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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: 17 Jan 2016, 19:11 
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Joined: 06 Apr 2009, 10:08
Posts: 1590
Location: US Pacific Northwest
I do love those little Woodford Reserve knobs. I still haven't found the right place to use mine yet. :D

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PostPosted: 17 Jan 2016, 19:19 
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Joined: 06 Jun 2008, 18:23
Posts: 5134
Location: Australia
Suncalc wrote:
I do love those little Woodford Reserve knobs. I still haven't found the right place to use mine yet. :D


I have a few spare so if you ever use the one you have and need another, give us a hoy!

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Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


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PostPosted: 17 Jan 2016, 20:42 
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Joined: 24 Nov 2015, 04:55
Posts: 19
Location: San Francisco, CA
mwhouston wrote:
I have a few spare so if you ever use the one you have and need another, give us a hoy!


I need to learn how to speak Australian... :D


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PostPosted: 17 Jan 2016, 21:39 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
babblefish wrote:
mwhouston wrote:
I have a few spare so if you ever use the one you have and need another, give us a hoy!


I need to learn how to speak Australian... :D


It means to call out and let me know. "Hoy"!

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Projects:"retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp | ”najah” - Raw 180W Tripath Class D power amp | "Icon" - Shuguang CV-181Z preamp


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PostPosted: 25 Jan 2016, 06:18 
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Joined: 25 Jan 2016, 06:09
Posts: 1
Location: Brazil
Hi! That's a really cool project, I have been looking at it for a while. (:

I have a question though!
I really like de power supply design, and it fits my needs for another project. But I need do supply 2 12x7's (in another project I need do supply 4 of them). My question is: despite having the power transformer with the right amperage, can I just supply the other filaments from the same point marked or do I need to repeat some part of the circuit?

Sorry for any writing mistakes, greetings from Brazil. :D

Thank you!


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PostPosted: 26 Jan 2016, 00:59 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
I feed my filaments from a DC regulated PS. The reg can handle 1A the plug pack can too. Never a problem.

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PostPosted: 27 Jan 2016, 22:36 
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Joined: 26 Jan 2016, 12:15
Posts: 1
Hey Matt,

I'd like to use this pre-amp as a standalone amp for my speakers. Due to the high output impedance, what would be the best way to lower it without having to use semiconductor (BJT common collector configuration or buffer op amp)


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PostPosted: 28 Jan 2016, 16:32 
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Location: Australia
Buffer it with a Pass B1. I did in a couple of builds. It works extremely well and is simple.

Put the pot between the 4S and the B1.

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PostPosted: 01 Feb 2016, 00:58 
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Joined: 04 Apr 2013, 07:04
Posts: 6
Hello Matt,
Thank you for sharing ss version of 4S Universal Preamplifier. I am planning to build one. What are the voltage ratings of 0.1 uF caps which one of them is before B+ and the other is before 12A?7 ?. Thanks.


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PostPosted: 02 Mar 2016, 16:46 
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Joined: 10 Sep 2015, 13:36
Posts: 33
Another builder joins the 4S Preamp club.
I like the simple circuitry and the fact I already have over two dozen 12A*7 tubes
made this a no brainer.
I finished it a few weeks ago and have been enjoying my music playing through it
during this time. I'm very pleased with the results.

This preamp plays very well with my DIY Tubelab SSE (Simple Single End) amplifier.

The first tube I tried is an RCA tall black plate 12AU7A, I enjoyed my music so
much with this tube in the preamp that I spent little time comparing other tubes.
I did try a GE 12AX7 and JAN 12AT7WC for a short time, these also played very well
but I have a preference for the 12AU7.
With the 12AU7 I get enough sound level with the volume pot at the 9 o'clock position.

I added the switch which Matt suggested for using the 6V tubes but I don't have any
of these, I'll get some later.

That is the good part. The not so good part is I have a bit of low level hum.

With the volume pot at minimum I can barely hear the hum with my ear close to the
speaker. It only becomes noticeble with the pot past the 12 o'clock position and at
the maximum position I can just barely hear it at my normal listening position about
seven feet away in a quiet room.

Having the ground lift switch open or closed doesn't make any difference the hum is
still there.

My Tubelab SSE is very silent even when I turn the volume pot to maximum.
It has three inputs, two goes through the volume pot and one is direct
bypassing the pot. My 4S preamp is connected via the direct input.

The cause of the hum may be due to my layout and/or wiring. I wonder if the heater
switch wiring could be the cause ?

Maybe I should have located the RCA jacks at the front to shorten the lead wires but
I personally dislike seeing cables sprouting up the front of my amplifiers.

I would appreciate it if folks have a look and offer suggestions. Photos are attached.

The hum is not getting in the way of my music enjoyment but I'm not quite satisfied
knowing it's there.

Thanks for looking.


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