EL34 PP PROJECT

el156 · 14th November 2010, 02:55 PM

Here are so fotos of my latest project...

E88CC as input tube

ECC804 as phase splitter

M Gregg · 14th November 2010, 03:09 PM

el156,

Nice project!

Palustris · 14th November 2010, 08:27 PM

I love the curved front and the overall design.

richwalters · 15th November 2010, 07:57 AM

Youre lucky getting rid of the heat isn't an issue.

el156 · 15th November 2010, 08:36 AM

Well, it is a newbie project,but i am not very happy with the sound ,it seems doesnt have enough power, but i will post the schematic to get your opinion about it, maybe i havesome mistake in there!
Thank you for your comments
EL156

richwalters · 15th November 2010, 10:58 AM

30W o/p with a pair of EL34's should be a breeze. Using 92dB/w LS sensitivity with good sized bass drivers should rock the room. This was a standard classic design of the 1960's and found amps of this everywhere in halls and theatres.

richy

artosalo · 15th November 2010, 12:53 PM

Quote:

it seems doesnt have enough power

Do you mean that the sensitivity is low, which means that your input signal can not give full output ?

Or do you mean that the output signal becomes distorted before the sufficient sound level is achieved ?

Can you show the chematic ?

el156 · 15th November 2010, 01:25 PM

Quote:

Originally Posted by artosalo

Do you mean that the sensitivity is low, which means that your input signal can not give full output ?

Or do you mean that the output signal becomes distorted before the sufficient sound level is achieved ?

Can you show the chematic ?

I think sensitivity is ok , the signal comes distorted before sufficient sound level is achieved, I have to draw the schematic first to post it later on or tpmorrow.
EL156

el156 · 20th November 2010, 05:15 PM

Okay ! Here is my schematic ! Maybe someone can tell me what is wrong with this schematic !
EL156
Sorry for the bad quality of pic
Thanks

toprepairman · 20th November 2010, 06:20 PM

Fair circuit so should work ok. I note there is no negative feedback so speaker impedance will have a big impact on the frequency respose (as per a typical guitar amp/combo) and matching the speaker impedance to the reflected output impedance will cosiderably affect power output. As a general rule you should load a typical 8ohm speaker to a 4 to 6 ohm tap to account for speaker impedance dips.
With the 380 volt supply I wouldn't expect much more than around 20 watts.
Here's another note for any other builders of ultralinear EL34 designs, you should never exceed a max of 420 for the HT, otherwise you will get flashovers between the screen grid and control grid, very nasty.
Incidentally this is my first posting on this site.

20th November 2010, 06:20 PM	#10
toprepairman diyAudio Member Join Date: Nov 2010	EL34 Fair circuit so should work ok. I note there is no negative feedback so speaker impedance will have a big impact on the frequency respose (as per a typical guitar amp/combo) and matching the speaker impedance to the reflected output impedance will cosiderably affect power output. As a general rule you should load a typical 8ohm speaker to a 4 to 6 ohm tap to account for speaker impedance dips. With the 380 volt supply I wouldn't expect much more than around 20 watts. Here's another note for any other builders of ultralinear EL34 designs, you should never exceed a max of 420 for the HT, otherwise you will get flashovers between the screen grid and control grid, very nasty. Incidentally this is my first posting on this site.

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14th November 2010, 03:09 PM	#2
M Gregg diyAudio Member Join Date: Jun 2010 Location: UK	el156, Nice project!

14th November 2010, 08:27 PM	#3
Palustris diyAudio Member Join Date: Aug 2006 Location: Cape Cod	I love the curved front and the overall design.

15th November 2010, 07:57 AM	#4
richwalters diyAudio Member Join Date: Sep 2003 Location: Alps:Tube amp designs over 150W, SMPS guru.	Youre lucky getting rid of the heat isn't an issue.

15th November 2010, 08:36 AM	#5
el156 diyAudio Member Join Date: Apr 2010 Location: ALBUFEIRA ;PORTUGAL	Well, it is a newbie project,but i am not very happy with the sound ,it seems doesnt have enough power, but i will post the schematic to get your opinion about it, maybe i havesome mistake in there! Thank you for your comments EL156

15th November 2010, 10:58 AM	#6
richwalters diyAudio Member Join Date: Sep 2003 Location: Alps:Tube amp designs over 150W, SMPS guru.	30W o/p with a pair of EL34's should be a breeze. Using 92dB/w LS sensitivity with good sized bass drivers should rock the room. This was a standard classic design of the 1960's and found amps of this everywhere in halls and theatres. richy

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