833a spud 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 24th November 2014, 10:25 PM   #1
diyAudio Member
 
Join Date: Oct 2010
Location: se england
Default 833a spud amplifier

Hi Thought I'd start a thread about building a very cheap, smallish, practical and safe 833a amplifier. I'm not planning a build in the magz vein, just read all the 'midlife crisis ' thread and was hugely impressed.
I picked up a pair of second hand but seemingly good rca's for 25 and then a 750va machine control transformer configurable for 480v for 35 delivered. a root about delivered two 350ma 10H chokes and half a dozen 900v polypropylene caps plus 1000v 3 A uf diodes etc.
Half hour spent on psud showed a doubler could deliver 300+ma at 1100v.
26 bought 2 x 12v@ 20A smp and a couple of 20A 1ohm ntc makes a usable filiment supply. I'm a big fan of Rods filiment boards, must have 8 in use, but this is meant to be a practical build so heat is my enemy. The smp were warm but not hot after 30mins. The ntc was hot but running @ 2/3 rated Diss so hopefully will be ok.
The achillies heal is obviously the output transformers. Hammond 5k 75w were tempting but at 500 a pair not an option.
Bezdz in China are sending me a pair of 5.7kg '75w' 6-7k se opt for $175 plus a not inconsiderable shipping charge, good for 2500v and 300+ma.
The spud comes in as I really don't need all the power an 833 can deliver. I use a 4p1l preamp amp and my cdp and phonostage produce 5.6v p-p so x 8 ish will deliver 40+ volts into the 'powerdrive' mosfet 'tubelabe C'. Rough calcs that should give 40 or so watts. If I need more I'll fit a 6e5p / dn2540 driver.
I've actually had music from the 833s by wiring them into my 6hv5a breadboard, sounded positive.
The work will be building a chassis that is completely safe. It will be a stereo chassis with everything on board. I'm thinking 30 x 60 by 75 high with the tubes enclosed and no burn or electrical hazards. These are not my first amplifiers and my last two were 1100v + but I am not taking any chances.

http://rs117.pbsrc.com/albums/o71/en...0?t=1416864141

I have a few bits left to buy and work out but hope to have a prototype by the end of Christmas holidays.
Any input as to the practicality of fitting chokes either side of the filiments to try and separate the smp and music would be appreciated! cathode will go to 0v via a current meter.

Enzo

Last edited by enzoastro; 24th November 2014 at 10:27 PM.
  Reply With Quote
Old 24th November 2014, 11:42 PM   #2
Magz is online now Magz  United States
diyAudio Member
 
Join Date: Oct 2009
Location: New Jersey, USA
Good luck! Should be an interesting build.
  Reply With Quote
Old 24th November 2014, 11:44 PM   #3
djn is offline djn  United States
diyAudio Member
 
djn's Avatar
 
Join Date: Oct 2004
Location: Waterford Michigan
Hi Enzo. When I clicked on the link, I saw your GM70 amp. How did you wire up the half wave rectifiers....They are some thing 22 right? Those are the same I have for my project but have not looked into how to wire them up.
__________________
My "Art" website http://home.comcast.net/~djnagle/site/
  Reply With Quote
Old 25th November 2014, 01:11 AM   #4
multi is offline multi  Australia
diyAudio Member
 
Join Date: Jan 2011
Enzo
I have imported lots of output and Power transformers from China; I have them shipped by China post surface $US60 for 20 Kilo's, have found it very reliable to Australia takes about 4 weeks.England is a lot further!!! I have built both Se & PP 805's about 45 watts Se similar spec's to the 833. Sound wonderful PP.
Interested how you like Bezdz.
Phil
  Reply With Quote
Old 25th November 2014, 08:26 AM   #5
diyAudio Member
 
Join Date: Oct 2010
Location: se england
Thanks for your replys!
DJN THE GM70 had 6d22s in a hybrid bridge with 3a 1000v uf54xx diodes, two damper diodes per phase to help with the 310ma draw.

I've not used Bezdz before but there finished amplifiers seem to get well reviewed in context. And they are very cheap! Communication seems good enough so far.
Who have you used for transformers multi?
Enzo
  Reply With Quote
Old 29th November 2014, 03:23 PM   #6
diyAudio Member
 
Join Date: Oct 2010
Location: se england
Bezdz transformers took 3 or 4 days from Hong Kong so that explains the shipping costs. The covers I ordered were missing but they replied to my email within Hours apologising and forwarded a link with a few different designs to chose from.
Just be aware that the product list states 4-8-16 ohm secondaries and 3.5-4.5k primaries but in fact the primary has b+ screen and plate connections and the secondary 8-4 and 0a and 0b one for 3.5 and one for 4.5k I generally use 16 ohm goodmans axioms so the 3.5k tap will be my first choice, 7k.

A little playing around shows I can get all the power supplies and opt's on the first 600 x 300 level so the second will just have the 833's with low noise fans under them and a toughened glass 300 x 600 window
Click the image to open in full size.

Last edited by enzoastro; 29th November 2014 at 03:29 PM.
  Reply With Quote
Old 5th December 2014, 06:42 PM   #7
diyAudio Member
 
Join Date: Oct 2010
Location: se england
Stuff for the chassis came today, 6mm angle and 4mm plate for the heavy bits. The 833 s sit on 3 mm sheet and I'm looking at fireguard type expanded steel for above the tubes

Click the image to open in full size.
  Reply With Quote
Old 7th December 2014, 03:13 PM   #8
djn is offline djn  United States
diyAudio Member
 
djn's Avatar
 
Join Date: Oct 2004
Location: Waterford Michigan
Hi Enzo, what does "SPUD" mean?
__________________
My "Art" website http://home.comcast.net/~djnagle/site/
  Reply With Quote
Old 7th December 2014, 03:48 PM   #9
wicked1 is online now wicked1  United States
diyAudio Member
 
wicked1's Avatar
 
Join Date: Jan 2008
Location: Midwest
Spud in this context means an amp w/ one tube.
Probably because people called them "one 'tubers'" or something, and a tuber is a potato, and a single small potato is a supd.
  Reply With Quote
Old 7th December 2014, 09:04 PM   #10
djn is offline djn  United States
diyAudio Member
 
djn's Avatar
 
Join Date: Oct 2004
Location: Waterford Michigan
Thanks wick.
__________________
My "Art" website http://home.comcast.net/~djnagle/site/
  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
Novar Spud :: A $200 sweep tube Spud with PCB tomchr Tubes / Valves 89 17th July 2014 11:32 PM
Spud Amplifier with 6E5P Tube tubeman813 Tubes / Valves 34 23rd June 2014 07:07 PM
SE 833A Help jmanriqu Tubes / Valves 3 22nd September 2009 09:15 PM
Amplifier using a 833A Tekko Tubes / Valves 17 15th September 2009 02:02 AM
tube 833a wasibi Tubes / Valves 0 22nd April 2005 10:00 AM


New To Site? Need Help?

All times are GMT. The time now is 03:10 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