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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: 13 Jun 2017, 04:40 
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Joined: 29 Oct 2014, 12:32
Posts: 95
Location: Russia Komi republic
Yes, a few pages ago I saw this photo. Maybe not in this thread.
I really liked that the panel was milled for display. Very beautiful.

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PostPosted: 14 Sep 2017, 23:48 
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Joined: 18 Jan 2017, 18:55
Posts: 37
Can I use a K40Y-9 200V output capacitor or do I need to find a 400V+ capacitor, having trouble locating the later? I have 0.22 uF K42Y caps in my KT88 Oddblocks and have been very pleased but don't have much to compare to other than SS.
Anyone tried a 1 uf K75-24 cap since these are available. I can find K75-10 also in 1.5uF or higher.


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PostPosted: 15 Sep 2017, 01:46 
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Joined: 08 Aug 2009, 03:11
Posts: 2208
Location: Chilliwack, BC
I'll agree those Russian caps are to the film world what a Nichicon MUSE or Elna Silmic-II is to the electrolytic, but if you can't rustle some up, try a Panasonic ECWF.... cheap enought to do ya until the Russian ones come along ;)

Cheers!

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* Ratings are for transistors - tubes have guidelines*
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PostPosted: 15 Sep 2017, 02:38 
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Joined: 24 Oct 2010, 07:05
Posts: 255
It seems you have digged a fortune of the Russian caps. :-)
Despite the quality I'd not use the 200V in this place. Yes, there is no such voltage across them in the mute point, but a preamp usually amplifies signal, so it is not uncommon to have a big "pulses" during some transitions. Second considerstion is the power amp connected: it could be seen vulnerable to a malfunction from the capacitor and cause the malfunction too. There should be noted also the age of the capacitors.
There is 400V versions available. You could also use FT-1 - FT-3 here with the same if not better result. I do not like K75, but it is only my taste.


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PostPosted: 24 Sep 2017, 12:02 
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Joined: 10 Sep 2015, 13:36
Posts: 29
The power transformer for this design is specified as -- Edcor XPWR08 200V@40mA + 8V @ 1.5A -- but I cannot find it on Edcor's website.

Is it still available, if so can someone post a link ? If not is there an available altrnative ?

I looked at this design a couple years back and am just returning to it.
Thanks.


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PostPosted: 24 Sep 2017, 12:58 
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Joined: 04 Jun 2008, 20:59
Posts: 3646
Location: Arizona, USA
XPWR083, Hi, this has been posted for years an no one noticed the error. Thanks. It is an inexpensive and quite useful trannie. It works in my phono preamps and headphone amps as well.

Good listening
Bruce

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PostPosted: 25 Sep 2017, 08:45 
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Joined: 10 Sep 2015, 13:36
Posts: 29
Thank you. I'm having a second look at your design deciding whether to go ahead with a build.


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PostPosted: 02 Oct 2017, 17:32 
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Joined: 24 Nov 2010, 14:39
Posts: 23
Location: California
I just completed my build of the Forewatt, and couldn't be more pleased. It sounds great. Thanks Bruce :) I didn't use a cathode bypass capacitor, but there is still plenty of gain available. I also didn't use regulators for the B+ supply, but there is absolutely no audible hum or other noise. I ended up with about 227 volts B+ and 70 volt DC bias on the heaters. Hopefully that's enough to prevent any pyrotechnics in the tubes :) . I did use regulated DC on the heaters. The Antek toroidal power transformer I used had two "6.3-volt" windings, so I used a voltage-doubler rectification setup on each to create two independent 12 volt regulated supplies. Lightly loaded, the rectified voltage from the transformer is high enough to use standard 7812 regulators. One supply powers the heaters, the other is used for the remote volume and source selector module. I used the older version of the module (a bargain :) ) as shown in Bruce's original design, not the newer one with digital readout. I believe there are a few different versions of these modules, so the info that I offer may not apply to all. It was mentioned that the power and signal grounds on these modules are common and can cause noise / hum issues. I studied the main board and found that the PCB traces are separate, but bridged together with a 10 ohm resistor and small parallel capacitor. I removed those two components and used the empty hole on the signal ground trace to solder in a jumper wire that connects to my signal ground bus. This eliminated a bit of hum that I initially had when I first fired it up. The power ground trace on the board also connects to the potentiometer housing, which, if you mount it in a metal chassis like I did, creates a really nice ground loop :) The signal and power grounds on the relay board are isolated, but I still removed the ground wire from the signal ribbon cable and connected the ground trace from the relay board to the signal ground bus, just in case.


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PostPosted: 18 Oct 2017, 09:45 
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Joined: 01 Apr 2017, 19:56
Posts: 47
Hello. I was searching the forum for the latest schematics and found one dated October 2014. But I have seen reference regarding a January 26th 2015 schematics, although I haven't found this schematics. Can someone point me to the right direction? Thanks.


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PostPosted: 02 Nov 2017, 22:29 
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Joined: 21 Apr 2017, 02:10
Posts: 24
Hi All,
I having building PreWatt, but I have issue to Lite VM02 Motorize Remote, I don't understand connecting, so is there someone else could be guide me how to connect them.
Thank you many much.


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