[AMRadio] Testing tubes

[DOXEMF at aol.com]

In a message dated 10/2/03 1:06:37 PM Eastern Daylight Time, 
jcandela at prodigy.net writes:


> Comment: Below is a link about modyifing CD players where the op amp after 
> the D-A has a tremendous effect on the perceived audio quality. One 
> explanation is that many op-amps have very noticeable cross over distortion, which 
> becomes more significant as the signal level drops into the lower portion of the 
> available dynamic range. One solution for some op-amps is to use a pull up, 
> or down resistor from the output of the op-amp to a power buss. The idea is 
> to require the output stage to sink, or source a little current to in effect 
> keep only one half of the output running, or to put it in other words: make it 
> act as a single ended amplifier, and therefore no cross over distortion. 
> You will also like the use of tubes following the D-A converter. Neat stuff!
> 
> Jim 
> WD5JKO
> 
> http://home.netcom.com/~wa2ise/radios/tubedac.htm
> 
> .

Thanks for the link. Have heard of that but hadn't found it yet. 
The early Magnavox/Phillips players were the subject of many Pooge (mod) 
articles
in Audio Amateur Mag in the 80's. Nowadays everything is surface mount and 
next to impossible to play with. It's remarkable how the vacume tube has 
resurfaced as 
a viable interface with digital. Have been real interested in the motherboard 
out now with a tube in the sound circuit.
I have a collection of tube type computer modules using pairs of dual triodes 
producing an op amp config.by Philbrick and single tube modules configured as 
other logic functions from a different mfg.
Enjoy,
Bill KB3DKS


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