Simple Symetrical Amplifier

[guitar89]

Originally Posted by Esperado

???
Please, use 1K in serial and 50 or 100pf to the ground. Are your speaker's cables long ?

I prefer not to use over 1 meter cable ( I always kept below 1 meter)
Just a curious, what is the relationship of adjusting the resistance against capacitance if we kept the cutoff frequency constant ? (example: what is the difference between using 1ohm &1uF against 1k ohm & 100pF ? )

Hey Shaan, I never saw you have those links below your post (signature I believe) Its a great job putting those together and compile it, thanks you ! LC would have save alot of job if I were to see those early ! (I just have so much question to ask ^^)

[naf]

Originally Posted by Lazy Cat

Compared to some commercial amp? Did you like it? Which speakers?

Hi LC.. sorry for late answer
I don't have any commercial Amp, it cost to high for me and speaker i use just DIY entry level speaker.. build by local senior DIYer.

I do compare with other great design Amp i've build from this great site.
i'm very satisfied with my Shan's SSA build ... such big sound coming from small Amp, nice treble, nice bass, clear vocal... no hum, no hiss.. play all music genre vocal, instrument, pop, rock, metal, jazz

PS:
i've upgrade my VAS Tr using 1360/3423 and more smooth treble.

[keantoken]

If you double series resistance, halve shunt capacitance. Triple resistance, divide capacitance by 3. And so on. This way LP corner will stay the same.

[shaan]

Hi naf. Great job.

I have just finished another P3A on a 2"x3" veroboard with superfast BJTs. I haven't listened to a VFB since the SSA re-incarnation. I wonder what kind of challenge I'm gonna get with the very good and popular VFB amp P3A.

[shaan]

Hi guitar89. Hope the links help you on your way to building your own SSA.

[guitar89]

Originally Posted by keantoken

If you double series resistance, halve shunt capacitance. Triple resistance, divide capacitance by 3. And so on. This way LP corner will stay the same.

well, what I mean is that what is the difference between using those different combination ? (while we still get the same Low Pass Cutoff Frequency)

Example: combination of high resistance & low capacitance will get what result ? affect phase or anything else ?

[shaan]

Hi guitar89. By using 1ohm/1uF instead of 1k/100pF you are going to kill your signal source brutally. With low R and high C you demand high AC current from the source. Best is to use 1k/100pF and it won't cause any sonic degradation.

[guitar89]

Originally Posted by shaan

Hi guitar89. By using 1ohm/1uF instead of 1k/100pF you are going to kill your signal source brutally. With low R and high C you demand high AC current from the source. Best is to use 1k/100pF and it won't cause any sonic degradation.

Thanks for your explanation and advise, didn't realise it before.

Would it be wise to integrate a volume pot after these filter ? could it be put before the filter (nearer to source)? (or is there anyway to make it foolproof of putting pot)

Just curious, what if I raise more resistant and less capacitance ? example of 10k ohm and 10pF. (My guess is low source input ?)

[shaan]

Originally Posted by guitar89

Would it be wise to integrate a volume pot after these filter ? could it be put before the filter (nearer to source)? (or is there anyway to make it foolproof of putting pot)

The RC lowpass filter should be as close as possible to the bases of the input BJTs, i.e. nothing between filter and SSA. This is foolproof enough.

Just curious, what if I raise more resistant and less capacitance ? example of 10k ohm and 10pF. (My guess is low source input ?)

The result is audible noise and poor frequency response, as SSA demands a low impedance source to work at its best and the 10k just adds itself up with the nominal output impedance of the source resulting into very low available drive current for an amp with 10k input impedance such as SSA, not good.

[guitar89]

Originally Posted by shaan

The RC lowpass filter should be as close as possible to the bases of the input BJTs, i.e. nothing between filter and SSA. This is foolproof enough.



The result is audible noise and poor frequency response, as SSA demands a low impedance source to work at its best and the 10k just adds itself up with the nominal output impedance of the source resulting into very low available drive current for an amp with 10k input impedance such as SSA, not good.

Ok, I will kept the minimum at front. What value of pot is recommended with this filter ? (in order not to reduce input drive current too low)
(As in my attachement ?)