My EL84 Triode PP Amp - diyAudio
Go Back   Home > Forums > Commercial Sector > Swap Meet

Swap Meet Sell your stuff here, who knows, some other fanatic might be interested!

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 6th March 2008, 11:49 AM   #1
diyAudio Member
 
sorenj07's Avatar
 
Join Date: May 2006
Default My EL84 Triode PP Amp

I've got too many other projects on deck, and not enough funds. Anyone in the Boston area?

http://boston.craigslist.org/gbs/ele/597223014.html
  Reply With Quote
Old 6th March 2008, 03:07 PM   #2
diyAudio Member
 
sorenj07's Avatar
 
Join Date: May 2006
craigslist deleted the ad, possibly for it being too long and detailed here it is for now... (asking $475)


A completely custom, hand-built and point-to-point wired tube amplifier. The chassis was lovingly pieced together using what was once a Tektronix 2213 oscilloscope. I really enjoy it in my current setup, but need to finance other audio projects I'm working on so I have to let it go...

Click the image to open in full size. Click the image to open in full size. Click the image to open in full size.

Schematic:
Click the image to open in full size.

This amplifier uses triode-wired EL84 tubes, for a bit over 6W (4.8W Class A). Distortion of the output stage with no negative feedback connection simulates at less than .5% (3rd) and .05% (5th). The tubes are run in fixed-bias, with individual controls precise to the .1mA level. The driver stage uses a 6DJ8/6922 in a long-tail pair phase splitter, with a very high negative voltage supply which decreases phase imbalance. The output transformers were designed for EL84's in pentode mode at around 15W, and derating by 60% can only further increase bandwidth.

I use high quality PRP resistors in one of the more critical spots, namely the plate load resistors for the phase splitter. Wiring is largely done using silver-plated teflon-jacket high purity copper interconnect. The coupling capacitors are the well-known Russian K42-Y glass-sealed paper-in-oil types. The power supply is very robust - it uses a pure choke-input topology, using a monstrous Hammond 193M, rated for 300mA (174% of the whole amp's quiescent current draw). The power transformer is rated for 175mA in a capacitor-input supply but should be good for well over 200mA in choke input. Since the amp operates largely in Class A, strain on the PSU is further reduced.

Inputs are two RCA's. Volume is adjusted with a high quality Noble potentiometer. A CD player connected directly to the amplifier is more than capable of driving it to very loud listening levels, but of course this also depends on speaker efficiency. Separate filament and high-voltage switches help prolong tube life.

So how does it sound? First of all, the amp is DEAD QUIET on 98dB-efficient speakers. The power transformer makes a tiny humming noise, but all the transformers are isolated from the chassis with rubber grommets so mechanical induction is not a likely problem. It has plenty of bass for only 6W or so, but where it really shines is in the vocals. Voices really leap out of the speakers at you. Granted, this isn't the singer's-breath-on-your-cheek experience I've had with McIntosh amps feeding insane B&W speakers, but for a fraction of the expense, who's complaining? Highs are very smooth but clear - just listen to some hi-hat/cymbal-heavy jazz and you'll see what I mean. I'm no expert on 3D soundstages, but this amp definitely has something that I haven't heard very often. I think you'll like it.

Local pickup and cash transactions are MUCH preferred. Feel free to set up a time to give it a listen! I have a pretty wide variety of music (a fair bit of MFSL/audiophile quality recordings), but your own reference discs are fine also. I'm using a modified Playstation 1 as source, and Cerwin-Vega D-7's as my monitors. <br><br>I can also email the complete PDF for the output stage simulation. A final note: since I designed and built this amplifier, you're free to come by and ask me to take a look at it at any time should you choose to purchase it. Of course, if the amp malfunctions or breaks due to a defect on my part, I'll repair it.

Thanks for looking!
  Reply With Quote
Old 6th March 2008, 04:02 PM   #3
diyAudio Member
 
sorenj07's Avatar
 
Join Date: May 2006
ad back up: a bit shorter, but you get the idea.

http://boston.craigslist.org/gbs/ele/597437574.html
  Reply With Quote
Old 14th March 2008, 08:13 PM   #4
diyAudio Member
 
sorenj07's Avatar
 
Join Date: May 2006
1-week mini-bump.

ad re-listed on Craigslist.
http://boston.craigslist.org/gbs/ele/606199905.html
  Reply With Quote
Old 23rd March 2008, 05:14 PM   #5
diyAudio Member
 
sorenj07's Avatar
 
Join Date: May 2006
bump number 2. I'm going down to $425.

http://boston.craigslist.org/gbs/ele/615814420.html
  Reply With Quote
Old 5th May 2008, 12:18 PM   #6
diyAudio Member
 
sorenj07's Avatar
 
Join Date: May 2006
New ad!

http://boston.craigslist.org/gbs/ele/668311625.html

any takers..?
  Reply With Quote
Old 17th June 2008, 02:01 PM   #7
diyAudio Member
 
sorenj07's Avatar
 
Join Date: May 2006
Price dropped. Asking $299 obo. Thanks
http://boston.craigslist.org/gbs/ele/722749185.html
  Reply With Quote
Old 19th June 2008, 04:13 PM   #8
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
Can you provide any details (brand/model) of the O/P transformers?
  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
EL84 fixed bias PP Triode DrewP Tubes / Valves 23 24th November 2013 08:17 PM
EL84 Triode PP Design sorenj07 Tubes / Valves 23 19th December 2007 05:01 AM
Which do you prefer - EL84 UL PP or EL34 Triode PP - and why? ray_moth Tubes / Valves 4 23rd February 2007 12:22 PM
triode => I.T. =>el84 good idea ? Jaap Tubes / Valves 9 7th January 2003 07:30 PM


New To Site? Need Help?

All times are GMT. The time now is 07:03 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