Just unscrew it all, and remount in the same order as you originally mounted it before soldering.
Very nice job with the wiring! You can do this
Is 330 uF okay instead of 220 in C2? I had an accident and dropped the back panel while moving the amp around to reassemble, and knocked off C2 on one channel. I can easily change C2 to 330 uF in both channels as I have the boards off the heat sinks. I have Elna Silmic II 330uF on hand. I completed the ground lift with 15 Ohm resistors, as well as cleaned up the boards and was going to listen tonight but…
Thanks for that!
I put in the 330 uF, screwed it mostly back together, and plugged it in. The hum is much quieter now. There is a hiss and hum audible, in my very quiet listening room, that is noticeable from about 3 feet away from the face of the Khorn. From the listening position, it isn’t audible per se, but the room is obviously quieter when the amp is off. The hum and hiss are lowest when there is nothing or shorting plugs plugged in to the amp inputs. My DIY tube amp builds are usually quieter. I used a 15 Ohm resistor when doing the ground lift mod. Would putting the power supply in a separate chassis cut down this hiss and hum?
well, when dealing with speakers so sensitive/efficient as yours, one need to take care of every link in chain - one of most important being gain distribution
read article
I didn't follow your struggle in thread lately ( having just so much energy I have) so I'm asking now - what you have for preamp?
hope something with 0db gain, so just some attenuator properly buffered
that's first, solving amp in best way goes second
read article
I didn't follow your struggle in thread lately ( having just so much energy I have) so I'm asking now - what you have for preamp?
hope something with 0db gain, so just some attenuator properly buffered
that's first, solving amp in best way goes second
Also, when working on the J alone - not including all other possible problematic equipment or effects of excess gain, cables and shields and all, the only way to assess the amps noise level alone is with shorted inputs.
If it is too noisy for you even then, more internal work is needed and you could consider an external PSU or trying to isolate the issue even further.
PS: I don’t remember from your pics, but did you put in the optional resistors to prevent oscillation (relevant for hiss).
Regards,
Andy
Some trouble shooting tips from page 68 of diyAudio member Bonsai's Ground Loop article:
Bonsai's Ground Loops Article
It is worthwhile to read the whole article.
In the end when the preamp, gain, and amplifier is sorted and there is still hum, then it may be that the power supply ripple is too high. The Aleph J is single ended so the noise rejection is lower than that of a push-pull amplifier. With 105dB speakers the ripple may be audible. I know that with my 103dB speakers, my single ended SIT amplifiers are hum free. However I recently finished Zen Mod's Redneck DEFISIT amplifier and it had a very quiet hum that was audible with my ear to the speaker. The difference between this amplifier and my other hum free amplifiers was CRC versus CLC power supply. In the end I replaced the 0.1R in the CRC with a Hammond 156B (1.5mH 0.07 Ohm) choke and the amplifier is hum free on my speakers.
Bonsai's Ground Loops Article
It is worthwhile to read the whole article.
In the end when the preamp, gain, and amplifier is sorted and there is still hum, then it may be that the power supply ripple is too high. The Aleph J is single ended so the noise rejection is lower than that of a push-pull amplifier. With 105dB speakers the ripple may be audible. I know that with my 103dB speakers, my single ended SIT amplifiers are hum free. However I recently finished Zen Mod's Redneck DEFISIT amplifier and it had a very quiet hum that was audible with my ear to the speaker. The difference between this amplifier and my other hum free amplifiers was CRC versus CLC power supply. In the end I replaced the 0.1R in the CRC with a Hammond 156B (1.5mH 0.07 Ohm) choke and the amplifier is hum free on my speakers.
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Thanks. I’ll have a look at the article on gain distribution. I don’t use a preamp. Lately it’s a PC source, with Tidal’s own volume control, to a DAC and then to the amp I am using. The hum is there with shorting plugs, or nothing plugged in, as well. I suspect that it is from residual ripple. I have 264000 uF of capacitance in the power supply, and just the usual number of resistors required for the supply without any of the additional optional ones.
I tried moving the wires down and along the chassis floor just now with no improvement to the hum/hiss. I don’t think the noise is from lead dress at this point.
The noise with shorted inputs is lower than with a source plugged in. I have not added the additional resistors for oscillation.
