Building a symmetrical PSU B1 buffer

[pmchoong]

pcb boards

I received my boards today. Thanks to Tea-bag, Salas, crt and everyone involved. The boards are beautiful.

 

[mr.duck]

Would this design be suitable for use as a headphone amp?

Assume that volume will not be a problem.

 

[Salas]

No.

 

[merlin2069er]

jfets?

Is anyone selling a set of matched jfets 2sk170 for the b1 buffer?

I could use a few.

 

[Cobra2]

Any common subs for the BC 517 ?

Arne K

 

[Salas]

BCX38C, MPSW45A and 2N6426. Watch out since their pin order is EBC when 517's is CBE as you face the flat front side. You got to place them subs against PCB's 517 orientantion.

 

[MashBill]

Do any of you know of a good USA source for R-core transformers? I would like to use one in my build.

Thanks,
Bill

 

[umut1001]

Is anyone selling a set of matched jfets 2sk170 for the b1 buffer?

I could use a few.

i have many quantities of 2sk170 quad matched.i also have 8pieces of 2sk389

 

[AndrewT]

Is anyone selling a set of matched jfets 2sk170 for the b1 buffer?

I could use a few.

the B1 does not need matched jFETs.
Just select similar Idss. Within 5% would be usable, 2% may improve performance.

 

[adamus]

my bag of leds are very tightly matched.. so tightly i cant piece them together to get the 5.4v.

all the led's measure 1.90 v @ 6ma.

do i need to get more LED' - how critical is the 5.4 v and 9.6v?

 

[grufti]

I have one Mez [proto] and one Hyp [production] each with those exact values for the LED strings. They work just fine and sound great. The design is rather forgiving.

my bag of leds are very tightly matched.. so tightly i cant piece them together to get the 5.4v.

all the led's measure 1.90 v @ 6ma.

do i need to get more LED' - how critical is the 5.4 v and 9.6v?

 

[AndrewT]

my bag of leds are very tightly matched.. so tightly i cant piece them together to get the 5.4v.

all the led's measure 1.90 v @ 6ma.

change the mA to tune in the ref voltage.

 

[adamus]

about 1.5ma gets me 1.8v.

 

[AndrewT]

1.5mA is maybe a bit too low. Try to find a CCS that passes ~3mA.
Test it at 5.7V (6mA CCS) first.

 

[merlin2069er]

I can't fit the output connectors onto the boards

Does anyone know what size drill bit I can use to slightly enlarge the holes?

I need to run out and get one at the hardware store.

 

[woodturner-fran]

Measure the output connector - or even bring it to the store with you. AFAIK, the board is single sided, but be careful enlarging the hole, you don't want to damage the plating too much if you can help it.


I'm thinking very strongly about mounting the DCB1 right inside my F5 amp (once I know its working OK!). Has anyone else here done that? I reckon I would leave one set of inputs somehow wired up so I could use the F5 as a power amp direct.

Anyone done this? I'm a little concerned about the heat (gets to 40degC inside my F5 case) but its still fairly low....


Fran

 

[Salas]

Watch its sinking to be good if you do, you better not afford DC rail out if one side PSU ever fails. This is a full DC coupled combo you are thinking to integrate. Why not starting with a capacitor between the two, at least for a trial period so to check basic reliability of parts and boxed in life?

 

[woodturner-fran]

Yep,

I'm hearin' ya. What I'll probably do is make it up and leave it on test for a while and see how it works. Prove the reliability etc.

But you raise an excellent point. Also, my F5 has the normal protection stuff disabled, so I'm doubly at risk!

mmmmmm

Fran

 

[Salas]

At least play with a set of small inexpensive speakers like a couple of plastic ones from an old desktop PC for 2 days burn in and reliability test, and cross your fingers for the years to come, if purist with no hint of a coupling cap nowhere. Are your speakers pricey? Those will get it if a failure ever occurs. There are relay power output protection circuits and kits that watch DC offset, introduce a delay to avoid power on thumps etc. to have too.

 

[woodturner-fran]

Right now, some Fe206 in a sachiko cabinet. So not mega expensive I know - but enough not to want to thrash them!

I'll build in a separate chassis for now and test reliability. Then afterwards reconsider the one-chassis-idea.

Fran