You know recently I was putting an ODS type amplifier together , doing some expected fine tuning after completion, and tunneled in on the bias power supply .
I started out using an old diode ( salvaged from an old fender silver face baseman ten Carcass I have been pulling parts from for years ), a pair of some modern name brand electrolytic from CEDIST (forget the brand), and a NOS unknown brand CF 2 watt resistor I had lying around. The bias pot tail resistor was a KOA CF off a CTS 10k pot. Bias grid resistors were KOA CF.
As a disclaimer , I actually measure component values and try to match as close as possible when making these installations , but there is almost always some deviation of a small percentage . Hard to find anything with an exact same value, but I try .
Well I started out swapping the KOA 220k bias grids with XICON . This wasn’t as bright and high focused. More bounce and give to the notes . Digging in had less transient peaks with the in your face frequencies .
Next, I replaced the electrolytics with some modern BC components brand capacitors . This gave more air and space to the tonality ; it felt less congested and and directional , more like the sound was all around you and not simply crawling out of the speaker .
Next, I swapped out the diode with a modern 1N4007. This was a very distinct difference . The high end clarity that felt like icepicks was tempered significantly. Again, digging in has more give , less dynamic but definitely not as potentially harsh .
Finally , I swapped the no name resistor with a modern ohmite. The amp came alive . Bouncy and forgiving . Bias range still ideally wasn’t where it needed to be so I replaced with a smaller value KOA. Magic disappeared. Paralleled ohmite over KOA, value difference small enough to work. Magic returned . At that point she was as fun as can be to play , and I closed her up .
Whereas I am not comparing these with dumble parts so to speak , ime these differences between components are enough to make or break an amplifier .
I have mentioned in another thread before about using all Takman brand resistors in an amplifier once. In fact it was this thread that inspired me to try them out . Perhaps they might blend well with other parts than what I chose to use, but until I swapped them all out that amplifier was like playing under a magnifying glass in the hot sun . I couldn’t play that thing for more than ten minutes without getting a headache. KOA , xicon , and dales solved that dilemma
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