only the AM pcb :
Phil.
An externally hosted image should be here but it was not working when we last tested it.
Phil.
C3, the mute, is tapped into the Signal Ground.
That might create unwanted noise.
The Main Audio Ground, or Star ground as many refer to it, is the underside of the Power Ground input terminal. That is where the Power Ground meets the Signal Ground and the Speaker Return and the MF decoupling Return.
There is no RF filter. Add it on.
If you use two Boards in a stereo chassis you will need to add a resistor+2diodes in the Signal Ground link. There is plenty of room on the top side between the two sets of 2pole terminals. drill 6 holes through for the 3 components and solder to the ground that runs along the front edge. Then cut the trace between the components leads.
There is a large loop area in the signal routing. I can't see what you can do to reduce that.
There is no HF decoupling. Add this directly to the Power pins and take a short Ground link to the MF decoupling Ground.
That might create unwanted noise.
The Main Audio Ground, or Star ground as many refer to it, is the underside of the Power Ground input terminal. That is where the Power Ground meets the Signal Ground and the Speaker Return and the MF decoupling Return.
There is no RF filter. Add it on.
If you use two Boards in a stereo chassis you will need to add a resistor+2diodes in the Signal Ground link. There is plenty of room on the top side between the two sets of 2pole terminals. drill 6 holes through for the 3 components and solder to the ground that runs along the front edge. Then cut the trace between the components leads.
There is a large loop area in the signal routing. I can't see what you can do to reduce that.
There is no HF decoupling. Add this directly to the Power pins and take a short Ground link to the MF decoupling Ground.
Thank's Andrew..
RF filter, ok
HF decoupling ok
but I don't understand "you will need to add a resistor+2diodes in the Signal Ground link"
What values and how ?
Phil.
RF filter, ok
HF decoupling ok
but I don't understand "you will need to add a resistor+2diodes in the Signal Ground link"
What values and how ?
Phil.
The power that I will use (missing two 10000 uF), transformer 20 volts 160VA :
An externally hosted image should be here but it was not working when we last tested it.
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When you run two or more amplifiers inside one chassis there is a ground loop as soon as you connect the second interconnect.
To reduce the current in that external loop you must increase the resistance between the Signal Ground and the Power ground so that the voltage drop along the signal return wire is reduced sufficiently.
thus for stereo you need two sets of:
1n4002 in one direction
in parallel another 1N4002 but facing in the opposite direction (these make up an inverse parallel pair).
and a 10r low power resistor in parallel to the diodes.
Fit one set to each PCB.
Some refer to this as a "lifted ground". Learn to stop using that phrase. "lifted ground" can mean very different topologies to different builders, one of which is potentially FATAL.
To reduce the current in that external loop you must increase the resistance between the Signal Ground and the Power ground so that the voltage drop along the signal return wire is reduced sufficiently.
thus for stereo you need two sets of:
1n4002 in one direction
in parallel another 1N4002 but facing in the opposite direction (these make up an inverse parallel pair).
and a 10r low power resistor in parallel to the diodes.
Fit one set to each PCB.
Some refer to this as a "lifted ground". Learn to stop using that phrase. "lifted ground" can mean very different topologies to different builders, one of which is potentially FATAL.
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Hi,
About heatsink, from an old ss amp I have this :
What is the best way, 2 LM's on the same heatsink like A, or separate like B..
LM is "TF" isolated, it is necessary to use thermal componant ?
Phil.
About heatsink, from an old ss amp I have this :
An externally hosted image should be here but it was not working when we last tested it.
What is the best way, 2 LM's on the same heatsink like A, or separate like B..
LM is "TF" isolated, it is necessary to use thermal componant ?
Phil.
You MUST use a thermal paste to exclude ALL air from the contact interface.
This can be VERY thin, just no air.
This can be VERY thin, just no air.
Hi,
Before purchase a nice box, I mount LM's on wood board, to listen what happen..
Some parts are missing, I hope received it in next days..
Before purchase a nice box, I mount LM's on wood board, to listen what happen..
Some parts are missing, I hope received it in next days..
An externally hosted image should be here but it was not working when we last tested it.
A guy told me on french forum about a serial RC.. He said that souding better, but I don't knaw why and how..
The schematic (in red) :
Thank's, Phil.
The schematic (in red) :
An externally hosted image should be here but it was not working when we last tested it.
Thank's, Phil.
C7=33nF sounds very wrong.
If it is needed and that is a BIG "if" then try 5pF in small steps to 47pF
R5 ~ R3
input RC is a low pass filter to attenuate RF interference.
You already have R6. Add C in parallel across R5. Try 1k and 470pF
C4 will need to be an electrolytic. Some say polarised, other say non polarised (Cordell),
Make the RC of R4*C4 big enough to NOT work as a LF frequency filter.
C1 & C2 are dual capacitors. See National datasheet. Cx or Cz?
If it is needed and that is a BIG "if" then try 5pF in small steps to 47pF
R5 ~ R3
input RC is a low pass filter to attenuate RF interference.
You already have R6. Add C in parallel across R5. Try 1k and 470pF
C4 will need to be an electrolytic. Some say polarised, other say non polarised (Cordell),
Make the RC of R4*C4 big enough to NOT work as a LF frequency filter.
C1 & C2 are dual capacitors. See National datasheet. Cx or Cz?
Hi,
Thank's Andrew, I'll drop this for now, and see after at sounding..
For network with 2 diode and resistor at ground input, I have the diodes but only 121 Ohm for resistor, not 10 Ohm..
It's work, or it's better with 10 Ohm.
Phil.
Thank's Andrew, I'll drop this for now, and see after at sounding..
For network with 2 diode and resistor at ground input, I have the diodes but only 121 Ohm for resistor, not 10 Ohm..
It's work, or it's better with 10 Ohm.
Phil.
Try the 121r for now.
You can measure the Vdrop and from that estimate the value of the current flowing along that Signal Ground to Power Ground wire. It should be very low, maybe into the nanoAmperes range.
You can measure the Vdrop and from that estimate the value of the current flowing along that Signal Ground to Power Ground wire. It should be very low, maybe into the nanoAmperes range.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Phil.
no.
The Disconnecting Network is between the Signal Ground Circuita nd the Power Ground Circuit.
These tow Circuits are kept intact. You ADD a link between the two.
You do not break either circuit and insert into that break.
The Disconnecting Network is between the Signal Ground Circuita nd the Power Ground Circuit.
These tow Circuits are kept intact. You ADD a link between the two.
You do not break either circuit and insert into that break.
Yes Andrew I read what you wrote, but I did that Sunday morning !!
And Sunday morning is't good to work..
I'll cut the trace between ground signal and power ground to place the disconnect network..
Phil.
And Sunday morning is't good to work..
I'll cut the trace between ground signal and power ground to place the disconnect network..
Phil.
Why did you not build the amp as stock, and make sure it works, before making "improvements". They normally sound pretty good as standard anyway.
Build it! Run it! then see if you can sonically improve it!
Build it! Run it! then see if you can sonically improve it!
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