DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 29 Mar 2020, 13:07

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 66 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 7  Next
Author Message
PostPosted: 11 Jan 2011, 13:15 
Offline
Editor
User avatar

Joined: 28 May 2008, 21:53
Posts: 4580
Location: Winnipeg, CANADA
Thanks for sharing this great info. I've book marked the thread and will definitely refer back to it in the future.
Cheers

_________________
[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


Top
 Profile  
 
PostPosted: 11 Jan 2011, 14:16 
Offline
User avatar

Joined: 05 Nov 2010, 21:07
Posts: 702
Location: South East US - Tennessee
Wow, Matt. That 5U4 is a saggy tube. I hadn't ever looked at the 5U4. I've looked at the 6CA4 and the 5AR4. I've a build on the back burner that will be using the 6CA4. I looked at the 5AR4 for that build, but I like the small size of the 6CA4 and its current handling is sufficient for my build. If I were needing something with a little more umph, I would consider the 5AR4. But after looking at the 5U4, I can't under stand any use for that one unless you just needed some real current hog of an amplifier. To over come that sag, you would need a pretty high voltage PT supplying it.

Good thread Matt. Definitely gets the brain juices flowing. :thumbsup:

_________________
The key to a successful build is to keep the smoke IN the circuit.
-Les

We cannot solve our problems with the same thinking we used when we created them. - Albert Einstien
_________________________________
LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board


Top
 Profile  
 
PostPosted: 17 Jan 2011, 08:30 
Offline

Joined: 22 Oct 2009, 08:47
Posts: 35
Location: Denmark
Hi
Dos anyone know the the Shuguang 274B rectifier tube,and are thy enny good,planning to use them in a single ended, b+ voltage abut 450-500 volts

nkdk


Top
 Profile  
 
PostPosted: 18 Jan 2011, 11:06 
Offline

Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
Here's a data sheet I found.
http://www.westernelectric.com/products/274b.html

Should be similar to the Shuguang.


Top
 Profile  
 
PostPosted: 24 Feb 2011, 13:01 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1620
Location: US Pacific Northwest
It's been a while but I was looking over a power supply design and I began to think about the rectifier voltage drop plot out of Herbert Reich's 1944 book "Theory and Applications of Electron Tubes", 2nd ed. shown here in this thread. I had originally thought that the straight lines were just approximations but then I wasn't so sure. So I went back to my plot of voltage drops vs peak plate current and changed the axes types from linear to log. These two plots show the result.
Attachment:
lin-lin Plot.png
Attachment:
log-log Plot.png

The first is just the plot of numbers taken directly off curves in the data sheets. The second is the same plot with the axes changed.

Now I am wondering if there is anything to be learned about how these tubes operate from these relationships. And why are the slopes of all the lines on the log-log plot nearly identical. This must correspond to some fundamental characteristic of the tubes but I'm not sure what. Is this behavior a consequence of Child's Law? Do the tubes lower on the plot represent those with cathode materials having lower electron affinity? Does anyone have any ideas here. I'm curious.


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.


_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 24 Feb 2011, 14:08 
Offline
User avatar

Joined: 28 Jan 2011, 11:51
Posts: 98
With mention of Chinese 274 rectifiers : don't bother ! You'll get better sonics from a USA 5Z3 which is a 5U4G on a UX4 base . Cheaper and no doubt more reliable too . Try a paralleled pair of 5Z3 and you may thank me later...

I'm a big fan of DH rectifiers such as 5Z3 CV31 U19 and type 83 :)

BDA


Top
 Profile  
 
PostPosted: 24 Feb 2011, 20:08 
Offline

Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
Probably not a good idea to use the 83 since It's a MV type and has the usual hazards associated with those type of tubes. Also I've heard Chinese 274B that did sound good, but NOS 5U4GB did sound better in the mono-blocks I heard them in.


Top
 Profile  
 
PostPosted: 24 Feb 2011, 22:05 
Offline
User avatar

Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
rock4016 wrote:
Chinese 274B that did sound good, but NOS 5U4GB did sound better in the mono-blocks I heard them in.


My 2A3 clients have said similar.

Cheers!

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


Top
 Profile  
 
PostPosted: 25 Feb 2011, 03:46 
Offline
User avatar

Joined: 28 Jan 2011, 11:51
Posts: 98
rock4016 wrote:
Probably not a good idea to use the 83 since It's a MV type and has the usual hazards associated with those type of tubes.

It's hearsay . I'm at a loss to find any reason why these devices are hazardous . Mercury is poisonous but is contained within the envelope . Yes there are caveats such as adding plate suppressor chokes and using an AM radio or search coil (a choke) to 'sniff' for RFI , if there is any , can be useful

MV's look good . MV's sound good...

What more can you ask for ?

BDA


Top
 Profile  
 
PostPosted: 25 Feb 2011, 10:17 
Offline

Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
If the following is hearsay then please disregard my previous statement.

1) MV rectifiers that are new or have been laid on their side for some reason need to have their filaments run for 20-30 minutes without HV applied to make sure that the mercury is vaporized and out of the filament and other tube electrodes where it can cause internal shorts.

2) Under voltage on the filament (like only 10%) can cause immediate tube failure because of inadequate mercury vaporisation.

3) All MV rectifiers need to have their filaments warmed up for 45-60 seconds before HV is applied to assure that the mercury is vaporized. Failure to ensure adequate warm up time can cause back bombardment of the filament and destroy the oxide coating in a matter of minutes. This means you will need a separate filament supply with a switch or time-delay relay.

4) Mercury vapor rectifiers are prone to "arc-over" or "flash-over" caused by under or over vaporization problems and just random weirdness. If you have never seen an MV rectifier flash over just wait, if you are using them, and eventually it will happen. Tube implosions are very rare (caused by disentegrating and flying pieces of tube elements) but that was one of the reasons MV rectifiers were frequently in cages. Most big transmitters always had a spare rectifier that could be switched in when one of the MV tubes arced-over. It will scare the pants off you when it happens.

5) MV rectifiers, because of the gas plasma, can generate huge amounts of broadband noise that need to be filtered out by special "hash chokes" in the anode leads and by invasive bypassing. This doesn't always happen but it does occur frequently. This was another reason that they were in shielded cages.

6) MV rectifiers are temperature sensitive and need to be operated over a realtively narrow range.

7) Don't drop one! When one inadvertently gets broken, there is sufficient elemental mercury in a cold tube to constitute a significant environmental and hence health hazard. Clean up depending on the surface it spills on can be problematic, in any event it is usually recommended that a local hazzmat specialist do the clean up. There are recommended clean up procedures for fluorescent lamps which generally contain a lot less mercury afaik.

The worst case scenario might be if an operating tube got broken and the vapor escaped because it will quickly condense leaving micro-droplets of mercury on everything it touches.


I know an 83 is a long way from an 870B but it still is subject to the same problems on a smaller scale


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 66 posts ]  Go to page Previous  1, 2, 3, 4, 5 ... 7  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: chow123 and 14 guests


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

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy