Aleph 30 the best choice of C1 C2 C3 on brian gt PCB

[tonimxp]

Who knows? You might just enjoy that!!

Hi!So.. I hope to get me are two beautiful nurses!

 

[Melon Head]

Ok!I think is stuff good end right

More importantly tell us how you are enjoying your amp.
I always love to hear a good story

 

[tonimxp]

More importantly tell us how you are enjoying your amp.
I always love to hear a good story

When i will finisch it i will let you know.

 

[wengtech]

short C1 you don't need it

pull out R10 , you don't need it

for C3 use decent cap

for C2 use Silmic , bypass it with 100nF MKC (polycarbonat)

i am doing this. already done.
before tweaks my dc out 0-10mV
after this tweaks dc out 70-80mV
why? is that normal?

btw the sounding indeed much more better after this tweaks, for me.

 

[Zen Mod]

70-80mV is nothing to write home about , but better to adjust it to zero

 

[tonimxp]

i am doing this. already done.
before tweaks my dc out 0-10mV
after this tweaks dc out 70-80mV
why? is that normal?

btw the sounding indeed much more better after this tweaks, for me.

You have to wait a few minutes before measuring the output voltage and you have to do with the load connected.
Have you done it?

 

[Zen Mod]

no

inputs shorted , no need for load , full temp ,lid closed

 

[tonimxp]

no

inputs shorted , no need for load , full temp ,lid closed

Ok!Good have known....

 

[wengtech]

when in balanced mode, dc out is 0-25mV
when in single ended mode (-in shorted with gnd), dc out is increased to 80mV
and it is peak at 300mV.

i am using Solen MKP 220uF/400v for the C2 bypass, is that the problem?

effect on the speakers : (with RCA connectors) there come some hiss and hum.
but no problem with the XLR mode.

 

[Zen Mod]

cap can't induce offset , excpt in case of broken (leaking ) one , which certainly isn't a case

few pics and some explanation will tell what's the reason for hiss and hum , when using unbalanced

 

[wengtech]

there is hum and hiss when setting like this: (dc out 80-300mV)

An externally hosted image should be here but it was not working when we last tested it.

but will be silent with this setting: (dc out 0-25mV)

An externally hosted image should be here but it was not working when we last tested it.

 

[Zen Mod]

1. setting DC offset and bias - all inputs grounded , amp hot , lid on (take it off just for quick re-set)

2. first pic is correct for unbalanced input

3.second pic is example of nada,zilch,hogwash ; neg leg input is floating , and you're not having full gain ; it is not balanced config

so - for proper operation - either connect it as per pic 1 , for unbalanced (RCA ) input , or bring proper balanced signal (as XLR wiring - remember that ? )

give us more pictures , so we can comment your grounding scheme and find culprit why you are having hiss & hum

 

[wengtech]

yes Zen Mod, i know how to wire XRL or RCA'
the pic above only to shown the changes dc output voltage with -IN shorted and unshorted.

this is basically i do with the amp:

An externally hosted image should be here but it was not working when we last tested it.

 

[Zen Mod]

you must ground both inputs (+ and - ) when setting offset

have you any pic of your PSU pcb layout ?

I mean , traces - that will help to see is there any room for improvement

 

[wengtech]

okay i see both + and - are grounded.

this is my PSU wiring:

An externally hosted image should be here but it was not working when we last tested it.

bleeder R and bypass Caps i mean:

An externally hosted image should be here but it was not working when we last tested it.

according to mr pass files,
there are no setting for this amp.

so, which component should be setting?

 

[wengtech]

i am using un matched IRFP244.
so voltage across each 0.47ohm are:
Right Ch: Left Ch:
R34 = 397mV 434mV
R35 = 517mV 486mV
R36 = 434mV 412mV
R37 = 508mV 496mV
R38 = 481mV 414mV
R39 = 363mV 438mV

original pass file, it should be 250mV across that resistors.

i am using this schematic:

 

[Zen Mod]

pcb seems adequate

so - for that pcb,best takeout point for gnd routing to output pcbs is point where you connected two wires from bridges , establishing gnd .

regarding Iq - do you hear benefit of increasing it , ref. original ?

 

[wengtech]

this is my first time to build aleph30 amp.
so i dont know what is the difference.

i am planning to re-wiring my PSU like this one:

An externally hosted image should be here but it was not working when we last tested it.

what do you think? will this solved the hum and hiss problems?

thanks.

 

[Zen Mod]

it'll be probably just fine

do not forget to put 10R/5A NTC between audio GND and chassis

 

[wengtech]

yes of course,
each channel will be equipped with :
- 2x2k2/2w as bleeder,
- 2x1ohm/5w in parallel on each rail to perform CRC,
- and 2xwima4.7uF/400v as bypass caps.

i hope this is enough for my aleph30.