Hi ericfe,
There ! I told you Cricklewood Electronics were reliable !
I've been buying from them for decades, when their product line-up was more R-TV dealer oriented.
Look them up on the 'net.
I telephone ordered 2SC5200 using my credit card after my last post yesterday, and genuine Toshiba parts arrived in the post this morning.
They were £ 3.50 each plus VAT.
Carriage was £ 4.00, and Post Office 'First class Recorded' !
I did ask how many they had left, and they said about eighty.
They stock the 2SC3421 as well, last price to me £ 0.75 each.
So I've got mine now,
The AABB is like class-A, or I would not have posted the design.
Happy soldering everyone.......... Graham.
There ! I told you Cricklewood Electronics were reliable !
I've been buying from them for decades, when their product line-up was more R-TV dealer oriented.
Look them up on the 'net.
I telephone ordered 2SC5200 using my credit card after my last post yesterday, and genuine Toshiba parts arrived in the post this morning.
They were £ 3.50 each plus VAT.
Carriage was £ 4.00, and Post Office 'First class Recorded' !
I did ask how many they had left, and they said about eighty.
They stock the 2SC3421 as well, last price to me £ 0.75 each.
So I've got mine now,
The AABB is like class-A, or I would not have posted the design.
Happy soldering everyone.......... Graham.
Graham ,
im curently interested in repalcing my 22 bd139 by 300 or so
bc550 , i apreciate your advice for the shop anyway.
i'm looking for the cheapest shop here on madrid.
and after all, this could be not so expensive , because , if i use 300 to92 devices, the heahtsink will not be necessary anymore,i think i can even let the 600 (300+300 a stereo pair) outside the box as part of the design...
furthermore, for over 100 pieces they offer you a 20% discount...
the only think is that i will have to solder more than 2000 points...
as a resistor emiter, i plan to use some 5 ohm resistors, as there will be 300 transistor it should be possible whith no problem right guys?
well thanks for the feedback... more news soon!
im curently interested in repalcing my 22 bd139 by 300 or so
bc550 , i apreciate your advice for the shop anyway.
i'm looking for the cheapest shop here on madrid.
and after all, this could be not so expensive , because , if i use 300 to92 devices, the heahtsink will not be necessary anymore,i think i can even let the 600 (300+300 a stereo pair) outside the box as part of the design...
furthermore, for over 100 pieces they offer you a 20% discount...
the only think is that i will have to solder more than 2000 points...
as a resistor emiter, i plan to use some 5 ohm resistors, as there will be 300 transistor it should be possible whith no problem right guys?
well thanks for the feedback... more news soon!
Re: Thanks!
I got mine from here:
http://www.mainelectronics.com/bulksemi.htm
Prices are close in CDN$ to what Graham paid in GBP:
2SA970 120V .1A .3A 100MHZ SI-P $0.39
2SC3421 AF/RF AMP DR 120V 1A 10W $0.83
Looks like they have Graham's choice too:
2SC5200 230V 15A 150W 30MHZ SI-N $2.76
RKH said:
I got mine from here:
http://www.mainelectronics.com/bulksemi.htm
Prices are close in CDN$ to what Graham paid in GBP:
2SA970 120V .1A .3A 100MHZ SI-P $0.39
2SC3421 AF/RF AMP DR 120V 1A 10W $0.83
Looks like they have Graham's choice too:
2SC5200 230V 15A 150W 30MHZ SI-N $2.76
right Graham,
they will have a greater C ... capacitance i suppose,
I was thinking about this...
but i was thinking... is capacitance so important?
will the shortcomings of capacitance be greater than the advantage produced by having lots of small transistor paralelled?
i know that tubes are different , but... it is a known fact that triodes have a greater capacitance than pentodes .
Despite its greater capacitance, the sound of a triode is considered to be more musical, more nice to the ears than the penthode sound that is a little more hard.
So maybe this greater capacitance is not an issue so important.
bd137 has an Ft of 190Mhz,
the 2sc5200 has "only"
an Ft of 30Mhz and a capacitance of 200pf
i could not find the capacitance of the bd139..so if anybody could tell it to me i will be very happy.
but the Ft is so high that de higher definition introduced is certanly something that anybody wishes.
how much increased capacitance should be accepted for an ft increased?
i have seen a design, an aabb amplifier (guess who's design
)
that uses 10 x 2sc3281, those have an ft of "only" 10Mhz
and the capacitance is increased by paraleling that much, i think that if this designs sound really good,well i do not see why 20 BD137 paralleled are not going to make a good chorus (less powerfull but well, i am here for musicality, and definition, power y a luxe that i can´t afford for now) especially considering that BD's have an ft more than six times higher.
