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Oddwatt Push Pull Tube Amplifier Projects
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Author:  gofar99 [ 22 Jan 2009, 23:12 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi, I'll post a schematic in a day or so. I just got a large batch of the 6H6s real cheap, NOS JAN ones. As you noted bigh tube amps are heavy. My next design will include a 2 horsepower motor to drive a set of wheels and a forklift to get it on the shelf (not!). Just the power transformer for the OD225 weighs 14 pounds. That is part of the reason for the design of the Odd Blocks, they are light weights at about 15 pounds each.

Good listening
Bruce

Author:  CrazzyAbtTubes [ 23 Jan 2009, 17:16 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Lucky you, my 800Vct 465mA hammond tranny and 500ma hammond choke are like two big concrete cinder blocks, kinda over kill for my williamson design, but would be perfect for a 3-500Z amplifier of 100watts, but I would rather stick with something I can use many tube types in, because the williamson amp will make up my main system.

The transmitter tube amp is just an idea, I like something that is different from the usual.

Author:  booangler [ 23 Jan 2009, 23:16 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi All,

I found a reference to Bruce's Amp in the February Issue of audioXpress. Here is the link to the tdl-tech website referenced on page 37 of the a for mentioned issue. You have to scroll down a bit to get to item 10, but it is there. I have not gotten through all the information. However here is a list of everything included in the download package.

Alan

File Contents
==========================================================
oddnotes.pdf The write-up on this version with photo captions
oddparts.pdf Parts list
oddtable.pdf Comparison table
figure1.pdf Input stage circuit diagram
figure2.pdf Output stage circuit diagram
figure3.pdf DC heater supply circuit diagram
figure4.pdf HV power supply circuit diagram
figure5.pdf SPICE circuit diagram
photo1.jpg Front view
photo2.jpg Rear view
photo3.jpg Inside view
photo4.jpg Alternate inside view
photo5.jpg ODD225-2 and ODD225-3 circuit boards
photo6.jpg ODD225-2 and ODD225-3 top view
photo7.jpg ODD225-2 and ODD225-3 bottom view
odd225-1.pcb CIRCAD circuit board file*
odd225-2.pcb CIRCAD circuit board file*
odd225-3.pdb CIRCAD circuit board file*
odd225-x.cir SPICE listing file (frequency response)
odd225-t.cir SPICE listing file (transient response)
NEW225.pdf Bruce Heran's changes dated 9/29/2008
Attachment:
odd225.zip

Author:  Gio [ 24 Jan 2009, 00:12 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Thanks for the heads up Alan. I will have to go check out the magazine.

Is it just a single reference or an article?

Cheers,
Gio

Author:  booangler [ 24 Jan 2009, 06:48 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Gio wrote:
Thanks for the heads up Alan. I will have to go check out the magazine.

Is it just a single reference or an article?

Gio,

It is a reference, and an obscure one at that, from a company called TDL Technology.

Alan

Author:  gofar99 [ 24 Jan 2009, 16:53 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi Everyone, I've seen the site and chatted with the individual. Different construction technique, but essentially the same circuit as the one I posted. It is nice to have confirmation that the amp can be built and works like the original. I have had several emails that already confirmed this though. I am aware of a number that have been built and so far no problems or complaints. If there are any please PM me so changes can get made if needed. The biggest problem most folks have is trying to figure out how it works. The second is getting the 25 ohm pots and the LM317HVs . The only source I have found for the pots is Radio Shack (of all places!) and the LM317HVs I get from Jameco (there are other sources though). An update on the pending kits. About 90% of the parts for the first batch are in stock now. We are waiting on the chassis cover (neat looking) and a shipment of transformers. Also if anyone knows a good source of three pin inline connectors with leads (like the ones on PC fans) with 1mm spacing I would appreciate it. They connect to the LM317 and save soldering and miss wiring of it.

Good listening
Bruce

Author:  gofar99 [ 13 Feb 2009, 15:14 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi Everyone, An important update. Another diyer (thanks Chris) ran into a problem with his output tubes. They would not stay balanced, much like the problems I encountered with the EH KT88s (different problem there though). It turns out that his heater voltage was rather high and the tubes were having thermal problems. It is uncertain exacly what the relationship was, but when he reduced the heater voltages to spec the amp behaved. My recommendation is to keep the heaters to between 6.0 and 6.2volts DC (mine run at 6.0). Over that you could have difficulties. An alternative power supply that works well is to use an inexpensive SMPS that delivers 12 VDC at over 2 amps for each Odd Block. I have one set running that way and it behaves perfectly.

Kits are soon for those following that idea. The hold up right now is that the company making the chassis put the power connections on the wrong side.

Good listening
Bruce

Author:  gofar99 [ 11 Mar 2009, 22:51 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi everyone, Another update. The initial 6 "beta" amps are here and three have been constructed and all work as well as the original designs. The production ones are soon to follow (about 3 weeks). The "betas" resulted in a product improvement. One main PCB in place of three smaller ones. Save a few $$ too. A web site is in progress as well (http://oddwattaudio.com) Right now it just says under construction, but it will have lots of info shortly. Another diyer active on this forum is doing the site construction (thanks Bernardo). Gio's advice has also been quite helpful (thanks). Trying to get a high quality kit like this into production in a price range that diyers can afford is a challenge. Anyone else who is considering this type of activity may wish to give me a PM. I'll be glad to point out some of the problems we have encountered. It might save you some grief.
Attachment:
Beta-OddWatt-Tube-Amplifier.jpg

Good listening
Bruce

Author:  Supernaut [ 12 Mar 2009, 16:53 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

hello, i'm new to this forum, but i'm glad to hear the kits are soon to be available! i was just wondering if the kits included the 6NO30 delay relays or if that was an optional method for delaying the B+

thanks!
~jeremy

Author:  gofar99 [ 14 Mar 2009, 18:50 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi Jeremy, Welcome to the forum. We had considered the 6NO30s originally as well as some of the variations and decided that they would be increasingly difficult to source. I bought a batch of them for my amps, but I don't really know how many are out there. They have been discontinued for several years. What we did in its place is to include a one transistor (horrors a transistor in a tube amp) delay circuit. The transistor does what the 6NO30 did and provides a delay for the B+ turn on. The delay is adjustable for up to a minute or so. It seemed to be a good solution.

Now for some more good news. I have two of the pre-production kits (I call them beta versions) up and running in my main system. They are every bit as good as the prototypes that were in the web posting. A lot less complicated to build as well. I plan on putting a few hours on them and then running a full set of tests to verify the performance. My ears tell me they are extremely similar to the earlier ones. Perhaps a very slight bit better on midrange detail and imaging. This could be the difference between the NOS RCA 12SL7s in the originals and the NOS Phillips 5751s in these amps. Both are excellent performers in these amps. I'll have to try the new production Russian 5751s in comparison with the Phillips to see if that is the source of the difference. Either way great sound. Just FYI, initially we are only planning kits with 5751s. Other stuff and variants are likely down the road.

Good listening
Bruce

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