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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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It is currently 16 Dec 2018, 13:57

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PostPosted: 04 Dec 2018, 08:19 
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Joined: 19 Oct 2018, 15:30
Posts: 35
Location: Montréal, Québec
What kind of resistor value have you used on the heater circuit ? The original 4S power supply diagram uses two 100R between the heaters and the ground, but the cathode follower adds two more heaters. Does it change the values ?


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PostPosted: 04 Dec 2018, 13:28 
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Joined: 20 Apr 2015, 01:30
Posts: 86
Those two one 100 Ohm resistors are there between each leg of the heater supply and ground in order to create a pseudo centre tap. They don’t change if you add more tubes to the heater circuit. Just use the same value.


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PostPosted: 04 Dec 2018, 13:36 
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Joined: 20 Apr 2015, 01:30
Posts: 86
Gab: Do use a bigger enclosure than I did (or smaller capacitors!). It’s best to have more room between the parts of the circuit in order to avoid oscillation by keeping a reasonable gap between components. I still haven’t corrected my hiss issue, although it is greatly reduced, despite the grid stoppers I added. Also, I probably have too much gain. You could also build a cathode ffollower without the gain stage if you really don’t need the gain and just need the buffer.


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PostPosted: 04 Dec 2018, 16:36 
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Joined: 19 Oct 2018, 15:30
Posts: 35
Location: Montréal, Québec
tizman wrote:
Gab: Do use a bigger enclosure than I did (or smaller capacitors!). It’s best to have more room between the parts of the circuit in order to avoid oscillation by keeping a reasonable gap between components. I still haven’t corrected my hiss issue, although it is greatly reduced, despite the grid stoppers I added. Also, I probably have too much gain. You could also build a cathode ffollower without the gain stage if you really don’t need the gain and just need the buffer.


I already built my 4S in the enclosure that I had at the time of my last comment. It is roomier than yours though. You can see what it looks like in my project tread
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=6392


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PostPosted: 04 Dec 2018, 20:36 
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Joined: 20 Apr 2015, 01:30
Posts: 86
Looks great. Very nice job. Mine looked pretty good, but ended up being pretty useless, as all my DIY amps have preamp sections and volume pots, and the 4S doesn’t work with either of the SS amps I have because of high output impedance. Adding the cathode follower made it too noisy to use at all in my application. I’ll probably strip it for parts at some point. Also, there is very little action or movement in this thread, so support is going to be minimal. If I were you, and I had an operational 4S that you are happy with, I would build a seperate buffer so it doesn’t mess up the perfectly good preamp that you have. I think that for me, the high sensitivity of my speakers was the biggest problem. That and a too tight chassis. Also, fewer stages are always better. That is always true in my experience.


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