James Burgess 2A3 Monoblocks - 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 15th May 2010, 07:24 PM   #1
diyAudio Member
 
Join Date: May 2010
Default James Burgess 2A3 Monoblocks

Hello all, I picked up a pair of James Burgess 2A3 SE monoblocks and as a newbie to DIY, I thought I'd use everyone's expertise on potential customizations.

First is the output transformers, the existing ones are 'Handwound' from David Lucas. I have read the numerous horror stories regarding his/their customer service, shipping etc., but I've read both positive and negative things about the transformers, if and when you receive them. With all that said, I'm thinking about changing to Hashimotos, but again with my lack of experience in this arena, I'm not quite sure which ones I need (primary impedance, etc.):

Hashimoto Products

Any suggestions or alternatives would be greatly appreciated.

The other thing I wanted to do was put in gain control so I can cut out the pre-amp. Suggestions on high quality stuff would also be appreciated.

As a side note, I won't be installing this stuff myself, I acknowledge my electrical ignorance and like being alive.

Thanks guys!
  Reply With Quote
Old 18th May 2010, 11:56 AM   #2
diyAudio Member
 
Join Date: Jan 2002
Location: nowhere
I'm sure those expencive Japanese OTs will look great, but is there something wrong with the amp as is? I've not heard of 'Davis Lucas OTs', but if they have a bad rep b/c of poor customer service, why do u care if the OTs are allready there?
Not to ruin your plan, and nothing wrong with upgrading something to the better, but perhaps a thorough testbench set of measurements, and ditto listening test, will reveal what mods if any should be looked at.
Just my nickle.
  Reply With Quote
Old 18th May 2010, 01:15 PM   #3
diyAudio Member
 
Join Date: May 2010
As far as the OT's go, I had read ALL bad things about customer service, but both good and bad regarding the performance. I spoke with James about these particular amps and it sounds like he was quite pleased with the OT's; which I should have assumed in the first place as I doubt he would have even entertained the idea of using a less than stellar component. So with that said, I completely agree on bench and listening tests before I go crazy with modifications.

However, I would still like to install volume pots. James said he prefers TKD's... Thoughts?

Also, is 3 - 3.5 watts enough to drive 100dB speakers off a turntable source, or will a phono stage more than likely be needed?
  Reply With Quote
Old 18th May 2010, 09:36 PM   #4
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
Quote:
Originally Posted by easymac77 View Post
Also, is 3 - 3.5 watts enough to drive 100dB speakers off a turntable source, or will a phono stage more than likely be needed?
You have enough power to drive speakers like that to reasonable levels for most listening. However, a phono stage is necessary for two reasons. One, the signal from a phono cartridge is around 0.5mV at 1kHz for an MC cartridge, and around 5mV for a typical MM cartridge. If your amp has a sensitivity of 1V full scale, for instance, you need to boost the signal for an MM cartridge by 10 fold, or 20dB (40dB for MC). Second, the treble is boosted and the bass is attenuated when the record is cut. So the phono stage also has to equalize for that. In short, yes you need a phono stage.

Sheldon
  Reply With Quote
Old 18th May 2010, 09:58 PM   #5
diyAudio Member
 
Join Date: May 2010
Sheldon, thanks for all the info! I tried to see if my turntable had the RIAA correction, but I highly doubt it, given it's simplicity (Rega).

I guess the next question is: what is a good all-tube pre-amp/phono circuit? I hear '26' quite a bit, but I also know they are a huge pain to build...
  Reply With Quote
Old 18th May 2010, 10:31 PM   #6
R.I.P.
 
Join Date: Dec 2001
Location: Schaffhausen Switzerland
Quote:
Originally Posted by Sheldon View Post
One, the signal from a phono cartridge is around 0.5mV at 1kHz for an MC cartridge, and around 5mV for a typical MM cartridge. If your amp has a sensitivity of 1V full scale, for instance, you need to boost the signal for an MM cartridge by 10 fold, or 20dB

Sorry, 5mV to one V is 200x, not 10x. And for a typical MC, you will need 2000x...

>>In short, yes you need a phono stage.
Yes, and a very good phonostage at that, as most phonostages are expecting a line stage's worth of gain before the poweramps.

REgards, Allen

Regards, Allen
  Reply With Quote
Old 13th August 2011, 04:04 AM   #7
brady is offline brady  Philippines
diyAudio Member
 
Join Date: Mar 2005
Location: Cebu City
does anyone have James Burgess email add? I found a tel number in his jewelry business, but I thought an email to discuss an amplifier build might be more suitable.
  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
6SN7-2A3 SE Amp - James Transformers christian.lenci Tubes / Valves 27 11th October 2010 09:07 PM
james 6123hs totaltech Tubes / Valves 4 29th August 2008 11:21 PM
WTB: OPTs for 2A3 or 45 SE; 240 v power tranny for 2A3 or 45 rick57 Swap Meet 0 8th November 2006 01:07 AM
James Blunt pinkmouse Music 39 31st July 2006 06:07 PM
James SE OPT for 300B & 2A3 on eBay argo Tubes / Valves 0 20th January 2005 11:21 AM


New To Site? Need Help?

All times are GMT. The time now is 02:43 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