My brew of the "Darling"

[arnoldc]

I made my first ever online order for a tube project some 4 years ago. That order is for a JE Labs 2A3 which was sent to Angela.com which also contained a pair of 8532 and 1626 - parts for the Darling amp.

I haven't put those tubes to use since the order arrived.

Yesterday, while I was waiting for my students to finish ther labs, I started scribbling something, which ended up like this-

(photo was taken after I completed the amp)

[arnoldc]

My chassis has only one hole sized for for a 9-pin tube, so I cannot use my 8532 on this circuit, as they're 7-pin and single triode. My bias towards the 407A sonics on my preamp led me to use a close "cousin" - the 2C51 (while I also have the Western Electric 396A, it will be put to service later) which is a 9-pin dual triode with 6.3V filaments (unlike the 20/40V of the 407A).

I got good results using the diyAudio CCS in my other project, so why not use it again. While my "RS Components design tool" shows the CCS set at 8mA, the actual circuit had 10mA because I don't have a 125R resistor. Tonight, I will put in a Bourns multi-turn variable resistor so I can dial it in at 8mA.

SY was a big influence on my choice with regards to biasing, so the 2C51 was biased using Yellow LEDs which should give me 2V or so.

I decided not to re-invent the wheel and went ahead with the original bias scheme of the 1626- a shared 500R, bypassed by a capacitor.

I have some left-over power transformer and output transformers (5K:8/16R) from a previous 807 project which I re-used for this amp.

Just before midnight I was able to complete assembly, did some voltage measurements which came very close to my scribble. With that, I hooked it up to my speakers and played some music.

[arnoldc]

Like most of my projects, there are no exotic parts, even though I'm tempted to use my Riken resistors and MultiCap RTX coupling caps.

You'll see on the photo that my 1626 cathode capacitor is a white-coffin bypassed with a generic 220uF electrolytic. The coupling caps are Auricaps, and the power supply is a simple CRCRC with generic electrolytics and white coffin as well.

By the way, there's 1K grid stopper to the grid of the 1626 (not in schematic) because my 220K grid leak resistors have too short leads

So how does it sound? It has a different character which I tend to like, sweet and mellow, for a change. I can't play really loud as my neighbors might complain but the vocals reproduction is glorious. It does not have the punch and kick of my 2A3 or 45, but it does bass deep enough to give me some satisfaction.

[Sal Brisindi]

Great job on the amp, nice, simple yet elegant. I have parts to build a Darling so one of these days, month or years I will get to it... :-)

Regards,
Sal Brisindi

[alexg]

That amp looks great!

Is the 2C51 similar to 5670? How much voltage swing you need to drive the 1626?

I would like to make one like your Darling!

Arnold, question: which in your opinion would sound better a 1626 or a 12b4 flea powered amp? Thanks.

[arnoldc]

Hi Sal, yes, it took me four years to do this

Hi Alex, you're right about 5670. I just need some 60Vp-p to drive the 1626.

On the 1626 vs. 12B4, I can't comment because have not made a 12B4 amp yet, but you're tempting me. However, the 1626 with its ST-bottle is physically very attractive for me

[alexg]

Originally posted by alexg
That amp looks great!

Is the 2C51 similar to 5670? How much voltage swing you need to drive the 1626?

I would like to make one like your Darling!

Arnold, question: which in your opinion would sound better a 1626 or a 12b4 flea powered amp? Thanks.

I know you like the 12b4 and I thought about you yesterday while looking at a 12b4 amp circuit, producing almost same power as the 1626.

[arnoldc]

Which one is that? The one driven by a 6AU6?

[alexg]

Originally posted by arnoldc
Which one is that? The one driven by a 6AU6?

I have not seen the one with the 6au6 driver, the one I was looking at is driven by half a 12ax7. It said to produce 0.9watt.

Am really tempted to do this 12b4 amp.

[arnoldc]

Ah, you're talking about the Abraxas audio I believe. Did he designed it for full range use?