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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: 23 Apr 2013, 00:20 
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Since I included the BoZ back-end with this preamp I thought I should take some measurements.

Firstly I could only get a swing of 3.3Vpp for 250mV in. The only way I can fix this (untested) is to increase the the B+ BoZ is powered by. But I'm not sure.

But -3db frequency range is 10hz to 45Khz at full power into 1.2Kohms. IK SQR wave was absolutely perfect the 10K had a rounded rise and fall and the 100hz a downward tilt to the rear of the plateau. OK but not stunning. Once more the 1K SQR wave at full power into 1.2K - perfect.

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PostPosted: 24 Apr 2013, 20:03 
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Who has seen this site? They have lots of schematics and some good looking projects. Hit the translation button.

http://www.moxtone.com/index.php

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PostPosted: 12 Oct 2014, 03:24 
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Hi Mark,
This would be my first time to build and not sure about the pin connections, please correct me if I am wrong:
Pin 9 - B+/Output; Pin 2 - Input; Pin 1 - 1k2 resistor ; Pins 4 & 5 - Heater. Thanks.


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PostPosted: 12 Oct 2014, 09:00 
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man_do_quest wrote:
This would be my first time to build and not sure about the pin connections, please correct me if I am wrong:
Pin 9 - B+/Output; Pin 2 - Input; Pin 1 - 1k2 resistor ; Pins 4 & 5 - Heater.

Hi and welcome to the forum.
The pinout for the 12A_7 tubes is shown in Figure 1 of the 4S Universal Tube Preamp project page.

Image

Pin 9 is the center-tap for the heaters. The B+/output connections are pins 1 and 6. Inputs are pins 2 and 7. The cathode resistors go to pins 3 and 8. One tube has two sections, so one tube can be used for a stereo preamp. Use pins 1, 2 and 3 for the left channel of the preamp and pins 6, 7 and 8 for the right channel.

Hope this helps clarify the tube connections.

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PostPosted: 12 Oct 2014, 15:30 
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Hi Gio,
Thanks for your helpful information. It will be a slow but forward move for me. Thanks a lot.
Have a nice day.


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PostPosted: 13 Oct 2014, 05:47 
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I think Gio has answered your question.

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PostPosted: 13 Oct 2014, 11:30 
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One quick note about that diagram. The pinout is as if you are looking at the bottom of the tube or socket. So that is the proper orientation if you are wiring the socket from the underside. Take a look at the underside of the socket below. You can actually see the numbers formed into the base by each pin.
Attachment:
9-Pin Socket.jpg
This way you get it right during the wiring of the circuit.

Many years ago (like 1978) I remember being very frustrated when I wired a circuit with all three sockets totally backwards. I hope to save everyone I can from that level of frustration.

Let us know how your build turns out.

Matt


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PostPosted: 13 Oct 2014, 12:16 
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When I wired up my 12A6-PP Stealth, I printed pieces of papers with the pin nos as well as description (a1, k1, g1 ...) and with a hole big enough to have the papers slide over the back of the sockets held in place with some scotch (not the drink). That helped a lot.

Image

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PostPosted: 13 Oct 2014, 12:25 
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I usually use a permanent marker to identify every other pin or so, what ever I have room for.

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PostPosted: 19 Oct 2014, 16:40 
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Well, I have another update to the tube list for the 4S Universal. This is a special case because you can only use this tube if your heater supply is capable of putting out a full 600mA into the filament. If so, the 12BH7 tube will expand your tube rolling capabilities. This tube is halfway between the 12AU7 and the 12AV7 from a gain perspective and is very low distortion. I don't have any on hand but if someone tries it, be sure to let us know how it sounds.

Here is the new tube performance list just for reference.
Attachment:
20141019 4S Tube List.png

Gio, Could we get this new table added to the project page?


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