Hi All,
With Zen and ACA and various other amps, there are clear test points where one can measure volts or current so as to make adjustments to allow for different component performance (range of bias voltages etc).
I have spent time playing with Spice on various transformer/autoformer gain stages for l'Amp/Zen/Mofo type simple amp. In simulation it appears there are wild changes in the gain vs frequency curve as the result of relatively modest changes in coupling capacitor and resistance to ground rail. I assume this is because you are effectively building RLC filters.
My question is: if one builds said entertainment, duplication of a modelled circuit is only as good as the tolerance on the parts and the accuracy of the models. So is there some practical way to optimize the performance without signal generator or spectrum analyser..., short of getting a big box of parts to swap in and out and listening. There are no "test points" that one can readily measure with a DVM...
thanks
Beardy
With Zen and ACA and various other amps, there are clear test points where one can measure volts or current so as to make adjustments to allow for different component performance (range of bias voltages etc).
I have spent time playing with Spice on various transformer/autoformer gain stages for l'Amp/Zen/Mofo type simple amp. In simulation it appears there are wild changes in the gain vs frequency curve as the result of relatively modest changes in coupling capacitor and resistance to ground rail. I assume this is because you are effectively building RLC filters.
My question is: if one builds said entertainment, duplication of a modelled circuit is only as good as the tolerance on the parts and the accuracy of the models. So is there some practical way to optimize the performance without signal generator or spectrum analyser..., short of getting a big box of parts to swap in and out and listening. There are no "test points" that one can readily measure with a DVM...
thanks
Beardy
You'd need some basic test equipment (and basic knowledge) for that.
If you have a PC/Mac, a scope with generator starts at around $100.
PicoScope 2204A 10MHz 2-Ch Oscilloscope (PP906) ($139.00) : Saelig Online Store
ADI has a very decent PC/Mac starter test system for only $99 for a limited time.
ADALM2000 Evaluation Board | Analog Devices
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Every point in a physical amplifier "is" a test-point. As rayma says: signal generator and audio voltmeter. BASIC audio tools, like a carpenter's level and tape. 'Scope used to be big and costly and not always best; today's digital 'scopes are more practical.
DC bias only needs a DC meter. $2.99 will buy a functional DMM with specs which would have amazed the audio workers of the past. (Build quality varies from decent to "amazingly" bad.)
There should not be "wild changes" in frequency response for "modest" changes of parts. Mostly double the capacitance gets you an octave further down in bass; and since we usually set bass cutoff very low the exact cutoff is not real important. Even in crossover filters, 20% caps cause little error and 10% are now affordable.
DC bias only needs a DC meter. $2.99 will buy a functional DMM with specs which would have amazed the audio workers of the past. (Build quality varies from decent to "amazingly" bad.)
There should not be "wild changes" in frequency response for "modest" changes of parts. Mostly double the capacitance gets you an octave further down in bass; and since we usually set bass cutoff very low the exact cutoff is not real important. Even in crossover filters, 20% caps cause little error and 10% are now affordable.
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