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sarrisk 19th October 2008 10:06 PM

6922 tube buffer
 
2 Attachment(s)
hi all,
I m thinking to build this ( see the schematic ) tube buffer using the 6922 tube as a mid stage between MP3 player (ipod) and my tube pre amp . I know this little tube that sounds pretty sweet, but never used it as a buffer. This schematic is the first draft. Has anyone used this tube in a single buffer stage ? any ideas ?

cheers
costas

chrish 19th October 2008 10:12 PM

I am not that smart when it comes to these things, but I am thinking: what are you trying to achieve? Your iPod will probably drive your amp directly with no buffer and no pre amp. Are you trying to change the sound of the iPod?

sarrisk 19th October 2008 10:32 PM

Quote:

Originally posted by chrish
I am not that smart when it comes to these things, but I am thinking: what are you trying to achieve? Your iPod will probably drive your amp directly with no buffer and no pre amp. Are you trying to change the sound of the iPod?

No its not a matter of changing the sound. Actually i need a little bit of amplification , something like a pre - pre amp for gaining up a little the MP3 player output .

costas

Geek 19th October 2008 10:50 PM

Hi,

Quote:

Originally posted by sarrisk
No its not a matter of changing the sound. Actually i need a little bit of amplification , something like a pre - pre amp for gaining up a little the MP3 player output .
Then a tube buffer is a bad way to go because the gain is always less than one.

How much gain do you need? That will determine tube type and topology.

But IMO, you can't go wrong with a 6922 mu-follower, you'll have gain and low output impedance.

Cheers!

sarrisk 20th October 2008 12:07 AM

Quote:

Originally posted by Geek
Hi,



Then a tube buffer is a bad way to go because the gain is always less than one.

How much gain do you need? That will determine tube type and topology.

But IMO, you can't go wrong with a 6922 mu-follower, you'll have gain and low output impedance.

Cheers!

So thats a good point.
As I know, the output of the ipod is about 0.9 V @ 1 Mohm. ( from the headphones jack is about 0.25 V @ 33ohms ) So for a gain of 9-10 db i need a gain about 2.8 Volts from my amp. Thats my first idea.


costas

Geek 20th October 2008 12:34 AM

A 6922 in mu follower will have a gain of 25 to 28 in my tests. as low as 17 with some bargain brands. You can use an input attenuator or volume control with a preset.

If you have 'em, 12B4's will do the job with a gain of 4-5.

Neat thing about the 6DJ8-class tubes is they are made for totempoles, one Vh-k is 50V for the bottom triode and the other unit Vh-k is 150V.

Cheers!

sarrisk 20th October 2008 12:46 AM

Quote:

Originally posted by Geek
You can use an input attenuator or volume control with a preset.

If you have 'em, 12B4's will do the job with a gain of 4-5.

Neat thing about the 6DJ8-class tubes is they are made for totempoles, one Vh-k is 50V for the bottom triode and the other unit Vh-k is 150V.

Cheers!


hmm.. thats sounds interesting ... ;) it will be under consideration ! thanks for the advise and for your reply !

regards
costas


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