The rollof on high frequencies, very high i think will not be something that anybody could apreciate, imho.
but in this we agree, i can see, now that paraleling more than 100 bc550 are not a good thin to do, because of the increaseof the capacitance that will be something near 0,5 uF or so, this is becoming to be perceptible i think...
thanks a lot for the feedback Graham, since i don´t kmow much about electronics , i apreciate every feedback that teaches me something, so thank you ...hem...please if someone can find the internal capacitance of the bd139 please tell it to me , thanks again
and remember a great sounding amp can always be improved .
See you later!
they will have a greater C ... capacitance i suppose,
I was thinking about this...
but i was thinking... is capacitance so important?
will the shortcomings of capacitance be greater than the advantage produced by having lots of small transistor paralelled?
i know that tubes are different , but... it is a known fact that triodes have a greater capacitance than pentodes .
Despite its greater capacitance, the sound of a triode is considered to be more musical, more nice to the ears than the penthode sound that is a little more hard.
So maybe this greater capacitance is not an issue so important.
bd137 has an Ft of 190Mhz,
the 2sc5200 has "only"
an Ft of 30Mhz and a capacitance of 200pf
i could not find the capacitance of the bd139..so if anybody could tell it to me i will be very happy.
but the Ft is so high that de higher definition introduced is certanly something that anybody wishes.
how much increased capacitance should be accepted for an ft increased?
i have seen a design, an aabb amplifier (guess who's design
)that uses 10 x 2sc3281, those have an ft of "only" 10Mhz
and the capacitance is increased by paraleling that much, i think that if this designs sound really good,well i do not see why 20 BD137 paralleled are not going to make a good chorus (less powerfull but well, i am here for musicality, and definition, power y a luxe that i can´t afford for now) especially considering that BD's have an ft more than six times higher.
The rollof on high frequencies, very high i think will not be something that anybody could apreciate, imho.
but in this we agree, i can see, now that paraleling more than 100 bc550 are not a good thin to do, because of the increaseof the capacitance that will be something near 0,5 uF or so, this is becoming to be perceptible i think...
thanks a lot for the feedback Graham, since i don´t kmow much about electronics , i apreciate every feedback that teaches me something, so thank you ...hem...please if someone can find the internal capacitance of the bd139 please tell it to me , thanks again
and remember a great sounding amp can always be improved .
See you later!
Hi ericfe,
Virgin Net was not connecting so I could not get back to you.
I understand exactly what you are saying, and I wish you luck with your empericism, we all need to know your findings.
But, are you sure that the circuit you are going to put all these devices in was already working at its best for your original comparison devices ?
Cheers ......... Graham.
PS. Here's one to play with.
Virgin Net was not connecting so I could not get back to you.
I understand exactly what you are saying, and I wish you luck with your empericism, we all need to know your findings.
But, are you sure that the circuit you are going to put all these devices in was already working at its best for your original comparison devices ?
Cheers ......... Graham.
PS. Here's one to play with.
Attachments
hello Graham,
the original circuit was a DoZ, wich was working just fine with the tip3055, but as i wanted to try it with some trasistors much faster,
i used those bd137, after all i don't know any power devices that have an ft of 190 Mhz...
i write to Rod Elliott to tell him about my little experiment , after all the DoZ is his design....and this is the answer:
"Interesting. I have contemplated a similar approach a few times, but never got around to doing anything with it. In theory, it should make a difference (mainly speed), but I would not have thought the difference would be audible."
so if the Master said "interesting" i'm glad to go on experimenting.
as soon as i can i wil try to build a smalller version of the class-a 20 in rod's website too, this time going even far, the goal is to replace each BD139 by 25 bc550 (looking the data sheet this trade is "fair") and as output devices 150 paraleled bc550, giving the maximum speed to the amp,to see if there is a noticeable efect.
the original circuit was a DoZ, wich was working just fine with the tip3055, but as i wanted to try it with some trasistors much faster,
i used those bd137, after all i don't know any power devices that have an ft of 190 Mhz...
i write to Rod Elliott to tell him about my little experiment , after all the DoZ is his design....and this is the answer:
"Interesting. I have contemplated a similar approach a few times, but never got around to doing anything with it. In theory, it should make a difference (mainly speed), but I would not have thought the difference would be audible."
so if the Master said "interesting" i'm glad to go on experimenting.
as soon as i can i wil try to build a smalller version of the class-a 20 in rod's website too, this time going even far, the goal is to replace each BD139 by 25 bc550 (looking the data sheet this trade is "fair") and as output devices 150 paraleled bc550, giving the maximum speed to the amp,to see if there is a noticeable efect.
