
| Re : 9v batteries | 01/01/70 00:00 | |
| Batteries which hum | 01/01/70 00:00 | |
| Re : Batteries which hum | 01/01/70 00:00 | |
| Bridging the divide | 01/01/70 00:00 | |
| I remember | 01/01/70 00:00 | |
| Noisy batteries | 01/01/70 00:00 | |
| Linear tech LT1533 | 01/01/70 00:00 | |
Re : Linear LT1533 | 01/01/70 00:00 |