Bryston 4B SST clone

[Malta]

I agree with amplitude; with good matching and high quality components its an excellent amplifierKSC2690/KSC2690A. the PN100 and PN200 used for the differential pairs in the pre and power amp are now obsolete and hard to find,

Most of Semiconductor are not obsolete, because now available as SMD

The SMD version of the KSC2690

is available as the FMMT625 or 2SC2881


or use KSC3503 and KSA1381 for excellent linearity and agin


How about heat in IDLE ?

KSC3503 is very popular using in discret Class D Comparator stage

 

[Fetamp]

Cut a rectangular piece of aluminium or copper, that should help.

Thanks Amplidude....what is your opinion about MJL21194 VS NJW21194,as I checked with NJW21194 and gave good weight of sound than MJL ?

 

[Fetamp]

Hi all.....please send a link for input board selector switch.....

 

[amplidude]

It's a c&k dpdt rocker switch on-off-on , can't remember its name but measure its leg pitch.
If you're only going to use RCA or xlr input just wire it.

 

[amplidude]

Thanks Amplidude....what is your opinion about MJL21194 VS NJW21194,as I checked with NJW21194 and gave good weight of sound than MJL ?

I have no clue, I just used the mjl21193/194, looking at data sheet they appear the same the njw21194 has a little lower hfe, I think it's just a new version of the old MJL21194, maybe chalky knows?

 

[chalky]

Fetamp, if you're going to experiment with output devices bear in mind that the parts you mentioned, and the ones that Bryston used, are quite slow devices - the ft is only 4Mhz. Using modern high ft power devices ( ft=30-60Mhz ) could lead to instability. Not inevitably but frequently. I'm pretty sure I got my switches from RS, or less possibly from Farnell. Even if you can't order from them you should be able to get the manufacturer part number from their online catalogue so you order from elsewhere. I'm away from home at present or I'd look up the details of my order for you. If you're still stuck after a few days let me know and I'll dig out the details for you whem I'm back home.

 

[amplidude]

The njw21194 is also 4mhz.

 

[Fetamp]

The njw21194 is also 4mhz.

Here are data’s

 

[chalky]

Indeed, I was just warning Fetamp what to expect if he got more adventurous.

 

[Fetamp]

Fetamp, if you're going to experiment with output devices bear in mind that the parts you mentioned, and the ones that Bryston used, are quite slow devices - the ft is only 4Mhz. Using modern high ft power devices ( ft=30-60Mhz ) could lead to instability. Not inevitably but frequently. I'm pretty sure I got my switches from RS, or less possibly from Farnell. Even if you can't order from them you should be able to get the manufacturer part number from their online catalogue so you order from elsewhere. I'm away from home at present or I'd look up the details of my order for you. If you're still stuck after a few days let me know and I'll dig out the details for you whem I'm back home.

Thanks Chalky....will try to find out part number if not contact you.that njw one is very cold at idling and little warm at higher gain.pleas study data sheet that I have upload and advise me.
Thanks

 

[Fetamp]

Hi chalky and Amplidude.....another issue Q3 and 4 in input board are hot but amp is working perfectly what could be the reason?please explain.
Thanks

 

[amplidude]

Sounds like they're biased to hard, did you use correct components? Is it the same on both boards? Is the board regulating to the correct voltage +/÷ 33 volt?

 

[Fetamp]

Sounds like they're biased to hard, did you use correct components? Is it the same on both boards? Is the board regulating to the correct voltage +/÷ 33 volt?

Thanks Amplidude I used BC546/556...voltages are 29 and 31 ???.....did not used CRD replace with 15k resistor.anything related to input ?.Q7/8 also hot(BD140\0/139).....same problem in both boards
Thanks

 

[amplidude]

It's difficult to say, you altered various components, and somehow it's not behaving correct, I build mine in a few hours with correct parts and it just worked, I would guess you need those constant current diodes installed.

 

[Fetamp]

It's difficult to say, you altered various components, and somehow it's not behaving correct, I build mine in a few hours with correct parts and it just worked, I would guess you need those constant current diodes installed.

Thanks Amplidude....another thing noted transistors become hot when input board output connect to AMP input only ?

 

[chalky]

Fetamp, did you readjust the bias after you used a different output devices? Did you mix NJW MJL transistors? The emitter resistors should take care of current sharing so after a period of use all of the output devices should feel equally warm.

 

[Fetamp]

Fetamp, did you readjust the bias after you used a different output devices? Did you mix NJW MJL transistors? The emitter resistors should take care of current sharing so after a period of use all of the output devices should feel equally warm.

Thanks Chalky....those are not the output transistors....input board Q3,4,7,8 become hot when connect to AMP input.cold when disconnected.I used BC546/556 and BD140/139 for above transistors. Please advise me
Thanks

 

[chalky]

Fetamp do you have a schematic with part numbers for your input boards? I ask because the one that you used is different to the one that amplitude and I used.

 

[Fetamp]

Fetamp do you have a schematic with part numbers for your input boards? I ask because the one that you used is different to the one that amplitude and I used.

Thanks....schematic attached.I feel any incompatibility between input board’s output with AMP’S input?

 

[chalky]

Hmm thats odd. So Q1 and Q2 are cold but Q3 and Q4 are hot - is that right? If so, that suggests that there is very unequal current sharing in the Q1/2 and Q3/4 differential pairs. Are D1 and D2 inserted the right way around?