DIYHiFi.org

For the sake of audio
It is currently Fri Feb 23, 2018 10:33 pm

All times are UTC




Post new topic Reply to topic  [ 98 posts ]  Go to page 1, 2, 3, 4, 5 ... 7  Next
Author Message
 Post subject: 6SN7 preamp
PostPosted: Thu Feb 12, 2015 4:51 pm 
Offline
Cow

Joined: Thu Dec 11, 2008 10:13 am
Posts: 193
Location: Catalonia New Europe State
I need to know the gain amd the output impedance of 6SN7 preamp, attached schematic.

TIA
Felipe


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Thu Feb 12, 2015 7:25 pm 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1179
Hi,

felipe wrote:
I need to know the gain amd the output impedance of 6SN7 preamp, attached schematic.


Low.

Both.

Maximum gain is 2.4 (volume up to max), so under 8dB.

Zout per section is around 8k open loop, two in parallel, 4k. Local feedback loop is around 17dB, so around 600 Ohm output Impedance, I'd say +50/-25% on that value.

Personally I like this one much better with a single 5687 section and the cathode RC taken out, cathode shorted to ground and a 3V battery in series with the grid (negative to grid of course), 10k anode load.

Also note, it inverts polarity.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Thu Feb 12, 2015 7:30 pm 
Offline
Cow

Joined: Thu Dec 11, 2008 10:13 am
Posts: 193
Location: Catalonia New Europe State
Thanks Thorsten, same B+?


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Thu Feb 12, 2015 7:44 pm 
Offline
Cow

Joined: Thu Dec 11, 2008 10:13 am
Posts: 193
Location: Catalonia New Europe State
It's OK the attached schematic?


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Fri Feb 13, 2015 4:27 pm 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1179
Hi,

felipe wrote:
It's OK the attached schematic?


No.

Take the original schematic.

Scratch one tube section and the parts on the cathode.

Scratch the parts on the cathode of the second tube section.

Place the battery IN SERIES with the grid (not to ground, nowhere else - literally cut the grid wire and wire the battery into the cut, negative to the grid.

Change Anode resistor to 10k. +B stays the same, anything between 200V and 300V at 20mA per channel should work okay, quality matters most.

Change the feedback resistors (100k, 240k) to suit. Formula for gain is same as inverting Op-Amp, minus a bit for the not near infinite gain of the tube.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Sat Feb 14, 2015 11:04 am 
Offline
Cow

Joined: Thu Dec 11, 2008 10:13 am
Posts: 193
Location: Catalonia New Europe State
Attached schematic, do you know the gain & output impedance?


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Sat Feb 14, 2015 5:26 pm 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1179
Hi,

I give up.

I'll draw it out if I find the time and take a snap with my phone.

But honestly, you should not build schematics you do not understand. And it is clear you do not understand this one.

For example- which part of: "IN SERIES WITH THE GRID" is unclear?

Maybe read the introductory part of the RCA Radiotron Manual Issue 10.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Sat Feb 14, 2015 7:06 pm 
Offline
Benjamin
User avatar

Joined: Mon Dec 13, 2004 3:29 pm
Posts: 4336
Location: Somewhere other than here.
Kuei Yang Wang wrote:
But honestly, you should not build schematics you do not understand.


Why not? Someone we all know (and have probably forgotten about) managed to be Head Designer, for Cary Audio, for a year or so.

Until they figured out he knew nothing about how tubes work.

Last report was he conned Nelson into giving him a job. So, you don't have to know what you are doing if you can get someone else to do it for you.


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Mon Feb 16, 2015 10:17 am 
Offline
Cow

Joined: Thu Dec 11, 2008 10:13 am
Posts: 193
Location: Catalonia New Europe State
Now?


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Tue Feb 17, 2015 5:45 pm 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1179
felipe wrote:
Now?


Yipppiiiieeeee....

Just viewed a boat (live on) in Hong Kong which I might buy and just retire from all this HiFi nonsense and become one of the "Boat People"... Very tempting. Shame about the current state of the Euro.

Oh, your schematic. It makes sense now.

It might even sound awesome. Or awful. One of them anyway.

But electrically it should work without smoke signals (fingers crossed).

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Tue Feb 17, 2015 6:58 pm 
Offline
Cow

Joined: Thu Dec 11, 2008 10:13 am
Posts: 193
Location: Catalonia New Europe State
Thank you!!!


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Tue Feb 17, 2015 9:31 pm 
Offline
Cow

Joined: Thu Dec 11, 2008 10:13 am
Posts: 193
Location: Catalonia New Europe State
Sound awesome :hello:


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Wed Feb 18, 2015 4:12 pm 
Offline
Board jester
User avatar

Joined: Mon Dec 13, 2004 3:08 pm
Posts: 2042
Kuei Yang Wang wrote:
felipe wrote:
Now?


Yipppiiiieeeee....

Just viewed a boat (live on) in Hong Kong which I might buy and just retire from all this HiFi nonsense and become one of the "Boat People"... Very tempting. Shame about the current state of the Euro.

Oh, your schematic. It makes sense now.

It might even sound awesome. Or awful. One of them anyway.

But electrically it should work without smoke signals (fingers crossed).

Ciao T

Whatever floats your boat...
:D

_________________
Elso


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Tue Feb 24, 2015 11:18 am 
Offline
Cow

Joined: Thu Dec 11, 2008 10:13 am
Posts: 193
Location: Catalonia New Europe State
T how many mA are biased each tube?


Top
 Profile  
Reply with quote  
 Post subject: Re: 6SN7 preamp
PostPosted: Tue Feb 24, 2015 2:07 pm 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1179
Hi,

felipe wrote:
T how many mA are biased each tube?


With the 5687WB (1/2 per channel) around 15mA/90V.

The Anode impedance is around 2.5k in this case and Zout becomes around 2k without feedback loop and gain without feedback loop is around 23dB. If you lower gain to 12dB (100K input, 430...470k Feedback) output impedance becomes around 500 Ohm...

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 98 posts ]  Go to page 1, 2, 3, 4, 5 ... 7  Next

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group