6AU6WA triode connected as a line amp?

grhughes · 6th October 2006, 02:53 PM

Anyone had any experience with this combination? Thanks a whole heap! Ray

kstagger · 6th October 2006, 04:43 PM

6AU6? no - but I've used the EF86 triode-connected for the past couple of years... I've built three preamps around it and have been very happy. My latest creation with it is the best so far... EF86 dc coupled to a 6922 White Cathode Follower, onboard regulation, tube rectifier...

I've been meaning to try the 6AU6 and/or the 6SJ7/6J7 family... but right now I have a bunch of parts to build a C3m linestage

grhughes · 6th October 2006, 08:20 PM

Several manufacturers are using the 6au6 as a triode in first stage of condenser microphones I guess for the low capacitance and high plate resistance. Gona try it as a bottom tube in a cascode. Thanks Ray

ray_moth · 6th October 2006, 11:39 PM

6AU6 has often been used in triode mode and is quite linear. The biggest problem is that quality varies quite a lot , so you need to select a tube that is not noisy or microphonic. I found GE to be very microphonic but RCA were OK.

I've used 6AU6A successfully in triode mode. For line amp use, where the signal is in the order of 1v RMS or more, it's best to strap suppressor and screen grids to plate, in the usual way for triode mode (using dropper resistors). It works well with plate current of around 6 to 10mA. Mu is abot 36 and maximum dissipation is about 3.5w.

If the signal is small, as in a preamp (say less than 100mv), you could try strapping both suppressor and plate to ground and using the screen grid alone as the anode. You get about the same mu but maximum dissipation is now only 0.65w, so a low current is called for. This arrangement offers good shielding, due to the plate being grounded. It is quite linear for low-level signals but not for large signals.

P.S. I have a pdf file about using the 6AU6 with the plate grounded, if anyone wants a copy.

Original Burnedfingers · 6th October 2006, 11:46 PM

I built a 6AU6 triode Aikido line stage. I am very happy with it. Very good all the way thru. Bass is good as is the midrange and high frequency. I did have to hunt thru a bunch of 6Au6's untill I found some quiet ones.

I tried a 6SJ7 triode line stage and wasn't pleased with the results.

wrenchone · 7th October 2006, 12:11 AM

I would think that the 6AU6 WA or WB would be more resistant to microphonics than the consumer grade tubes, as they are specified and constructed to resist shock and vibration. Correct me if I'm wrong...

tubelab.com · 7th October 2006, 01:16 AM

I have tried some of most all of them. They tend to come in 3 flavors, ones that sound great, ones that are microphonic, and ones that are noisy. The noisy ones have a background noise that can come and go. It can be a hiss (common) a rumbling sound, or a random snap, crackle, pop. Some of the old Japanese ones (Fujitsu Ten comes to mind) are often noisy, and some sound great. I have found some military surplus ones that are noisy also.

Poindexter · 7th October 2006, 04:00 AM

Too much gain; Mu of 36.

Least gain, without bypass cap in the cathode circuit, about 16. Too much.

Look for a lower Mu device.

Aloha,

Poinz

coresta · 8th October 2006, 06:42 PM

Hi , 6AU6 was used as output line amp on the vintage recording systems of the former ORTF . ALCATEL loved this as Cathode follower with 40Hys inductor under 160v on Va/Vg2/Vg3 (also triode connected) . A 2,2uF cap serial loaded with 9k allowed driving a 600ohm line amp . A VERY VERY NICE solution !

alejo · 9th October 2006, 03:48 PM

Hello ray_moth, please seendme the pdf about 6au6 plate ground...

6th October 2006, 02:53 PM	#1
grhughes diyAudio Member Join Date: Mar 2005 Location: Cubicle Sweet Cubicle, SW, MO, USA	6au6wa triode connected as a line amp? Anyone had any experience with this combination? Thanks a whole heap! Ray __________________ "The gift of imagination is the gift of the gods imparted to a few for which they receive innumerable kicks in the a$$ their entire life." Le Corbusier (Edward Jenneret)

6th October 2006, 08:20 PM	#3
grhughes diyAudio Member Join Date: Mar 2005 Location: Cubicle Sweet Cubicle, SW, MO, USA	Several manufacturers are using the 6au6 as a triode in first stage of condenser microphones I guess for the low capacitance and high plate resistance. Gona try it as a bottom tube in a cascode. Thanks Ray __________________ "The gift of imagination is the gift of the gods imparted to a few for which they receive innumerable kicks in the a$$ their entire life." Le Corbusier (Edward Jenneret)

7th October 2006, 01:16 AM	#7
tubelab.com diyAudio Member Join Date: Jul 2005 Location: South Florida	I have tried some of most all of them. They tend to come in 3 flavors, ones that sound great, ones that are microphonic, and ones that are noisy. The noisy ones have a background noise that can come and go. It can be a hiss (common) a rumbling sound, or a random snap, crackle, pop. Some of the old Japanese ones (Fujitsu Ten comes to mind) are often noisy, and some sound great. I have found some military surplus ones that are noisy also. __________________ Too much power is almost enough! Turn it up till it explodes - then back up just a little.

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6th October 2006, 11:39 PM	#4
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	6AU6 has often been used in triode mode and is quite linear. The biggest problem is that quality varies quite a lot , so you need to select a tube that is not noisy or microphonic. I found GE to be very microphonic but RCA were OK. I've used 6AU6A successfully in triode mode. For line amp use, where the signal is in the order of 1v RMS or more, it's best to strap suppressor and screen grids to plate, in the usual way for triode mode (using dropper resistors). It works well with plate current of around 6 to 10mA. Mu is abot 36 and maximum dissipation is about 3.5w. If the signal is small, as in a preamp (say less than 100mv), you could try strapping both suppressor and plate to ground and using the screen grid alone as the anode. You get about the same mu but maximum dissipation is now only 0.65w, so a low current is called for. This arrangement offers good shielding, due to the plate being grounded. It is quite linear for low-level signals but not for large signals. P.S. I have a pdf file about using the 6AU6 with the plate grounded, if anyone wants a copy.

6th October 2006, 11:46 PM	#5
Original Burnedfingers diyAudio Member Join Date: Nov 2002	I built a 6AU6 triode Aikido line stage. I am very happy with it. Very good all the way thru. Bass is good as is the midrange and high frequency. I did have to hunt thru a bunch of 6Au6's untill I found some quiet ones. I tried a 6SJ7 triode line stage and wasn't pleased with the results.

7th October 2006, 12:11 AM	#6
wrenchone diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	I would think that the 6AU6 WA or WB would be more resistant to microphonics than the consumer grade tubes, as they are specified and constructed to resist shock and vibration. Correct me if I'm wrong...

7th October 2006, 04:00 AM	#8
Poindexter diyAudio Member Join Date: Oct 2004 Location: Maui, Hawai'i, USA	Too much gain; Mu of 36. Least gain, without bypass cap in the cathode circuit, about 16. Too much. Look for a lower Mu device. Aloha, Poinz

8th October 2006, 06:42 PM	#9
coresta diyAudio Member Join Date: Mar 2005 Location: Paris	Hi , 6AU6 was used as output line amp on the vintage recording systems of the former ORTF . ALCATEL loved this as Cathode follower with 40Hys inductor under 160v on Va/Vg2/Vg3 (also triode connected) . A 2,2uF cap serial loaded with 9k allowed driving a 600ohm line amp . A VERY VERY NICE solution !

9th October 2006, 03:48 PM	#10
alejo diyAudio Member Join Date: Jun 2004 Location: bs.as.	Hello ray_moth, please seendme the pdf about 6au6 plate ground...

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