Big thanks to Jacco Vermeulin,
he finds that the bd139 has a capacitance of 5,6pf, a little lower than the bc550.
i hope i will construct the matrix array of the bc560 and bd137(139) so i can actually measure the actual characteristics.
then i will post th detalled results so we can compare it with the toshiba more powerfull devices.
thanks for you interest Graham,
cheers.
he finds that the bd139 has a capacitance of 5,6pf, a little lower than the bc550.
i hope i will construct the matrix array of the bc560 and bd137(139) so i can actually measure the actual characteristics.
then i will post th detalled results so we can compare it with the toshiba more powerfull devices.
thanks for you interest Graham,
cheers.
Of course it all makes sense and goes a long way to explain why your iteration of DOZ using multiple bd 137/139 devices sounds the way it does as the following explanation by Andy Groves formerly of HI-FI WORLD and nowdays AUDIO NOTE designer wrote in reply to a readers query in theFeb '95 issue of HI-FI WORLD DIY supplement wrote>:" ls it just coincidence that some of the best sounding solid-state amplifiers use multiple pairs of output devices? This cuts the current density in each of the transistors, reducing or eliminating trans conductance droop."< btw any chance of a layout drwng of this version please? cheersTC
Qwad hello,
i have posted the schematic the pcb and the technique i am using to parallel all those transistors.
i do not use a pcb for the paralleled transistors,i simply wire them "by air", if this is well done, i can assure you tha absolutelly no hum will occur .
if you paralel 50 transistor for each of these amps you will have
equivalent of a Pd=625W, and a capacitanceof 280pf transistor at an ft of 190Mhz
to compare it with the nice 2sc5200 devices, ve can see that those are rated 150w each so we will need at least 4 of them
so we will have 600W Pd , (less tah the buch of bd137 i know...)
an ft of 30Mhz....
but at a capacitance of 4x200=800pf, imho this capacitance is starting to cause an roll off at higher frequecies
(after all this is 0.8uF).
anyway the 2sc5200 are very nice devices, so if you like those, you will probably love the 50xbd137, 50 for each amp is a nice number since in the store they will give me a 20% discount for 100 devices, i can have 100xBD137 for somehing like 15 euros,
even cheaper than 4 X 2sc5200! (at least in this store).
anyway, i'm starting my classes at the university, so i'm afraid that i will have to leave my experiment for now...
anyway , please if someone has tried this, write to me especially if you think that the results are not good, i am very interested since a plan to calculate (design is a too big word for me) an A-class , single ended, that works with single power supply (not a +0- power supply), i think the best , maybe ,is to modify
rod's design of the 20watts a-class.
i do not like the version of dual power supply because , there is some transistors that do not draw always the same current, as rod explains it is perfectly normal for a single ended with dual supply .
well, any way il will be comming here to see the posts,
cheers to all!
i have posted the schematic the pcb and the technique i am using to parallel all those transistors.
i do not use a pcb for the paralleled transistors,i simply wire them "by air", if this is well done, i can assure you tha absolutelly no hum will occur .
if you paralel 50 transistor for each of these amps you will have
equivalent of a Pd=625W, and a capacitanceof 280pf transistor at an ft of 190Mhz
to compare it with the nice 2sc5200 devices, ve can see that those are rated 150w each so we will need at least 4 of them
so we will have 600W Pd , (less tah the buch of bd137 i know...)
an ft of 30Mhz....
but at a capacitance of 4x200=800pf, imho this capacitance is starting to cause an roll off at higher frequecies
(after all this is 0.8uF).
anyway the 2sc5200 are very nice devices, so if you like those, you will probably love the 50xbd137, 50 for each amp is a nice number since in the store they will give me a 20% discount for 100 devices, i can have 100xBD137 for somehing like 15 euros,
even cheaper than 4 X 2sc5200! (at least in this store).
anyway, i'm starting my classes at the university, so i'm afraid that i will have to leave my experiment for now...
anyway , please if someone has tried this, write to me especially if you think that the results are not good, i am very interested since a plan to calculate (design is a too big word for me) an A-class , single ended, that works with single power supply (not a +0- power supply), i think the best , maybe ,is to modify
rod's design of the 20watts a-class.
i do not like the version of dual power supply because , there is some transistors that do not draw always the same current, as rod explains it is perfectly normal for a single ended with dual supply .
well, any way il will be comming here to see the posts,
cheers to all!