Johann wrote:

Hi Romy, i want to use the 6E6P-DR (triode mode) as driver in my tube 45 amp. I use a D3A (triode mode) with Anode choke at 180V, 12mA. Grid 2 is connected via 50 Ohm resistor to anode. Grid 3 (pin 8) is connected to cathode. The 6E6P-DR (also 6E6P-E) and the D3A have the same pin layout. If i look to your schematic of the 6-Channel Melquiades DSET Amp, where you use the 6E6P-E (triode mode) the pin 8 has no connection to cathode. What should i do, if i use the 6E6P-DR instead of the D3A ? Should i let pin 8 connected to cathode or not ?  The B+ voltage will be adjusted to 170V, 18mA. I have too much gain with the D3A (mu=77). Thank you.   Johann

Johann,

6E6P and D3A are virtually interchangeable. The 6E6P has more bias voltage. I do not know what biasing principle you use. Set the 6E6P around 4V, or to have 170-200V on plate. You shell not worry about pin 8. This is shield and it is completely insulated from the tube. In my amp the pin 8 does sits on “cathode” but my cathode in all my channels beside the MF is grounded. If you use cathode bias then I would not connect the pin 8 (shield) to cathode but rather to ground. However, it is completely lifted from anything else and you might connect it to anything you wish. I would not surprise if you report some sonic difference by connecting shield the different pins or even to some kind of external PS. I reasonably did not experiment with it.

Do not use the 6E6P-I this is not good tube at all. This tube is made for pulse application for whatever reasons doe not sound right then I tried it. Also it is smaller and I presume it has less ability to dissipate heat.

In my MF channel the 6E6P-DR drives a tube similar to your type 45, in fact I do have ability to plug in it type 45 as well. I do not use anode choke loading but what we might have similar is the excessive gain from those tubes. The 6E6P has 30-33 times gain and if you use your amp from high-output front-end (some contemporary DACs give 5-6V at 0dB) Then you will drive you type 45 very deep into grid currents. I am sure you do not want to do it. The 6E6P with 4V on grid will swing 120V, this will driver type 45 into very deep distortions. In my MF channels I was trying to reduce the 6E6P gain.  If you look at my circuit:

http://www.GoodSoundClub.com/TreeItem.aspx?PostID=10915

Then you will see that cathode use not the “signature” Milq bias with resistor in grid but regular cathode bias. What is irregular in there is that the cathode resistor is not shunted by a cap. This reduced the gain of the tube dramatically what was exactly what I needed.

It would be interesting to hear your comments about 6E6P vs. D3A. I did research this subject and made many test with those two tubes. They are different and have different benefits depending from application. I will not share my concussions with you I do not want you to be predisposed, not to mention that they might work differently with choke loading. So, if you wish then post your comments on the subject of 6E6P vs. D3A as you get your feeling about it.