I have used these ones you said...they sound good
But i found them fragille...i had some of them burned...well.... read my name, Destroyer x means extra Destroyer....this is what i use to make, to burn parts.
2SC4793 and counterpart are better... see the capacitance and compare.... this one 20pf and 2SC2238 is 25pf.... watch the maximum frequency..the same...watch power...the same... 4793 does not need insulators..also the number is higher, means it is more modern.
I understand that more modern does not mean better.... about BD139/140, the higher numbers, the most modern ones are worse...it can happens with these units we are discussing too..but i have listened both...and for sure 2SC4793 sounds better...matches better to the amplifier voltage..i have tried one into high voltage unit...was an old model.... Troyan i think.
Already ordered?.. then good luck to you...i suggest you to order the 2SC4793 and complementary too.
regards,
Carlos
But i found them fragille...i had some of them burned...well.... read my name, Destroyer x means extra Destroyer....this is what i use to make, to burn parts.
2SC4793 and counterpart are better... see the capacitance and compare.... this one 20pf and 2SC2238 is 25pf.... watch the maximum frequency..the same...watch power...the same... 4793 does not need insulators..also the number is higher, means it is more modern.
I understand that more modern does not mean better.... about BD139/140, the higher numbers, the most modern ones are worse...it can happens with these units we are discussing too..but i have listened both...and for sure 2SC4793 sounds better...matches better to the amplifier voltage..i have tried one into high voltage unit...was an old model.... Troyan i think.
Already ordered?.. then good luck to you...i suggest you to order the 2SC4793 and complementary too.
regards,
Carlos
Last edited:
Carlos, I've imported SPICE models for them as well and they don't give any better result than the MJE1503x. The fT for the pair you suggest are not well matched, 100MHz vs 70MHz, so I'm not sure they will be good drivers.
The best pairs I've found so far are Toshibas 2SA968B & 2SC2238B and Sanyos 2SA1011 & 2SC2344.
I should get my old Toshibas within a few weeks, I'll post observations when I install them
The best pairs I've found so far are Toshibas 2SA968B & 2SC2238B and Sanyos 2SA1011 & 2SC2344.
I should get my old Toshibas within a few weeks, I'll post observations when I install them
Last edited:
Cannonica... we cannot listen 70 Megahertz
What will happens there is not something to worry about, unless this appear into the capacitance in between transistor leads.
This mismatch will appear into harmonics that will produce interference into VHF radio band.... will not bother humans.
regards,
Carlos
What will happens there is not something to worry about, unless this appear into the capacitance in between transistor leads.
This mismatch will appear into harmonics that will produce interference into VHF radio band.... will not bother humans.
regards,
Carlos
It is always difficult to describe how the amplifier now sounds, but I will try.
The sound is now quite open the bas is very very deep and tight.
The amp sounds now NOT more laid back, and there is much more emotion in music what I find very important.
The Dx Blame MKIII-Hx can play so hard without that it irritates but dangerous for the tweeters.
This was a huge difference than before.
The last modifications will be and my 2 big 2 x 42V 2000VA torroids with or without the Mundorf 47000uf / 80VDC, MLytic® HC
And the switch from 180pf to 100pf.
Can someone tell me what the sound of the amplifier will be, if I solder the 100pf silver mica?
All the best wishes for 2013
Regards,
Rudy
The sound is now quite open the bas is very very deep and tight.
The amp sounds now NOT more laid back, and there is much more emotion in music what I find very important.
The Dx Blame MKIII-Hx can play so hard without that it irritates but dangerous for the tweeters.
This was a huge difference than before.
The last modifications will be and my 2 big 2 x 42V 2000VA torroids with or without the Mundorf 47000uf / 80VDC, MLytic® HC
And the switch from 180pf to 100pf.
Can someone tell me what the sound of the amplifier will be, if I solder the 100pf silver mica?
All the best wishes for 2013
Regards,
Rudy
Hi Rudy-
My opinion is that no one can answer your question because no one has your ears or your brain except you. I encourage you to make this change and evaluate the results for yourself. From a technical standpoint the slew rate of your amp should increase with the change in Cdom. Whether this will be audible to you is unknown. So you need to make the change if you want to know.
