My single ended 811

ask your general tube related questions here

My single ended 811

Postby DeathRex » Sun Feb 16, 2014 12:36 pm

I finally finished my 811 se integrated. Used Valve World's schematic, but didn't want a pentode in the front, because I didn't want global feedback. I started with 6AQ7s, but they didn't have quite enough gain, so I switched to 6SN7s cascaded. Getting about 10 watts out.

My firsts for this amp:
first DHT
first time using 6BD5GT (have to see how long they last) did have a used one that was gassy
first time veneering
first swirl pattern on aluminum

The big transformer is the 6.3 volt filament for the 811s.
There are additionally a power transformer, and 3 chokes underneath.
The lowest hum I could get down to was 8mvpp. With the volume pot in front of the 6AQ7s, hum was at 10mvpp. With the volume pot in front of the 6SN7s, I was getting 20mvpp. I tried putting DC on the filaments and everything else, just couldn't get it down. Even with DC on the filaments of the 811s, the 50 ohm adjustment pot is very touchy.
Attachments
811-small_zpse30bef15.jpg
811-small_zpse30bef15.jpg (254.45 KiB) Viewed 3966 times
811se mine_zpsttqrurd5.gif
811se mine_zpsttqrurd5.gif (74.41 KiB) Viewed 3966 times
Last edited by DeathRex on Sat Jul 15, 2017 12:01 pm, edited 3 times in total.
At first I wanted to be a ET. Now I are one.
User avatar
DeathRex
KT88
 
Posts: 1014
Joined: Wed Nov 18, 2009 8:13 pm
Location: Cortez, CO

Re: My single ended 811

Postby kheper » Sun Feb 16, 2014 2:36 pm

DeathRex wrote:The big transformer is the 6.3 volt filament for the 811s.
There are additionally a power transformer, and 3 chokes underneath.The lowest hum I could get down to was 8mvpp. With the volume pot in front of the 6AQ7s, hum was at 10mvpp. With the volume pot in front of the 6SN7s, I was getting 20mvpp. I tried putting DC on the filaments and everything else, just couldn't get it down. Even with DC on the filaments of the 811s, the 50 ohm adjustment pot is very touchy.


If there is room underneath, you could put chokes on the filament supplies. You might get away with one choke if you paralleled the secondaries and lost the hum-pots. Make sure the filament diodes can handle the current.

Nice retro-deco style on the wood and metal. The amp would have a more stunning appearance if you re-painted the old transformers.
User avatar
kheper
KT88
 
Posts: 1252
Joined: Wed Dec 21, 2005 10:14 pm
Location: Philly, PA

Re: My single ended 811

Postby Geek » Sun Feb 16, 2014 2:58 pm

Sweet! :))

Is the hum balance pot a multi-turn?

You can likely also reduce hum with a resistor loading the grid. 5-10K-ish.

Cheers!
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
User avatar
Geek
KT88
 
Posts: 3585
Joined: Sun Oct 21, 2007 3:01 am
Location: Chilliwack, British Columbia

Re: My single ended 811

Postby DeathRex » Sun Feb 16, 2014 6:55 pm

kheper wrote:If there is room underneath, you could put chokes on the filament supplies. You might get away with one choke if you paralleled the secondaries and lost the hum-pots. Make sure the filament diodes can handle the current.

Nice retro-deco style on the wood and metal. The amp would have a more stunning appearance if you re-painted the old transformers.

Like the lady said working at the hotel during the democratic convention in New Orleans "Aint got no more room." The diodes are 17 amp schottkys. With most of my amps, I wanted a old and used look. Didn't want a old and then new look. And I like the diagram on front of the Triad.
Geek wrote:Sweet! :))

Is the hum balance pot a multi-turn?

You can likely also reduce hum with a resistor loading the grid. 5-10K-ish.

Cheers!

Nope just a single wire wound Alpha. You can adjust it and see the waveform change on the oscope. I just turned it to minimum. I can't hear the hum and better yet there is no hiss. I guess 8mvpp is about 2.8 mv rms. When you first turn it on, the 6BD5GT has ALOT of 60 Hz on it, in a perfect sinewave. It took me a while to figure out it would since there is no load on it. I had to really lower that second B+ to bias the 811s, I didn't know what would happen if I did add a load onto the cathode, so I didn't.
At first I wanted to be a ET. Now I are one.
User avatar
DeathRex
KT88
 
Posts: 1014
Joined: Wed Nov 18, 2009 8:13 pm
Location: Cortez, CO

Re: My single ended 811

Postby 20to20 » Mon Feb 17, 2014 9:42 am

I wanted a old and used look. Didn't want a old and then new look. And I like the diagram on front of the Triad.


