Yeo's Simple EL84 with a twist

sorenj07 · 17th October 2006, 02:42 AM

I have an antek 275-0V 275-0V 500mA + 2x 6.3V 5A power transformer, a Hammond 193K choke (2.6H 21R 300mA) and a 16x8x3 aluminum box. I figure I might as well throw together one of these because honestly the parts aren't being used. The thing is, I figure I want to build this amp so I can take it to college, so I'd like to make it integrated.

Here's my idea (too lazy to write everything out so i'll just cut and paste schematics)

cut off the input stage of the Simple El84, right where the 220K resistor is:
http://diyparadise.com/ultracompact.html

tack on the following linestage, maybe with a 100K alps pot in front:

here's the power supply. i'm getting a steady 320v into 160mA and around 255V into 16mA for the input stage. power across the 4K resistor peaks at around 1.4 watts so 5 watts should be plenty. the power transformer is set at 290V to allow for house AC being over 115V, into .5A with 4% regulation. That cap input should be 22uF as the 5u4GB's max seems to be 40.

edit: i was thinking either hammond 1608's or, for super budget, the edcor XPP10-8-8K for output.

how does it look? or am i seriously deranged personally, my only gripe is needing a filament transformer for the 5u4, but i needed its big voltage drop to make this work.

ErikdeBest · 17th October 2006, 05:57 AM

Hi

Hmm...the use if a 12AU7 may imply that some people around here won't reply

so I do that... first...it should work! I believe that the input sensitivity for full output will be around 1VRMS, enough for standalone CD and DVD players, but you mention you will use this amp in college. I figure you may be using some portable source (MP3 player) and I don't know if those put out a full 1VRMS.

Erik

ray_moth · 17th October 2006, 07:18 AM

Erik, I think you might be referring to me! Sorry

Anyway, I promise I won't go on about the @#$$$ 12AU7 any more!

Seriously, though, I would just say that an SRPP stage seems to have worked better for other people - I've never tried it - with higher mu tubes. For example, 6SL7 has reportedly given better-sounding results than 6SN7. So, it may be that a 12AT7 or 12AX7 would be better in this case than a 12AU7.

ErikdeBest · 17th October 2006, 09:35 AM

Hi Ray_moth

Actually I was referring to you, to SY, to EC8010, to Morgan Jones...

Offtopic

If I understood well you have an amplifier based on Morgan Jones Crystal Palace. Could you share the schematic?

Erik

Sherman · 17th October 2006, 01:29 PM

You don't really need a line stage with the Simple EL84. It will produce full output with a CD player or a tuner with a 'high' output connection. Even a standard tuner should be pretty close to full output.

I wouldn't complicate things if it isn't necessary. Just build it according to the schematic with the 100K pot in place. If you need a source selector you can use either a rotary switch for multiple inputs or a DPDT switch for two sources.

ray_moth · 17th October 2006, 01:36 PM

Sorry Erik, I don't even know what the 'Crystal Palace' is like. I've never read Morgan's books or seen his designs.

My amp is my own design, with 6SL7 LTP splitter, 6SN7 differential driver and EL34 triode-strapped PP OP stage with fixed bias. It has cross-coupled NFB from OPT plates to splitter plates, similar to the arrangement used by Thorsten Loesch. The splitter has a pentode CCS in the tail. The splitter plates are coupled to the driver grids using step networks and there is plate-to-plate NFB between splitter and driver, for good balance.

sorenj07 · 17th October 2006, 05:23 PM

Supposing I wanted to use some NFB, with maybe a 12AT7 in the totem pole instead to provide the gain that it would burn off, what would I connect to what to make it happen? The 8-ohm tap resistively connected to...?

nickds1 · 17th October 2006, 08:19 PM

Quote:

Originally posted by ErikdeBest
If I understood well you have an amplifier based on Morgan Jones Crystal Palace. Could you share the schematic?

I think that was SY - I asked in another thread if anyone had heard one as I have a bunch of 13E1s, and SY replied that he'd heard one with LS3/5As:
Newcomer, where to start?

giulio · 17th October 2006, 08:46 PM

Quote:

Hi Ray_moth

Actually I was referring to EC8010, to Morgan Jones...

I thought EC8010 WAS Morgan Jones ...

