♫♪ My little cheap Circlophone© ♫♪

Elvee

Member
2006-09-08 2:04 pm
Quasi comp is when the P transistor of a regular complementary PP is replaced with a CFP having a PNP as an input.
The C has nothing in common with the traditional topology: the OP transistors need to be of the same polarity, otherwise it cannot work.
For practical reasons, I opted for two CFP's as output, but it can work with two darlingtons or MOSFETs, and if you search the thread, you will see that members have implemented such versions, often "inverted" to be able to use N OP devices.
"Circlo" in the name refers to the similarity with the Circlotron topology, but without the folklore and inconvenience of floating supplies, etc.
 
Hi Katiyar

Mr Aditya. As you are from India I will advise you not to buy crap Chinese BD140 available very easily in the Indian market. You should instead purchase CDIL make BC546, BC556 and BD140. These transistors are genuine and performance is excellent. They will sustain the rated voltage. KSC3503 is an excellent choice for VAS. These are video transistors with 150Mhz BW.

As advised by Mr Minek 4.7pf capacitor is to be added between BC of KSC3503.

Good Luck

Hey Rajesh,

Hope you all are doing well - as per you’re advice I got CDIL mostly ..

BC546B - CDIL
BC556B - CDIL or PHILIPs
2N3051 - CDIL
2N5551 - kE brand
KSC1845 -
BD140 - CDIL
MJL21194 - ONSEMI ( RSComp )

All resistors mfr
Caps will be mostly cog(npo) and input cap philips bipolar or Muse ( if I get it )

Hope this is all ok - will be assembling board
 
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Mr Aditya,

Why are you using 2N3051. Its Vce is only 20V. It will fail in VAS. You should use 2N3019 in VAS up to 25v Rail. Use KSC3503 in VAS if rail voltage is higher. Other selection is perfect.

You will love Circlophone with its audio quality and stability. My MOSFET version of Circlophone stereo is powered on for more than two months and all parameters are within its limit. Quiescent current is well maintained at 160ma. Offset is ~5mv.

Best wishes for your build.
 
Hi Katiyar

Mr Aditya,

Why are you using 2N3051. Its Vce is only 20V. It will fail in VAS. You should use 2N3019 in VAS up to 25v Rail. Use KSC3503 in VAS if rail voltage is higher. Other selection is perfect.

You will love Circlophone with its audio quality and stability. My MOSFET version of Circlophone stereo is powered on for more than two months and all parameters are within its limit. Quiescent current is well maintained at 160ma. Offset is ~5mv.

Best wishes for your build.

hey thank you for the catch, ( my dyslexia ) But i correct my self and have bought 2N3019, about 45/- each. was looking for KSC3503 but didnt find it.

i got the boards from Prasi, so the board part is sorted - now is input selection board and cabinet and sweet labour of love... going to use my exisitng transformer that used to give me around 21 or 22 volts dc so lets see " will take TIME "

will keep posted, is there something i need to keep in mind
 
Please check the genuiness of 2N3019. Is it from CDIL or from BEL or imported?. DIYAUDIOCART.com was selling it at a very heft price of Rs 200 each.

Yes I am aware of those sold by DAC, but it depends brand to brand and on element 14 there is one from multicomp I think it’s sold for 113/-

And there are mil stand ones sold for 1000/- made by Microchip ( they make microcontrollers - “pic16F, 18F” series and also recently acquired atmel )
 

Elvee

Member
2006-09-08 2:04 pm
You can try 180pF, but make sure that there are no signs of instability.
A good test is a ~10kHz squarewave with the output nominally loaded: the edges should be neat, without ringing or overshoot, something like this:

224263d1306308817-little-cheap-circlophone-10khzinfini-1-jpg
 

Elvee

Member
2006-09-08 2:04 pm
In this case, stay on the safe side: use 820pF. It is safe and proven with countless device types, and the published specs apply to this case.
Using a lower cap will improve the dynamic performances with suitable devices, but refrain from using one until you have the means to check its viability: you certainly do not want to fry your tweeters
 
Hi Aditya,

The price of CDIL 2N3019 is quite reasonable. Is this vendor also sells online?. Please share address.

I have also build prototype one channel with BJT in past and experimented with 2N3055 and 2N3773 transistors as op device with CDIL BC546, BC556 and BD140 transistors at 35-0-35V DC Rail with excellent results. I also found no difference in audio quality between BJT and MOSFET versions.