Either way will work fine.
The coil adds protection from capacitive loading but we are talking values in the tens of nF region and higher here. There is no significant capacitive load connecting straight to a speaker protection relay and in any case the 0.22 ohm series output resistor gets you 90% of the way there stability wise even without a coil.
So no problems whichever way you configure it 🙂
The coil adds protection from capacitive loading but we are talking values in the tens of nF region and higher here. There is no significant capacitive load connecting straight to a speaker protection relay and in any case the 0.22 ohm series output resistor gets you 90% of the way there stability wise even without a coil.
So no problems whichever way you configure it 🙂
Print the PCB 1:1 on a piece of paper to use it as fit and function replica, where you will route the wiring etc.
Just built two of these but messed up the diodes on one and I think I took out a FXC596 diode. Built the second one using the picture provided by Geoff.
Any advise on testing these boards? Just hook up the +-43 volts dc from the psu board and then one of the 32 volt ac secondaries. After do I just look for continuity between left in and left out? I tried doing this and I dont have any continuity between the speaker inputs and outputs.
Any advise on testing these boards? Just hook up the +-43 volts dc from the psu board and then one of the 32 volt ac secondaries. After do I just look for continuity between left in and left out? I tried doing this and I dont have any continuity between the speaker inputs and outputs.
Attachments
Firstly, connect a moderate load resistor (1K say) between left output / ground and between right output / ground.
- Power on/off test
Connect a tone to the left input. With no power applied to your PSU, you should see no tone at the output. Now turn on your PSU and you should see no tone at the output for a few seconds then the tone should appear. Turn off the PSU and you should see the tone immediately vanish from the output. Repeat for the right channel. - Voltage offset test
To verify correct function of the dc offset voltage shutdown, maintain the tone input and output load as for the previous test then power up the PSU. After the turn on delay, the tone will appear at the output. Now apply around 4-5Vdc to the output and verify the tone disappears almost immediately (remember there's a time constant on the voltage offset circuitry). Do this for both a +ve and a-ve dc voltage. Do this for both channels.
C6 is one of those parts where you will find various descriptions of it function. Back when this was designed it was common practice to see such a part. Its function never seems to be explained in designs and if you look at various circuits for amps some have it and some don't. The Hafler DH-500 picking one at random is one that does.
In practice it can help in square wave testing on some amps by speeding up the turn on and turn off of the driver stage when driven by fast rise time high amplitude signals. That is where I have observed it makes a difference. It can also possibly give a tiny increase in open loop gain at HF and reduce distortion a fraction. You will see values anywhere from 1uF to 47uF or even higher.
Good question and there is little info on this.
In practice it can help in square wave testing on some amps by speeding up the turn on and turn off of the driver stage when driven by fast rise time high amplitude signals. That is where I have observed it makes a difference. It can also possibly give a tiny increase in open loop gain at HF and reduce distortion a fraction. You will see values anywhere from 1uF to 47uF or even higher.
Good question and there is little info on this.
I have a 37V dual secondary toroidal transformer.
It makes +/-48V with load I guess.
Is is acceptable for this amp?
It makes +/-48V with load I guess.
Is is acceptable for this amp?
The basic design is fine with that voltage provided you ensure the current source and VAS transistors run within acceptable limits. Measure the off load voltage of the transformer and calculate the rail voltage that gives and then make a decision based on that,
Hi Mooly
sorry , i do not read the complete thread.
amp is nearly finished...Output network is missing and
C2 is 150pF and what i downloaded on BOM it should be a mica cap?
C4 should be 47F 63V or 4,7F as goeff1 wrote?
thanks in advance
chris
sorry , i do not read the complete thread.
amp is nearly finished...Output network is missing and
C2 is 150pF and what i downloaded on BOM it should be a mica cap?
C4 should be 47F 63V or 4,7F as goeff1 wrote?
thanks in advance
chris
It should be 47uF 63V (see post 1801).
As far as C2 goes, I've used an NP0 ceramic chip for this. - I'm assuming your building my SMD layout as you quote me in the earlier post). Mooly will be along soon to confirm what you need.
Geoff
Hy
...sorry...
is it recommended to connect IP GND to GND with extra cable, as i can see on some pics?
...sorry...
is it recommended to connect IP GND to GND with extra cable, as i can see on some pics?
The value for C4 shouldn't be all that critical. Anything from 4.7uF to 47uF should be fine. Mooly's original schematic has it at 47uF.
C2 can be a ceramic C0G/NP0 or a poly MKP film cap.
C2 can be a ceramic C0G/NP0 or a poly MKP film cap.
I've just looked back at this and it was actually to do with the speaker protection 🙄 so please disregard it. I'll go back to sleep now...