Mezmerize B1 Buffer Preamp

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outtek

Member
Joined 2017
Need some clarifications

Hi guys, I need some help regarding some components used on the Mezmerize B1, the PCB/BOM says to use 2x68 Ohms resistor in parallel, I have checked the schematic posted and it says 470 Ohms in parallel, wich is correct? would just using what the BOM says make a working buffer?, also in the schematic the BJ transistors specified are BC546. What should I use? Normally BC546 should do just fine also. Where the ones specified in the BOM behaving better than what is the schematic?
Thanks in advance,
Florin
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Don't take that Eagle schematic as definitive parts or symbols reference. It was just made from handy library parts with right dimensions to produce the board layout. Use 2x68 or 2x47 which is 3x68 equivalent. First is little current for no sinks, second is some more current for small clip-on sinks.
 
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outtek

Member
Joined 2017
Salas said:
Don't take that Eagle schematic as definitive parts or symbols reference. It was just made from handy library parts with right dimensions to produce the board layout. Use 2x68 or 2x47 which is 3x68 equivalent. First is little current for no sinks, second is some more current for small clip-on sinks.
Click to expand...

Thanks for the fast reply, so I will just use what the BOM says wich matches the PCB I have received, thanks again, I have some BC546 also in my stock:) .
The 1N4001 are not that critical so I can even use 1N4007.
Thanks again.
 
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outtek

Member
Joined 2017
Hi, one more thing, my local supplier did not had in stock IRFP9240 so I ordered the 9140, can I use it along with the IRFP240? or I realy need the 9240? The NEC relay mentioned as a substitute for the one in the BOM I could not get it localy, I did found this one : Panasonic TQ2-L2-12V, as far I checked it seems to be similar, it has allmost the same pareameters as the NEC mentioned on the forum, is it ok to use this one?
Thanks in advance,
Florin
 
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outtek

Member
Joined 2017
Thanks Salas, I deleted from my order, unfortunately the supplier is not very clear about latching or unlatching on the descrption or maybe I am not looking where I should, I found this one also : TE CONNECTIVITY 1462033-5 (made by Axicom ), is it ok? I have checked the datasheet and i can't find nowhere if its non latching or not.
Thanks.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Monostable means non latching I think. There are many parameters in a relay and I can't recommend other than known working parts in this circuit unless you are willing to experiment with those alternatives seeming fit.

About the transistor use a BC550 with a 0.1uF across its collector and base pins when you can't get 517 or equivalent Darlington
 
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outtek

Member
Joined 2017
Thanks, I will order from Mouser later the one made by NEC, I did found a BC517, this variant of it : BC517_D74Z made by Fairchild, I will take this one, I wont have more than 30V in this build anyway. The BC550 I was asking what can I use to replace it, I have some BC546.
Thanks again.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
BC546 can replace a lower voltage BC550 in this since all that transistors family covers our voltage spec here with ease but it has looser noise spec I believe. Since this is a low noise regulator section better get and use the 550/560
 
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AndrewT

R.I.P.
Joined 2004
The DCB1 NEEDS a low noise high gm device for the two input jFETs (4 in stereo), if you want to mimic B1 performance.
It also needs a low Vpinchoff device in the regulator part.
All the other jFETs can be cheaper medium gm, or low gm, devices. Don't waste expensive LSK170s where they are not needed.
 
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AndrewT

R.I.P.
Joined 2004
you NEED one low Vpinch off in each regulator.
An lsk170a, or 2sk170gr, or similar, is needed to get that low Vpinchoff. It has to operate as a Constant Current Sink with only one Vbe (~600mVbe) as it's Vds and this should be around 2times Vpinchoff for good CCS performance.
Look at the sch and analyse what is happening around each device. Read the Thread for back up information on how the circuit operates.
 
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