Wavebourn · 17th October 2006, 09:13 PM

Quote:

Originally posted by sorenj07
Supposing I wanted to use some NFB, with maybe a 12AT7 in the totem pole instead to provide the gain that it would burn off, what would I connect to what to make it happen? The 8-ohm tap resistively connected to...?

You may use a resistor from a speaker output to the cathode of El84 if you want some feedback. Soundcard, iPod, CD player can give enough of power to drive el84 without any "pre". Use an input transformer like 600:10K if you need more, also with a symmetrical input you will eliminate a ground hum.

17th October 2006, 02:42 AM	#1
sorenj07 diyAudio Member Join Date: May 2006	Yeo's Simple EL84 with a twist I have an antek 275-0V 275-0V 500mA + 2x 6.3V 5A power transformer, a Hammond 193K choke (2.6H 21R 300mA) and a 16x8x3 aluminum box. I figure I might as well throw together one of these because honestly the parts aren't being used. The thing is, I figure I want to build this amp so I can take it to college, so I'd like to make it integrated. Here's my idea (too lazy to write everything out so i'll just cut and paste schematics) cut off the input stage of the Simple El84, right where the 220K resistor is: http://diyparadise.com/ultracompact.html tack on the following linestage, maybe with a 100K alps pot in front: here's the power supply. i'm getting a steady 320v into 160mA and around 255V into 16mA for the input stage. power across the 4K resistor peaks at around 1.4 watts so 5 watts should be plenty. the power transformer is set at 290V to allow for house AC being over 115V, into .5A with 4% regulation. That cap input should be 22uF as the 5u4GB's max seems to be 40. edit: i was thinking either hammond 1608's or, for super budget, the edcor XPP10-8-8K for output. how does it look? or am i seriously deranged personally, my only gripe is needing a filament transformer for the 5u4, but i needed its big voltage drop to make this work.

17th October 2006, 01:29 PM	#5
Sherman diyAudio Member Join Date: Feb 2004 Location: Chicago area	You don't really need a line stage with the Simple EL84. It will produce full output with a CD player or a tuner with a 'high' output connection. Even a standard tuner should be pretty close to full output. I wouldn't complicate things if it isn't necessary. Just build it according to the schematic with the 100K pot in place. If you need a source selector you can use either a rotary switch for multiple inputs or a DPDT switch for two sources. __________________ --Sherman

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17th October 2006, 05:57 AM	#2
ErikdeBest diyAudio Member Join Date: Mar 2003 Location: Itoculo	Hi Hmm...the use if a 12AU7 may imply that some people around here won't reply so I do that... first...it should work! I believe that the input sensitivity for full output will be around 1VRMS, enough for standalone CD and DVD players, but you mention you will use this amp in college. I figure you may be using some portable source (MP3 player) and I don't know if those put out a full 1VRMS. Erik

17th October 2006, 07:18 AM	#3
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	Erik, I think you might be referring to me! Sorry Anyway, I promise I won't go on about the @#$$$ 12AU7 any more! Seriously, though, I would just say that an SRPP stage seems to have worked better for other people - I've never tried it - with higher mu tubes. For example, 6SL7 has reportedly given better-sounding results than 6SN7. So, it may be that a 12AT7 or 12AX7 would be better in this case than a 12AU7.

17th October 2006, 09:35 AM	#4
ErikdeBest diyAudio Member Join Date: Mar 2003 Location: Itoculo	Hi Ray_moth Actually I was referring to you, to SY, to EC8010, to Morgan Jones... Offtopic If I understood well you have an amplifier based on Morgan Jones Crystal Palace. Could you share the schematic? Erik

17th October 2006, 01:36 PM	#6
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	Sorry Erik, I don't even know what the 'Crystal Palace' is like. I've never read Morgan's books or seen his designs. My amp is my own design, with 6SL7 LTP splitter, 6SN7 differential driver and EL34 triode-strapped PP OP stage with fixed bias. It has cross-coupled NFB from OPT plates to splitter plates, similar to the arrangement used by Thorsten Loesch. The splitter has a pentode CCS in the tail. The splitter plates are coupled to the driver grids using step networks and there is plate-to-plate NFB between splitter and driver, for good balance.

17th October 2006, 05:23 PM	#7
sorenj07 diyAudio Member Join Date: May 2006	Supposing I wanted to use some NFB, with maybe a 12AT7 in the totem pole instead to provide the gain that it would burn off, what would I connect to what to make it happen? The 8-ohm tap resistively connected to...?

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