Happy New Year and regards,
Steve
Hi Martin-
I recently installed the 2SD669A in the VAS position and the 2SB649A in the CCS. These are used in several Randy Slone designs and I had several on hand. I also like the fact that the collector-base capacitance is lower (14pf) than many of the other candidates. I did not change the drivers. Output clipping is now symmetrical until about 4 Khz where some negative side rail sticking appears. The "dent" was previously eliminated by removing the BS cap.
Steve
I do not think so....one works as a fixed resistor, the CCS does not operate ...
dinamically...almost all transistors manufactured in this world, that is able to face the voltage we have there in our circuit (from colector to emitter) and that is able to face the current we have there (from colector to emitter) will fit the task as a CCS driver transistor..have to respect only if NPN or PNP.
But the VAS transistor is the most important transistor we have in our amplifier, it is responsible by the generation of all swing of voltage that gonna appear in the output, this one operates dinamically and is not making pair with anyone..it stand alone just feeded by the first VAS stage.
I do not think you should use pairs...this will not change anything...but if you want this way..also will not harm the circuit.
CCS represents a fixed resistor... a kind of fixed resistor that does not suffer the consequences of load variations.... the current is stable...so...it is a clever resistor let's say this way..but does not operate dinamically in high frequencies alike audio...it works in very low frequency, almost zero, just controling the current...it is more a power source than an amplifier.
The VAS goes dinamically, beeing the most important transistor in the circuit...it also senses the output variation of impedance...this stage is the most important, and the amplifier performance also depends, a lot, on this circuit...this transistor can increase or decrease the power amplifier performance.... transconductance happens there too, as in the differential pair you have swing of current, no voltage swing...you cannot see waveform in the differential pair load using scope...but the VAS "generates" all the voltage swing that gonna be transfered to the output that will only increase current following the voltage generated.
Several years ago i have used these transistors (2SD669A and 2SB649A).... a very high gain transistor but die like a bird....they die easy..fell down almost dead when sick...poor bird close eyes and fell down..when reach the floor it is already dead..... this transistor die so easy as a bird... i have lost all six 6 pairs i had...this seems, at least to me, they are not that reliable...or strong...or resistant.
For they are good transistor...no doubts about that.... my experience with them was not so good as they have not survived.. but when working, produced nice sonics, had excelent gain and very low noise..high frequency response was excelent.
regards,
Carlos
dinamically...almost all transistors manufactured in this world, that is able to face the voltage we have there in our circuit (from colector to emitter) and that is able to face the current we have there (from colector to emitter) will fit the task as a CCS driver transistor..have to respect only if NPN or PNP.
But the VAS transistor is the most important transistor we have in our amplifier, it is responsible by the generation of all swing of voltage that gonna appear in the output, this one operates dinamically and is not making pair with anyone..it stand alone just feeded by the first VAS stage.
I do not think you should use pairs...this will not change anything...but if you want this way..also will not harm the circuit.
CCS represents a fixed resistor... a kind of fixed resistor that does not suffer the consequences of load variations.... the current is stable...so...it is a clever resistor let's say this way..but does not operate dinamically in high frequencies alike audio...it works in very low frequency, almost zero, just controling the current...it is more a power source than an amplifier.
The VAS goes dinamically, beeing the most important transistor in the circuit...it also senses the output variation of impedance...this stage is the most important, and the amplifier performance also depends, a lot, on this circuit...this transistor can increase or decrease the power amplifier performance.... transconductance happens there too, as in the differential pair you have swing of current, no voltage swing...you cannot see waveform in the differential pair load using scope...but the VAS "generates" all the voltage swing that gonna be transfered to the output that will only increase current following the voltage generated.
Several years ago i have used these transistors (2SD669A and 2SB649A).... a very high gain transistor but die like a bird....they die easy..fell down almost dead when sick...poor bird close eyes and fell down..when reach the floor it is already dead..... this transistor die so easy as a bird... i have lost all six 6 pairs i had...this seems, at least to me, they are not that reliable...or strong...or resistant.
For they are good transistor...no doubts about that.... my experience with them was not so good as they have not survived.. but when working, produced nice sonics, had excelent gain and very low noise..high frequency response was excelent.
regards,
Carlos
Last edited:
- Status
- Not open for further replies.