Again, a preamp tube choice.

redzi · 16th March 2006, 10:59 AM

Hi.
For some time now I've been planning to use the tubes that lay in my cellar, and now, at last I have some spare time, so I decided to build a low mu linestage preamp for my solid state amp.
The construction of this preamp would be the common cathode configuration followed by cathode follower, to decrease the output resistance (however not necessary as my solid state amp has quite high input resistance).

My question is which of the following tubes according to You would be the most appropiate for this design : JJ ECC99, EH 12BH7, EH or Sovtek 6SN7,JJ E88CC / EH or Sovtek 6922,EH 12AU7 or maybe Sovtek 6N30P?

Which of them would be the most linear, the least microphonic, best sounding etc.?

I searched diyaudio forum but i haven't found the anwsers satisfactory.

Original Burnedfingers · 16th March 2006, 11:42 AM

I happen to be a 6SN7 fan and highly recommend Franks line stage.

I built this and I am very happy with it. The performance is very good and sonically very pleasing.

Brian Beck · 16th March 2006, 01:24 PM

This circuit can probably be improved by simplifying it: remove the coupling cap between the stages, the 220K resistor and the 820 ohm resistor. Directly connect the cathode follower's grid to the first stage's plate. Slight readjustment of the 10K value may be necessary depending on the plate voltage of the first stage. It appears that it can then be increased in value to maintain the 7.15mA shown in the schematic. A higher B+ wouldn't hurt with 6SN7s. A CCS instead of the 10K would be better still, but departs from the inherent simplicity of the design.

This unnecessary AC coupling between a common cathode first stage and CF second stage shows up periodically for some reason. Usually in a well designed common cathode stage the plate sits at roughly 1/2 of the B+ (which can be made higher in this design). This voltage is usually an ideal bias point for the grid of the CF anyway, so why add the colorations of a cap if you don't need to?

Giaime · 16th March 2006, 01:34 PM

Just NOT use ECC82/12AU7

redzi · 16th March 2006, 11:19 PM

Ok.

So 6SN7 would be nice and ECC82/12AU7 not.

What about the other tubes? Which of them sound better in general (and yes, I know it depends on the used circuit)?

The replies from those of You who have experience and comparison of mentioned tubes would be very helpful.

Ryssen · 16th March 2006, 11:36 PM

Quote:

(and yes, I know it depends on the used circuit)?

I like the 6SL7.

lndm · 16th March 2006, 11:42 PM

I prefer the 6sn7, it is clean sounding and revealing.

The 12au7 is a more modern equivalent to the 6sn7. A somewhat richer sound, less microphonic. Some sound very good, some don't.

I read in another thread that the EH e88cc is especially non microphonic.

arnoldc · 16th March 2006, 11:59 PM

I am not a fan of 6SN7. However, based on the list of tubes you have there, I would be tempted to go for the 6SN7.

On the other hand, based on what I have heard on a BAT (Balanced Audio Technologies) pre-amp that uses the 6N30-pi, I might experiment with that, if I were you.

redzi · 17th March 2006, 11:49 AM

Quote:

I like the 6SL7.

Yes, but it has mu at level of 70 - might be good for RIAA preamp or guitar one, but not a linestage.

Now the 6SN7 starts to be my favourite, but what version to choose EH or Sovtek?

And what about ECC99? I heard it is very linear and also well sounding.

Quote:

I am not a fan of 6SN7. However, based on the list of tubes you have there, I would be tempted to go for the 6SN7.

I've listed just the tubes that are easily accesible in Poland, however I'm open to Your suggestions in this matter. Please tell me about Your favourites.

Original Burnedfingers · 17th March 2006, 11:53 AM

Quote:

I prefer the 6sn7, it is clean sounding and revealing.

The 12au7 is a more modern equivalent to the 6sn7. A somewhat richer sound, less microphonic. Some sound very good, some don't.

I don't know how you figure the 12AU7 is a modern equivalent to the 6SN7. Except for use as a phase splitter I can see no other value for it.

16th March 2006, 10:59 AM	#1
redzi diyAudio Member Join Date: Jul 2004 Location: Gdynia	Again, a preamp tube choice. Hi. For some time now I've been planning to use the tubes that lay in my cellar, and now, at last I have some spare time, so I decided to build a low mu linestage preamp for my solid state amp. The construction of this preamp would be the common cathode configuration followed by cathode follower, to decrease the output resistance (however not necessary as my solid state amp has quite high input resistance). My question is which of the following tubes according to You would be the most appropiate for this design : JJ ECC99, EH 12BH7, EH or Sovtek 6SN7,JJ E88CC / EH or Sovtek 6922,EH 12AU7 or maybe Sovtek 6N30P? Which of them would be the most linear, the least microphonic, best sounding etc.? I searched diyaudio forum but i haven't found the anwsers satisfactory.

16th March 2006, 01:24 PM	#3
Brian Beck diyAudio Member Join Date: Dec 2004 Location: South Florida, USA	This circuit can probably be improved by simplifying it: remove the coupling cap between the stages, the 220K resistor and the 820 ohm resistor. Directly connect the cathode follower's grid to the first stage's plate. Slight readjustment of the 10K value may be necessary depending on the plate voltage of the first stage. It appears that it can then be increased in value to maintain the 7.15mA shown in the schematic. A higher B+ wouldn't hurt with 6SN7s. A CCS instead of the 10K would be better still, but departs from the inherent simplicity of the design. This unnecessary AC coupling between a common cathode first stage and CF second stage shows up periodically for some reason. Usually in a well designed common cathode stage the plate sits at roughly 1/2 of the B+ (which can be made higher in this design). This voltage is usually an ideal bias point for the grid of the CF anyway, so why add the colorations of a cap if you don't need to? __________________ Brian

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16th March 2006, 01:34 PM	#4
Giaime diyAudio Member Join Date: Oct 2004	Just NOT use ECC82/12AU7

16th March 2006, 11:19 PM	#5
redzi diyAudio Member Join Date: Jul 2004 Location: Gdynia	Ok. So 6SN7 would be nice and ECC82/12AU7 not. What about the other tubes? Which of them sound better in general (and yes, I know it depends on the used circuit)? The replies from those of You who have experience and comparison of mentioned tubes would be very helpful.

16th March 2006, 11:42 PM	#7
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	I prefer the 6sn7, it is clean sounding and revealing. The 12au7 is a more modern equivalent to the 6sn7. A somewhat richer sound, less microphonic. Some sound very good, some don't. I read in another thread that the EH e88cc is especially non microphonic.

16th March 2006, 11:59 PM	#8
arnoldc diyAudio Member Join Date: Apr 2003 Location: Makati	I am not a fan of 6SN7. However, based on the list of tubes you have there, I would be tempted to go for the 6SN7. On the other hand, based on what I have heard on a BAT (Balanced Audio Technologies) pre-amp that uses the 6N30-pi, I might experiment with that, if I were you.

17th March 2006, 11:53 AM	#10
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Quote: I prefer the 6sn7, it is clean sounding and revealing. The 12au7 is a more modern equivalent to the 6sn7. A somewhat richer sound, less microphonic. Some sound very good, some don't. I don't know how you figure the 12AU7 is a modern equivalent to the 6SN7. Except for use as a phase splitter I can see no other value for it.

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