edit: maybe additionally try the same with line level grounds. It might break up some more ground loops.
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Shorty update.
Talked to Jim again and implemented a star ground. 1 ground wire from each amp board to the star. RCA input grounds to star. Speaker negatives to star. Huge improvement! Moving wires around makes a difference. On my crappy test speakers I thought I killed all the hum. Well, JBL Hartsfields don’t lie. Right channel has no hum, and a tiny bit on the left. I bet moving the wires around a little will take care of it.
I hear a touch of noise in right channel that was probably hiding under the hum. It’s audible with my ear next to the compression driver. Let’s see what happens to that when I try Schottky’s instead of the current bridges. I’m also doing to make a Quasimodo and then implement snubbers.
What a difference this makes with the lower noise floor. Amazing.
More news when my big Digikey and amazon orders show up next week and I get more bench time.
Talked to Jim again and implemented a star ground. 1 ground wire from each amp board to the star. RCA input grounds to star. Speaker negatives to star. Huge improvement! Moving wires around makes a difference. On my crappy test speakers I thought I killed all the hum. Well, JBL Hartsfields don’t lie. Right channel has no hum, and a tiny bit on the left. I bet moving the wires around a little will take care of it.
I hear a touch of noise in right channel that was probably hiding under the hum. It’s audible with my ear next to the compression driver. Let’s see what happens to that when I try Schottky’s instead of the current bridges. I’m also doing to make a Quasimodo and then implement snubbers.
What a difference this makes with the lower noise floor. Amazing.
More news when my big Digikey and amazon orders show up next week and I get more bench time.
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I also have an Aleph Mini based on BrianGT boards. (Later converted to Aleph J and Not-Mini, just single pair, but that‘s another story.)
I only got completely rid of the hum (100 dB/W efficient speakers) when I twisted every pair of wires together. Actually, from PSU to amp board it is tripletts, V+,V-, and Ground. And when I then also routed the input wires along the wires from PSU to amp board as much as possible.
The keyword here is „minimizing loop area“ (all possible loop areas
)
Best regards, Claas
I only got completely rid of the hum (100 dB/W efficient speakers) when I twisted every pair of wires together. Actually, from PSU to amp board it is tripletts, V+,V-, and Ground. And when I then also routed the input wires along the wires from PSU to amp board as much as possible.
The keyword here is „minimizing loop area“ (all possible loop areas
)Best regards, Claas
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Have you got the DS1054 unlocked for higher bandwidth and more storage? Is transformer ringing audible from the speaker and how would you know you had ringing or does every amp have a degree of it?
Twitchie,
I can't say for sure how much ringing. But since I'm working on 6 amps, learning as I go, and trying for as quiet as possible, I'm going to put snubbers on for good measure. Snubber parts themselves are cheap, but the scope and q-jig costs a bit more.
Thanks for the tip on the scope hack. I'll do that soon!
I can't say for sure how much ringing. But since I'm working on 6 amps, learning as I go, and trying for as quiet as possible, I'm going to put snubbers on for good measure. Snubber parts themselves are cheap, but the scope and q-jig costs a bit more.
Thanks for the tip on the scope hack. I'll do that soon!
They follow me home like a stray pet! Here's an F5 clone I just picked up. Some things look cleaner than the older builds, but some "classics" still are there. Safety ground and the secondaries to chassis. It's in the queue for new PSU board (stereo style CRC), dual rectifiers, proper AC mains, CL-60's, etc etc. Can't wait to have a J vs. F5 shootout on my horns!
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3 more rawsons rebuilt.
1st pic is an Aleph J mono block. It went fast with the previous one next to it for a template to go by. Component placement, wire routing, etc was a breeze.
Next one is a gainclone. Bought from a friend who thought it was an F5. Oops. All I did was fix the safety ground and the loose mains disconnect crimps.
Next is a rawson F5. I put in a different PSU board from the “alternate” first watt power supply thread. Just finished it and bench tested. Great sound on crappy test speakers. Dc offset and bias looked good. Checked gain on scope, looks good.
Next up, take power supply boards out of tall boy and shorty amps for transplant in 2 mono blocks for my buddy. I have the “alternate” PSU boards built up and ready to drop in. And the rectifier boards with snubbers are ready. It’s a drilling and wiring exercise, and the bottoms of those amps will look like Swiss cheese.
1st pic is an Aleph J mono block. It went fast with the previous one next to it for a template to go by. Component placement, wire routing, etc was a breeze.
Next one is a gainclone. Bought from a friend who thought it was an F5. Oops. All I did was fix the safety ground and the loose mains disconnect crimps.
Next is a rawson F5. I put in a different PSU board from the “alternate” first watt power supply thread. Just finished it and bench tested. Great sound on crappy test speakers. Dc offset and bias looked good. Checked gain on scope, looks good.
Next up, take power supply boards out of tall boy and shorty amps for transplant in 2 mono blocks for my buddy. I have the “alternate” PSU boards built up and ready to drop in. And the rectifier boards with snubbers are ready. It’s a drilling and wiring exercise, and the bottoms of those amps will look like Swiss cheese.
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