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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 29 Sep 2011, 21:36 
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I recently picked up a nice pair of NOS Zenith branded 6V6G ST envelope tubes.
Attachment:
Zeneth 6V6Gs.jpg

I had expected these to be more mellow than the JJs but they are in fact far more detailed. They seem to be handling the lower voltage and UL mode better than the JJs. They are weaker in the bass but that may have to do with the fact that I've only been listening to them for a few hours. It will be interesting to see how these sound after really being broken in. I intend to leave them in the amp for a few weeks to really get a feel for their tone and to allow them to settle. Then I'll do a head to head comparison against the nicely broken in JJ 6V6S tubes.


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PostPosted: 01 Dec 2011, 03:45 
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matt thats bloody marvellous work there mate - well done - kudos dude.

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PostPosted: 12 Jul 2012, 09:44 
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@Matt: Noticed no bypass caps on the driver side. Is this to instigate a little NF??

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
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PostPosted: 13 Jul 2012, 09:36 
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mwhouston wrote:
Matt: Noticed no bypass caps on the driver side. Is this to instigate a little NF??

I actually did this for three reasons. 1; To limit the gain so there was less chance of over driving the output tubes. 2; To ensure that the driver stage's bass response was entirely due to coupling and not cathode bypass transition (this helps support bass response). 3; As you said, to introduce a little NFB in the driver to limit higher order harmonics. In the writeup you'll note that I picked a lower load value for the 6SN7 specifically to help warm up the sound (enhance 2nd order harmonic response). This little bit of NFB helps keep the other nasty harmonics under control in the driver stage when the load is low.

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PostPosted: 13 Jul 2012, 18:22 
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I have been thinking about having the bypass cap on the 6SN7 of the 807 amp switchable in/out. I have felt in the passed with the bypass cap out the overall sound is better with other amps and preamps. Its an easy enough mod. so I may give it a go.

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PostPosted: 27 Aug 2013, 13:17 
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Matt,
Did you develop a load line for the 6V6 in Ultralinear mode? If so, would you care to share the diagram?

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PostPosted: 18 Sep 2013, 02:35 
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Matt: I like those Zenith tubes. I have some Ozzies black glass 6V6 very old. They were under a house nearby for about 40 years but I can get a matched pair. I just sole Arabella and your 6V6 is next on the radar. But with a sadistic twist to component selection. I intend to stay with your schematic and value of components as marked.

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
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PostPosted: 18 Sep 2013, 04:40 
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mwhouston wrote:
Matt: I like those Zenith tubes. I have some Ozzies black glass 6V6 very old. They were under a house nearby for about 40 years but I can get a matched pair. I just sole Arabella and your 6V6 is next on the radar. But with a sadistic twist to component selection. I intend to stay with your schematic and value of components as marked.

Of course that should be sold and not sole though Arabella did have sole.

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PostPosted: 25 Sep 2014, 08:05 
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I have just finished building this amp, I eschewed the volume and I run it from an Audio Note kit 'The Mentor' pre-amp http://www.ankaudiokits.com/L5-Mentor-T ... ifier.html. It realy is very quiet, much more than the Quad 303 I was running it through. this is my third build, but as the other two (ANK DAC4.1 and ANK Mentor) were kits this is my very first 'self build'. Thank you very much for that Matt, I am realy impressed with the design. The detail and finess are outsanding - I'm realy happy with this.
I do have a problem however, it is extremely bass light. I know the pre-amp produces a good bass balance but I'm rather ignorant about electronics (but learning as fast as my 62 year old brain will allow) so I could do with some advice on this. Not all the components are exactly as you used but they are all very close, for instance the RC from pin 8 is 470uF and 360R instead of the 500uF 350R you used. I used high quality parts, Takman carbons, Elna Silmics, Mundorf MLytics, silver signal wire etc. Can anyone shed some light on this or suggest someway to increase bass response?
Thanking whoever helps me in advance.
Yours, Keith.


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PostPosted: 25 Sep 2014, 08:53 
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Just looking at a few other 6V6 designs I notice that the bipass cap on the 6V6 tube is 33 to 47uf where here it is 500uf. Could there be a clue here? We really need Matt to answer this. There is a big difference here, in fact one order of magnitude.

Can you try a 47uf bipass across the cathode resistor Rk?

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
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