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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: 18 May 2020, 12:10 
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Joined: 05 Apr 2020, 10:39
Posts: 10
Location: Tuscany, Italy
[quote=And if you put two 2.2uF in series you only get half the capacitance 1.1uF[/quote]
Yes i know, im low on skills but not so deep under the sea level :D
I try to simulate it with LTSpice and with my current values i get 2dB attenuation at 20Hz and 6dB at 10Hz... Am i doing something wrong?
Attached schematics used for simulation and frequency plot
Thank you for helping


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PostPosted: 19 May 2020, 01:49 
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Joined: 23 Feb 2017, 02:02
Posts: 677
Just increace the capacitance sizes, ideally the attenuation should be 1dB or less at 20hZ
You are not doing anything wrong except there is also output impedance from the cathode follower so in reality the attenuation is slightly less thna 2dB in real life


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PostPosted: 19 May 2020, 14:21 
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Joined: 05 Apr 2020, 10:39
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Location: Tuscany, Italy
Ok i will try it.
Thanks for helping :up:


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PostPosted: 05 Jan 2021, 12:37 
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Joined: 10 Sep 2015, 13:36
Posts: 36
For the past five years I’ve been enjoying listening to music with my 4S preamp.

I saw this cathode follower version Matt put up several years ago and now I’m thinking of building one.
I have a NAD solid state power amp that I haven’t used in years but I’ll admit it’s more a desire to build
another 4S with an additional tube on it.

A few questions please…..

Can I use the heater switch that permits in the 4S section, the use of either 12A*7 or 6A*7 tubes, running
separate heater wires to the switch and to the 12AU7 cathode follower ?

Is the Allied 6K49VG power transformer suitable for the 4S - 460VCT at 50ma. and 6.3V at 2.5 amp - or
is the voltage too high and the 50ma. current supply too low ? This one is more than $30 cheaper than
the Hammond 269EX or 269GX at Mouser.CA

I didn’t need to use the bypass cap on the cathode resistor in my 4S but just for information is it optional
on the CF version too ?


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PostPosted: 05 Jan 2021, 17:09 
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Joined: 06 Jun 2008, 18:23
Posts: 5318
Location: Australia
harrydutt wrote:
For the past five years I’ve been enjoying listening to music with my 4S preamp.

I saw this cathode follower version Matt put up several years ago and now I’m thinking of building one.
I have a NAD solid state power amp that I haven’t used in years but I’ll admit it’s more a desire to build
another 4S with an additional tube on it.

A few questions please…..

Can I use the heater switch that permits in the 4S section, the use of either 12A*7 or 6A*7 tubes, running
separate heater wires to the switch and to the 12AU7 cathode follower ?

Is the Allied 6K49VG power transformer suitable for the 4S - 460VCT at 50ma. and 6.3V at 2.5 amp - or
is the voltage too high and the 50ma. current supply too low ? This one is more than $30 cheaper than
the Hammond 269EX or 269GX at Mouser.CA

I didn’t need to use the bypass cap on the cathode resistor in my 4S but just for information is it optional
on the CF version too ?

Regardless of current the 460VCT Tranni seems to higher voltage. You can use limiting resistors to bring it down. Adding Ck will increase gain but may also help with bass extension.

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Projects: "Sortilege" - 180W Tripath Class D Mundorf upgrade amp | “Mantra” - tube MM phono preamp | "Carbon” - MM phono preamp | 180W RAW Class D amp |


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PostPosted: 05 Jan 2021, 20:13 
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Joined: 06 Apr 2009, 10:08
Posts: 1727
Location: US Pacific Northwest
harrydutt wrote:
Can I use the heater switch that permits in the 4S section, the use of either 12A*7 or 6A*7 tubes, running separate heater wires to the switch and to the 12AU7 cathode follower ?
Yes. So long as the switch is only changing the preamp socket you should be ok.
harrydutt wrote:
Is the Allied 6K49VG power transformer suitable for the 4S - 460VCT at 50ma. and 6.3V at 2.5 amp - or is the voltage too high and the 50ma. current supply too low ?
The voltage may be a little high. 230V*1.41 ≈ 325V. This is at the top end of the B+ range where I like to run this circuit. The cathode followers draw about 3mA and the 4S channels pull between 2mA and 4mA. So a B+ dropping resistor of about 5kΩ should get your B+ down around the 300 volt level where I like to run the 4S these days. A half watt resistor is fine as these current levels.

I hope this answers your questions.

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It's all about the Glass!
http://www.CascadeTubes.com
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PostPosted: 06 Jan 2021, 09:19 
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Joined: 10 Sep 2015, 13:36
Posts: 36
Thanks for your responses Mark and Matt.

So where should I put the 5K resistor, on the B+ wire connection to the tubes or
on the center tap wire ?

Harry.


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PostPosted: 06 Jan 2021, 21:31 
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Joined: 06 Apr 2009, 10:08
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Location: US Pacific Northwest
harrydutt wrote:
So where should I put the 5K resistor, on the B+ wire connection to the tubes or
on the center tap wire ?
Neither. Place it between the reservoir capacitor and the filter choke in the power supply.

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Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


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PostPosted: 07 Jan 2021, 09:30 
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Joined: 10 Sep 2015, 13:36
Posts: 36
Suncalc wrote:
harrydutt wrote:
So where should I put the 5K resistor, on the B+ wire connection to the tubes or
on the center tap wire ?
Neither. Place it between the reservoir capacitor and the filter choke in the power supply.


Great. Thanks again Matt.

Harry.


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