The Sopht Good Girl

[liddokun]

Does anyone have any experience with this circuit? I did a search and could only find info on the 12v project.
It's posted here:

http://www.sophtamps.ca/mambo/index.php?option=com_content&task=view&id=35&Itemid=50

Including the 12v sopht amp, I am also interested in building this one. I've been looking for a nice clean amp, this seems to be it. Looks to put out close to 18 watts from the description, and is designed to be super clean.

I'm just a bit confused as to which power transformers and output transformers to get. For power, the voltages are listed:
Wall : 123.6V
B+: 388
B+1: 376
B+2: 361
b+3: 260

I guess the primary is there, what kind of secondary am I looking at? And for the output transformer, what would be a nice one to get?

[GibsonGM]

Neat little amp there, looks like something to mess around with!   The power transformer is a Hammond 270EX,   Output is a 2.5K to 8ohm.  You can find these at Antique Electronic Supply (think the URL is www.tubesandmore.com)

The data on the 270EX says its' a 275v output, center tapped.   The 123V is AC line in from the dude's house,  388 is right after the rectifier (secondary), B+1 etc are shown on the schema.  The voltages are higher than the rating of the transformer because the filter caps charge, and with the type of rectifier/filter used, it boosts the voltages before and during filtering.  It should also have a filament winding to power up those heaters, not shown on the schema. 

For the output tranny, possibly a Hammond 1627SEA.  I would write to the guy from the site to ask if that is an appropriate one...it's in the right range for power and impedances, but couldn't tell you what he used!  IIRC, he's pretty friendly about giving that info out.

Good luck, looks like a fun project!! 

~Mike

[liddokun]

Thanks for the info mike. Those transformers are pretty pricey eh? The 1627SEA is $120. Yikes. I wonder if there's any less expensive alternative...I still have to purchase tubes, the chassis, and hardware too.

[liddokun]

Just one more quick question, might be a bit noob. Where are the heaters getting voltage from?

[slacker]

The power transformer has 6.3 volt taps that provide the heater voltage, it's just not shown on the schematic.

http://www.hammondmfg.com/pdf/5c0026-27.pdf

[liddokun]

Right. Should have looked at that first. That's all I needed to know. Thanks.

[liddokun]

I did a bit of searching...the most expensive part seems to be the output transformer. The 1627SEA seems to be the best one, but would the Hammond 125J work as well?

[liddokun]

Alright.

For those interested, I emailed Stephane, the designer of this amp.

For the power transformer, it's the 270EX, and for output, you have 3 choices:

Hammond 125 FSE, Hammond 125 GSE, or the Heyboer 20W transformer from Doberman amps (http://shop.dobermanamps.com/category-s/27.htm).

Tubes and more carries both 125 FSE and GSE, GSE is cheaper, as well as the 270EX.

Doberman amps carries both Heyboer 20W tranny and the 270EX.

Cheers

[mth5044]

Any updates? did you end up dropping the project?

[liddokun]

mth, I posted in your other thread about low wattage high headroom. I am planning on building this project in the summer, once I have enough money to do so. Hopefully.