DIY SET Tube Amplifier - Tubelab SSE

[radium7]

Amp looks great, with good components. Toroidal power transformer, Hammond choke, good caps and resistors. Designing the output transformer for single ended amp is very difficult. You may aware of airgap, without airgap core will saturate and OPT failed soon. It also affect life of tubes and PWR TXR. Interleaved tranny is good but insulation sheet should be thin otherwise OPT capacitance rises. Silicon core is best but very hard to find, try CRGO.Vacuum Impregnation also important. UL mode normally gives a wide bandwidth, but triode mode gives sweet music. Try oil caps.

Rajkumar

 

[bibin3210]

Finally got some time to finish the SSE:



Thanks,
Bibin

 

[greenhorn]

why did you switch to hammond OPT's instead of the local ones?

 

[bibin3210]

why did you switch to hammond OPT's instead of the local ones?

Just wanted to try and hear what difference it makes. I still have the local one in another setup paired to my Frugel Horn. The Low and high really improved with Hammond, I still prefer the mids from the local OPT.

Thanks,
Bibin

 

[har297]

@Bibin,

Can you please let us know the input impedance you went with for Hammond Output transformer (3.5k / 5k).


Thanks
Harsha

 

[bibin3210]

@Bibin,

Can you please let us know the input impedance you went with for Hammond Output transformer (3.5k / 5k).


Thanks
Harsha

Hi Harsha,

I went with 5K Hammond (1628SEA), but actually it will work very well with 3.5K if using EL34. Are you going to build one?

Thanks,
Bibin

 

[har297]

Hi Bibin,

Yes, i am planning to build a SSE, now contemplating if it is better to go with 3.5k or 5k.

I want the OP transformers to be useful for other Tube implementations (other SE designs apart from SSE) as well, so considering it as one time investment.

So your recommendation would be 5k in this regard ?


Thanks
Harsha

 

[bibin3210]

Hi Bibin,

Yes, i am planning to build a SSE, now contemplating if it is better to go with 3.5k or 5k.

I want the OP transformers to be useful for other Tube implementations (other SE designs apart from SSE) as well, so considering it as one time investment.

So your recommendation would be 5k in this regard ?


Thanks
Harsha

Hi Harsha,

There is no such all rounder OPT, though it will work but it may not be the correct matching one. 3.5K will work with 300B and 2A3 as well. For SSE you please go with 5K.

Thanks,
Bibin

 

[GeorgeO]

I had a similar discussion with US OPT designer and mfr Bud Purvine, who makes Onetics OPTs. I was contemplating 300B and 45 designs. He clearly said that each tube has different characteristics, and while 300B and 2A3 were similar( not identical), the 45 was a different animal and needed an OPT that was different. To know more about each, you need to spend time and read up a little more about them(like I did). I have a 45 SE(The Wavelength Audio Bugle design) which is very nice, and am now doing the Tom Christiansen, Neurochrome DG300B, which is almost completed-both have different OPTs best suited to each triode.

His observations are reproduced below:
The 300 B and 2A3 have very similar requirements and the 2A3 is far more flexible in it's needs than is the 300 B. The 4.545kZ impedance for the 300B provides you with the widest possible linear transform range. I have included an analysis of the 300B linearity, the measurements at the bottom are just a precision distance between the intersection points.The 45 tube is an odd duck here. Close to the same reflected impedance but about twice the inductance and half the current capability because the 45 is a medium Mu tube and the other two are low Mu tubes.

Each tube's OPT has different characteristics, the winding is different and the prices reflect this-the OPTs for 45s are about 10% more than the 300B or the 2A3 OPT.

Hope this helps you in your journey of understanding!

 

[bibin3210]

One more TubeLab SSE completed, this time went with a solid wooden enclosure. Instead of PU coating (which gives plastic/synthetic feel) I decided to go with oil finish to maintain the natural look and texture of wood.












Thanks,
Bibin

 

[Hari Iyer]

Looks nice and excellent photography skills. Just wondered if the heat from the tubes will be borne by the wooden chassis.

 

[bibin3210]

Looks nice and excellent photography skills. Just wondered if the heat from the tubes will be borne by the wooden chassis.

Thank you Hari, heat from the tubes won't cause any serious damage to the wood. There may be a slight discoloration in the future, but again that color gradient will only enhance the rustic look.

Thanks,
Bibin

 

[sadik]

The Amp looks Very Beautiful

 

[keith_correa]

Looks very handsome Bibin. Well done! Mind sharing more details about the oil finish? Preparation, application, what oil etc...

 

[pugalenthi]

Nice and good finish

 

[anilva]

Superb looking amp. Great finish.

 

[har297]

Awesome looking kit, can you please let us know on the OPT's used .

 

[HormusPeston]

Beautiful work. The finish on the metalwork looks professional. Well done.
Cheers,
~hp

 

[bibin3210]

Looks very handsome Bibin. Well done! Mind sharing more details about the oil finish? Preparation, application, what oil etc...

Thank you. I have used Danish Oil which is now available online in India. Applying oil is an easy task, we can use lint free cloth to apply it over the wood. Preparing the wood surface requires some patience, as we can't use wood sealer it requires lot and sanding to get a smooth surface. I applied 7 coats with a drying time of 5 days between each coats.

There are lot of youtube videos available regarding oil finish.

 

[bibin3210]

Awesome looking kit, can you please let us know on the OPT's used .

Thank you.
The OPTs are made by Mr. Mathews.

Thanks,
Bibin