Hugh,
Thanks for the reply. I will build the offboard RL circuit between the output and the speaker posts and proceed with testing.
MM
Thanks for the reply. I will build the offboard RL circuit between the output and the speaker posts and proceed with testing.
MM
Oh Try keep the same Nad amp , change NPN by PNP .
some one can tell me reason using Quasi stage at output ?
some one can tell me reason using Quasi stage at output ?
@chermann,
Warning Post# 2763 by dungdochi1978 is not the modification we are talking about. Read post's #2758 - #2760 and you will see the mod we are talking about.
The mod is making a connection from the - side of C7 to the anode of the 3.3V zener. Some schematics have the connection from the - side of C7 to the cathode of the 3.3V zener.
If your schematic does not have the mod, do not be alarmed, the amp will work. If you want to try the mod and see if it makes a difference in what you hear or what you measure, if you have the right equipment, that is up to you.
Regards,
MM
Warning Post# 2763 by dungdochi1978 is not the modification we are talking about. Read post's #2758 - #2760 and you will see the mod we are talking about.
The mod is making a connection from the - side of C7 to the anode of the 3.3V zener. Some schematics have the connection from the - side of C7 to the cathode of the 3.3V zener.
If your schematic does not have the mod, do not be alarmed, the amp will work. If you want to try the mod and see if it makes a difference in what you hear or what you measure, if you have the right equipment, that is up to you.
Regards,
MM
R21 in your modified circuit must go from emitter of the PNP to the output point (R20). Otherwise it does not work to protect the output stage from thermal runaway.
One Quasi channel tested with Thiago's pcb, with no wire from C7- to cathode of 3.3V zener. Not much drama, no smoke, led's lit up, bias at 45mV over 0.33 ohm resistors for about 150mA. Offset hovered around +/-2mV. Heatsink and transistors are warm to the touch. One surprise is that the 100W-8ohm resistor that was attached to the amp output and one of the grounds on the amp board did not heat up at all (possible I hooked up incorrectly).
Anyways, I hooked it to the speaker and played some music for an hour or so, watching the meters and making sure everything was OK. I am quite impressed with what I heard. I played some old rock ballads and probably could have listened all night as the sound was so natural and non fatiguing. Only problem I had was some slight hum from the speaker that was noticeable from 4 feet away from the speaker. Hopefully I can get rid of this when completing the build in a proper chassis.
I have attached a pic of my rats nest of wiring😉. I am content and will start on the second channel.
Anyways, I hooked it to the speaker and played some music for an hour or so, watching the meters and making sure everything was OK. I am quite impressed with what I heard. I played some old rock ballads and probably could have listened all night as the sound was so natural and non fatiguing. Only problem I had was some slight hum from the speaker that was noticeable from 4 feet away from the speaker. Hopefully I can get rid of this when completing the build in a proper chassis.
I have attached a pic of my rats nest of wiring😉. I am content and will start on the second channel.
Congratulations Myles! You have done a good build and it it should last a long time.
150mA is a good quiescent, a little high perhaps but it should sound very mellow and fruity.
Impressed by Thiago's elegant pcb. He laid it out very well and by adding the power supplies, positive left and negative right on the same pcb, the layout makes it much easy to wire up.
Take care with your grounding and be sure to have R3 (10R) ground bypass in place. Ensure the power ground is connected to the chassis, which should be earthed to the mains. This shows the FFT of this amp at 1KHz and +20dBU. It is H2 dominant at -73dB, H5 at -92dB, and successive harmonics descending evenly. Distortion is not low, it's typically 0.025% in the simulation, but it is musical. This is why this amp sounds a bit 'fruity', a warm sound. Many do not like this sound, they say it's distorting, but then many like tube amps too and they distort at less ten times more. So you make your choice.......
Cheers,
Hugh
150mA is a good quiescent, a little high perhaps but it should sound very mellow and fruity.
Impressed by Thiago's elegant pcb. He laid it out very well and by adding the power supplies, positive left and negative right on the same pcb, the layout makes it much easy to wire up.
Take care with your grounding and be sure to have R3 (10R) ground bypass in place. Ensure the power ground is connected to the chassis, which should be earthed to the mains. This shows the FFT of this amp at 1KHz and +20dBU. It is H2 dominant at -73dB, H5 at -92dB, and successive harmonics descending evenly. Distortion is not low, it's typically 0.025% in the simulation, but it is musical. This is why this amp sounds a bit 'fruity', a warm sound. Many do not like this sound, they say it's distorting, but then many like tube amps too and they distort at less ten times more. So you make your choice.......
Cheers,
Hugh
Chris, yes the same ones.
Hugh, thanks for support and the info for grounding. I can dial back the bias easily. I tried it at various stages from 120mA - 150mA. R3 is in place and the power inlet will be ground to chassis( dirty ground) along with the transformer static shield wires.
Questions:
1. I was attaching the speaker return to 1 of the 2 ground tabs on the pcb, is that correct?
2. Should I ground the heatsinks to the dirty chassis ground?
3. Does the pcb need to be ground to the chassis somehow ? If so, what is the proper method ?
Grounding has always been my nemesis so thanks for the help. Now to continue with building the 2nd channel, chassis, etc.
MM
Hugh, thanks for support and the info for grounding. I can dial back the bias easily. I tried it at various stages from 120mA - 150mA. R3 is in place and the power inlet will be ground to chassis( dirty ground) along with the transformer static shield wires.
Questions:
1. I was attaching the speaker return to 1 of the 2 ground tabs on the pcb, is that correct?
2. Should I ground the heatsinks to the dirty chassis ground?
3. Does the pcb need to be ground to the chassis somehow ? If so, what is the proper method ?
Grounding has always been my nemesis so thanks for the help. Now to continue with building the 2nd channel, chassis, etc.
MM