My Little Darling amp

[Sal Brisindi]

Here is my first Darling amp I put together last night. I only drilled the holes and mounted everything so now its time to wire it together. I am going away on business this week so I will assemble it in the hotel room. I'll update this post when I am done. Its built on a compact chassis 10"x6"x2".

Regards,
Sal

PS: I completed the amp and here is the updated photos of it.

[TomMcNally]

That looks good on the small chassis Sal -
what are the output transformers ?

[SDS-PAGE]

Those OPTs seem to be the TF103-48 SE Champ OPTs available at Tiode Elec: http://store.triodestore.com/tfchxfwi48oh.html.
I wonder what would be the smallest Darling one can make? So, you're using LeBong's version with 12SL7, Sal? Good job! -Min

[TomMcNally]

I made a couple of 5 x 8 x 3 Darlings with no ugly transformers showing.

[Sal Brisindi]

Thanks for the compliments,
I would have used my Edcor 15 watt transformers I bought for this amp but the Edcor transformers are larger than the Hammond transformers and since I bought a 2" high chassis, I could not hide them. That is why I used the Triode Electronic transformers I had on hand. They are rated for 100hz-20khz at 5 watts so I am hoping the bandwidth would go a little lower for a little more bottom end.

I personally like the transformers on top of the chassis, maybe I should paint the audio transformers black to match the power transformer.

Tom, transformer beauty is the eye of the beholder... Yellow_Light_Colorz_PDT_08

Sal

[TomMcNally]

The transformers look pretyy cool with the thick candy style
paint Soren and others have done. Actually, the reason I
hide the open frame jobs under the chassis is safety. Yellow_Light_Colorz_PDT_16

[EWBrown]

Those little "champ" trannies should do pretty well with the relatively low Darling amp power levels around 750 mW.

Looks good!

/ed B in NH

[Sal Brisindi]

Ed,
Thats what I am hoping.

Thanks,
Sal

[EWBrown]

I'm still thinking of trying a PP version, using the 6SL7 / 12SL7 PI circuit from the 1949 ARRL Radio Amateur's Handbook. Might as well keep the circuit design to WWII-era standards, since the tubes are of that vintage Yellow_Light_Colorz_PDT_06

From the description on Triodes pages, it appears that this trannie will have improved overall freq response with less plate current - IIRC the 1626 runs around 25 mA.

/ed B in NH

[hembrook]

I wonder what would be the smallest Darling one can make? -Min

My vote goes for http://www.roehrentechnik.de/html/darling.html

That is one small Darling.

[Pyre]

My vote goes for http://www.roehrentechnik.de/html/darling.html

That is one small Darling.

Interesting, has anyone else made a Darling with a 717A driver? It looks like a mushroom.

[hembrook]

713A and 717A are basically the same tube, the 717A just adds a metal shield and 8th pin to the base. They were designed back in 1943 by Western Electric (but made by Tung-Sol under contract) to have the shortest leads possible internal to the tube for HF use in radar. They happen to amplify audio signals really well, and 713As are not terribly expensive ($8 a pop in quantity). I think they are mostly in the 50 year old range, but some were made as late as the 80s. They were replaced with the 6AK5 in a conventional envelope on a 7-pin mini base

"Western Electric introduced this WE-713A pentode in 1943. It was called a "mushroom" tube, for obvious reasons. Although it has a standard octal base, the electrodes are mounted horizontally inside the small envelope, to allow short connecting leads for high frequency operation. It is a predecessor of the miniature type 6AK5, which was used extensively in radar receiver IF amplifiers from WW II onward."
http://www.hem-usa.org/web-gallery.shtml

[EWBrown]

Sal,

How do those TF-103s sound? I just bot a pair of them fromTriode, originally for something else (EL84 UL "noise maker" but maybe I'll Darlingize them... Then the Chinese "specials" will do for the El84s...

I also got a similar set of small Chinese 5W, 5/7K SE OPTs from "Musical Power Supplies", they should arrive friday or saturday. These are really teeny...
But then the low price was just "tempty" enough to go for the plunge... Yellow_Light_Colorz_PDT_06

/ed B in NH

[hembrook]

Its small, but its rated for 5W, so I figure it can handle 750mA

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0001769473

It has a 7.5k primary, which is good for Darlings, I guess, with a 1626 tube. What are popular impedances for 1626 SE outputs? I have seen 5k and 7.5k


I think the little transformers I bought would also work for a SE PCL86, I think.

[Sal Brisindi]

Sal,

How do those TF-103s sound? I just bot a pair of them fromTriode, originally for something else (EL84 UL "noise maker" but maybe I'll Darlingize them... Then the Chinese "specials" will do for the El84s...

/ed B in NH

Hello Ed,
So far the amp sounds pretty nice with the cheapie Radio Shack speakers I have connected to them. I tried the amp on a pair of KLH model 23 speakers but the amp could not drive them so well. I am away on business again so I didn't try them on my 96db Cerwin Vegas D5. I will get to that sometime next week. I will also put a scope and audio generator on it.

I updated the photo above to show the finished product.

Sal