QB2/250 amplifier - 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 2nd February 2012, 06:08 PM   #1
diyAudio Member
 
Join Date: Mar 2011
Location: Jarna
Default QB2/250 amplifier

Some big boxes has been waiting to become an ampm for a long time now.

Click the image to open in full size.

My original idea was triod driving triod connected.

Click the image to open in full size.

I have some descent 5k irons so something in the 7-800v range was in mind.

Then Schade was brought in the picture by a friend and here i am.

Whats the way to go is Schade better then triode ?

It gives better power with triode like behavior but is it as good?
  Reply With Quote
Old 2nd February 2012, 06:32 PM   #2
GloBug is offline GloBug  Canada
Banned
 
Join Date: Jun 2011
Good thing I have my boner pants on.
I vote for schade, not for lack of power though.
  Reply With Quote
Old 2nd February 2012, 06:51 PM   #3
Jebem is offline Jebem  Portugal
diyAudio Member
 
Jebem's Avatar
 
Join Date: Dec 2011
Location: Lisbon
Nice Pentode tubesYou have there!
With those 4 tubes, I would build a nice stereo retro Push-Pull amplifier.

Kinkless tubes or beam power tubers as they call it (KT series) have appeared in the market as improved tetrode tubes that fixed the "kink" on the conventional tetrode tube transfer curves, fixing the linearity and power problems of tetrodes. Pentodes don't have that "kink" problem.

So a KT series tube have its virtues, specially now that the KT120 is out in the market, showing lots of power and good linearity, but a good pentode like the EL34 can make very musical amplifiers as well as long as You don't need too much output power.

As for triode tubes, I like them above all kind of tubes, in particular the 211 and 845. They are excellent as single-ended class A amplifiers if You can live with just 15 Watt of power.
Of course a Push-Pull class A amp with 845 tubes driven by 300B triodes transformer coupled (like the Marantz T1) is really hard to beat in sonic terms and retro style.

It all depends on one needs and tastes after all.
__________________
If You need something done properly, do it yourself (and ask help from DIYaudio... )
One of my SE 211 tube amps: http://sites.google.com/site/sunajeb...ificador-211se
  Reply With Quote
Old 2nd February 2012, 07:13 PM   #4
diyAudio Member
 
Join Date: Mar 2011
Location: Jarna
Ok so Shade is to be investigated.

For driver i have C3g or D3a at hand if youre not suggesting anything else.

Anyone tried this one in shade configuration and at which working point ?
  Reply With Quote
Old 2nd February 2012, 07:22 PM   #5
diyAudio Member
 
Join Date: Apr 2009
Great audio tube, I prefer them triode strapped ...

I have many 813 tubes, but I've never seen those ones made by Philips.

813 DH Pentodes (QB2-250, 5C-100A, 4T100, U3, CV26, CV143, CV177)

813 VT-144 | Facebook

Good luck with project!!!
__________________
tubes.rs
  Reply With Quote
Old 2nd February 2012, 07:31 PM   #6
diyAudio Member
 
Join Date: Mar 2011
Location: Jarna
Philips made in France stamped on them.
  Reply With Quote
Old 2nd February 2012, 07:39 PM   #7
diyAudio Member
 
Join Date: Apr 2009
Made in RTC France factory for Philips
__________________
tubes.rs
  Reply With Quote
Old 2nd February 2012, 07:47 PM   #8
diyAudio Member
 
Join Date: Mar 2011
Location: Jarna
What i used to call an oversized rectifier tube is a good sizematch this time

Click the image to open in full size.

Finally an amp to use a couple of 3B28 in
  Reply With Quote
Old 2nd February 2012, 08:13 PM   #9
diyAudio Member
 
Join Date: Apr 2007
I've done some experiments with this tube in triode mode A2 SE. Sounds very good but I run them at 900-1000V with 10k load. I would guess that 5k would be OK at the lower voltage you are planning. However output resistance will be quite high with 5k, Ri in triode is close to 2k.

/Olof
__________________
I'm not allowed to do magic, union rules...
  Reply With Quote
Old 2nd February 2012, 08:23 PM   #10
diyAudio Member
 
Join Date: Mar 2011
Location: Jarna
Ill always prefered high voltage over current so thats a thing to think about.

I played around with it as SE and ended up with 1400v for triod strapped 10k.

I have to read up on schade and descide if that or triode is the way to go.

Still need more opinions on what sounds best to you people.
  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
M&M PA-250 amplifier investigated tsmith1315 Car Audio 20 4th December 2009 05:13 AM
Need help with a Radford HD 250 amplifier gaetan8888 Solid State 2 4th July 2007 05:59 PM
Omnitronic P-250 amplifier wimdehaan Solid State 3 20th September 2006 02:07 PM
The amplifier of M -250 Vanya Solid State 1 14th June 2005 08:04 PM
Kustom 250 amplifier, well done Lenny Solid State 0 20th May 2004 05:57 PM


New To Site? Need Help?

All times are GMT. The time now is 09:42 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