• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Whats a Good 6L6 circuit?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
SY

SY

Ex-Moderator
Joined 2002
SYclotron.com
EC8010 said:
I've been searching desperately to find the article (I think it was Hafler), but I just can't seem to find it I have a feeling that the coupling capacitors were made quite a bit bigger, perhaps 1.5uF.
Click to expand...

Hafler and Keroes, Audio Engineering, reprinted in Audio Anthology v2, "Ultra-Linear Operation of the Williamson Amplifier".

from Hafler and Keroes

The low frequency time constants of the original circuit's interstage coupling networks were the same for both such networks. This is not particularly desirable in a feedback amplifier... Increasing one pair of coupling capacitors from 0.05uF to 0.25uF... increases the low frequency stability margin at nominal increase in cost.
Click to expand...
 
analog_sa

analog_sa

Member
Joined 2002
Hacknet

Andy's suggested circuit is much better than a Williamson. That is if you want to build a modern sounding amp and not just something of historical value.

Going as far back as the sixties amp builders noticed the Williamson plays better in mono than stereo. Lots of NFB keeps the sound strictly in the speakers, kills dynamics and soundstaging and together with the excessively repetitive use of 6SN7 produces cold and boring (for a tube amp) mids.
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
Hi,

Lots of NFB keeps the sound strictly in the speakers, kills dynamics and soundstaging and together with the excessively repetitive use of 6SN7 produces cold and boring (for a tube amp) mids.
Click to expand...

As an example:

I have a PP 2A3 amp that uses only local FB, no global loop whatsoever...
The soundstage that little amp can throw is little short of amazing.

With any decent recording you can plunk the speakers down, even only 4-5 foot apart, you just can't tell the sound comes from those speakers.
That's not to say the amp is perfect, it isn't.
For what it cost me however it's a joy to listen to.

Cheers,;)
 
A

arnoldc

Member
Joined 2003
RoadToNirvana.net
fdegrove said:
I have a PP 2A3 amp that uses only local FB, no global loop whatsoever...
The soundstage that little amp can throw is little short of amazing.
Click to expand...

Hi Frank, i've been wanting to make a PP 2A3 and been contemplating on the JE Labs PP 2A3. However, I want to try one of yours. Is that at all possible? Share the schematic or is this a commercial amp?
 
andyjevans

andyjevans

Member
Joined 2003
artsandmedia.com
That's not to say the amp is perfect, it isn't. For what it cost me however it's a joy to listen to.>

That's exactly my response to taking off the global feedback loop - joy! The sound just makes you like it - happy pills. Haven't got a clue how this effect measures, but I was just grinning when I heard the sound without feedback. If I'm reading the language correctly, others seem to have a similar response. Not to say that others don't grin when they add feedback - I'm sure this happens too.
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
Hi,

Hi Frank, i've been wanting to make a PP 2A3 and been contemplating on the JE Labs PP 2A3. However, I want to try one of yours. Is that at all possible? Share the schematic or is this a commercial amp?
Click to expand...

ArnoldC,

It's not a commercial amp but I still have to draw a schematic.
I'll post it when it's done.

In the mean time, thamks for the confidence you put in me.;)
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom