oops
Today I reached forward to adjust the volume of the stereo and spark.
A static discharge from my body to the metal knob of the switched attenuator made a sharp "crack" coming from the speakers.
I adjusted the volume down and on one channel the woofer cone jumps almost end stop to end stop.
If I turn down the source signal, I can hear that the same channel has gone noisy, about 1mVac to 2mVac of substantially white noise (from both woofer and tweeter.
Checked the DC at the amp. OK. The DC blocker at the input is doing it's job.
Checked the DC at the B1 output. Oh dear, 9mVdc wavering to 10mVdc.
Turned the source back on and music plays pretty normally from both channels and hides the white noise.
It appears that the B1 jFETs did not like that static discharge and have suffered some damage.
I don't know yet whether it's the Source Follower or the CCS that has gone noisy. Maybe both.
Any ideas on how to prevent this happening again on the DCB1?
Today I reached forward to adjust the volume of the stereo and spark.
A static discharge from my body to the metal knob of the switched attenuator made a sharp "crack" coming from the speakers.
I adjusted the volume down and on one channel the woofer cone jumps almost end stop to end stop.
If I turn down the source signal, I can hear that the same channel has gone noisy, about 1mVac to 2mVac of substantially white noise (from both woofer and tweeter.
Checked the DC at the amp. OK. The DC blocker at the input is doing it's job.
Checked the DC at the B1 output. Oh dear, 9mVdc wavering to 10mVdc.
Turned the source back on and music plays pretty normally from both channels and hides the white noise.
It appears that the B1 jFETs did not like that static discharge and have suffered some damage.
I don't know yet whether it's the Source Follower or the CCS that has gone noisy. Maybe both.
Any ideas on how to prevent this happening again on the DCB1?
the good channel has no DC offset. I doubt the pumpimg can be regulator connected, since both B1s run from the same reg.
Is the knob connected to the signal ground you are telling you have on the PCB? If you, you could try to tie it through a ground breaker with just the diode bridge:
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
Since its only in one channel, then the suspicion firstly turns to the audio jfets naturally.
chassis is not connected to Safety Earth.
Using the nut & thread might allow a separate wire feed to ground but it would have to be to signal ground.
The same arrangement is going to be used in the Mezmerize, as a dedicated pre-amp with remote control. Ah! don't fit any knobs on the outside. Totally remote control. Nah.
I've got my DCB1 back up and running with the high CCS current now. 10.4 ohms at R1, I've got about ~170 mA flowing. My heatsink arrangement is running plenty warm. I don't have a way to measure it but I would guess upper 40's at least. Sorry no pics yet. I swapped out the black/gold Elna Silmic's for the brown/white ones. Replaced the LED electrolyctic's with Vishay MKP1837's, .1 uF on top (fits perfect), and another in parallel underneath hot glued to the pcb. My R1's (a trio of 1W PRP's) hang underneath the pcb "bomber style", spaced off of the board just a bit. That took a little creative lead forming / soldering. Swapped out the Takman's for PRP's in one buffer, the PRP's feed my satellite amp right now. I also lowered the PLLXO frequency to my satellite speakers (NHT XDS's) because I miscalculated before, and had a slight depression in the upper bass. So, lots of changes, and all this stuff needs to settle in. But, early impression is good. Another step up, more "3D" and more relaxed, without losing any of the details / transparency / dynamics it's always had. Man, I don't know how you could make this thing much better, maybe a pair of "Big Blues" in a balanced configuration? Maybe a balanced set of LDR's for attenuation in front of that? And maybe a Salas "Big Baby" shunt to run that? An ESS dac with opc's "beast" output stage, a pair of balanced F5's. hmmm....
I would be crying if I ever had to sell my DCB1I betrayed the DIYAudio mantra and bought a beautiful (used) commercial preamp. Hence, my recently completed B1 is now FS over in the swap meet forum. Anyone interested in skipping the building process can have a look over there.
Regards,
Dan
For substituting it with another preamp, this one should be a monster. Can we know what model it is?William, why placing two paralleled Vishay MKP1837's of the same 0.1uF value?
I would be crying if I ever had to sell my DCB1
I had to compromise. I had a family revolt and my man cave has to do my two-channel and alittle home theater too. So I managed to get an exceptional deal on a used Anthem D2 D2v - Welcome to the New Official Anthem® Audio Video Website. So far I haven't found any obvious shortcomings.
Regards,
Dan
WOW!! By the pictures and the description, it seems to be a great beast. Looks impressive with all those inputs and outputs compared with my DCB1, which has 1 input 1 outputI had to compromise. I had a family revolt and my man cave has to do my two-channel and alittle home theater too. So I managed to get an exceptional deal on a used Anthem D2 D2v - Welcome to the New Official Anthem® Audio Video Website. So far I haven't found any obvious shortcomings.
Regards,
Dan
WOW!! By the pictures and the description, it seems to be a great beast. Looks impressive with all those inputs and outputs compared with my DCB1, which has 1 input 1 output
I might even have to hook up my son's XBox to it!
Regards,
Dan
File under FWIIW ...
I have just started the build of a hypnotize with populating the board. Knowing that I probably needed to buy some more solder before I started, I went browsing for the best choice I could find. This ended up being Cardas Quad eutectic solder. I am very pleased with this stuff for these reasons.
1. First of all, I make a point to use a eutectic solder when quality is important. I missed the point about the value of solder being eutectic for quite some time. I had mistakenly thought that I just needed to use a hotter iron for the same results. What I had not considered was what happens with solder as it reverts back to its solid form. With eutectic it is almost certain that it will recrystallize correctly as it transitions to solid again. Non-eutectic may not with even the smallest of vibrations or impurities.
2. Melting point 170C / 338F. This solder works as well with a 25 Watt iron as what I was using with a 45W one. I have read of a few people having problems with the pads lifting off the circuit cards. I have to think that the lower temperature that can be used with the Cardas that it will help with this. It may be smarter to use something that has a higher melting point for components that operate at a high temperature. Which is what I intend to do.
3. I have no affiliation with Cardas and have nothing to gain if anyone buys it. I have found some very reasonable prices for smaller quantities on eBay.
I wrote this for the benefit of those that don't happen to have a friend that took the NASA class for advanced soldering.
I have just started the build of a hypnotize with populating the board. Knowing that I probably needed to buy some more solder before I started, I went browsing for the best choice I could find. This ended up being Cardas Quad eutectic solder. I am very pleased with this stuff for these reasons.
1. First of all, I make a point to use a eutectic solder when quality is important. I missed the point about the value of solder being eutectic for quite some time. I had mistakenly thought that I just needed to use a hotter iron for the same results. What I had not considered was what happens with solder as it reverts back to its solid form. With eutectic it is almost certain that it will recrystallize correctly as it transitions to solid again. Non-eutectic may not with even the smallest of vibrations or impurities.
2. Melting point 170C / 338F. This solder works as well with a 25 Watt iron as what I was using with a 45W one. I have read of a few people having problems with the pads lifting off the circuit cards. I have to think that the lower temperature that can be used with the Cardas that it will help with this. It may be smarter to use something that has a higher melting point for components that operate at a high temperature. Which is what I intend to do.
3. I have no affiliation with Cardas and have nothing to gain if anyone buys it. I have found some very reasonable prices for smaller quantities on eBay.
I wrote this for the benefit of those that don't happen to have a friend that took the NASA class for advanced soldering.