872b or 6gj5a for a homebrew bass amp - 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 23rd May 2012, 08:21 PM   #1
m3vuv is offline m3vuv  United Kingdom
diyAudio Member
 
Join Date: May 2012
Default 872b or 6gj5a for a homebrew bass amp

hi all,can any one point me in the direction of a schematic for a bass amp using a 572b or 6gj5a sweep tube?,i have a built a rf linear amp using 572b valves with a b+ of 2400volts and it works a treat(2x572b in grounded grid),i have a 2400v psu and a dc filament psu plus valves and sockets,thats the reason for wanting to have a go at a bass amp,also just a thought,would it be possible to use a pi network to match the output impedance to the speaker?,this is often done in rf applications but not so sure about audio!,cheers all,Paul m3vuv
  Reply With Quote
Old 24th May 2012, 03:02 AM   #2
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
just a thought,would it be possible to use a pi network to match the output impedance to the speaker?
A PI network like those found in RF amps is designed to work at a single frequency and must be retuned if the frequency is changed. A bass amp must cover 40 Hz to several KHz without retuning.

You need an output transformer to match the high impedance tubes to the low impedance speaker over the audio frequency range. It works like the broadband balun seen in a solid state HF amp, only it is much larger since it operates at a lower frequency.

A bass amp will need a few stages of preamp gain and a suitable output stage. The 572B is better suited to RF amp use since the higher voltages and impedances that these tubes need makes the design of the output transformer much more difficult. It would probably not be an off the shelf part.

Sweep tubes make excellent audio amplifiers. You can lift the preamp schematic from a tube bass amp that you like. Look at this thread for a power amp that works with sweep tubes. I have used it for guitar amp duty.

George KB4LRE
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 24th May 2012, 03:44 AM   #3
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
George, OT but how about a report on the Hamvention. What did you buy, sell and saw but didn't buy.
__________________
"I regard the brain as a computer which will stop working when it's components fail. There is no heaven or afterlife for broken down computers. That is a fairy story for people afraid of the dark." ~Stephen Hawking
  Reply With Quote
Old 24th May 2012, 10:33 AM   #4
m3vuv is offline m3vuv  United Kingdom
diyAudio Member
 
Join Date: May 2012
cheers for that,i realised about a pi network after i posted the thread!,the psu i have has a voltage doubler so the output from the transformer is 1.2kv at 1amp,the reason i wanted to use sweep tubes or 572b s,was due to me having them around,this is a project for a friend,he has a ss 50w amp but gets drowned out by the drums!,i was thinking about using the ss amp to drive the tube one,if that makes sense,as regards the matching transformer i was thinking of homebrewing one,i have a lathe and plenty of ironwork for one!,i was looking for about 100wats output but wanted to do it with the bits i have in the junk box,any help with component values much needed,thanks for the replys,keeep em comming,cheers all de m3vuv.
  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
FS: Homebrew B1 KatieandDad Swap Meet 1 24th February 2012 03:57 PM
FS: Homebrew 6V6 PP tube Amp $60.00 Sal Brisindi Swap Meet 2 11th July 2007 02:09 PM
Homebrew Spectrum Analyzer Duo Everything Else 44 14th March 2007 09:44 PM
Is it possible to homebrew better than the big guys? walker Solid State 63 12th January 2004 01:47 PM
Homebrew poweramp... koolscooby Solid State 13 27th December 2003 03:10 PM


New To Site? Need Help?

All times are GMT. The time now is 04:00 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