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I'm still kinda new to tube DIY and I'm planning to build my 1st SET, the 3/4 watt Darling using single stage 1626 output tubes.
Most of what I've read in the archives and the net suggests the Hammond 125E or now the 125ESE (designed for single ended) output transformer.
That OPT is rated 15w....I don't understand why a 3/4 amp needs a 15 w opt?
It's not so much a question of cost but of size....
Hammond has much smaller versions, such as the 125BSE rated at 5 watts.....seems like that should be fine.....or am I missing something here?
Any help with this question or suggestions on the Darling in general would be appreciated.
robert
Follow Ups:
I can second the recommendation on the James, they are really good; fairly cheap as well!
Hello,I have a double DC Darling, with these iron. I chose these iron after seeing Joseph Esmillas report on it. He compared 4 units of 125ese to a Tango (or Tamura?) unit, and found that 3 measured pretty similar to the very expensive iron except the extended freqs. One unit measured poorly. I think they have improved quality control, as we built 3 Darlings with this iron and all do fine. He also auditioned the 125ese vs Tango, and found that the Tango sounded more hifi, but the ese had better tone. My experience is very similar, if you go for typical hifi sound, look for sg else, if you like live music this is the cheap iron for you, and you will be sore until you find an iron with such tone.
A note on the 125ese: the only reason to get this 15w rated unit for a Darling is because you can decrease the gap size by manually adjusting it, thus increasing the inductance, and getting very good base response. I have not performed this surgery on mine yet... however, I heard the best double bass reproduction from a 125ese Darling (not mine), and the best organ reproduction from mine. (Tone and bass quality, speed, imaging, not brute quantity). These units are not hopeless in the base department, perform more life-like than hiend iron which overshoot and present bass in a dry, cold way - live music never sounds like that to my ears.
Good luck with the Darling amps! They are awesome, sturdy, I put 6000+ hrs in mine, and tubes are still strong, n' my ears happy. I am working on several amp projects at all times, but the Darling stayed the main amp all the while. If you build, I very warmly recommend building the direct coupled version, and use single driver speakers.
janos
Kelly:
There are many transformers out there available to you. I have used the James transformers on my Double Darling. They measure and sound very good.I also feel that there's real value there. You can also look at the Hashimoto brand of iron. They are more money, but excellent!Regards,
George
http://tubesusa.com/glcorner.html
...and it depends on how you measure them. Hammond MAY measure at 1kHz sine wave, 10% distortion (guitar amp?) - whereas you want 20Hz-20KHz, maybe 1% distortion. I think Paul Joppa of "Valve" magazine measured this transformer and rated it at 0.5W for "HiFi" use.Hope this helps!
I tested the 125E - man, that was YEARS ago!. It is not an air-gapped design, and it falls apart pretty quickly when running DC current.The 125ESE, and in fact the whole 125-SE series, ARE air-gapped. (Note the 125ESE is much larger than the 125E.) The only one for which data are provided is the ESE, and it has a bit less than 10 henries inductance. That's just barely adequate for 2500 ohms; using it at 5000 ohms means the bass will suffer. Read the notes on the Hammond page; they are very up-front and honest about what these transformers are and are not! The design philosophy is probably similar among the various units, and I would expect them all to have nearly the same primary inductance. You can pick a smaller one as long as it's rated for at least as much current as you plan to use (I forget the Darling current requirement). The difference will be small; a smaller unit might have slightly more extended treble.
The winding geometry is uncomplicated, which means the treble is limited in extension. Fortunately it also means the capacitance is low, which often results in what treble is there being fairly sweet sounding. As I recall (many years later) the 125E had pleasant treble.
Why not get a cheaper, smaller one, and leave room for a hifi transformer in case you really like this little amp? Have fun!
you have all given me some very helpful points to consider. I have a decent electrical background and understand the various relationships between power/freq/inductance etc, but when it comes to applying it to diy audio quality I am very much on a steep learning curve.....although I have no doubt that using the right stuff makes a difference.
I will certainly ponder all of this information before I move forward.
thanks
robert
I expect the choice of a 125SE was because many DIYers probably had a pair laying around rather then the 125SE being exactly the spec needed. Sometimes people use larger Hammond universal output transformers (like the 125 series) then they need hoping for better bass from bigger iron. If your budget can swing James 6115s at $145, slightly more then twice the 125ESE price, they look better and are almost as universal for future projects. But its a great sounding amp reguardless off the outputs you choose and you will enjoy building it.
Matt
and thanks for the James OPT suggestion also, I'll consider it.
I am also building my 1st SET & a DARLING also, keep in touch..I allready have used 5k SE OT's to use, so I am good there, also have the tubes, just need my PT. I am not sure on your question though, so I am of no help.
Cool, lets get in touch. You can e-mail me through the forum. This project is going to be a slow one for me (too many projects already)but I have all the tubes (1626 and 6J4WA)and the wood work and metal work is a cinch, so I'm going to decide on some xfmrs and get it started.
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