Hi Guys, have not been doing much on the amp side as I am making pickups and guitars right now.... Strats and Teles.
But... I am ready to hand off this little champ to my Grandson ( he is on a guitar tear right now ), so I was wondering about reducing the hum just a wee bit. Its not bad at all, but next to my silver face champ it does have a slight bit more hum. I seem to recall an idea that added some additional filtration on the power caps? I am including my current layout and would appreciate any thoughts on getting the hum lowered.
It looks like the 33u will be your new resevoir cap, then dropping across the 47R to the first 47u (original rez cap). Yes you'd want to remove that wire jumper from the rectifier to the (+) of the 47u...
Or not use the 47R and parallel the 33/47 though that won't do much.
Are you sure the hum in your amp is from the supply line?
Hey Surfsup, thanks for chiming in. I am not sure where the hum is coming from? I don't have a 47r on hand. Will a 470r 3 watt do there? Also I have a recommend to reroute the OT common to the neg side of the new reservoir and then ground the speaker jack to the chassis.
I did chopstick around and did not hear any issues with wire layout.
I think you'd want to move the OT's B+ connection to the top of the original 47uF so you have cap-resistor-cap before the supply hits the OT. The bigger the resistor, the more ripple you can kill (up to a point), but that also drops more and more voltage and, hence, the resistor will have to be rated for more and more power. With a 6V6, a 47R will only drop a couple of volts and won't get very hot. Even 1W is plenty. 100R would be better, still dropping only 4-5 volts. To use the amp with larger output tubes though, you have to take into account the increased current requirements which impact the voltage drop and the needed power rating.
SE amps can also pick up heater hum in the output, even if well wired. Elevating the heater supply helps a lot.
Ok, so I did a light bulb test and all was well with out tubes, then with tubes. Hum has reduced dramatically, and it was quite low to start. There is a very very low swoosh, almost sounds like a fan, you have to put your ear right at the speaker to hear it, so no worries there. Here's how I ended up. I moved the OT common to the ground side of the new cap. I moved the ground there to the chassis and away from the board. I used a 33uf as the new cap and a 200r ( all I had ). I re-grounded the speaker jack to the chassis. Thanks for the support, and Colossal for the PM's.
Nice to know that even with a long absence one can get help on projects.
Angelodp, as Firestorm said you should move your OT B+ connection to after the 200R, on the 47u. This allows the 33u/200R to act as a CR filter to reduce the ripple hum. Might reduce the hum even more. In terms of less voltage (a few volts) I find the lower voltage sounds slightly more smooth to me anyway.
Nice work. The ground on the chassis is better than on the board.
I have been sending my amps up to my son in Fort Collins, Colorado where he is creating video demos of them. I have not supplied him with the correct recording gear but you can see from this demo that he does play well and get some great tones out of the amp... tonight I ordered an SM57 for him and looking forward to some more clips.
My name is Jeremey and I've been introduced to the world of amp building by my dad, RJ Guitars (I don't actually call him by that name). I've played for several years, but am a rookie when it comes to building. I enjoy gleaning from his insight and have really loved playing on his amps. I'm looking forward to learning from you guys as well. Thanks for the opportunity.
Wow! Amp building heir apparent! Hey, Jeremey, RJ gave us all a fright when he took a break from this board. So we need to you absorb ALL his knowledge quick, in case he tries that again.
I build and repair tube amps. http://amps.monkeymatic.com
Your dad is good people - I value his friendship and enjoy tossing 'round amp ideas with him. He knows which end of the soldering iron to hold and does a fine job with it. I love his enthusiasm for amps and treasure what he has brought to this community.
Welcome aboard, Jeremy! I haven't been here long, and I think I came in about the time RJ was starting his hiatus, so I haven't had any direct dealings with him yet. But I can tell you, from reading many of the discussions here, that RJ is a highly respected and honored member of this great community.
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