Simple Symetrical Amplifier

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...at least what datasheet says. :)
Did-you notice that our civilization tend to eradicate those kind of things ?
Where are all those fantastic huge books from PMI, Analog devices, Harris, Texas instruments etc... with all those beautiful curves full of promises, witch followed us during decades ?

To naf, you can follow L.C. advice, using the best temp measuring instrument on your Zeners: Your finger ;-)
 
Did-you notice that our civilization tend to eradicate those kind of things? Where are all those fantastic huge books from PMI, Analog devices, Harris, Texas instruments etc... with all those beautiful curves full of promises, witch followed us during decades?

They are in the net. But for eager(but inexperienced and often naive) diyers like me and, say, naf and many others, reading the manual is often the last job when the gadget doesn't work :rofl: :eek:. What helping would electro-gods like Esperado do in diyaudio if our civilizations always did their homework. ;) See how naf, being not-so-experienced in this field, went for a half-watt before asking LC or you or others if it was okay. In fact it is still okay if the zener blows(hopefully won't), as this would teach him important facts about zeners, and, he might actually download and read the datasheet, and then become hungry for more electro-info, which will only do good.



Anyways, I am currently simulating my SSA with a servo, in order to eliminate my headaches/confusions/doubts/caring about offset once and for all, concentrating solely on the bias of the input and VAS. I would feel glad to see the SSA as an amplifier which even a fresh diy-er can build and enjoy, without thinking about the fusses that comes with CF topology and without the danger of accidentally blowing his 49$ fullrange, like many simple LTP based amps which use commonly available and cheap parts, work fine even if one just throws the said parts to said places and doesn't care about device matching. I think this is the only way to popularize SSA, truly simple and easy to build.

This is not to say that I'm not building the advanced CCS which is bound to bring SSA to its full bloom, but I need to buy better speakers first.
 
LC i do trust your calculatio on zener current, i draw the shematic in LTSpice and yes it's the correct value.

Shaan i do trust you on what of you have experienced during building SSA amp, today i've asked my friend to source for me 1 watt zener and thanks he have it.

and Esperado yes i have the best thermal sensor in the word, my fingertip.

to all of you thank you very much, i'll gain more experience and more fun building this amp.

regards
naf
 
Anyways, I am currently simulating my SSA with a servo, in order to eliminate my headaches/confusions/doubts/caring about offset once and for all, concentrating solely on the bias of the input and VAS. I would feel glad to see the SSA as an amplifier which even a fresh diy-er can build and enjoy, without thinking about the fusses that comes with CF topology and without the danger of accidentally blowing his 49$ fullrange, like many simple LTP based amps which use commonly available and cheap parts, work fine even if one just throws the said parts to said places and doesn't care about device matching. I think this is the only way to popularize SSA, truly simple and easy to build.

This is not to say that I'm not building the advanced CCS which is bound to bring SSA to its full bloom, but I need to buy better speakers first.

Yes, that's the way to bring SSA to the masses. Nice job Shaan, I'll follow and fully support you if needed. CFB has to be presented in its simplest form and at the same time as "bulletproof" design. This will attract and bring a lot new CFB fans to SSA amp around the globe. Thanks Shaan :up:
 
A mistake in the PCB

Hi naf, Cambe and others.

The 10K input to ground resistor is missing in the PCB. You can connect it parallel to the 22pF capacitor, on the underside of the PCB between the red-marked pads.

My apologies. I will upload the corrected PCB shortly.
 

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Maybe something in this way ...;)

I am simulating something in this way. ;)

Red trace is amp freq response with 10uF input cap. Green trace is servo response. As simmed, the servo with the shown values would work at about 0.2Hz and quickly fall in response in both sides. I used this with my DOZ amps and it worked pretty well, the thing to keep in mind is not to provide voltage gain in the VLF zone where the servo will work.

:2c:
 

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I am simulating something in this way. ;)

Red trace is amp freq response with 10uF input cap. Green trace is servo response. As simmed, the servo with the shown values would work at about 0.2Hz and quickly fall in response in both sides. I used this with my DOZ amps and it worked pretty well, the thing to keep in mind is not to provide voltage gain in the VLF zone where the servo will work.

:2c:


Is the 1M is not too high? How much input offset it can handle?

Sajti
 
Is the 1M is not too high? How much input offset it can handle?

Sajti

Yes. Thanks for the tip. With 100K resistor from servo to input it can handle +-5V of output offset(will it ever happen? dunno).

If the servo is just removed then the default offset with the 10K from input to ground is about +900mV, with the currents in the upper and lower halves balanced.

When I tried a servo on my fetzilla the nice qualities were lost ( transparency, spaciousness & bass integrity ) unless I set the -3db point to an incredibly low subsonic frequency so I will be interested to hear your before & after impressions.

Good Luck !

Yes this happened in my listening tests with DOZ too and I had to increase the capacitor at the servo from 1uF to 4.7uF and decrease the feed resistor from 100K to 33K, with a -3dB of about 0.4Hz. Obviously the servo was adding its own voltage gain to the amplifiers LF response. There was funny cone excursion with the default values.

I will add the servo to my SSA and update ASAP.
 

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