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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: 22 Jul 2016, 03:44 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
I think better without the bypass cap.

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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: 22 Jul 2016, 05:59 
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Joined: 20 Apr 2015, 01:30
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I put a switch in and the bypass caps. I listened for a short time, and so far I like it better with the caps in the circuit. It's noisier, but sounds more real to me, with better imaging. Not a big difference gain wise though.


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PostPosted: 31 Jul 2016, 09:43 
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Joined: 20 Feb 2014, 10:35
Posts: 59
Location: NZ
Just a bit of info for those who run tube rectifiers: I discovered another rectifier tube that would be suitable for the 4S - the 6BW4.
It is fairly close to the EZ80/6V4 in specifications, the only difference being the cathode comes off pin 9 instead of pin 3.

It appears that if you jumper pins 3 & 9, then you should be able to run the 6CA4/EZ81, 6V4/EZ80 or the 6BW4. Comments on the web suggest this is possible, but also say that some datasheets have pin 9 as an internal connection on the 6CA4/EZ81 & 6V4/EZ80.
Inspecting my stash of these tubes, it appears there is no connection. Some have the wire from pin 9 terminating just inside the glass envelope, others have the wire going up to the bottom mica but no further.

I've ordered some to try, as they can be found cheap, just a few dollars for NOS.


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PostPosted: 11 Aug 2016, 18:12 
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Joined: 21 Jul 2016, 01:23
Posts: 8
Location: Idaho
Still being relatively new to building tube amps, I decided to try Matt's 4S Preamp and have a question about wiring the AC side of the transformer. I have 120V at my outlets and the AC side of the Hammond 269EX white/gray 115V, white/black 125V Tap, which do I use for my IEC receptacle? I am using the Schaffner 388-6 3-1 fuse, switch and IEC. Also, what type of fuse do I use in this preamp? This unit I have has two slots for fuses.

One other question, I have tied all signal grounds to the bare copper wire that runs off the second filter capacitor to the terminal strip between the input and output jacks. The 12a?7 socket and input/output jacks tie into this wire. Am I correct to do so?

I have enclosed some pictures.

Thanks,

Patrick


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PostPosted: 12 Aug 2016, 06:48 
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Joined: 20 Jan 2016, 09:16
Posts: 8
Location: Johannesburg, South Africa
Hi,

I am very new to tube amps. In fact I have only done 2 builds of the NP-100v12 Headphone amp, and simply love them (the sound). I am now waiting for a HiFiMeDIY T1 Tripath amp from China and am interested in a "tube front end" for the Tripath. Will this 4S Preamp be suitable as a tube front end? I.e. running from a laptop usb to a DAC, to the 4S Pre-amp, to the Tripath, to the speakers? Will the 4S need tweaking, or do I have to search for something else? Sorry, I know this is not a Tripath Amp Forum, but I need to start somewhere.

- Jerry


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PostPosted: 12 Aug 2016, 08:39 
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Joined: 06 Jun 2008, 18:23
Posts: 5141
Location: Australia
I have built and sold four Tripath T4s and now building another with the latest amp module. Where the problem lays is the amps are low impedance inputs - 22K. A 4S would like to see a much higher I input impedance better than 100K or better still 250K like most valve amps.

A Pass BoZ, single JFET preamp will drive a 600ohm load or better.

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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: 12 Aug 2016, 15:34 
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Joined: 21 Jul 2016, 01:23
Posts: 8
Location: Idaho
Perusing this thread I did find the correct AC wiring and proper fuse values.


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PostPosted: 12 Aug 2016, 17:27 
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Joined: 21 Jul 2016, 01:23
Posts: 8
Location: Idaho
Have it now playing through my audio sector lm3875 amp with klipsch lab 1.1 speakers in the garage, one word gorgeous!


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PostPosted: 12 Aug 2016, 18:00 
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Location: Australia
Reaper996 wrote:
Have it now playing through my audio sector lm3875 amp with klipsch lab 1.1 speakers in the garage, one word gorgeous!


Got some images of the complete setup?

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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: 12 Aug 2016, 23:50 
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Joined: 21 Jul 2016, 01:23
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Location: Idaho
Fourth post down on this page shows some of what I have done. Waiting for the case to dry before final assembly.


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