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   Home » Melquiades Amplifier » 6E6P-DR in triode mode (4 posts, 1 page)
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07-13-2011 Post does not mapped to Knowledge Tree
Johann
Frankfurt Germany
Posts 2
Joined on 07-13-2011

Post #: 1
Post ID: 16676
Reply to: 16676
6E6P-DR in triode mode
fiogf49gjkf0d
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
     
07-14-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,549
Joined on 05-28-2004

Post #: 2
Post ID: 16678
Reply to: 16676
6E6P vs. D3A as driver.
fiogf49gjkf0d

 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.

Rgs, Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-14-2011 Post does not mapped to Knowledge Tree
Johann
Frankfurt Germany
Posts 2
Joined on 07-13-2011

Post #: 3
Post ID: 16679
Reply to: 16678
6E6P-DR
fiogf49gjkf0d
Hi Romy,
thank you for your answer. On weekend i will rebuild my amp for the 6E6P-DR. You are right, the tube datas shows that pin 8 is a screen. On D3A pin 8 is Grid 3 connected to screen.
I will try it with pin 8 lifted and connected to ground. I have bought 6 pairs 6E6P-DR. In your forums you mention, that the E version is not for audio.
I use cathode bias for driver and output tube. I have tried fixed bias for the output tube 45, but i didn't liked the sound. (LCLC-PSU)
I can not remove the cathode capacitor with plate choke or transformer, because then the Ri will rise extremly. I don't have the formula on hand but i think it is: Ri total= Ri * mu+1
My Classe CDP-10 has 2 Volt RCA-output, but with D3A the volume is too loud. At beginning the potentiometer has channel unbalance and when i turn it a little more it is allready too loud.
I have a small room 4m * 3.5m and use 100db Goodmans+Pioneer loudspeakers.
I like the sound with plate-choke or transformer loading best, but i know the drawback is full mu of the tube. I like my PSU with LCLC.
Give me 2 weeks for burn in, then i will report my sound impressions.
Regards    Johann

 
07-14-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,549
Joined on 05-28-2004

Post #: 4
Post ID: 16680
Reply to: 16679
Using the tube shield to study Wagner?
fiogf49gjkf0d
Johann, in any case I would not leave lifted. You do not want to have inside tube anything that has no referent to anything, it is like a transformer – you do not want to have in it any coils that are not connected to anything. I would say the to ground the pin 8 is very safe bet but might be there is any way to use the tube shield as some kind of screen that might reemit something or catch the stray electrons. Who know you might discover that applying +1000V to the shield would make tube to translate the German operas to English and with -1000V to do revere translation…
 


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
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