hi, amp keep destroying, clipping then burning resistors. already have 470pf comp caps, up from 100pf. 10ohm resistors keep burning out. 36v+/- and 15k bias. can i increase bias resistor, make it more stable? gate stopper from 100ohm to higher to more stable? what are my options? thank you.
my homemade pcb ground very bad. but i want it work here. so i need make it more stable, worse sound
my homemade pcb ground very bad. but i want it work here. so i need make it more stable, worse sound
Last edited:
Can you post some pictures? The circuit design is fine so you must have some other issue going on, even a bad or fake device somewhere causing you problems. If your layout is bad or the board itself has a fault you may be forced to move your components to a known good layout and make a new set of boards. No point trying to 'fix' it if there is some very fundamental problem causing your greif.
Hi Everyone!
Probably, as you know, in time, some web sites, web pages and links disappeared.
Right now, even the link posted by CACABEST at post #1623 disappeared:
https://www.dropbox.com/s/9ya4qm30j5kzcvl/vssa.lay6
It seems no longer available, i tried to contact CACABEST but i failed.
If someone saved this file (vssa.lay6), please, send me a private message and I will give you my E-mail address.
Hoping you can help me, thank you very much.
Probably, as you know, in time, some web sites, web pages and links disappeared.
Right now, even the link posted by CACABEST at post #1623 disappeared:
https://www.dropbox.com/s/9ya4qm30j5kzcvl/vssa.lay6
It seems no longer available, i tried to contact CACABEST but i failed.
If someone saved this file (vssa.lay6), please, send me a private message and I will give you my E-mail address.
Hoping you can help me, thank you very much.
Hi jannsvej.
Congrats on your successful build.
With +/-19V PS you can safely drive 2 ohm speakers with this amp.
Cheers and happy listening.
shaan
Thank you shaan!
Hi Shaan,I think increasing the board size a bit will solve the accommodation problem for all the parts near the power section. Try not to overlap a component's marker by another and I think this will leave ample space for adequate placement of the zobel and the triple jumpers. And also, the zobel should be terminated at the center ground point, not on either side.
After listenting to Janson's VSSA, I had to build this, just for fun. Attached is my build(pardon the background mess), only one channel..Since I didnt have any heatsinks available, I used my antiquated broken PC's processor cooler as a heat sink (fan supply was from cheap led strip power supply, which got blown after about an hour of service, cheap Chinese goods
).Here are the measurements. didnt do any matching, nor did put much effort to adjust the offset and bias.
-ve side, +ve side in mA
Total Quiscient current -132.3, 132.5
front end +VAS current -24.3, 24.5
Vas current -20.4, 20.4
front end current -3.9, 4.1
FET current -108, 108
DC offset 48mV
Had a listen on test speakers for about an hour. Sounds too good, PCB size is only 55 mm x 77mm.
there is a slight hum , even with mobile as input, probably need to jumper the ground lifter circuit, also when i/p cable is moved,the hum changes.this could be the culprit. even after an hour of listening (before fan supply was blown), heat sink was cool and vas heatsinks were warm (could keep my fingers on them for more than 10sec without much discomfort.) All components were either available or salvaged from previous unsuccessful builds
.I am not very skilled in etching and drilling, so mounting of components /vas heatsinks was a challenge.
Probably, a salvaged SMPS (from friends) could be an idea as it will have 24V and 12V both.
reg
Prasi
Attachments
![IMG_20151129_161207[2].jpg](/community/data/attachments/471/471701-43a85c910704235ff627e4e726c24442.jpg)
Hi Prasi!
Congrats! Looks good.
Just two little pointers,
1. I am sure the hum will be gone if you use shielded wire for input.
2. Looks like you are returning the speaker ground path to amp board. This can become the mother of a load of problems. Best to terminate the speaker return ground directly to the PS capacitor bank's ground point.
What supply voltage are you using?
Congrats! Looks good.
Just two little pointers,
1. I am sure the hum will be gone if you use shielded wire for input.
2. Looks like you are returning the speaker ground path to amp board. This can become the mother of a load of problems. Best to terminate the speaker return ground directly to the PS capacitor bank's ground point.
What supply voltage are you using?
Hi Prasi!
Congrats! Looks good.
Just two little pointers,
1. I am sure the hum will be gone if you use shielded wire for input.
2. Looks like you are returning the speaker ground path to amp board. This can become the mother of a load of problems. Best to terminate the speaker return ground directly to the PS capacitor bank's ground point.
What supply voltage are you using?
Thanks shaan!
1. I plan to use shielded cable for the final amp, when I put together the other channel.
2. will do. return the spk return to PS ground. (Haven't tried for this amp, although this didn't make a difference in hum in VSSA, shorting the ground lifter resistor did.)
3. +/- 35VDC.
must make a capable supply for fan. what are the heatsink recommendations for two channels on the same heatsink with above supply voltage and without forced cooling? I have a single 182mm x 100mm x 20mm with 1.2K/w.
prasi
Last edited:
