NightFlight said:
You really want to set each half to have the same current running through it, not whatever current is required to produce the same plate voltage as the other side.
-PB
Modifications to run e80cc/12bh7a/5687 for Crack+Speedball
- Thread starter kscwuzhere
- Start date
You really want to set each half to have the same current running through it, not whatever current is required to produce the same plate voltage as the other side.
-PB
NightFlight
New member
Caucasian Blackplate said:
Okay. Can you expand on that?
NightFlight said:
If you have a really dead triode and you adjust the current strongly to counteract that, then plug in a good tube, your voltages will be way off. There's also the general philosophy that if you don't need to provide an adjustment for a particular aspect of an amplifier, you probably shouldn't.
The Crack is reasonably tolerant of wandering driver stage voltage, so that's not as much of a concern as it might be in a circuit like the Paramount 2A3. Or, for another example of matching plate voltage, the Mainline offers an adjustment to set the plate voltage to the ideal value, which allows the amplifier to produce the most power.
How do I set up the 12BH7's using one DPDT? It's hard to tell from the picture (from Snaari's mod) where the wires go and where to put the resistors. I should have went the easier route by installing two SPDT's instead but I thought I could make it easier by just having one switch for the 12BH7's. Oh well. If you guys can help me install this or show me some clearer pictures to how the wires are connected I would really appreciate it. Thanks!
Jim
Jim
You really want to put one switch on each board.
If you need to pop a board off, it will be pretty hairy to get all that apart.
After a week of modding I finally got my SPST's and DPDT's installed to run the 12BH7/7119's!
For the resistance mod, I added a 330 ohm instead of a 350 ohm because I did not have it in my resistor pack. Voltages came out a bit higher than the range mentioned.
T1/T5:
7119: 88/88
12BH7: 81/78
12AU7: 100/100
Are these voltages okay?
For the resistance mod, I added a 330 ohm instead of a 350 ohm because I did not have it in my resistor pack. Voltages came out a bit higher than the range mentioned.
T1/T5:
7119: 88/88
12BH7: 81/78
12AU7: 100/100
Are these voltages okay?
The 100V kind of sucks, are you getting that with the stock resistors, or the 330 Ohm resitors? (The 330's are not to be used with the 12AU7)
So I tried using a higher ohm resistor to try to get my voltages down. First I tried to add a 22 ohm in series with my 330 ohm but my voltage ratings only went down slightly. (Btw, before I added the 22 ohm in series with the 330ohm my 12AU7's were around 85/85. In my last post I think I may have forgotten to turn the switch off XD.)
T1/T5
7119: 86/86
12BH7: 76/73
12AU7: 84:84
I replaced the 22 ohm with a 47 ohm resistor but got near ratings. Then I replaced the two resistors in series with a single 470 ohm resistor
T1/T5
7119: 83/83
12BH7: 75/72
12AU7: 82/82
Should I keep replacing it with higher resistors till I get between 70 - 80?
T1/T5
7119: 86/86
12BH7: 76/73
12AU7: 84:84
I replaced the 22 ohm with a 47 ohm resistor but got near ratings. Then I replaced the two resistors in series with a single 470 ohm resistor
T1/T5
7119: 83/83
12BH7: 75/72
12AU7: 82/82
Should I keep replacing it with higher resistors till I get between 70 - 80?
The high voltage just indicates a 12AU7 that isn't super fresh.
-PB
-PB
TheCoolDoc
New member
Just installed the Tungsram E80CC alongside a Sylvania 7236 (replaced 237's with 470 Ohm Resistors on the A and B boards) and my background hiss was immediately gone (faulty 12AU7 I guess). It sounds glorious.
I still get crackling at high volumes, but I don't play at those insane volumes anyway so it's all good.
One question, I was only supposed to replace those resistors, correct? 1 237 resistor on A and B? Nothing else?
I still get crackling at high volumes, but I don't play at those insane volumes anyway so it's all good.
One question, I was only supposed to replace those resistors, correct? 1 237 resistor on A and B? Nothing else?
Yes.TheCoolDoc said:
-PB
Thanks to Snarii's diagram of kscwuzhere's mods, I've modded mine using a DPDT switch for the bias current and 4PDT to switch between 5687 and 12au7 wiring topology. The DPDT switch allows me to switch the current on both channels simultaneously.
