Bo;
NPN and PNP devices are build up differently, so you normally don't get the same Vbe (or Hfe).
Take a look in the OnSemi MJE15032/33 datasheet. On page 3 you see the Vbe curves.
NPN and PNP devices are build up differently, so you normally don't get the same Vbe (or Hfe).
Take a look in the OnSemi MJE15032/33 datasheet. On page 3 you see the Vbe curves.
Thanks for that Jan! I read up on the datasheets. It's a bit of hard melted information for me. It has been 15 years since those lessons at the uni.
Anyway: Both left and right channels are up and running again. 😀
I measure slightly different bias current over the output emitter resistors. Most of them are close to 10 mV, some are 9, others 11.
Would you say it's safe for me to replace those F1A fuses on the output rails to T16A ones?
Also, there is some humming when I put my ears close to the speakers, but not audiable at listening distance. If I connect my computer or my Soundbridge (audio streaming device) it becomes really audiable. Hopefully it will be quiet when I connect it to my preamp.
For now, all is good!
Best regards,
/Bo
Anyway: Both left and right channels are up and running again. 😀
I measure slightly different bias current over the output emitter resistors. Most of them are close to 10 mV, some are 9, others 11.
Would you say it's safe for me to replace those F1A fuses on the output rails to T16A ones?
Also, there is some humming when I put my ears close to the speakers, but not audiable at listening distance. If I connect my computer or my Soundbridge (audio streaming device) it becomes really audiable. Hopefully it will be quiet when I connect it to my preamp.
For now, all is good!
Best regards,
/Bo
Why so big?bomellberg said:
T16A fuses in the supply rails will deliver at least 3kW into 4r0 continuously without blowing.
Possibly half that as a speaker output fuse.
AndrewT said:
Well, in the QAG, Jan writes: "3.5A * 4 = 14A, and then some extra."
What would you suggest? I have T4A and T6A as well. All others are fast blowing.
Best regards,
/Bo
Hi Bom,
where are the fuses? in the speaker lead or in the supply rails?
Quasi and I have found that the maximum rms current into your load needs a Fast fuse value of 0.5*Irms fitted to each supply rail. A pair of F6A fuses will suit a 500W into 4ohm amplifier.
I would expect the speaker fuse value to be equal to maximum Irms, but I never use this method and cannot comment on whether nuisance blowing would be a problem.
where are the fuses? in the speaker lead or in the supply rails?
Quasi and I have found that the maximum rms current into your load needs a Fast fuse value of 0.5*Irms fitted to each supply rail. A pair of F6A fuses will suit a 500W into 4ohm amplifier.
I would expect the speaker fuse value to be equal to maximum Irms, but I never use this method and cannot comment on whether nuisance blowing would be a problem.
The fuses are located on the rails. One on +DC and the other on -DC.
The output devices each has approx 3.5A output capabilitites. 3.5 x 4 = 14 -> 16A fuse, if you want to be able to use your amps full capabilitites.
Best regards,
/Bo
The output devices each has approx 3.5A output capabilitites. 3.5 x 4 = 14 -> 16A fuse, if you want to be able to use your amps full capabilitites.
Best regards,
/Bo
Hi,bomellberg said:
music is transients. These short term currents do not blow fuses.
Full power testing can and does blow fuses. Oscillation can blow fuses.
To enable your amp to be nuisance free and deliver maximum power both continuously and during transients, but still offer adequate fuse protection, the supply rail fuses should not be matched/sized to the maximum current capability of the output devices when specified cold (Tc=25degC).
Instead, a satisfactory protection and current delivery can be obtained by using the Quasi recommendation quoted earlier.
Maximum power and load impedance converted to Vpk and Ipk or to Vrms and Irms can be used to calculate a suitable fuse for the supply rails.
Bo;
Back to scool 😀
Listen to AndrewT 😉
Music is transient. Go for a 4AT to start with. If it blows up during normal output, go to next level.....
