this is the reverse engineered chip from technics, sv2004. very close to synchro bias but is not primary bias generator in itself rather an add-on to the power transistor, preventing complete turn off for power transistors. You can compare this to a charge suck-out capacitor in Self EF-II but unlike the charge suck-out capacitor, this provides non switching whereas suckout capacitor facilitate faster ''OFF'' or ''ON'' of the power trannies.
Attachments
clarification.
SV2004 diode+ resistor doesnot generate bias rather act similar to charge suck-out mechanism. Q7 is the bias generator.
Synchro bias is bias generator and a controller for non switching function.
SV2004 can be added to any hi-fi existing class-AB amp.Presumably without much disturbance to sonics.
Synchrobias is meant to be dynamic/sliding bias genertor and thermal ditortion needs to be carefully considered wrt to high programme material processing.
SV2004 diode+ resistor doesnot generate bias rather act similar to charge suck-out mechanism. Q7 is the bias generator.
Synchro bias is bias generator and a controller for non switching function.
SV2004 can be added to any hi-fi existing class-AB amp.Presumably without much disturbance to sonics.
Synchrobias is meant to be dynamic/sliding bias genertor and thermal ditortion needs to be carefully considered wrt to high programme material processing.
clearly at high freq, at 10khz, the thermal intertia that affects any standard bias generator (including sliding bias) is much more prominent as shown in cyan and purple graph.
any non linear bias scheme is not free from this kind of thermal ditortion (bias scheme lags music signal change rate) despite the fact that non linear function/equation does not include temperature co-efficient (negligible).
any non linear bias scheme is not free from this kind of thermal ditortion (bias scheme lags music signal change rate) despite the fact that non linear function/equation does not include temperature co-efficient (negligible).
post 824
EDIT:
Post 824 is not correct.
Both the SV chip and the Technics synchro bias shown in previous posts work on the similar principle.
My apologies.
EDIT:
Post 824 is not correct.
Both the SV chip and the Technics synchro bias shown in previous posts work on the similar principle.
My apologies.
Thank you atiq and Kzeprf... I have clicked on the simulator
til' my mouse was hot
and I am leaning toward the pass designs..
As the test OP stage I use a typical leach triple. With all this
biasing info I am overwhelmed and might take a couple days
to assimilate all of it..(borg)
OS
til' my mouse was hot
and I am leaning toward the pass designs..As the test OP stage I use a typical leach triple. With all this
biasing info I am overwhelmed and might take a couple days
to assimilate all of it..(borg)
OS
Just some juicy info, I recieved today an amplifier to repair, a caudio pulse from a friend which has a nightclub. At first I thought he wanted to exchange this amp for another one of mine as he has done in the past but as he has been having a rough time financialy so he just wanted this one repaired. This amp is used in the VIP room, a 650w using a SMPS. The output trannies and drivers have all gone to heaven, as I started to remove the outputs I noticed some extra circuitry around the outputstage, what do you know, it employs my fav cfp ef2 outputstage but this one employs the technics non switching biasing scheme. 😀 😀
Does technics have a patent on those old schemes of theirs???
Does technics have a patent on those old schemes of theirs???
Don't be stingy now, a real working circuit deserves to be shared,
even a pix would be cool (closeup)..
OS
How long is a patent valid for ?? A lawyer told me its not worth it when it comes to electronics, just change a resitor value here and there, transitor connected as a diode instead of diode and voila, patent bypassed.
Os, I hope you dont mind but I have abominated your fruga3 as I finished some projects and now have some time to play around. Out went your input stage, in my fav one, a tweak here and there and around 120db THD class AB no nonswitching stuff. 😀 😀
Tommorrow I will look at the compensation putting in my outputstage better bias circuit and using my prefered devices on this, it looks good and I think its going to kick my blameless type s *ss when this is done. I need to have a second look at that vas though, I dont like those caps near signal paths.
Os, I hope you dont mind but I have abominated your fruga3 as I finished some projects and now have some time to play around. Out went your input stage, in my fav one, a tweak here and there and around 120db THD class AB no nonswitching stuff. 😀 😀
Tommorrow I will look at the compensation putting in my outputstage better bias circuit and using my prefered devices on this, it looks good and I think its going to kick my blameless type s *ss when this is done. I need to have a second look at that vas though, I dont like those caps near signal paths.
I dont have means to take digital pics but I am trying to find schematics, its the exact circuit you placed on the fruga. Four resistors and 2 diodes.
You mean the one with the diodes and 150k resistor??
the first one..?
