Hi all,
Following the simple two channel mixer, I have now drawn up a design for a basic four channel mixer. This version has two balanced XLR inputs with preamps (channels one and two) and two unbalanced stereo inputs (channels three and four). All channels need to go to an unbalanced output. As this will be used live on stage, a “popless” mute switch is required for all four channels.
I have attached the schematic and I was hoping people would be kind enough to critique the design.
The preamp stage for channels one and two is based upon the Dantimax ThatMic design with a few changes to the variable gain stage, the addition of an OPA137 opamp and the removal of the phantom power supply circuit (dynamic mics will be used). The OPA137 is to drive down the DC output to 0V as per the recommended design for the INA217 (as seen here – page 7).
For channels three and four, 0V DC output is achieved using C303/R306 and C403/R406 and is taken from Douglas Self’s Small Signal Audio Design (p. 341).
Are these methods the best to get DC output to 0V – thus avoiding pops and clicks when the channel is muted? If not, what changes should I make?
Are there any other goofs I have made (quite likely being me!)?
Sorry for the questions again, but I would really appreciate any help.
Thanks very much!
Following the simple two channel mixer, I have now drawn up a design for a basic four channel mixer. This version has two balanced XLR inputs with preamps (channels one and two) and two unbalanced stereo inputs (channels three and four). All channels need to go to an unbalanced output. As this will be used live on stage, a “popless” mute switch is required for all four channels.
I have attached the schematic and I was hoping people would be kind enough to critique the design.
The preamp stage for channels one and two is based upon the Dantimax ThatMic design with a few changes to the variable gain stage, the addition of an OPA137 opamp and the removal of the phantom power supply circuit (dynamic mics will be used). The OPA137 is to drive down the DC output to 0V as per the recommended design for the INA217 (as seen here – page 7).
For channels three and four, 0V DC output is achieved using C303/R306 and C403/R406 and is taken from Douglas Self’s Small Signal Audio Design (p. 341).
Are these methods the best to get DC output to 0V – thus avoiding pops and clicks when the channel is muted? If not, what changes should I make?
Are there any other goofs I have made (quite likely being me!)?
Sorry for the questions again, but I would really appreciate any help.
Thanks very much!