I started this project about 5 years ago using Brian GT's boards. The amp has been built for over a year and it sounds great. However, it only powers up when connected to my computer and an old B+K prologic preamp. The computer connects with a 3.5mm miniplug to male phono plug. The B+K uses balanced outputs.
When I hit the power switch, with nothing connected to the inputs, the LED indicators from the power supplies come on but the amp stays cold. If I connect anything else to it, it stays cold. I have tried changing the order of the power up sequence, but it makes no difference. I would really like to be able to use a source other than my computer.
The amp is configured as two monoblocks in one chassis. Both channels behave in the same way. Common grouds are tight. The transistors are all matched pretty tightly, so they could behave similarly between two channels, even if they do not share circuitry other that the switch and ground. Could it have something to do with the input transistors not turing on because of a mismatched voltage or impedance? Admittedly, I haven't tried poking it with a multimeter to see what might be going on.
When I hit the power switch, with nothing connected to the inputs, the LED indicators from the power supplies come on but the amp stays cold. If I connect anything else to it, it stays cold. I have tried changing the order of the power up sequence, but it makes no difference. I would really like to be able to use a source other than my computer.
The amp is configured as two monoblocks in one chassis. Both channels behave in the same way. Common grouds are tight. The transistors are all matched pretty tightly, so they could behave similarly between two channels, even if they do not share circuitry other that the switch and ground. Could it have something to do with the input transistors not turing on because of a mismatched voltage or impedance? Admittedly, I haven't tried poking it with a multimeter to see what might be going on.
Aleph 30 only works with computer as source?
I started this project about 5 years ago using Brian GT's boards. The amp has been built for over a year and it sounds great. However, it only powers up when connected to my computer and an old B+K prologic preamp. The computer connects with a 3.5mm miniplug to male phono plug. The B+K uses balanced outputs.
When I hit the power switch, with nothing connected to the inputs, the LED indicators from the power supplies come on but the amp stays cold. If I connect anything else to it, it stays cold. I have tried changing the order of the power up sequence, but it makes no difference. I would really like to be able to use a source other than my computer.
The amp is configured as two monoblocks in one chassis. Both channels behave in the same way. Common grouds are tight. The transistors are all matched pretty tightly, so they could behave similarly between two channels, even if they do not share circuitry other that the switch and ground. Could it have something to do with the input transistors not turing on because of a mismatched voltage or impedance? Admittedly, I haven't tried poking it with a multimeter to see what might be going on.
I started this project about 5 years ago using Brian GT's boards. The amp has been built for over a year and it sounds great. However, it only powers up when connected to my computer and an old B+K prologic preamp. The computer connects with a 3.5mm miniplug to male phono plug. The B+K uses balanced outputs.
When I hit the power switch, with nothing connected to the inputs, the LED indicators from the power supplies come on but the amp stays cold. If I connect anything else to it, it stays cold. I have tried changing the order of the power up sequence, but it makes no difference. I would really like to be able to use a source other than my computer.
The amp is configured as two monoblocks in one chassis. Both channels behave in the same way. Common grouds are tight. The transistors are all matched pretty tightly, so they could behave similarly between two channels, even if they do not share circuitry other that the switch and ground. Could it have something to do with the input transistors not turing on because of a mismatched voltage or impedance? Admittedly, I haven't tried poking it with a multimeter to see what might be going on.
No way, the amp has to turn on no matter what he sees at his inputs. I think you won't get far without actually checking the amp.
Hannes
Hannes
We need pictures. Good, in-focus, well-lit pics of the inside and the back with the inputs. Perhaps you used a switching input plug somewhere, or something. Is there a soft-start circuit?
Also, when you say 'the amp stays cold' do you mean that you get no output, or the amp physically doesn't heat up?
Also, when you say 'the amp stays cold' do you mean that you get no output, or the amp physically doesn't heat up?
just a though, all being = to what you have said. those 2 preamps are somehow closing a open cir. and that could mean they are passing current they are not made for.
you might want to stop using them on this amp until you get her fixed.
you might want to stop using them on this amp until you get her fixed.
6L6, both. There is the slightest mechanical hum from the transformers (which always happens when you flick the power switch), but absolutely nothing coming from the speakers (no electrical noise of any kind), and the heat sinks are room temp. When it's running, the sinks could be used to heat a small room in the winter.
