SE 6V6 Filtering

[g1]

Also understood that it's only the first filter cap that needs to be limited in capacitance for the 5Y3. But, all the data I'm finding shows 10uf.

See pg.2 of this datasheet under 'capacitor input filter'

[DG1911]

See pg.2 of this datasheet under 'capacitor input filter'

Guess I didn't find the right data sheet.

http://tdsl.duncanamps.com/dcigna/tu...ia/syl-49h.gif

http://www.triodeel.com/5y3_p1.gif

Thanks.

[eschertron]

And while Fender schems for SF champs show 20uF for the first filter node after a 5Y3, I believe later ones (I have a '76, others corroborate seeing the same in theirs) have a 40uF as first node in the multi-cap cans.

[DG1911]

Update

I fixed it. First, in my defense, I didn't build this amp, and I am definitely more of a hack than I am an amp builder. That said, I'm still a dumbass for assuming that the builder knew what worked best in terms of grounding his amp.

There is a small turret board that holds the filter caps. This board was grounded to/with the pots and input jack. The 6v6 cathode bias resistor also grounds back to this board. The PT center taps were grounded, along with the AC line in ground, to a PT bolt. I moved the line ground to it's own bolt. I disconnected the ground from the pots to the PS filter turret board and ran a new ground from the board to where the CT's were grounded. Besides neatening up the grounding to the pots, that was it. The hum went from a level that you could hear outside of the room to a very low level hum that you can only hear right near the speakers. Night and day difference, and I'm kicking myself for the easy fix not dawning on me months ago when I got this little thing. Also, the amp sounds much, much better without all that crap behind the music.

I did order a Choke before sorting this out. Doesn't look like I need it. But, if I hadn't spent the 20 bucks on it I never would have figured out the hum issue despite how stupid easy it should have been. Story of my life.

Well folks, thanks again for the help.

[Leo_Gnardo]

Good work all around! You have pretty much de-hacked that amp. If you can manage to cram the choke in there, that last bit of hum may very well disappear. In the order of getting things done right, you did well to move the power supply & bias grounds as you did. What's surprising, some manufactured amps did that same kind of grounding scheme, bring it all to the input jack, it gives me the heebie jeebies when I see that. What if the input jack mounting nut works loose, as they often do?

[Tom Phillips]

Yes. Good work. We didn't realize that the hum was that bad. It's hard to evaluate troubleshooting situations with verbal descriptions since everyone's idea of good/bad, normal/unacceptable is different. This was complicated by the fact that all stock Champ type amps hum a little.

[DG1911]

Thanks gents. I have seen some schemes where the filter nodes for the preamp tube/tubes are grounded separate from the node/nodes of the power tubes (in fact, my Marshall clone is grounded this way). At any rate, this little SE amp does have a separate filter node for the 6SL7. I moved it over along with the rest of the supply nodes, it was easier to do so. But I was fully prepared to try grounding it, alone, with the pots. The level of hum now is so low that it's not worth the bother. However, since I bought the choke, I will clip it in and see what effect it has. I am hesitant to install it for reasons of both weight and space. It's a small chassis. There isn't enough residual hum to bother with now so unless it adds a significant tone benefit, I probably wont go further than clipping it in just to experiment with. We'll see.

Again, I appreciate all the help. Thanks.