Love the Art Deco look. Where did you get the inlaid front piece?
Headed for Tishomingo to sing in a can...
User avatar
20to20
KT88
 
Posts: 566
Joined: Wed Apr 21, 2010 1:48 pm
Location: W-S, NC

Re: My single ended 811

Postby DeathRex » Mon Feb 17, 2014 1:54 pm

Made it, got some veneer from ebay, cut it, and contact cemented down. The sides are cherry.

I think I'll try some linseed oil on the transfomers to liven them up. And adjust the white balance on the camera.
At first I wanted to be a ET. Now I are one.
User avatar
DeathRex
KT88
 
Posts: 1014
Joined: Wed Nov 18, 2009 8:13 pm
Location: Cortez, CO

Re: My single ended 811

Postby 20to20 » Mon Feb 17, 2014 2:08 pm

DeathRex wrote:Made it, got some veneer from ebay, cut it, and contact cemented down. The sides are cherry.

I think I'll try some linseed oil on the transfomers to liven them up. And adjust the white balance on the camera.


WOW. Great job on getting those 3 center pieces to join up. Did you use a scalpel on those cross-grain cuts?
Headed for Tishomingo to sing in a can...
User avatar
20to20
KT88
 
Posts: 566
Joined: Wed Apr 21, 2010 1:48 pm
Location: W-S, NC

Re: My single ended 811

Postby DeathRex » Mon Feb 17, 2014 3:33 pm

Guillotine paper cutter.
At first I wanted to be a ET. Now I are one.
User avatar
DeathRex
KT88
 
Posts: 1014
Joined: Wed Nov 18, 2009 8:13 pm
Location: Cortez, CO

Re: My single ended 811

Postby Hotsauce » Tue Feb 18, 2014 5:39 am

Great job.

Not easy to do symmetrical veneer. Inside corners are tough.

John
User avatar
Hotsauce
 
Posts: 88
Joined: Sun Sep 21, 2008 5:56 pm
Location: Bronxville

Re: My single ended 811

Postby Geek » Tue Feb 18, 2014 5:40 am

DeathRex wrote:Guillotine paper cutter.


THAT is something I'd not thought of. Nice tip! :))
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
User avatar
Geek
KT88
 
Posts: 3585
Joined: Sun Oct 21, 2007 3:01 am
Location: Chilliwack, British Columbia

Re: My single ended 811

Postby TomMcNally » Tue Feb 18, 2014 10:53 am

I thought those things were for cutting aluminum? ;)
User avatar
TomMcNally
Darling du Jour
 
Posts: 2729
Joined: Sat Nov 19, 2005 2:19 pm
Location: Northfield, NJ

Re: My single ended 811

Postby DeathRex » Tue Feb 18, 2014 4:27 pm

Here's a post lineeded pic with Oreo.
Attachments
811-small2_zps1cd94eb0.jpg
811-small2_zps1cd94eb0.jpg (64.63 KiB) Viewed 3965 times
Last edited by DeathRex on Sat Jul 15, 2017 12:03 pm, edited 1 time in total.
At first I wanted to be a ET. Now I are one.
User avatar
DeathRex
KT88
 
Posts: 1014
Joined: Wed Nov 18, 2009 8:13 pm
Location: Cortez, CO

Re: My single ended 811

Postby Geek » Tue Feb 18, 2014 5:01 pm

You KNOW you have a winner when it's kitty approved! :))
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
User avatar
Geek
KT88
 
Posts: 3585
Joined: Sun Oct 21, 2007 3:01 am
Location: Chilliwack, British Columbia

Re: My single ended 811

Postby DeathRex » Tue Feb 18, 2014 6:59 pm

Gregg, is that a Hammarlund? Looks an awful lot like the HQ180 I have.
Attachments
HQ-180s_zpsdd9592df.jpg
HQ-180s_zpsdd9592df.jpg (177.94 KiB) Viewed 3966 times
Last edited by DeathRex on Sat Jul 15, 2017 12:01 pm, edited 1 time in total.
At first I wanted to be a ET. Now I are one.
User avatar
DeathRex
KT88
 
Posts: 1014
Joined: Wed Nov 18, 2009 8:13 pm
Location: Cortez, CO

Re: My single ended 811

Postby Geek » Tue Feb 18, 2014 7:02 pm

DeathRex wrote:Gregg, is that a Hammarlund? Looks an awful lot like the HQ180 I have.


Yup! HQ-170 :))
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
User avatar
Geek
KT88
 
Posts: 3585
Joined: Sun Oct 21, 2007 3:01 am
Location: Chilliwack, British Columbia


Return to tube 101

Who is online

Users browsing this forum: No registered users and 11 guests

cron