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 8th December 2009, 12:49 AM   #11
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Matt,

The Emerson chassis has a 9 pin socket and a pair of 7 pin sockets. If you recycle the sheet metal, 5 WPC is what you'll get, but mid 90s efficient speakers are OK with 5 W. The 6BQ5/EL84 suggested previously is a fine tube, but it needs a 9 pin socket. OTOH, the 6AQ5 (data sheet here) is fine too and it takes a 7 pin socket.

There all sorts of single ended circuits you can use. I suggest you use a 12AX7 voltage amplifier to drive an ultralinear (UL) mode 6AQ5. You will get the gain you need to drive the mandatory NFB loop. The most cost effective way to get a quality B+ supply is via a well executed Greinacher ("full wave") voltage doubler. A Triad N-68X, which costs $11.41 is perfect for the needs of this project. You will need heater power. The $8.39 "Rat Shack" catalog # 273-1352 disposes of that item.

Forget tone controls. Tone controls done "right" require fairly sophisticated circuitry, including gain, and (IMO) are not in character with this project. Just use separate left and right channel volume controls. Alpha Taiwan makes OK controls that cost little money.

Edcor's model GXSE15-8-5K is a good fit for the 6AQ5. The 15 W. power rating is not overkill, as magnetic headroom is needed to avoid core saturation from a NFB error correction signal.
__________________
Eli D.
  Reply With Quote
Old 8th December 2009, 09:30 AM   #12
Jaap is offline Jaap  Netherlands
diyAudio Member
 
Jaap's Avatar
 
Join Date: Dec 2002
Location: Netherlands
Quote:
Originally Posted by Eli Duttman View Post
Matt,



There all sorts of single ended circuits you can use. I suggest you use a 12AX7 voltage amplifier to drive an ultralinear (UL) mode 6AQ5. You will get the gain you need to drive the mandatory NFB loop.
Do a search on the RH-84 amp. This is simple (low parts count), should sound excellent and doesnot have the NFB loop.
Attached Images
File Type: gif el84_rh84.gif (11.1 KB, 240 views)
  Reply With Quote
Old 8th December 2009, 07:09 PM   #13
diyAudio Member
 
Join Date: Nov 2009
Location: Texas
After listening to everyones comments and looking at my tube stash I am going to start looking for a EL34 12AU7 Amp to build and put it in the Emerson cabinet. I want tone control and volume only. I think I want to build a Single Ended amp not sure yet. Any suggestions welcome

Kashmire thanks for the enthusiasm. Here is a photo of the chassis, Not pretty but functional.

Click the image to open in full size.
  Reply With Quote
Old 8th December 2009, 07:24 PM   #14
diyAudio Member
 
Mosquito's Avatar
 
Join Date: Sep 2009
Location: Santa Fe, Argentina
Quote:
Originally Posted by Jaap View Post
Do a search on the RH-84 amp. This is simple (low parts count), should sound excellent and doesnot have the NFB loop.
the 100K between anodes isn't NFB?
nice design by the way...
__________________
If I only had a dollar for every song I've sung...
  Reply With Quote
Old 8th December 2009, 11:34 PM   #15
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
Originally Posted by Mosquito View Post
the 100K between anodes isn't NFB?
nice design by the way...
Of course it's NFB. The loop is short, not global. That will work with high quality O/P "iron". OTOH, GNFB can help when the O/P trafos to be used are not quite full range. It's quite possible to combine both approaches in an RH84 variant. Not much in the way of GNFB will be necessary, as it's primary role is to linearize the O/P trafo. The short loop takes care of O/P tube linearity and damping factor.

Yet another possible tweak is g2 B+ regulation via LR8 ICs (1/"final").
__________________
Eli D.
  Reply With Quote
Old 8th December 2009, 11:47 PM   #16
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Quote:
Originally Posted by TexasAudio View Post
After listening to everyones comments and looking at my tube stash I am going to start looking for a EL34 12AU7 Amp to build and put it in the Emerson cabinet. I want tone control and volume only. I think I want to build a Single Ended amp not sure yet. Any suggestions welcome

Kashmire thanks for the enthusiasm. Here is a photo of the chassis, Not pretty but functional.

Click the image to open in full size.
Dude,

That little chassis will not acomodate EL34s and appropriate O/P trafos. The space is insufficient. Also, to use 12AU7s requires cascaded gain stages. The μ of the 'U7 is too low, at 20.

I've attached the schematic for a single channel of "proper" tone controls. Even if the cathode followers are replaced by ZVN0545A MOSFET source followers, you need a pair of 12AX7s, just for tone controls. A quad of tubes is needed if you forego "sand". Again, I ask, where's the room?

Build a RH84 variant that uses 6AQ5 O/P tubes. Look here, where a RH84 variant with 6V6 "finals" was worked out. For all practical purposes, the previously mentioned 6AQ5 is a 6V6 in a 7 pin mini package.
Attached Images
File Type: jpg Tone_Control.jpg (31.3 KB, 179 views)
__________________
Eli D.
  Reply With Quote
Old 8th December 2009, 11:48 PM   #17
diyAudio Member
 
Mosquito's Avatar
 
Join Date: Sep 2009
Location: Santa Fe, Argentina
Thanks! And besides, I very much appreciate all the useful data that you share at post 11
__________________
If I only had a dollar for every song I've sung...

Last edited by Mosquito; 8th December 2009 at 11:55 PM.
  Reply With Quote
Old 9th December 2009, 01:14 PM   #18
diyAudio Member
 
Join Date: Nov 2009
Location: Texas
Eli, Thanks for all the info, I have decided to scrap the ideal of using the old chassis at all. I will build a amp from scratch and use the cabinet only to get the old school look. Later today I will have to gather parts once I decide which way to go. I think I will try to build it to be a nice amp if I have to start from scratch. Until I ge tthe parts I have decide to use the amp below to play with. Any suggestions on it would be appriciated.....thanks, matt

Click the image to open in full size.
  Reply With Quote
Old 9th December 2009, 11:21 PM   #19
Cassiel is offline Cassiel  Libya
diyAudio Member
 
Cassiel's Avatar
 
Join Date: Sep 2004
Location: Madrid
[QUOTE]Any suggestions on it would be appreciated/QUOTE]

Here's a nice suggestion: redo all the first triode's circuit. Follow the attached
schematic. ECL86 is a very good sounding tube, but doesn't last that long so maybe you will need a new one for best sonics.


R2 sets the amount of feedback, here personal taste dictates but a value between 1.2 K -3.9 K. should be OK.
__________________
DIY Corporal

Last edited by Cassiel; 9th December 2009 at 11:32 PM.
  Reply With Quote
Old 9th December 2009, 11:24 PM   #20
Cassiel is offline Cassiel  Libya
diyAudio Member
 
Cassiel's Avatar
 
Join Date: Sep 2004
Location: Madrid
Damn, file was too big.
Attached Images
File Type: jpg ecl86.jpg (26.6 KB, 81 views)
__________________
DIY Corporal

Last edited by Cassiel; 9th December 2009 at 11:28 PM.
  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
Personal Planars. tade Planars & Exotics 19 28th March 2010 02:11 AM
Your own personal TradeMark Steerpike Construction Tips 3 18th November 2009 11:06 PM
quick update on my personal HT room project JinMTVT Multi-Way 1 18th August 2008 02:55 AM
My OLD Project....... cheap tube audio project!!! tube-lover Tubes / Valves 4 8th May 2008 09:26 PM
personal jobs rumors Tubes / Valves 10 2nd April 2007 09:03 AM


New To Site? Need Help?

All times are GMT. The time now is 07:23 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