I’d add those since you are in work mode anyways. 180-220R for example should do fine, if I remember correctly.
as Ben said .......... I believe there is a need for better filtering, for Klipsch Horns
think about including proper chokes, so having CLC instead of CRC
not to mention another detail - it is wise following Papa's logic with FW and most of PL amps - Donut is near front plate, always away of input connectors and input side of pcbs
if you mount Donut vertically ( big hefty L Bracket, buy one for work in construction, for 4*4 wood) you'll have plenty of space left for chokes
think about including proper chokes, so having CLC instead of CRC
not to mention another detail - it is wise following Papa's logic with FW and most of PL amps - Donut is near front plate, always away of input connectors and input side of pcbs
if you mount Donut vertically ( big hefty L Bracket, buy one for work in construction, for 4*4 wood) you'll have plenty of space left for chokes
A small note on you audio gnd wires. I perhaps was unclear earlier. Having them mounted after filtering is good. But you can also achieve a further reduction in noise by soldering them together at the same point of the PCB. This is because by having one at each side, you create a loop area between the left and right side of the board. And this loop area is connected together through the noisy high current junction between the two psu halves.
I’d also put the dc wires from the recitifiers alongside, and not on top, of the transformer, as Dennis suggests. These steps may help reduce, but perhaps not eliminate, the noise. Turning the tranny a bit may take you another step. But CLC or more capacitance, or both, may be the ultimate remedy.
All FW amplifiers process the input signal straight away, as soon as it enters the amplifier. For this, we'd need a re-designed Aleph J AMP PCB.
The power supply ground points are also not the same, as mentioned above. Here's something I posted earlier; it is a beginers' PS PCB design of one of the meberes here on forums. The proper common routing back to the PS PCB shouild look something like this:
The FW amps also do not use local decopling of DC rails, on the AMP PCB. I playerd with this a lot recently; I do not understand why the FW amps don't have it. Anyhow, try the local decopling yourself and see what it does to the sound. When playing with this, use an osciloscope and enure that the amplifier is stable.
Also, the Pass Labs amps process and amplify the sound... as soon as it eneters the amp:
The power supply ground points are also not the same, as mentioned above. Here's something I posted earlier; it is a beginers' PS PCB design of one of the meberes here on forums. The proper common routing back to the PS PCB shouild look something like this:
The FW amps also do not use local decopling of DC rails, on the AMP PCB. I playerd with this a lot recently; I do not understand why the FW amps don't have it. Anyhow, try the local decopling yourself and see what it does to the sound. When playing with this, use an osciloscope and enure that the amplifier is stable.
Also, the Pass Labs amps process and amplify the sound... as soon as it eneters the amp:
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I will go through the ground loops article.
I don’t have the 156B on hand, but I have literally dozens of the 154B. It is 3mH at 1.5 amps and .14 Ohms of resistance. Can I use one (or more of) these instead? Does a pair in parallel give me 1.5mH at .07 Ohms resistance and double the current capability? I can add two per rail for a total of four in the power supply. Is the 1.5 amp rating enough for the Aleph J? A single 154B would provide 3mH rather than the 1.5mH of two in parallel.
I am going to the hardware store tomorrow to buy a big L-bracket to mount the toroid vertically. This will allow me to move the rectifiers more towards the middle of the amp and away from the circuit PCBs. I really don't think there is much to be gained in the area of lead dress, but placing the toroid vertically will allow more room for the chokes that are needed to bring down the ripple of the power supply. Rather than removing the resistors from the power supply and replacing them with a choke, should I add an additional LC after the existing CRC of the power supply to make it CRCLC? I have several pairs of large electrolytics of 33000uF and 64000uf, and dozens of Hammond 154B that I can use. Putting the toroid upright will give me plenty of room to put in these extra components.
I will run the wires from the rectifier along the bottom of the chassis. I'll have a look at the termination of the ground wires on the power supply PCB and see if I can get them closer together at the star point. Once I get the toroid vertical, there will be more room for a more careful arrangement of the parts, and for the additional inductors and additional capacitance if required. I just posted a response to Ben Mah asking about adding an additional LC to the existing supply rather than replacing the R in the CRC with an L. So a CRCLC.