Wanted to run my voltages by everyone to see that these make sense. The initial power up sounds great. It is LOUD to say the least. The OD seems a little high. Is it possible the tube may be affecting the readings?
It is built from the 101HRM schematic. I used a Master Volume Quad Reverb Head (Twin basically) w/ 4 6L6 adding in Henry's rev/loop he did for a Super Reverb conversion. The tubes currently in there are from the Quad. The 6L6 tubes look like winged C's and the 12AX7s I am not sure about. I set the power tubes up at 35mv using the 1 ohm resistor from cathode to ground deal. The first dropping resistor in the power supply I have set up to switch between the Quads choke, or a 390R 5W. These voltages are with the resistor.
CL1 198.9 1.83
CL2 210.7 1.63
OD1 218.4 1.79
OD2 224.3 1.73
PI 276/279 53.7
Rev send (12AT7 into Fender rev xform) 411 5.5
Rev Ret (1) 265 1.96
Rev Ret (2) 259 2.0
D'lator Send 301 35.1
D'lator Ret 236 1.99
Screens 421
B1 432
I was also planning on sometimes running it with 2 EL34. I don't think I can run 4 of them as too much current draw from the heaters. I am not sure where unity gain is for the d'lator loop. It is hard wired in with no switch, but setting it at 3.5 for both is very very loud to say the least.
ahh, I did not. I put in 141K (as that is what I have). It definitely dropped the CL and OD voltages. These look pretty good. Thanks.
CL1 1.58/170
CL2 1.4 181.2
OD1 1.64/200.2
OD2 1.59/205.4
The rest are fairly similar
PI 53.1/273 & 276
Rev send (12AT7) 5.5/411
Rev Ret 2.02/256 & 1.93/262
d'lator send 35.2/300.7
d'lator ret 1.99/236
screens 422
B1 434
Correct me if I am wrong, my understanding on the d'lator is that what I have here is pretty good. 300v for the send cathode follower and low 200v for the return.
Looks good. You may want to add some pf to ground like I suggested, to simulate the cables if you had an external unit. Then you can try a 47pf bright cap on the OD master! You'll need to go big... Maybe 180pf to ground from the OD masters wiper. Them add a 180pf to ground after the loop. Reason for putting it on the master and not the entrance to the loop is so the cleans stay chimier.
Make sure you have a 47uf cap on the recovery amp bypass cap in the loop. Not 4.7uf.
Stanz wrote:ahh, I did not. I put in 141K (as that is what I have). It definitely dropped the CL and OD voltages. These look pretty good. Thanks.
CL1 1.58/170
CL2 1.4 181.2
OD1 1.64/200.2
OD2 1.59/205.4
The rest are fairly similar
PI 53.1/273 & 276
Rev send (12AT7) 5.5/411
Rev Ret 2.02/256 & 1.93/262
d'lator send 35.2/300.7
d'lator ret 1.99/236
screens 422
B1 434
Correct me if I am wrong, my understanding on the d'lator is that what I have here is pretty good. 300v for the send cathode follower and low 200v for the return.
dogears wrote:Looks good. You may want to add some pf to ground like I suggested, to simulate the cables if you had an external unit. Then you can try a 47pf bright cap on the OD master! You'll need to go big... Maybe 180pf to ground from the OD masters wiper. Them add a 180pf to ground after the loop. Reason for putting it on the master and not the entrance to the loop is so the cleans stay chimier.
Scott,
How is putting a cap to ground at the MV wiper any different compared to putting it at the entrance of the loop?
I done guite a few built in loops and my experience has been if you use 250K linear pots in the loop, unity is 08:30 to 09:00 on both knobs. WIth 250K audio taper pots unity is around noon on both pots. The loop adds depth to the tone but in a good way, where you want to leave it on all the time. It is good to have a loop enable/disable (bypass) switch just for a sanity check on loop volume or lack of it. My rationalization for not using bleeder caps to simulate cable lenghts is that I almost never include bright switches on built in loops and almost always turn on a bright switch when using an external type loop. YMMV
Check out these tiny AllenBradly 1/8" send/return pots:
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I only use it on the OD master. I was referring to HRM amps. Both masters get the 47pf, but the OD gets the bleed to ground.
jelle wrote:
dogears wrote:Looks good. You may want to add some pf to ground like I suggested, to simulate the cables if you had an external unit. Then you can try a 47pf bright cap on the OD master! You'll need to go big... Maybe 180pf to ground from the OD masters wiper. Them add a 180pf to ground after the loop. Reason for putting it on the master and not the entrance to the loop is so the cleans stay chimier.
Scott,
How is putting a cap to ground at the MV wiper any different compared to putting it at the entrance of the loop?