Regarding the hum, it's must likely due to the internal wiring.
Keep power and signal wires separated. Bread the power wires as PMA told you in an earlier thread.
Are your input RCA isolated from the chassis?
Back to scool 😀
Listen to AndrewT 😉
Music is transient. Go for a 4AT to start with. If it blows up during normal output, go to next level.....
Regarding the hum, it's must likely due to the internal wiring.
Keep power and signal wires separated. Bread the power wires as PMA told you in an earlier thread.
Are your input RCA isolated from the chassis?
Just wan't to let everyone know that the amp is now in place in my living room, playing beautifully on my Carlsson OA58.2's. I put T4A on the output rails.
Regarding the hum, it's not present with the inputs empty. As soon as I connect something, computer, preamp etc, it starts humming. Is that any clue?
The RCA's are isolated from the chassis, but grounded by one wire each to the 0V inside the amp. There are some non braided wires, but those are single ones for the 0V.
Here are some pictures:
The amp itself from above:
Connected to the receiver.
Once again, thanks to everyone that has helped me with this project! I can't believe I actually have a working amp now.
Best regards,
/Bo
Regarding the hum, it's not present with the inputs empty. As soon as I connect something, computer, preamp etc, it starts humming. Is that any clue?
The RCA's are isolated from the chassis, but grounded by one wire each to the 0V inside the amp. There are some non braided wires, but those are single ones for the 0V.
Here are some pictures:
The amp itself from above:
An externally hosted image should be here but it was not working when we last tested it.
Connected to the receiver.
An externally hosted image should be here but it was not working when we last tested it.
Once again, thanks to everyone that has helped me with this project! I can't believe I actually have a working amp now.
Best regards,
/Bo
Hi,
disconnect the input RCAs grounds from the PCBs.
Try connecting all the input RCA grounds together with a short thick copper wire.
Connect the midpoint of this grounding wire to the main Audio star Ground.
How does the signal ground in the PCBs get to the main Audio Ground?
Where is the Main Audio star Ground?
Do you have two completely separate Audio Grounds, one to each channel?
disconnect the input RCAs grounds from the PCBs.
Try connecting all the input RCA grounds together with a short thick copper wire.
Connect the midpoint of this grounding wire to the main Audio star Ground.
How does the signal ground in the PCBs get to the main Audio Ground?
Where is the Main Audio star Ground?
Do you have two completely separate Audio Grounds, one to each channel?
Excellent
Hi Bomellberg, looks like you have built yourself a fantastic Lynx amp. Congratulations. Just a quick question; what are the 2 pcb`s that I can see either side of what looks like a Peranders soft start pcb? I cannot quite make out the wiring connections.
I am still some way off starting my build as time just runs away from me at the moment. I have most of the components so I am just waiting for a quieter time at work so I can get on with it. When I do, I hope I can do as good a job as you have on the construction.
Cheers. Jerry
Hi Bomellberg, looks like you have built yourself a fantastic Lynx amp. Congratulations. Just a quick question; what are the 2 pcb`s that I can see either side of what looks like a Peranders soft start pcb? I cannot quite make out the wiring connections.
I am still some way off starting my build as time just runs away from me at the moment. I have most of the components so I am just waiting for a quieter time at work so I can get on with it. When I do, I hope I can do as good a job as you have on the construction.
Cheers. Jerry
Thats a very nicely built amp
Regarding your hum
In my younger days I made a design with trafo close to inputs
The result was HUM, and lots of it
Once trafo was away from inputs the hum was completely gone
Now I always try to get the trafos as far away from inputs as ever possible
Ehhh, try shielded cable connections on input
Ah, I see you have that
And looks like two supply ground wires to input chassis ground 😕
How is amp boards getting ground connect 😕
Regarding your hum
In my younger days I made a design with trafo close to inputs
The result was HUM, and lots of it
Once trafo was away from inputs the hum was completely gone
Now I always try to get the trafos as far away from inputs as ever possible
Ehhh, try shielded cable connections on input
Ah, I see you have that
And looks like two supply ground wires to input chassis ground 😕
How is amp boards getting ground connect 😕
Re: Excellent
When you start building, try to follow Jan's excellent Quick Assembly Guide as closely as possible. I didn't, which cost me some weeks and some money, not to mention Jan's money! ;-)
Also, as I said earlier, there is no hum at all if I leave the inputs empty, only if something is connected.
