Deci's debut deluxe

[deci belle]

I put this board in my ex Crate V-15 cab and had a .060" aluminum chassis made to fit its 17" width.

No standby. There's a little eyelet-board for the filament CT resistors. The PT is 380v 100mA and the 5v winding has 4A, as does the filament supply. The 15w 8kΩ OT is a clone for a Vox AC15 I'd put in the Crate that had EL84s. The speaker is a 40w 16Ω ceramic Tone Tubby~ which is why I was able to go a little lighter in the caps than most would have.

I wanted a choke (5Hy 160Ω 75mA) and an extra filter stage for the preamp. The 470Ω 3w R after the PI's filter cap drops the pre's voltage by only 1v. I also put some extra wires under the board to enable me to add another pwr node in order to starve the first triode for a harp channel. There's one bare GND lead under the board that grounds the two input leads' shields. I grounded the volume lead's shield to the back of the volume pot.

But right now its for an especially middy-sounding cobalt-pu Strat and an ES-175 w/coil cuts and a vari-tone switch that likes nasty loud rock, bossa nova+jazz, so I have the usual cap mods on the board, but went to a 680p at the TS; the bright channel's coupling cap is .033uF and its grid resistor is 33k. I separated V1's cathode bypasses and put an 1800Ω R on the normal channel's to give it a little patina. I wanted to voice ch-1 edgier and ch-2 smoother.

I only have one signal GND and it is quiet! All the voltages are normal. The plates are 373v and the screens are 340v. The cathode has 22v.

There were a couple problems though… When the OTs 8+16Ω taps are used, I had to join and float the 4Ω tap and its lead to its winding to GND …but I didn't, so I was pretty bummed for a day and a night before I found out my mistake. The only other issue was oscillation cuz my B+ to OT CT was too close to the PT's CT lead to GND.

I have some NOS 5Y3 tubes from my dad (we're both hams), but only had one NOS RCA 6v6 and a new EH/GT I swiped from my 63 reverb RI that now sports a 6k6. I'm going to get a pair of TAD 6v6 tubes soon.

Sounds and feels pretty dang righteous, mates!!

[deci belle]

The 680p helps a lot, but the .047 coupling cap for the bright channel is back in.

[deci belle]

I changed ch-1's .02uF coupling cap for a .01uF and V2's preamp .02uF coupling cap to a tubular .01uF audio cap and it sounds much cleaner— allowing full timbre without the mud in both channels. It would still be easy enough to get that, if I wanted it…

Also, for my (still getting used to the 5E3's interactive thing) guitars, I've found that keeping both volumes at around 9 allows me to easily control the clarity of the sound as in this position, varying the two volumes only slightly changes the thickness of the tone considerably.

[deci belle]

Thanks goes to Loudthud's and R.G.'s ideas and suggestions on grounding strategies and Bruce's and tubeswell's for dealing with heater and power section considerations

[deci belle]

I recently put two sets of primary filter caps in series on the back of the chassis under a DR doghouse. A pair of 47uF for NOS 5y3/6v6 and a pair of 100uF for 5AR4/JJ6v6s. I used a DPDT (on-off-on) to switch between these filter caps. The bass attack sounds really good with this arrangement.

Even though I have a separate pwr node dedicated to V1, it needs to be at least 10uF (my 10uF is really 12uF). I found out because when I tried an 8uF to power V1, it didn't sound as tight in the bass response as with the 10uF. Amazingly, the factory arrangement uses the single 16uF to supply all the power for all four preamp triodes.

I've put a diode between the screen's pwr node and the first preamp's pwr node (PI+2nd gain stage) to prevent the power section from siphoning current from the preamp's filter caps.

I'm happier with a 2.2uF 100v Xicon cap in channel 1's cathode bypass, but I still might try a .0068uF coupling cap (Bruce mentioned a .0075~ but I didn't locate a source for that value), with the 2.2 and the usual 4.7uF.