Yesterday i recieve my new jetprinter and dedicate transparent sheet for printing on pcb uv transfet file. So i hope to etch new VERSATIL 50 board this weekend. I manage to reduce pcboard size and pcboard foot print (with TO264 devices) by using some more 1206SMD resistors...See under. Board size is yet 88x98mm
Marc
Marc
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Thanks and the here will be next step with -/+44vdc rail (SMSPS 500R). Board size is 120x88mm direct derived from 50 front end version. My hope is to have the whole pleasure i have with BG1-MJL4281/4302. Since this version is on proto chassis i spend plenty time to listening session...realy magic moment...
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😱 
5cm?
Gentlemen, can anybody beat this micro VSSA!!!
Nice job Acca.
There could be some optimizations possible with your design but I think these won't be needed at all since you have proved earlier that VSSA can run stable even in perfect spaghetti mode!
Lookin' forward to see the smallest pure class-b VSSA board populated with darling-tons! 😉 😀
shaan
In principe yes but for value i can't simulate schematucs to confirm. Some later advices has been given to me on CSS : replace Trim 1K//680 by Trim 1k with 100R in serie so you have alway at min 100r as for previuos version if you set Trim to 0 you have emitter to bas from T4 direct connected.
Have you Thermal Track in stock....they are becoming tricky to find and very expensiv
Marc
R3,R4 --> wrong value, should be 100R
T5 --> better use some screw mount transistor
T6,T7,T1,T2 --> they not high voltage friendly, use some higher voltage transistors. This amp without vas boostrap is not very efficient, it is wasting approx 5-7V each voltage rail (this is a lot). I am using +/- 44V supply with single pair of o/p transistors.
R13,R14 --> I would use higher values here, 47-100R
The bias servo - I do not know how about thermal stability in that kind of circuit but standard one is working really good (did many tests on the prototypes) - so there is no need to make the circuit more complicated.
Trafo 200VA 2x30V ac, one channel driven I am getting only 70W at 8R !! In the same config I will get around 110W at 4R load (cause psu voltage drop). So IMHO there is no need to put 2 pairs at output at this psu voltage.
I just spotted that you have thermaltrak transistors from motorola, I have found some info that motorolas thermaltrak transistor diodes arent acurate at all (have to confirm that), in sanken transistors diodes are doing the job all right. You must do some research about this anyway.
Idefixes
Just bare in mind that MJL you have are really powerfull transistors, there is no need to put 2 pairs at 2x45V supply. I am running one pair of 2sc5200/1943 at that psu and all is great.
ACCA
Great work
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You are right borys, but over +/-35Vdc it's safer to use 2 output pair if you want to drive speaker less than 4 ohm...that's why i think Versatil 100 (with NJW3281/1302) wili be a good allrounder : about 100w/8r 200/4r and able to driver lower inpedance speakers...in compact size
Marc
+/-35V psu, You are loosing approx 6 volt each rail so in reall life you have only +/-29V psu not +/-35V psu in this case!!. Under load transformer will drop voltage, full load even 5-6V so we are getting even less power.
From 2x24V 100W transformer psu (around 72V DC all together), one chanel driven there is only +/-24V swing at output - clipping!!!
Power around 35W at 8R load and 70W at 4R (if transformer voltage will not drop down further). There is no need in this case to use more transistors at o/p stage cause amp is not efficient.
Hi borys,
With my PSU : 300Va/2x25Vac and 2x22.000uf/40V (per chanel) rail voltage (mesure just befor output collector) don't go under 35V even at high volume during music.
Marc
I can make it smaller 🙂
5cm?
Gentlemen, can anybody beat this micro VSSA!!!
Nice job Acca.
There could be some optimizations possible with your design but I think these won't be needed at all since you have proved earlier that VSSA can run stable even in perfect spaghetti mode!
Lookin' forward to see the smallest pure class-b VSSA board populated with darling-tons! 😉 😀
shaan
I not using PCB,I only make projects in 3D 🙂
I make it pcb for few days,when bought PCB 😉.
You didnt get my point. On the collector you will have let me say 35V per rail but amplifier is a bastard and is stilling aprox 6V from it - so at emiter You will have approx 28V max amplitude with clipping!!
Hi borys i was refering to these words
as in my case i even don't loose the 5-6V when transformer is under load, but for sure i will loose the 6 other Volt in amp it self.
Marc
What you say for this?
5cm?
Gentlemen, can anybody beat this micro VSSA!!!
Nice job Acca.
There could be some optimizations possible with your design but I think these won't be needed at all since you have proved earlier that VSSA can run stable even in perfect spaghetti mode!
Lookin' forward to see the smallest pure class-b VSSA board populated with darling-tons! 😉 😀
shaan
4 x 4cm 😉
