Long time lurker - first build a tubelab Simple SE - Page 2 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Tubelab

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Reply
 
Thread Tools Search this Thread
Old 28th August 2008, 02:15 AM   #11
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Yes. For operation under 350 volts R14 and R24 should be eliminated. Replace them with a jumper wire. These resistors were added to lower the dissipation in the CCS at high B+ voltages. Distortion is seen with some 12AT7's with these resistors on low B+ voltages.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 28th August 2008, 02:22 AM   #12
cjkpkg is offline cjkpkg  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Roswell GA
I see about the power supply. Would I be better of sticking with the 6L6's and cutting back the resistance on R17 and R27 or maybe trying a pair of EL34's?
  Reply With Quote
Old 28th August 2008, 02:28 AM   #13
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Sorry fore a small negative remark but while some of your solder joints looks perfect, some others looks not so good(cold soldering ?)...would be a shame if such a nice amp fails because of that
__________________
sometimes we know very little, and sometimes we know too much
  Reply With Quote
Old 28th August 2008, 05:22 AM   #14
diyAudio Member
 
Join Date: Jan 2006
Location: south of the border
Default (Human) off topic...

Quote:
Originally posted by tubelab.com
I have been recovering from surgery so I missed the start of this thread. I am not even supposed to be out of bed now, so I will be seen here sporadically over the next few days.
Wish you a good recover George (& thanks for your previous efforts on diyaudio.com!)!
Cheers,
  Reply With Quote
Old 28th August 2008, 08:03 PM   #15
waam68 is offline waam68  United Kingdom
diyAudio Member
 
Join Date: Apr 2007
I was reading George's comments today & realised I had a 12AU7 & not an 12AT7 in my Simple SE as the driver... when I got home today I dug into the junk box & found a NOS Brimar AT7.....what a revelation...sound was good before...but a bit thin with some music...much more of a warm sound & bass with the AT7...I'm running a Hammond 374BX, EL34's & the stock resistors & a 1960 russian 5U4. I guess I wasn't paying attention when I built it 6 months ago!
  Reply With Quote
Old 28th August 2008, 09:08 PM   #16
diyAudio Member
 
Join Date: Jun 2008
Quote:
Originally posted by waam68
... I guess I wasn't paying attention when I built it 6 months ago!
Can I interest you in a career in the automotive manufacturing industry?
  Reply With Quote
Old 28th August 2008, 09:33 PM   #17
waam68 is offline waam68  United Kingdom
diyAudio Member
 
Join Date: Apr 2007
Thanks for the offer.. but I'll stick to designing nuclear reactors
  Reply With Quote
Old 28th August 2008, 09:54 PM   #18
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
Quote:
Originally posted by waam68
I was reading George's comments today & realised I had a 12AU7 & not an 12AT7 in my Simple SE as the driver...
I've been thinking about intentionally trying a 12AU7 in the driver tube position. I think it might work better if R10 and R20 were changed to 1000 ohm (instead of 220). That should get the grid about -10 volts from cathode, and put the line into what looks like a more linear region. It'll also keep the dissipation up to about the same as what George designed for the 12AT7.

What I don't understand is how it will impact the driver's output impedance. I think the relationship between that and the final's input impedance is what ultimately affects the amplifiers overall bandwidth.

Why would I want to do this? Well, the 12AT7 just has a lot more gain than I feel like I really need. It can swing 50 volts with a 1 volt input. While you need this much to fully drive a KT88, I don't think it's necessary for a 6L6 or an EL34. I think they only need about 35 volts. Besides, most of the time I like to listen to it quietly. I'd like to have a little more range of motion in the volume knob.
  Reply With Quote
Old 31st August 2008, 07:59 PM   #19
cjkpkg is offline cjkpkg  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Roswell GA
Update...I finished soldering everything to the board.
Click the image to open in full size.
Click the image to open in full size.

I think I will take George's advice and upgrade the power transformer to the 6K7VG. Hopefully Allied has a decent return policy.

I received the top plate from mouser, a Hammond 10X12 unit man I can not wait to get everything mounted!

I am traveling for work to Belgium all next week so hopefully when I get back I'll have my upgraded power transformer and my Edcor OPT's.

Thanks for the advice.
Carl
  Reply With Quote
Old 7th September 2008, 03:49 PM   #20
cjkpkg is offline cjkpkg  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Roswell GA
Got the 6K7VG hooked up and I am having some problems...

Yellow = 540V
Red = 414V
Red/Yel = 0
Green = 35V

Something seems very wrong with this, any ideas?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
(YATSE) Yet Another Tubelab SE (sorry...long) rknize Tubelab 12 23rd June 2009 06:39 AM
Nubie first build Tubelab simple SE Mungo Park Tubelab 65 27th May 2009 05:41 PM
Long time lurker - Intro! hack247.co.uk Introductions 1 29th May 2006 08:54 PM
First time caller, long time listener... smallangryboy Introductions 15 19th March 2005 08:10 PM
Forgot to do this long long time ago chris ma Introductions 2 30th October 2003 10:53 PM


New To Site? Need Help?

All times are GMT. The time now is 05:23 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2