Did you use FET inputs?? I am using the FA3 with the "baseline"
leach triple , no cascodes with KSA 1381/3503 and
wow, with no load at all on VAS.. it rocks w/-105 - 110 db dist.
if you have a input trick ...share...
the first one..?
Did you use FET inputs?? I am using the FA3 with the "baseline"
leach triple , no cascodes with KSA 1381/3503 and
wow, with no load at all on VAS.. it rocks w/-105 - 110 db dist.
if you have a input trick ...share...
As in your post 741, just different values used, didnt think id see this on a pa amp, but this amp looks pretty good, ltp vas, good choice of devices, good design but for the slow output devices, Id say it would give Mike s sym a hiding.
Os I use jfet bjt cfpin all my ltp and current feeback designs, sometimes in a vas too. Have done so for 15 years and havent found anything better sounding as yet although in this setup I dont know, will have to build it. I am simming your file, triple outputstage with 60 ma bias, with the changes made as said. I will need that cascode for my outputstage, just be used unlike the atp. I cant get the vas I use on my blameless to be stable so thats out, I have no fear for high feedback designs, the bad rap it gets is a joke. I built a non feedback amp, and the only thing better was the midrange, not better just different, the bass is awfull, I beefed this up with more and more trannies but it still lacked. I dont particularly like triples, hassle to get perfectly stable and besides one can get better performance from a cfp ef and as I dont like using output coils these are pretty stable without them.
If you keep downloading "FA3K.asc" , it will auto update every
hour, for a"play by play" realtime as I work on it..
Upload any .asc you might be working on (but include a text file
with any models that might be unique to yours.. 😉
If you look at my
http://71.203.210.93/pdf1/Electronics/Service_manuals/Power_amp/
Folder I now have full technics new class A amp schemas.
OS
It all depends on the route you want to take, Im looking at the fa3hp file, the k file is the one with the diamond buffer output. This is easy if you want to drop distortion, just place a emiter folower before vas ala self run it at 1ma and the vas to maybe 1.5ma so that you can use small signal devices for best performance and it should take you to around -120db THD, with second being dominant. To lower the 3rd more increase vas current and use higher power tranny.
It a completely different ballgame when it comes to a vas thats loaded and as this vas is pushpull as soon as its loaded tends towards 3rd harmonic if one doesnt use a cascode. Ideally I would like to get rid of this cascode but I havent managed to. I wont build a amp that displays more odd order harmonics and this at low powers, will not be good at all at high power. The cap accross the emitter i dont appreciate either, performance is a lot worse without it, but what sonic imprint does it have. It would maybe require a high quality polypropolyne which cost more than the entire rest of the frontend.
It a completely different ballgame when it comes to a vas thats loaded and as this vas is pushpull as soon as its loaded tends towards 3rd harmonic if one doesnt use a cascode. Ideally I would like to get rid of this cascode but I havent managed to. I wont build a amp that displays more odd order harmonics and this at low powers, will not be good at all at high power. The cap accross the emitter i dont appreciate either, performance is a lot worse without it, but what sonic imprint does it have. It would maybe require a high quality polypropolyne which cost more than the entire rest of the frontend.
sim suggestions
Os,
Couple of spice suggestions:
Set spice directive: .option plotwinsize 0 to get your
sims noise floor lower and get rid of the peak above 100k.
Set step size smaller and let a few cycles go by before starting.
.tran 0 .002 .001 .01u (might even increase the stop - start
delta to capture more cycles - this makes the peaks narrower)
The first one also speeds up the time lost by setting step size
smaller in the second.
Os,
Couple of spice suggestions:
Set spice directive: .option plotwinsize 0 to get your
sims noise floor lower and get rid of the peak above 100k.
Set step size smaller and let a few cycles go by before starting.
.tran 0 .002 .001 .01u (might even increase the stop - start
delta to capture more cycles - this makes the peaks narrower)
The first one also speeds up the time lost by setting step size
smaller in the second.
yet another non-switching amp
I found that STK8260II in some amp - still can't figure how this works, but on some polish electronics magazine I found something similar from Pioneer amp. In this thread I found something about Pioneer patent, but no schematic or patent number (did I overlooked something) - so can You tell me more?
Here is datasheet:
http://www.datasheet4u.com/html/S/T/K/STK8260II_Sanyo.pdf.html
I found that STK8260II in some amp - still can't figure how this works, but on some polish electronics magazine I found something similar from Pioneer amp. In this thread I found something about Pioneer patent, but no schematic or patent number (did I overlooked something) - so can You tell me more?
Here is datasheet:
http://www.datasheet4u.com/html/S/T/K/STK8260II_Sanyo.pdf.html
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