One more thing: the left channel seems to get hotter than the right. It's still touchable, but noticeably warmer than the other side. Could this be because I have 27R instead of 33R at R118 and R119?
Best regards,
/Bo
The rca ground is already connected to audio ground (I'm guessing by "Audio ground" you mean the 0V between the rails?). Both rca's have a separate wire from rca ground to star ground. The shield of the cable is connected to the input ground on the pcb, I could try to remove that. I don't have two separate audio grounds, all grounds come together in the star on top of the transformer, and they are coupled to safety ground by 10R||100nF.AndrewT said:
Hi Jerry! Thanks for the nice words! The two cards you see are the speaker protections, bought from aussie amplifiers.jerryo said:
When you start building, try to follow Jan's excellent Quick Assembly Guide as closely as possible. I didn't, which cost me some weeks and some money, not to mention Jan's money! ;-)
Pheeww, I'll try to get time for this. Perhaps a better idea would be to take a close photo and add some text and arrows?Ragnwald said:
Yes, the input cables are shielded. But there is only one wire to chassis ground. That wire is connected to chassis via 10R||100nF and was added after the first photo was taken. I think you're mistaking the two blue wires from the rca's for chassis wires. The rca's are isolated from the chassis. The amp cards gets ground at three spots: input ground from rca shield, input GND from 0V and output GND from 0V.tinitus said:
Also, as I said earlier, there is no hum at all if I leave the inputs empty, only if something is connected.
One more thing: the left channel seems to get hotter than the right. It's still touchable, but noticeably warmer than the other side. Could this be because I have 27R instead of 33R at R118 and R119?
Best regards,
/Bo
Hi Bo,
For sure the only problem I see is 'bad grounding' AND the toroid position.
If that case is the one I know, you can swap front and rear panels. This way you get rid of toroid near any 'signal' path (yes, I know... toroids have low emissions, but they still have emissions).
Take a close up photo of the supply.
edit:
forget the photo, I found a good one 'dsc_4926)... I can't get one thing... Maybe I'm noot seeing it the right way, but... Where are you connecting the 'center' bus of capacitor banks? The white wire is not connected in the best place... You have some ground issues there... Can you put there a small cooper bar as capacitor bank 0V? those small centimeters of wire plus the connectors can inject noise (hum).
For sure the only problem I see is 'bad grounding' AND the toroid position.
If that case is the one I know, you can swap front and rear panels. This way you get rid of toroid near any 'signal' path (yes, I know... toroids have low emissions, but they still have emissions).
Take a close up photo of the supply.
edit:
forget the photo, I found a good one 'dsc_4926)... I can't get one thing... Maybe I'm noot seeing it the right way, but... Where are you connecting the 'center' bus of capacitor banks? The white wire is not connected in the best place... You have some ground issues there... Can you put there a small cooper bar as capacitor bank 0V? those small centimeters of wire plus the connectors can inject noise (hum).
Found it!
tinitus pointed me in the right direction, when he questioned the two blue wires going to the chassis (actually the rca gnd).
When you look at the picture from above, it's quite obvious that with the two rca-cables connected, they form a big, nice ground loop with those two blue wires.
I connected just one channel and it was dead silent. Then I unhooked one of those blue cables and connected the other channels as well. Still dead silent, and the problem was found.
Would disconnecting them both be a bad idea? It's a bit difficult to see in the schematics if the input ground is connected internally on the card to some other ground. Jan, for future versions of the schematic, perhaps you could have different symbols for the different grounds?