No soft start. Just a metal oxide varister, a fuse and a thermal switch for each transformer. I left out the inductors. There is power at the outputs of both power supply sections regardless if the amp is hot or cold as long as the power is switched on. I could bypass the MOVs to see what happens, but those should either work or fail. There is no relay action of any kind. There would be on the thermal switch, on the other hand. With a high inrush current, would they open? Still not sure how the source would impact this.
Sakellog, I am presuming that they are not passing current as that would show up as heat on the sinks or some unfortunate resistor, cap or ground. Heat would have to show up somewhere, right.
The switch could be the defective link as it is the only part of the path common to both circuits. But, i find it hard to believe that the switch is an issue if the only thing changed from one trial to the next is the source device.
I'll take some pics in the next couple of hours. It's Valentines Day. I have to pay some attention to my wife or I'll never hear the end of it.
No soft start. Just a metal oxide varister, a fuse and a thermal switch for each transformer. I left out the inductors. There is power at the outputs of both power supply sections regardless if the amp is hot or cold as long as the power is switched on. I could bypass the MOVs to see what happens, but those should either work or fail. There is no relay action of any kind. There would be on the thermal switch, on the other hand. With a high inrush current, would they open? Still not sure how the source would impact this.
Sakellog, I am presuming that they are not passing current as that would show up as heat on the sinks or some unfortunate resistor, cap or ground. Heat would have to show up somewhere, right.
The switch could be the defective link as it is the only part of the path common to both circuits. But, i find it hard to believe that the switch is an issue if the only thing changed from one trial to the next is the source device.
I'll take some pics in the next couple of hours. It's Valentines Day. I have to pay some attention to my wife or I'll never hear the end of it.
Are you using the amps Balanced inputs, or the RCA?
Have you tried another source? Even an ipod into the RCA inputs would help.
Have you tried another source? Even an ipod into the RCA inputs would help.
heat... i would think so. i was thinking heat inside the output stage of the pre.
i need to say these guys have forgot more than i know. that being said, the first thing that came to mind was reading somthing on the opamps in a sound card dose somthing diffrent with its ground ref. i dont remember what. i then thought maybe the output of the B&K is the same.
like i said i dont know allot, so im just going to watch and learn.
i need to say these guys have forgot more than i know. that being said, the first thing that came to mind was reading somthing on the opamps in a sound card dose somthing diffrent with its ground ref. i dont remember what. i then thought maybe the output of the B&K is the same.
like i said i dont know allot, so im just going to watch and learn.
The B+K is older. Its pro-logic- AVP 1000. I'm hoping your on to something. I have the inputs on the amp set up for balanced or single ended interconnects. Each channel has both balanced and phono jacks. I inserted a miniature switch physically between the jacks. When I want balanced, I switch it toward the balanced jack. This closes the contacts in the switch, connecting the negative pole of the XLR plug to the negative pad on the pcb. When I want single ended input, I switch it toward the phono plug. This grounds the negative pole on the XLR jack.
This is what I tried next. Plugged the amp in and turned on with no sources connected. The LEDs come on, but the circuit is cold, the MOVs are cool to the touch (they usually heat up and get too hot to touch comfortably). I connect the BK using the phono plugs. I switch the mini switch back and forth a couple of times- no change. The amp is cold.
I disconnect the BK and reconnect using the balanced cables. Immediate sound. MOVs get hot and sinks heat right up.
I disconnect the balanced plugs with the music playing, and plug the BK back in using the single ended phono plug. It stays on.
I'm still not sure why the computer is the only source that will turn the amp on with single ended from the start. There may be some king of active ground system on the computer output that acts like a balanced signal. I'm pretty sure the computer uses an audio codec with built in voltage amps rather than external op-amps. It might have a current sink on the negative or even balanced voltage outputs for each channel. I'll look into it more in the AM.
This is what I tried next. Plugged the amp in and turned on with no sources connected. The LEDs come on, but the circuit is cold, the MOVs are cool to the touch (they usually heat up and get too hot to touch comfortably). I connect the BK using the phono plugs. I switch the mini switch back and forth a couple of times- no change. The amp is cold.
