Just as I've managed to get all the parts I need to build my M2x, my circumstances have somewhat changed. We're moving to a new house and SWMBO (she who must be obeyed) has expressed a very strong desire for a wireless sound system throughoutSo I now find myself heading in the direction of needing a really nice headphone amp so I can retire into my own little musical world without disturbing anyone else.
Gary
I'm getting to where I cringe every time I see the acronym SWMBO.
I'm still married to my 1rst wife and do understand that compromises are needed.
As does she.
However, SWIBO (she who is being obeyed) getting a whole house wireless system and you a corner with a set of headphones is not only inequitable, it's demeaning.
to batty #1624
Good Morning batty,
my M2X drives my 2-way Loudspeakers (4 Ohm) with a sensitivity of ca. 91dB / 1W/1m with ease to very loud levels.
If I use my BA-3 Preamp (pretty high gain) I seldom go over 1/4 - 1/2 turn of
the volumeknob.
Most of my sources put out around 2V.
I was surprised how powerful it is.
Greets
Dirk
Good Morning batty,
my M2X drives my 2-way Loudspeakers (4 Ohm) with a sensitivity of ca. 91dB / 1W/1m with ease to very loud levels.
If I use my BA-3 Preamp (pretty high gain) I seldom go over 1/4 - 1/2 turn of
the volumeknob.
Most of my sources put out around 2V.
I was surprised how powerful it is.
Greets
Dirk
I'm building the M2X and have a problem. After stuffing and soldering both amplifier boards I tested for proper voltage at the secondaries, diode boards, and the PSU output blocks. No problems found. I then wired and connected the left channel board. I tested with the dim bulb tester first. The bulb lit and dimmed quickly. I took that to mean no shorts. I then removed the tester and started to set offset. I used a shorting plug but no dummy load tester as I don't have that. After a few minutes I saw smoke coming from the board in the Q2 area. I shut down immediately. The resistor at R14 looked a little smudged. I put my finger on it and it was too hot to keep there.
I've confirmed that the output devices at Q1 and Q2 are installed correctly. I confirmed that I installed the resistors in the right locations. They all measure OK except for R12, which is a 100 ohm resistor measuring 83 ohms. I've confirmed that the Keratherm is OK - no tears, holes or anything that might impede full contact with the heatsink. I powered up again, same result except I think I saw smoke coming from Q7 but I'm not sure because I shut it down really quickly. I removed the board from the heatsink and looked for anything that might help to locate the problem. I didn't see anything obvious. I did confirm that the optoisolator at Q5 was installed with Pin 1 in the right place. Same for the Edcor signal transformer.
I decided to test the right channel. I disconnected the left channel. No smoke or bad smell so I guess whatever I did wrong on the other board wasn't repeated on this one, although there's problems there too. Offset fluctuates from 0.00 to about 3.0. Very low audio output and badly distorted. I'm going to concentrate on the first board for now. Any thoughts on what could be causing the behavior I described? I won't be surprised if some parts will have to be replaced. R14 looks pretty bad.
Thanks,
Gary
I've confirmed that the output devices at Q1 and Q2 are installed correctly. I confirmed that I installed the resistors in the right locations. They all measure OK except for R12, which is a 100 ohm resistor measuring 83 ohms. I've confirmed that the Keratherm is OK - no tears, holes or anything that might impede full contact with the heatsink. I powered up again, same result except I think I saw smoke coming from Q7 but I'm not sure because I shut it down really quickly. I removed the board from the heatsink and looked for anything that might help to locate the problem. I didn't see anything obvious. I did confirm that the optoisolator at Q5 was installed with Pin 1 in the right place. Same for the Edcor signal transformer.
I decided to test the right channel. I disconnected the left channel. No smoke or bad smell so I guess whatever I did wrong on the other board wasn't repeated on this one, although there's problems there too. Offset fluctuates from 0.00 to about 3.0. Very low audio output and badly distorted. I'm going to concentrate on the first board for now. Any thoughts on what could be causing the behavior I described? I won't be surprised if some parts will have to be replaced. R14 looks pretty bad.
Thanks,
Gary
Attachments
I know nothing about your problem. But are you going to run the PSU without the Heatsinks to the devices? Not saying that is where your smoke is coming from, but I would not venture a full test without those.
I repeat, I know little about this, it's just something I wouldn't do myself.
Good luck with the amp.
Best regards,
Rafa.
I repeat, I know little about this, it's just something I wouldn't do myself.
Good luck with the amp.
Best regards,
Rafa.
Then I was right about one thing: "I know nothing..."
Thanks for the clarification.
I'm sure that's far from the truth. Thanks Rafa.
garyalex, the last guy who reported burned up 0.47 ohm resistors, discovered the cause via a simple continuity check.
He unplugged his M2X from the mains, waited 10 minutes, disconnected the amplifier boards from the PSU. Then he used a digital multimeter to measure resistance between the MOSFET mounting bolt, and each of the MOSFET Drain, Gate, Source. If there's low resistance from the mounting bolt (a/k/a the heatsink) to any of D, G, S .... that's wrong. In his case, he had a small metallic burr on his heatsink which pierced the Keratherm insulating pad and shorted the MOSFET package to the heatsink. Ouch!! It kept doing this every time he replaced the MOSFETs, which he did more than once. Ouch!!
He unplugged his M2X from the mains, waited 10 minutes, disconnected the amplifier boards from the PSU. Then he used a digital multimeter to measure resistance between the MOSFET mounting bolt, and each of the MOSFET Drain, Gate, Source. If there's low resistance from the mounting bolt (a/k/a the heatsink) to any of D, G, S .... that's wrong. In his case, he had a small metallic burr on his heatsink which pierced the Keratherm insulating pad and shorted the MOSFET package to the heatsink. Ouch!! It kept doing this every time he replaced the MOSFETs, which he did more than once. Ouch!!
Perhaps a few fotos from your pcb? Optocoupler 4N35 in correct direction.
Rail voltages o.k.?
What kind of insulation between FETs and heatsink? LM385 in correct direction?
LM385 1.25v version?
Foto of your wiring?
Diodes D1-D3 in correct direction?
I know: questions over questions...
Greets
Dirk
Rail voltages o.k.?
What kind of insulation between FETs and heatsink? LM385 in correct direction?
LM385 1.25v version?
Foto of your wiring?
Diodes D1-D3 in correct direction?
I know: questions over questions...
Greets
Dirk
Hi Dirk,
Jim has graciously agreed to have a look at my amp boards. They're packed and will be shipped tomorrow. Rail voltages were good. Keratherm between MOSFETs and heatsink. As far as I could tell 4N35 has good contact and LM385 in the correct direction. Hopefully Jim will be able to sort this.
Thanks for the reply.
Gary
Jim has graciously agreed to have a look at my amp boards. They're packed and will be shipped tomorrow. Rail voltages were good. Keratherm between MOSFETs and heatsink. As far as I could tell 4N35 has good contact and LM385 in the correct direction. Hopefully Jim will be able to sort this.
Thanks for the reply.
Gary