Burning Amp BA-3

[BDP]

Originally Posted by nkdk

Hi
Thx for the answers
I have swap p1-p2 too 1kΩ and the volts over R10-11 is 1,0 volts now, then this okay ,
there is running 45 ma , but how about Q1-2 there is only running 4 ma,is that a problem ??
600 Ω drain resistor? , there is no 600 Ω resistor only 10 Ω with a 100 Ω pot
Nkdk

The 4 ma is why you had to increase the drain resistance. I think the Idss was specified to be 10 ma. Problem, I don't know? Have a listen and see what you think.

The 600 ohm was the combined total drain resistance, but that doesn't matter now that you have put in the new pot.

[nkdk]

Hi
Okay thx, i give it a try and make some listen tests, and ma by fiddle with q1-2

Nkdk

[Pwrs]

Hi there, i was hoping that someone could point me in the right direction regaring some measurements on the front end. I have a dip/overshoot on the negative curve that i would like to understand.

Voltage on the resistors are:
Left
R3/R4 = 64.66 - 64.69mV
R10 = 1.042 V
R11 = 1.037 V

Right
R3/R4 = 65.08 - 65.10mV
R10 = 1.038
R11 = 1.036

Here are som waveforms from the scope, the blue ones are for left channel and red for right. The input is 2Vp-p @ 5k, 50k and 100kHz.
Measured across R13.
2Vpp_5Khz_Left.gif2Vpp_5Khz_Right.gif
2Vpp_50kHz_left.gif2Vpp_50kHz_Right.gif
2Vpp_100Khz_Left.gif2Vpp_100Khz_Right.gif

[Zen Mod]

fiddle with P3

[noSmoking]

Hi
Would some one help me out here I don't know where to connect the connection from the ba 3 to the bias board ,Like what connects to D+ or D- or S
Thanks
NS

[tinitus]

Originally Posted by noSmoking

......Like what connects to D+ or D- or S
Thanks
NS

according to new BA3 frontend schematic, +D is signal out(to power amp)
I reckon -D would be signal ground

S ...? I only find that on old BA1 frontend, so I guess it goes nowhere now with new BA1/BA3 ?

[Zen Mod]

who made these pcbs ?

[generg]

Diyaudio store

Output of One side of the BA-3 frontend to D (GS) and ground G of One bias board, the same with the other output of the BA-3 Frontend and the other bias board.
D+ and D- are Only for the bias and S is the feedback sensing the bias current.

[Zen Mod]

so there must be a blog somewhere ?

D+ and D- are reminding me on BA3 balanced

sorry - I just didn't follow birth of pcbs

[generg]

Unfortunately Nelson's PDF and the bias and output board nomenclature are a bit different

I always had to think twice when connecting these parts and often.......did it the wrong way.
In this case D+and D- refer to the drains of the upper and lower outputstage and their bias. D (GS) !GS means gainstage, is the real input and the ground point nearby is for he shielded cable.