There should be at least a 1k stopper on each and every grid, and tight by the pins. I'd be looking at lead dress and the physical location of power supply decoupling.
If you have a scope, I'd start probing around. If you don't, I'd buy/beg/borrow one.
If you have a scope, I'd start probing around. If you don't, I'd buy/beg/borrow one.
All grid resistors now 1K.
The C6 cap did make a difference. between the 47 and 0.47uF cap.
Would lowering this to 0.1uF make much of a difference?
Also the 100K resistor R5 can be disconnected??
Not sure where to go from here. (no scope available).
It seems to be picking up this hissing from the input signal cable after the pot.
If I touch the signal cable after the pot but before it connects to the board then it amplifies the hissing significantly.
The same happens to my SS amp with the metal top off. The top seems to act as a grounding shroud.
But I should be able to solve this without a metal chassis.
The C6 cap did make a difference. between the 47 and 0.47uF cap.
Would lowering this to 0.1uF make much of a difference?
Also the 100K resistor R5 can be disconnected??
Not sure where to go from here. (no scope available).
It seems to be picking up this hissing from the input signal cable after the pot.
If I touch the signal cable after the pot but before it connects to the board then it amplifies the hissing significantly.
The same happens to my SS amp with the metal top off. The top seems to act as a grounding shroud.
But I should be able to solve this without a metal chassis.
Brit,
I would check the grounding of the ground buss bar in your home. I know your are not in the US but electricity acts the same everywhere. Sounds like a grounding issue. check the connection where the ground wire from the buss bar connects to the ground rod or rebar in the concrete foundation. You do have a ground plug on the power, yes? And your not using "cheater plugs".?
Ron
I would check the grounding of the ground buss bar in your home. I know your are not in the US but electricity acts the same everywhere. Sounds like a grounding issue. check the connection where the ground wire from the buss bar connects to the ground rod or rebar in the concrete foundation. You do have a ground plug on the power, yes? And your not using "cheater plugs".?
Ron
Brit01 said:
FWIW, I soldered an additional ground lead to the ground pad on Bas's PS board (where the grounds and B+ run out to the Aikido boards), and I ran this and the ground lead from the volume pot to a 20 ohm R and connected the other end of the 20 ohm R to chassis ground. A 20 ohm ground lift, basically.
The shields from all of my signal coax's are tied together at the volume pot, and tied to the ground wire from the vol pot running to the 20 ohm R. The other end of the coax shields terminate at the -ve signal pads on the Aikido boards and on the -ve of the RCA jacks, so they are hopefully grounded at one end only, hard to explain.....
I was chasing hum, if you have a hiss, have you tried other tubes, etc?
I can touch and move the signal coax wires all over the place with no change in hum.
You don't happen to have a wiring diagram of that set up do you?
I have one of the grounds from the psu to the ground of the Aikido. Do you mean by additional the second ground connection of the psu?
Hi,
I'm getting hum too with my 6SN7 tubes.
I'm using JB's akido pcb. Right now, I floating
the DC heaters with a cap. I in the process of rewiring, new layout.
My question is who out there uses DC heaters
and TO-220 Volt. Reg? I'm using an LM1084
with an Avvid TO-220 PCB mount type heat sink.
I'm not sure at this time if this heat sink is sufficient
to dissipate the 12watts, especially in an enclosure
with some vent slots. If I need to go with a bigger heatsink.
thanks.
I'm getting hum too with my 6SN7 tubes.
I'm using JB's akido pcb. Right now, I floating
the DC heaters with a cap. I in the process of rewiring, new layout.
My question is who out there uses DC heaters
and TO-220 Volt. Reg? I'm using an LM1084
with an Avvid TO-220 PCB mount type heat sink.
I'm not sure at this time if this heat sink is sufficient
to dissipate the 12watts, especially in an enclosure
with some vent slots. If I need to go with a bigger heatsink.
thanks.
Brit01 said:
You don't happen to have a wiring diagram of that set up do you?
I have one of the grounds from the psu to the ground of the Aikido. Do you mean by additional the second ground connection of the psu?
I may be able to draw a crude diagram of the signal wires tonight.
Yes, I soldered another ground wire to the ground pads on the bottom side of Bas' PSU board, and ran that to ground first, then to ground through the 20 ohm R as of last nite. So, off of the PSU board ground pads, I have a ground wire going to each Aikido mono board, and an additional wire going to the 20 ohm ground R.
Freecrowder said:
FC,
Yes it is possible, no I don't know how either. sorry.
What type of rectifier tube is that? Nice looking Pre BTW.!
Ron
Well I played around until late last night with different connections. Too late in fact. Now I'm suffering at work. I come in at 6am!
I managed to reduce the hissing noise. I have the RCA shields wired to the pot and also wired to the copper bar. I do not have the shield wired to the ground points on the input of the main board.
I have one wire connected from Bas's psu ground to the main ground point on the Aikido then this is connected directly to the copper bar.
I'm thinking I may ry to attach the volume pot directly to the board from below and use an extension shaft to the front panel of the chassis I need to build.
Might even try the set up on Post#80.
Think I've been a real dumb...s here.
I didn't connect the shield of the microphone cable to the earth!! Effects of getting up at 5am every day! I'm using the microphone wire as internal shielded wiring. It's all I had available but I guess it does the same job as some expensive labelled hi-fi shielded wiring.
When I get home I will take the outersleeve shield and connect this to the wiring going to the copper bar. Hopefully this will reduce noise.
But still even if I can attach the volume pot to the board with an extension shaft this would be much better.
I didn't connect the shield of the microphone cable to the earth!! Effects of getting up at 5am every day! I'm using the microphone wire as internal shielded wiring. It's all I had available but I guess it does the same job as some expensive labelled hi-fi shielded wiring.
When I get home I will take the outersleeve shield and connect this to the wiring going to the copper bar. Hopefully this will reduce noise.
But still even if I can attach the volume pot to the board with an extension shaft this would be much better.
Freecrowder said:
You can post multiple images directly in the post with the IMG button (right above the text box), but the image has to reside somewhere on the web, like an image hosting site. Once you click on IMG button, it will ask you for an http: address where the pics are located.
The rectifier tube is 5U4GB. The lettering is engraved and then infilled with paint. The top plate is from Front Panel designer which is a great site! Allows our designs to come much closer to commercial product.
RG
RG