The valve (tube) amps have the feedback AC coupled, as taken from the secundary of the output transformer.
The SS amps have the feedback DC coupled, not only the AC signal (music) are taken (how it should be), a DC from the output can be superimposed.
This are indesirable, as write years ago in the french magazine L'Audiophile:
Document sans titre
In the datasheet of the TDA2004 the feedback are as the '(e) variante' drawing:
http://www.datasheetcatalog.org/datasheets/166/378181_DS.pdf
Someone knows more AC coupled feedback SS amps?
The SS amps have the feedback DC coupled, not only the AC signal (music) are taken (how it should be), a DC from the output can be superimposed.
This are indesirable, as write years ago in the french magazine L'Audiophile:
Document sans titre
In the datasheet of the TDA2004 the feedback are as the '(e) variante' drawing:
http://www.datasheetcatalog.org/datasheets/166/378181_DS.pdf
An externally hosted image should be here but it was not working when we last tested it.
Someone knows more AC coupled feedback SS amps?
As I understand it, SS amps have to be balanced midway, that provides for equal + and - signals with respect to either 0volts or ground with a capacitor. A valve amp is biased at each stage and does not require DC feedback. The greater the negative feedback, SS and valve, the less the gain and overall noise. A happy medium is therefore achieved, if possible.
Hope that helps.
Hope that helps.
Here's one:
It's the Power amp for the Peavey Pacer100 guitar amp and the PA100 4 channel PA mixer, both a very conservative 45W RMS@8 ohms.
Simple and robust, many still in use.
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