I disconnect the BK and reconnect using the balanced cables. Immediate sound. MOVs get hot and sinks heat right up.
I disconnect the balanced plugs with the music playing, and plug the BK back in using the single ended phono plug. It stays on.
I'm still not sure why the computer is the only source that will turn the amp on with single ended from the start. There may be some king of active ground system on the computer output that acts like a balanced signal. I'm pretty sure the computer uses an audio codec with built in voltage amps rather than external op-amps. It might have a current sink on the negative or even balanced voltage outputs for each channel. I'll look into it more in the AM.
Do you have RCA inputs on your amplifier? Try them.
Do you have any other input other than the computer? DVD players play CD's, remember...
And again, I implore you to please take some photos of your trouble wiring and your amp.
Do you have any other input other than the computer? DVD players play CD's, remember...
And again, I implore you to please take some photos of your trouble wiring and your amp.
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"When I want balanced, I switch it toward the balanced jack. This closes the contacts in the switch, connecting the negative pole of the XLR plug to the negative pad on the pcb. When I want single ended input, I switch it toward the phono plug. This grounds the negative pole on the XLR jack."
if i understand this correctly, i see what you are doing. but I'm not sure that is the correct way of doing it. when you switch from XLR to rca all you want to happen is the shorting of XLR pin 1 (XLR ground) and XLR pin 3 (XLR -).
I.E. flip the switch for rca and it shorts G to -.
as for the rest I'm unsure.
i would take some good pics as 6L6 asked and post. he been around the pot awhile he knows where the handle is.
he would be the better bet.
sounds to me like a wiring hook up issue to the diff pair. but for the life of me cant figure out why that would prevent the 244 fets from heating up?
im gunna learn to!
if i understand this correctly, i see what you are doing. but I'm not sure that is the correct way of doing it. when you switch from XLR to rca all you want to happen is the shorting of XLR pin 1 (XLR ground) and XLR pin 3 (XLR -).
I.E. flip the switch for rca and it shorts G to -.
as for the rest I'm unsure.
i would take some good pics as 6L6 asked and post. he been around the pot awhile he knows where the handle is.
he would be the better bet.
sounds to me like a wiring hook up issue to the diff pair. but for the life of me cant figure out why that would prevent the 244 fets from heating up?
im gunna learn to!
As a PURE GUESS.
If the amp is working in one configuration then it is not the amp at fault.
Are you SURE that you are not connecting HOT and COLD together + - -, when you should be connecting COLD and GND, - - 0V.
If the amp is working in one configuration then it is not the amp at fault.
Are you SURE that you are not connecting HOT and COLD together + - -, when you should be connecting COLD and GND, - - 0V.
I agree, although there is a possibility that there is a sever wiring error in the amp's inputs. Won't know until we see some photos.
Yes, i have other sources. But the point is that none work other than the B+K and computer. The computer sounds OK but the B+k is lousy. Id like to be able to come right from my NOS DAC, fed from a transport. But these are single ended.
Sakellogg and KatieandDad,
Lets say there is a wiring problem at the phono inputs (i get what you are saying, ill check this weekend). Lets say the computer presents as a balanced source because of the chipset circuit so the wiring problem is canceled. We can say that at least it works with a balanced source. But, the amp doesn't draw any power without a source plugged in. Just switching it on does nothing without a source plugged in. What would cause the amp to become active only when it sees a source? 😕
Could this behavior be normal?😕Ive never had another class A amp. Its as if the input transistors are acting like a relay for the entire circuit to pass current- open at the input transistors and won't latch without the input signal. Isn't he whole amp is a current sink, controlled buy the voltage at the input transistors. Maybe it just cant sink without the input transistors activating? Am I way off here?
Thanks for hanging in there.
I'll try to post pics on Saturday.
no its not normal.
ive used mine as a space heater before with no input.
i cant say what would cause this to happen unless you are opening the power to the fets, and then closing the open whith the cir in the preamps.
i cant say for sure.......but i think its got to do with a open ground. but i would wait for more experance and pics.
ive used mine as a space heater before with no input.
i cant say what would cause this to happen unless you are opening the power to the fets, and then closing the open whith the cir in the preamps.
i cant say for sure.......but i think its got to do with a open ground. but i would wait for more experance and pics.
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