Which PT for Overtone Special?

Kassie · Post by **Kassie** » Wed Jul 31, 2013 6:55 am

BrianWitty · Post by **BrianWitty** » Thu Aug 01, 2013 9:45 pm

Pretty work- nice and clean

Structo · Post by **Structo** » Thu Aug 01, 2013 10:10 pm

Looking good.
Remember that one of the Dumble things is to run the plates and cathodes of the first two tubes together.

As shown below.

Kassie · Post by **Kassie** » Fri Aug 02, 2013 2:53 pm

Thanks.. offcourse it stabelises due to negative feedback. Plate and cathode are out of phase.

Kassie · Post by **Kassie** » Sun Aug 04, 2013 12:27 pm

Some more pictures.

[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02243.jpg[/img]

[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02250.jpg[/img]

[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02252.jpg[/img]

[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02245.jpg[/img]

[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02248.jpg[/img]

[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02249.jpg[/img]

Structo · Post by **Structo** » Sun Aug 04, 2013 4:26 pm

That suede looks great!

Do you have ventilation openings in the front valence?

Kassie · Post by **Kassie** » Sun Aug 04, 2013 7:43 pm

Thanks structo.. Yeah it does look great.. better then I expected. But I found for suede, use the correct glue.. not a spray glue since it gets too wet and will soak in the hairs of the suede.. forming a big dark brown spot. I used BisonTix, which is greasy enough and doesn't soak the material.

You mean holes in the grill? No I don't. Should I? Is it really necessary for circulation?

Structo · Post by **Structo** » Mon Aug 05, 2013 1:26 pm

Yes having holes in the grill will allow a cross flow of air through convection.

But having said that, I have a head cab that doesn't have holes that seems to work fine.

Kassie · Post by **Kassie** » Tue Aug 06, 2013 7:57 pm

So changed the lead dress a bit. Does this resemble a dumble? Anode/Cathode and another Anode together. But I don't understand. Anode and Cathode of the same triode are out of phase... and Anode and Anode of two different triodes also. Therefore stabalising the amp. But one cathode and anode of different triodes are IN phase.. therefore creating positive feedback... so what's the deal with these 3 wires?

[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02271.jpg[/img]

Lead dress of the power tubes. I did a mix of dumble and ceriatone. Dumble routed his PI wires to the back of the chassis, and the 3k3 grid stopper backwards across the base of the tube (as not to crosstalk with the OT primaries presumably?). The two PI wires are close together untwisted but with pieces of shrink tubing (also out of phase, and thus negative feedback/stabalising.. but presumably killing high end as well?).
[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02272.jpg[/img]
[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02273.jpg[/img]

Finished wiring without the Transformers. I am still waiting on those, should be here this week to finish off.
[IMG:800:600]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02276.jpg[/img]

[IMG:800:395]http://i932.photobucket.com/albums/ad167/kassie1987/DSC02274.jpg[/img]

Structo · Post by **Structo** » Wed Aug 07, 2013 3:22 pm

Some people run the power tube grids twisted while others don't
I don't think that is too critical as long as you keep them away somewhat from AC power wires.

As far as the power tube grid resistors, Dumble and others usually float those above the tube from pin 5 with a connecting wire from V4 to V5 and a wire from V6 to V7.

I have never really liked that idea so I mounted small terminal strips on the socket screws and run the screen and grid resistors from that to the tubes.
Makes it a bit more crowed but they are secure.

larsvictor · Post by **larsvictor** » Fri Aug 09, 2013 9:53 am

Hi Kassie,

maybe WELTER AUDIO ELECTRONIC in Germany could be an alternative solution for a PT. They are a lot cheaper than the replacement transformers from hammond. Im not sure if they do fit in your chassis. Check out N7/3+4 or N11/U (for bridge rectifier).

http://www.welter-electronic.de/bauteil ... _trans.htm

Victor

Kassie · Post by **Kassie** » Sat Aug 10, 2013 12:29 pm

larsvictor wrote:Hi Kassie,

maybe WELTER AUDIO ELECTRONIC in Germany could be an alternative solution for a PT. They are a lot cheaper than the replacement transformers from hammond. Im not sure if they do fit in your chassis. Check out N7/3+4 or N11/U (for bridge rectifier).

http://www.welter-electronic.de/bauteil ... _trans.htm

Victor

Hey Lars du guten nachbar!

Thanks for the info.. can you tell me a bit more about Welter? It is the first time I am hearing about it. How is the 'sound' quality (usually German electro/engineered products are very solid).

Sadly and/or Gladly, the Hammond transformers are ordered/payed and shipped allready from Mouser USA. Expect them to arrive any day to finish the amp.

Checked out the prices.. and they are cheaper compared to Hammond if you buy Hammond at tubetown.de. But if you buy them at Mouser or Jukebox-revival.. then Hammond still works out cheaper.

larsvictor · Post by **larsvictor** » Mon Aug 12, 2013 7:34 am

Kassie,

I have no experience with the Welter transformer yet, but I just ordered the N11/U for a #102 project. The Hammond 290FEX and the Fender 125P34AX is around 140 Euro plus shipping and it is center taped, wich is not required for the #102. The Welter PT costs 113 Euro + shipping.

Lars

bluesfendermanblues · Post by **bluesfendermanblues** » Mon Aug 12, 2013 2:10 pm

Hi Lars and Kessie,

Welter Transformers:
Most of the German Amp manufacturers (H&K, ENGL Diezel, Tube Thomsen, Frank'N Tone (50 Special)) use Welter transformers.

So they are probably ok. I haven't tried them myself, yet

Ritter Transformers:
Another German alternative is Ritter Transformer: http://www.roehrenendstufen.de

The NT150 models are plentiful for 50w amps.

I have bought 4 high quality transformers from Ritter for dual mono KT88 amps.
HIFI Power amp. Top quality products and delivery.

Kassie · Post by **Kassie** » Tue Aug 13, 2013 7:21 am

Wow,

Another new transformer company... also looks interesting.. I wish I knew that before just to be a 'pioneer' sorta in the build. But then again... I would have no reference to make any decent claims.

What this forum really needs is probably A/B/C/D/E/F/G comparisons.

Mount a whole bunch of Output Transformers on a triplex plate. With the OT primaries/centertap/ground wire) going outside the chassis via a copper tube or something. And just do comparisons.

Similar set-up, similar knobs, similar speakers.. and just record it High Quality. I wish I had that much money to spare just to experiment like that for fun. That would make some real reference material, and everyone could choose their own.

We could do something like that if we get a group of people satisfied enough to buy the different transformers from that 'test' person afterhands.

The Amp Garage

Which PT for Overtone Special?

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Re: Which PT for Overtone Special?

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Re: Which PT for Overtone Special?

Re: Which PT for Overtone Special?

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Re: Which PT for Overtone Special?