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Oddwatt Push Pull Tube Amplifier Projects
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Author:  gofar99 [ 31 Jan 2018, 10:56 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi, Really professional looking metal work. Mine always looks like something a 10 year old would do.

Good listening
Bruce

Author:  Geek [ 31 Jan 2018, 14:19 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Fantabulous work! :thumbsup:

gofar99 wrote:
Mine always looks like something a 10 year old would do.


Hahaha, I've been told that mine is :blush:

Author:  Gio [ 31 Jan 2018, 21:54 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi victorzwk, great work.

I'm curious to know how the ventilation slots were cut out.

Author:  victorzwk [ 01 Feb 2018, 12:27 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi. All the slots and most of the holes were done by a CNC Punching Machine. Not as flexible as a CNC waterjet cutter, but its renting time is much cheaper!

The matte and glossy finished were done by hand, using a Mini Grind-O-Flex, a Bosch abrasive sponge and a buffing wheel with polishing paste.

Author:  Trackhappy [ 03 Feb 2018, 04:15 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi all,
Glenn from Brisbane, Australia. I want to build a stereo amp for my lounge. 15-25 watts is plenty. I have pretty much settled on the Oddblock Octal series 2 with EL34 or KT77 (long way off that decision). I want to order the most expensive parts and start using the transformers to design a layout. I was looking at Hammond equivalents, but I think I will stick to the specified Edcors for best compatibility with the design and best chance at successful outcome. I am thinking of going single chassis, and maybe using a single XPWR117 power transformer. I'd rather not have overheating issues though, should I stick to dual power supplies for that and/or any other reason? The trannies are 8 weeks away from order and significant shipping cost after already getting done over by the exchange rate. :( I have loads of electronics experience (since Jan 1980) but little tube experience since way back.
Any other comments on potential gotchas or parts sources in Aussie are welcomed.
Thanks,
Glenn.

Author:  Watermelon [ 04 Feb 2018, 04:29 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi all, I woud like to start my first post in this thread by thanking Bruce for it's beautifull desing and even more for the amazing support and help he provides to all of us DIYers.

I have made my own oddwatt as a dual monoblock in a single chasis with EL34 tubes. It sounds really good to my ears.

Now, I have a problem, my EL34 are red plating at the standard current specified in the desing, 62mA. B+ is around 450v. I have tested two EL34 manufacturers, TAD and Tung-Sol. The TAD were worst, both "master" tubes were red plating, for some reason the "slaves" were not. With the Tung-Sol I have only a faint red plating in one of the "masters".

Any ideas why?

Author:  Trackhappy [ 04 Feb 2018, 04:35 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Bit the bullet and ordered the two OPT's today. 8 weeks away, and the scary postage and currency conversion, but at least I have a known quantity to start with. Still to decide about the power side of things, but plenty of time I guess.

Author:  poty [ 04 Feb 2018, 08:27 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Watermelon wrote:
... EL34 are red plating at the standard current specified in the design, 62mA. B+ is around 450v...Any ideas why?

- Not balanced?
- Wrong connection?
- Broken LM317HV?

Author:  Watermelon [ 04 Feb 2018, 11:53 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

poty wrote:
Watermelon wrote:
... EL34 are red plating at the standard current specified in the design, 62mA. B+ is around 450v...Any ideas why?

- Not balanced?
- Wrong connection?
- Broken LM317HV?

Hi Poty

They are balanced and stay balanced. I suspected that the panel meter was fooling me but I checked with the voltmeter and measurements are acurate.

I have checked but can’t find any error.

Do not think the LM317 are wrong, they are regulating the current and voltages seem good to me. I have around 32v on the cathodes and 444v on plates.

Author:  gofar99 [ 04 Feb 2018, 14:06 ]
Post subject:  Re: Oddwatt Push Pull Tube Amplifier Projects

Hi, They should not do that, but if they are then try reducing the current a bit. Try 55 ma. Change the cathode /317 resistor to 12 ohms if you are using the 10 ohm ones. The sound will not be changed and the output will be nearly identical. I have never had the EL34s red plate, a bad batch of KT120s yes. If you go to 55 ma and they still red plate then something is wrong.

Good listening
Bruce

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