BTW, the warm attitude of one of the channels came from too high bias. Am I the only one that thinks the potentiometer is a tad too sensitive?
Good night all, and thanks for helping out. You bet I'll be there for anyone who needs help in the future!
Best regards,
/Bo
tinitus pointed me in the right direction, when he questioned the two blue wires going to the chassis (actually the rca gnd).
When you look at the picture from above, it's quite obvious that with the two rca-cables connected, they form a big, nice ground loop with those two blue wires.
I connected just one channel and it was dead silent. Then I unhooked one of those blue cables and connected the other channels as well. Still dead silent, and the problem was found.
Would disconnecting them both be a bad idea? It's a bit difficult to see in the schematics if the input ground is connected internally on the card to some other ground. Jan, for future versions of the schematic, perhaps you could have different symbols for the different grounds?
BTW, the warm attitude of one of the channels came from too high bias. Am I the only one that thinks the potentiometer is a tad too sensitive?
Good night all, and thanks for helping out. You bet I'll be there for anyone who needs help in the future!
Best regards,
/Bo
Nice to hear you found it
And that you dont need to rearrange the whole amp, despite our worst fear
I prefer each supply ground connected directly to amp board ground
And speaker negative/ground directly from there, soldered directly to the supply ground wire(I use solid core), close to board
My input RCA are always isolated from chassis
Well, actually my present chassis is wood, so no chassis ground
I suppose speaker terminal are always isolated from chassis
Im certainly no expert on chassis grounding, but if needed I would connect it to supply midpoint/ground, maybe with the resistor you mention
But if your RCA inputs have chassis contact, it may be different
And that you dont need to rearrange the whole amp, despite our worst fear
I prefer each supply ground connected directly to amp board ground
And speaker negative/ground directly from there, soldered directly to the supply ground wire(I use solid core), close to board
My input RCA are always isolated from chassis
Well, actually my present chassis is wood, so no chassis ground
I suppose speaker terminal are always isolated from chassis
Im certainly no expert on chassis grounding, but if needed I would connect it to supply midpoint/ground, maybe with the resistor you mention
But if your RCA inputs have chassis contact, it may be different
No, I just can't go to bed.
When I measured the amp with nothing connected, I noticed that without those two blue wires I have no connection between input ground and the 0V. That is either a good or a bad thing, and I'm guessing it's bad, from the PSU drawing in the QAG.
Connected one rca cable and voila! Now there is a connection from input gnd to 0V. I turned out to be a chain from pre-out on the receiver (with has no safety ground) to inputs from my HTPC (which HAS safety ground), via safety ground in the mains connector, to the amp.
Now, this can't be a good way of connecting those two grounds, but unhooking the shield from the input at the card, as Andrew suggested, doesn't seem right either, since that ground point would not be defined (right, Jan?)
Perhaps I should not connect together the two capacitor banks' 0V at all? Then I would have two separated PSU "channels", each decoupled from the chassis by 10R||100nF, with no chance of the two input grounds "seeing" each other.
Best regards,
/Bo
When I measured the amp with nothing connected, I noticed that without those two blue wires I have no connection between input ground and the 0V. That is either a good or a bad thing, and I'm guessing it's bad, from the PSU drawing in the QAG.
Connected one rca cable and voila! Now there is a connection from input gnd to 0V. I turned out to be a chain from pre-out on the receiver (with has no safety ground) to inputs from my HTPC (which HAS safety ground), via safety ground in the mains connector, to the amp.
Now, this can't be a good way of connecting those two grounds, but unhooking the shield from the input at the card, as Andrew suggested, doesn't seem right either, since that ground point would not be defined (right, Jan?)
Perhaps I should not connect together the two capacitor banks' 0V at all? Then I would have two separated PSU "channels", each decoupled from the chassis by 10R||100nF, with no chance of the two input grounds "seeing" each other.
Best regards,
/Bo
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