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PostPosted: 24 Apr 2009, 13:02 
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Joined: 04 Jun 2008, 20:59
Posts: 4256
Location: Arizona, USA
Hi Everyone, Nothing is simple!! We sent the chassis back to the fab guys for quality issues. If they can deliver.... the first kits ought be be ready around May first. Anyone who is interested should email me at support@oddwattaudio.com. For those who want to roll their own, I'll be posting a project with the final schematics and such in the next few weeks.

We will start collecting names etc for those with interest. I don't want to turn this into an advertising stint, but everone asks about cost. KT77 mono blocks (with JJ KT77s .. I like these the best) are set now at $475 each and KT88s (with Gold Lions) at $550.

Good listening
Bruce

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PostPosted: 24 Apr 2009, 15:30 
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Joined: 06 Jun 2008, 14:03
Posts: 272
Location: Tulsa, Oklahoma
Man Bruce I need to get on here more and read the posts lol, nice to see you are getting the kits going.
I might have to start saveing my pennys for one.


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PostPosted: 30 Apr 2009, 23:09 
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Joined: 30 Apr 2009, 22:36
Posts: 24
Location: Australia
I want to build the Oddwatt amplifier, but I am not sure which one yet. I also want to build a preamp with it.

I want a design with tone controls and have two options in mind.
1. The STA1 Stereo Tube Pre-Amp - Low Gain Version from LH Electrics.
http://www.lh-electric.4t.com/sta01.htm
This uses a twin triode (ecc82/12au7) per channel with the tone controls between, followed by a cathode follower.

2. STEREO TUBE TONE CONTROL Model TL from S5 Electronics.
http://www.s5electronics.com/ltone.html
This uses a single triode using a 5670 triode.

The S5 circuit uses less components and I would appreciate comments on whether one is more suitable than the other.

Thanks


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PostPosted: 01 May 2009, 19:49 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, The amps take about 1.5 to 2.0 volts of drive. The STA1LG should be fine. You can tap the needed power if you desire from one of the amps. I do not know how well the S5 preamp works. That preamp was designed to go with the K-8 and K-16 amps. Both of them are poor performers. So..... Kind of a unknown. The STA1 is quite sensitive to hum pick up and should be built in a metal enclosure. Pay particular attention to the tone control area. This is BTW common with tube preamps. Often this part of a circuit has a rather high impedance and is prone to hum and noise pickup. Unless your source equipment (CD etc) or the speakers are deficient in bass, you do not need tone controls with these amps. If built according to the plans on the site particularly with the same output transformers, they will easily be flat in response below 20HZ and past 20KHZ on the top.

Incidentally the amps work well with solid state preamps as well. I occasionally use a Velleman 8021 solid state preamp in place of my preferred Velleman 8020 tube preamp. The tube one is rather highly modified, but the ss one is not. Both of those are available as kits.

Write back if you need more information
Good listening
Bruce

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 Post subject: Re: Oddwatt SMPS
PostPosted: 04 May 2009, 14:06 
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Joined: 26 Oct 2008, 13:48
Posts: 70
Location: Central California coast
Hi All:

I'm in the process of developing my version of the Oddwatt. :) I am not familiar with the 12V-3A SMPS. :geek: Although I have done a search at Digikey and here in the forum, I can't find out anything about 12V-3A SMPS. I presume it is a discreet device. What have any of you been specifying/using for your projects? My first source for something like that is Radio Shack, then maybe my local electronics shop, then either Digikey or Mouser. If you have part numbers and/or URL, I'd appreciate it, Thanx! :up:


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PostPosted: 04 May 2009, 16:11 
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Joined: 28 May 2008, 21:53
Posts: 4591
Location: Winnipeg, CANADA
12V-3A SMPS is not a model number. It is a Switch Mode Power Supply that can deliver 12 Volts at 3 Amperes.

Any SMPS with those ratings should be fine.

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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 Post subject: Re: Oddwatt SMPS
PostPosted: 04 May 2009, 17:12 
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Joined: 26 Oct 2008, 13:48
Posts: 70
Location: Central California coast
Hi Gmilitano,

Actually I had that part figured out [Switch Mode Power Supply that can deliver 12 Volts at 3 Amperes]. So its not a discreet device but an assembly. What I found at Mouser for instance was a Mean Well #PS-45-12 which is rated 12V-3.7A (44.4W is closer to my needs) 120VAC60Hz in, about 5"x3"x1" costs $25 and is the assembled package of PCB, caps, tranny, rectifier, VR, heat sink, "chopper" IC(s), etc.

OK, learning something new. Any problem with noise that I have to be careful about? This one switches at 65KHz with max ripple & noise of only 100mVp-p ("measured by using twisted pair terminated with .1 and 47uF // caps"). I would power with twisted leads, but would you recommend the // caps also?

Thanx for your help :headphones:


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PostPosted: 05 May 2009, 12:18 
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Location: Winnipeg, CANADA
Yes, it is a separate unit. You can see the unit that Bruce in the top right hand side of the photo (black plastic rectangular box)
Image
Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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PostPosted: 05 May 2009, 12:45 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, The SMPS will be fine. There are several similar ones in the same price range. I have used Madewells before. They are ok. I use a 1000uf /25 volt electrolytic and a .1uf poly on the outputs of them as they do generate some noise. A consideration for all SMPS used for heaters in these amps is that the SMPS outputs can not be tied to the ground (back through the SMPS to the Mains). This is because of the "bias" voltage taken from the B+ (about 1/3 of the B+) to the heater circuit. The heaters likewise can not be grounded at any point. The bias draws no current, but through leakage keeps the heaters at around 1/3 of the B+. This protects the SRPP driver tubes. Without the bias it is easy to exceed the heater to cathode rating of the tube and cause it to fail. I found this out the hard way by smoking a pair of ECC802S drivers. Also be sure to use the 2uf connected from the center of the bias connection to the ground. It makes a major contribution to keeping noise levels low.

Good listening
Bruce

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PostPosted: 05 May 2009, 12:54 
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Joined: 04 Jun 2008, 20:59
Posts: 4256
Location: Arizona, USA
Hi Everyone, Just FYI for all the folks following the progress toward kits. The web site is up and about 99% correct. (http://oddwattaudio.com) There are still a few additions to add to it. I will be updating the schematics (small changes) on the diyAudioProjects posting and write up shortly. Mostly refinements. That way you can build your own just like kits if you chose.

Good listening
Bruce

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