The resistors I used are 470 ohm in the off position for E80CC. 475 ohms in parallel for 12AU7, and 196 in parallel for 12BH7. I'll have to do some measurements with the 5687 to see if I can get away with 138 ohms.
I'll likely regret it long term, but I epoxied the 4PDT switch to keep it firmly in place since I didn't want to wait for the special tape I ordered, which happened to arrive today that I used for the DPDT. I was worried about the adhesion of run-of-the-mill double-sided tape when used in a high temperature environment, so I bought 3M VHB 5952 tape, which withstands up to 250F long-term exposure. At $15 for 1/2" x 5yds it was on par price-wise with the better stuff Home Depot carries. And 3M does not publish maximum temperatures for the consumer-grade stuff, they only spec application temperature.
I'm running a Sylvania 12BH7 at the moment which sounds even better when biased properly. My Tungsol 5687's will be here this week and I'm hoping to be wowed based on the reviews I've read.
The resistors I used are 470 ohm in the off position for E80CC. 475 ohms in parallel for 12AU7, and 196 in parallel for 12BH7. I'll have to do some measurements with the 5687 to see if I can get away with 138 ohms.
I'll likely regret it long term, but I epoxied the 4PDT switch to keep it firmly in place since I didn't want to wait for the special tape I ordered, which happened to arrive today that I used for the DPDT. I was worried about the adhesion of run-of-the-mill double-sided tape when used in a high temperature environment, so I bought 3M VHB 5952 tape, which withstands up to 250F long-term exposure. At $15 for 1/2" x 5yds it was on par price-wise with the better stuff Home Depot carries. And 3M does not publish maximum temperatures for the consumer-grade stuff, they only spec application temperature.
I'm running a Sylvania 12BH7 at the moment which sounds even better when biased properly. My Tungsol 5687's will be here this week and I'm hoping to be wowed based on the reviews I've read.
kscwuzhere
New member
Maxhawk said:Thanks to Snarii's diagram of kscwuzhere's mods, I've modded mine using a DPDT switch for the bias current and 4PDT to switch between 5687 and 12au7 wiring topology. The DPDT switch allows me to switch the current on both channels simultaneously.
The resistors I used are 470 ohm in the off position for E80CC. 475 ohms in parallel for 12AU7, and 196 in parallel for 12BH7. I'll have to do some measurements with the 5687 to see if I can get away with 138 ohms.
I'll likely regret it long term, but I epoxied the 4PDT switch to keep it firmly in place since I didn't want to wait for the special tape I ordered, which happened to arrive today that I used for the DPDT. I was worried about the adhesion of run-of-the-mill double-sided tape when used in a high temperature environment, so I bought 3M VHB 5952 tape, which withstands up to 250F long-term exposure. At $15 for 1/2" x 5yds it was on par price-wise with the better stuff Home Depot carries. And 3M does not publish maximum temperatures for the consumer-grade stuff, they only spec application temperature.
I'm running a Sylvania 12BH7 at the moment which sounds even better when biased properly. My Tungsol 5687's will be here this week and I'm hoping to be wowed based on the reviews I've read.
Beautiful modding! What headphones are you driving? What kind of music do you listen to? I've tested a lot of 5687/7119 varieties on many different headphones with my mod, I could potentially have some recommendations depending on your headphones/music choice.
kscwuzhere said:
The cans I listen to most often are Sennheiser HD800. My music tastes are quite varied although I tend to gravitate towards jazz or vocals. Classic rock, rock, some classical, most types of jazz, new age, hip hop every now and then. It's easier to say that I don't typically listen to rap, opera, or country.
On the way are NOS tung-sol 5687 and RCA 5687. In my repertoire of input tubes:
12AU7: RCA long black plate, Westinghouse, Sylvania (stock), RCA clear tops (currently in my MC240)
5814: CBS-Hytron (angled D-getter), GE
12BH7: Sylvania, RCA (currently in my MC240)
Mullard CV4003
My output tubes:
GE 6080 (stock), Sylvania GB6080, Mullard CV2984, Tung-sol 5998
My favorite input tubes are the Sylvania 12BH7 and CBS-Hytron 5814. For output I like the 5998 and GB6080.
