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Millett UniAmp Build Thread
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=828
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Author:  Bluesman [ 11 Jun 2010, 08:03 ]
Post subject:  Re: Millett UniAmp Build Thread

I cut the two traces between the socket and the solder pads marked RECT P1 and RECT P2. For those who haven't built this amp yet, all these traces do is connect the power transformer to pins 4 and 6 of the rectifier tube, so I just bypassed that by directly wiring to the socket. The problem vanished completely after doing this AND cutting the traces. Without cutting the traces, connecting the transformer leads directly to the socket pins does nothing except introduce the voltage at the other end of the traces, which allows the voltage to run right to where the problem is, the solder pads.

I can't think of anything else it could be other than somehow the solder pads were shorting to the ground plane. I may have done something to cause it in the process of soldering. It's a new one on me. Glad I was using my variac.

This is a different pcb than I used in my ill-fated first build, and I had no such problem with it.

Cheers,
Greg

Author:  Gio [ 12 Jun 2010, 10:44 ]
Post subject:  Re: Millett UniAmp Build Thread

Do you guys think that the blue Edcor power and output transformer will look bad matched up on a chassis with a black Hammond choke?

Author:  Bluesman [ 13 Jun 2010, 11:37 ]
Post subject:  Re: Millett UniAmp Build Thread

Gio,
To be perfectly frank, I don't like the sound of that combo, but I would recommend doing a mock up to see what you think. Ultimately, you'll be the one to look at it all the time. If you don't like it you can always change it. I'm definitely going to paint mine after seeing the real deal, fully assembled.

Due to comments from Edcor, I was under the impression that painting over the powder coat would not be feasible. But a fellow forum member was kind enough to inform me that painting the powder coating on the Edcors is not a problem, as long as you use the right products. He has many years experience in the auto refinishing business. He also said if you want to go the other direction, and paint to match up with the Edcor blue, Edcor has the paint code listed on their site. Any decent supplier can mix up paint to match.

Cheers,
Greg

Author:  Gio [ 19 Jun 2010, 16:46 ]
Post subject:  Re: Millett UniAmp Build Thread

I've started a thread for my build: Gio's Peter Millett Uniamp Build. I would really appreciate it if you guys could give me some feedback on my layout.
Cheers

Author:  giaspyr [ 30 Nov 2011, 10:56 ]
Post subject:  Re: Millett UniAmp Build Thread

Hi all.
I have decided to build this project as you all did, I plan building it in stereo mode as I already have a power tranny and a couple of output trannies. The question is if the power tranny I have can be used for this amp so I give you here the voltages of it and wait for your response:

primary: 220V @50Hz--> secondary 1: 350V/0.2A secondary 2: 400V/0.4A secondary 3: 2x3.15V/7A secondary 4: 2x3.15/7A secondary 5: 7.0V/0.1A

I'm located in Greece so primary input is 220V

Please if someone can help how could I use this particular transformer for uniamp as it is 100% new and I cannot afford buying another right now.

Author:  Gio [ 03 Dec 2011, 13:39 ]
Post subject:  Re: Millett UniAmp Build Thread

Hi giaspyr, the PT for one channel is listed as:
T2- Power transformer 800VCT(400-0-400)@200mA, 6.3VCT@4A, 5V@3A

On your transformer is Secondary 2 center tapped? You will also need to drop the voltage to the 5V heaters of the rectifier.

Cheers

Author:  ernesto [ 18 Dec 2011, 00:37 ]
Post subject:  Re: Millett UniAmp Build Thread

Hi all I'm knew to this forum, but was hoping to pick your brains if I may.

I am a complete novice with electronics so please keep this in mind, I would like to build a tube amp for use with some reasonably sensitive Electrovoice speakers (claimed 97db). I have been looking at either the Tubelab simple push pull, or the uniamps from Pete Millett. The simple pp is appealing as George has put together comprehensive build instructions and even supplies a kit to populate the pcb. As a novice this would obviously be of great benefit. Equally I would prefer to build a pair of monoblocks such as the uniamps, looking at Petes site it is clear that it is a relatively straightforward build, however there isn't quite the same level of newbie friendly clarity as with the simple pp.

My question to the people here who have built the uniamp design is wether it is something that an inexperienced builder could tackle and wether there were any unforeseen tweeks etc that are not clear from the schematic etc. I want to keep my budget as tight as reasonably possible so will be sticking with Edcor for the transformers, perhaps even for the phase splitter if their solution (or alternatively the Altronics) is a suitable alternative to the Sowter, although if this were to make my life complicated I would spend the extra for the Sowter option.

I would be very grateful for any and all advice or guidance that people on this forum would be kind enough to provide.

Thanks

Matt

Author:  mwhouston [ 18 Dec 2011, 16:01 ]
Post subject:  Re: Millett UniAmp Build Thread

I have not built the Millet but have had an amp which used the brds. etc. built by some one else (Dan). The amp is excellent and so was Dan's build. Because you are working with a cct. brd. either build should be do-able. When you get the PS that is where things may get a little tricky.

Edcor trannies are good. As long as you pick the right ones you can't go wrong here.

Author:  Gio [ 19 Dec 2011, 13:16 ]
Post subject:  Re: Millett UniAmp Build Thread

Hi Matt, welcome to the forum. Both are on PCB so they are relatively easy to build. Plus there are many who have built these projects so it will be easy to find help for either build on a diy forum.

Cheers

Author:  ernesto [ 19 Dec 2011, 18:19 ]
Post subject:  Re: Millett UniAmp Build Thread

Thank you both, I am hoping to draw on the knowledge of the people on these forums, there certainly seem to be a lot of experienced and helpful people on here. If I had the money, I would build both, the SPP first because of Georges in depth assembly guide and then the Uniamp which is my ideal set up. In fact if money was less of a factor I wold probably look at the Dynakit Mk3 kits as I think from what I have read and looking at the kits themselves they would be perfect for a beginner like me. Anyway it's too late for Santa to bring any of them for Christmas so no rush.

Thanks again.

Matt

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