Super Triode Connection Amplifier Build with 6BM8 and 6AK5 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 25th June 2006, 07:49 AM   #1
DerFly is offline DerFly  Australia
diyAudio Member
 
Join Date: May 2006
Default Super Triode Connection Amplifier Build with 6BM8 and 6AK5

Well, I've been lurking about here for a while, also been doing a bit of research on the net about first tube/valve amplifier projects.

Iíd actually been researching simple morse transmitters using a 6BM8 and stumbled across quite a bit of info on STC amps using this tube. It seemed a good contender for a first project as I had several 6BM8 on hand, inexpensive output transformers are able to be used and construction doesnít look too daunting.

As they say, fortune favours the brave (or stupid), so here we go with some thought, but probably not enough, already put into the project.

The original schematic available here (http://www2u.biglobe.ne.jp/~hu_amp/amput3e.htm) shows a requirement of 6.3v at 2A and a HV transformer of 220v output rated at 30VA.

Not wanting to invest too much in a project which may or may not work, I'm going to back-to-back a couple of cheap transformers for a simple power supply.

In the picture, the two respective transformers are 30 and 15VA. I should be able to take 6.3V at 1A out from the first and then step back up for 240V at about 60mA of HV.

I know this is only half of the power requirement so I guess the simple answer is to build two monoblocks!

Being newish to all this, I'd most appreciate any advise along the way. I'll also be posting questions as I certainly do not have all the answers yet.

This may well be a drawn out affair, so I hope you'll bear with me as this project takes its course.
Attached Images
File Type: jpg power transformers.jpg (89.6 KB, 1878 views)
  Reply With Quote
Old 25th June 2006, 11:22 AM   #2
DerFly is offline DerFly  Australia
diyAudio Member
 
Join Date: May 2006
These are the output transformers Iíll use. They are 5k Ohm input with a tap for 2.5k and the output is multitap with 2, 4, 8 and 16 Ohms out. The original article above shows a transformer with 3.5k in/8 Ohm out but Iíve also seen a few schematics with two OPTís per side.

This chap (http://www.atatan.com/~s-ito/amp/yakinori.html) is using two output transformers with specs 7k Ohm in/8 Ohm out with the inputs paralleled and the outputs in series.

As these were really cheap, I bought four so I guess Iíll use two each per monoblock. Not sure how Iíll wire these yet. Any suggestions? Has anyone else built one of these?

DerFly.
Attached Images
File Type: jpg output transformers.jpg (81.1 KB, 1757 views)
  Reply With Quote
Old 25th June 2006, 11:45 AM   #3
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Even after reading the explanation, I'm clueless about the "stopping diode." Could you elaborate on that? What happens when it reverse biases? How does it function when it's forward biased?
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 25th June 2006, 03:10 PM   #4
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
These "magic diodes" keep showing up in various schematics. I tried a "stopper diode" in the plate lead of one of my sweep tube SE amps. The only thing that it stopped was good sound.

I noticed a definite change in the output signal when the amp was driven to clip with a strong bass note. What was previously a single cycle event with the top whacked off of a transient, now affected about 3 cycles and there was some funny ringing effects. Yes there is some definite speaker interaction here. It may sound good to some people with some music, but I didn't like it.

I have an EL-34 SE amp playing now. I will put in a diode and see what happens.

Disclaimer:

My experiments have been in triode or UL mode. The authors experiments were in pentode mode.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 25th June 2006, 04:48 PM   #5
Giaime is offline Giaime  Italy
diyAudio Member
 
Giaime's Avatar
 
Join Date: Oct 2004
Send a message via MSN to Giaime
I think we should distinguish the diode in the screen lead from the one in the plate lead.

Just from a rapid guess, the one in the plate lead looks very very suspect to me, the experience that George mentioned makes me think about interactions between the power supply and the power stage.

The diode in the screen path, however, puzzles me. Is the screen grid supposed to have a one-way current allowed, like the plate? So what's the effect of the diode?

I remember we already touched this subject:
Diode trick?
  Reply With Quote
Old 25th June 2006, 04:53 PM   #6
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
So what's the effect of the diode?
Same as the plate diode: to convince the builder that he's done something different and clever.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 25th June 2006, 04:54 PM   #7
diyAudio Member
 
Brian Beck's Avatar
 
Join Date: Dec 2004
Location: South Florida, USA
The more scientific answer is that they confer pixie dust.
__________________
Brian
  Reply With Quote
Old 25th June 2006, 04:56 PM   #8
Giaime is offline Giaime  Italy
diyAudio Member
 
Giaime's Avatar
 
Join Date: Oct 2004
Send a message via MSN to Giaime
Quote:
Originally posted by Brian Beck
The more scientific answer is that they confer pixie dust.


Now I'm really confused. I'm starting digging into the RDH4 to find a chapter about "pixie dust"
  Reply With Quote
Old 25th June 2006, 04:57 PM   #9
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Brian, that's twice today!
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 25th June 2006, 05:05 PM   #10
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
Now I'm really confused. I'm starting digging into the RDH4 to find a chapter about "pixie dust
You need the "Disney Edition".
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  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
new thread, 6BM8 PP build begins... Nanook Tubes / Valves 8 13th December 2007 06:08 AM
6AN8 Triode connection + EL 84 PP Tobruk Tubes / Valves 3 2nd May 2007 02:42 AM
6AK5 Triode Curves dsavitsk Tubes / Valves 2 29th March 2007 06:20 PM


New To Site? Need Help?

All times are GMT. The time now is 08:38 PM.


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