Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

OPT Project for EL84 SE
OPT Project for EL84 SE
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
Thread Tools Search this Thread
Old 7th August 2006, 07:27 AM   #21
Toober is offline Toober
diyAudio Member
Join Date: Jun 2005
Location: Romania
Send a message via Yahoo to Toober
What do you think about DC coupled amplifiers? Maybe like this.....
Anyway, I ask only for my general culture, I am decided to build the modified RH84 design.
Attached Images
File Type: png el84-dc-se1.png (10.0 KB, 591 views)
  Reply With Quote
Old 7th August 2006, 07:43 AM   #22
Mas Penk is offline Mas Penk  Indonesia
diyAudio Member
Join Date: Nov 2003
Location: South China Sea
Default Direct Coupled

Direct Coupled offer advantages of capacitor weakness (best coupling cap is no cap). But during building you must pay attention since motorboating behaviour could be an issue. not to mention the risk when driver tube fails, that could bring the output tube to death too.
I have built one EL84 direct coupled, it sound almost like RH84 but RH84 has more Bass while DC-EL84 has brighter (more open?) and detailed sound.

Mas Penk
  Reply With Quote
Old 7th August 2006, 07:56 AM   #23
Miles Prower is offline Miles Prower  United States
diyAudio Member
Miles Prower's Avatar
Join Date: May 2005
Location: USA
Originally posted by Toober
What do you think about DC coupled amplifiers?
I tend to favor getting rid of as many coupling capacitors as possible. Every time you add another AC coupled stage, you're also adding a phase shifter as well as a high pass filter. Those extra phase shifts can compromise stability under feedback, and can also compromise bass performance. I also like DC coupled cathode follower final grid drivers to eliminate distortion under transient overdrive, get the slew rate up, and force a few extra watts out of a class AB1 design that can slip partially into ClassAB2. I did an 807 design with a nominal 26.5W with a v(i)= 45Vp-p (just puts the 807 Vgk(max)= 0V). With 35W Hammonds, I can push that to over 30W because the cathode follower drivers can get that little bit extra out of it by taking the grids positive. Of course, this also requires fixed bias, which automatically results from the DC coupled cathode followers.

I also like lots of extra "head room", and the design maxes out when the OPTs saturate, not when any stage clips.

Of course, I do high fidelity, so very little of that will apply to a gee-tar amp.
There are no foxes in atheistholes
  Reply With Quote
Old 8th August 2006, 04:31 AM   #24
TonyTecson is offline TonyTecson  Philippines
diyAudio Moderator
TonyTecson's Avatar
Join Date: May 2003
Location: Palatiw, Pasig City
OPT Project for EL84 SE
Originally posted by Toober
I haven't found those schematics you have suggested, but I have something here and here
What do you think about them?

Anyway, does anybody wants to share a OPT project with me? Please.....I already have the lamination (grain oriented, EI 28 mm tongue), it's only missing the project.

Thank you!

i have one, uses a 7/8 inch square stack, on a bobbin for 7/8 inch sq. core...has 5400turns #34 magnet wire on primary, 3 layers, wired in series, then two layers #30 awg for 216 turns paralleled, so this OPT has 5 layers interleaved, for the gap i use file folder cardboard material.. hope this helps...good luck!

Click the image to open in full size.
planet10 needs your help: Let's help Ruth and Dave...http://www.diyaudio.com/forums/plane...ml#post5010547[B
  Reply With Quote


OPT Project for EL84 SEHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
5W EL84 drive EL84 SE Audio_idiot Tubes / Valves 31 31st May 2012 08:38 PM
Help on EL84 / ecc83 SE project -very low volume mcgaag Tubes / Valves 28 8th June 2009 01:11 PM
EL84 DC 10Y Project korneluk Tubes / Valves 5 19th May 2008 05:03 AM
SE EL84 project for my friend akimball442 Tubes / Valves 17 28th June 2007 10:04 PM
Beginners Project: Need a schematics for a small simple EL84 SE (or PSE) amp Erik Johansson Tubes / Valves 2 15th May 2002 11:35 AM

New To Site? Need Help?

All times are GMT. The time now is 02:40 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio