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Old 18th January 2013, 03:51 PM   #441
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I think 16 ohms tap isn't suitable for my 300 ohms headphones.
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Old 18th January 2013, 03:56 PM   #442
cotdt is offline cotdt  United States
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Quote:
Originally Posted by merlin el mago View Post
I think 16 ohms tap isn't suitable for my 300 ohms headphones.
You need custom 300 ohm transformers then. There are several makers who can do it for you. It is a good lifelong investment.
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Old 18th January 2013, 04:00 PM   #443
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What specifications I have to give him the manufacturer of custom transformers?
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Old 18th January 2013, 04:08 PM   #444
cotdt is offline cotdt  United States
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You can go a little overkill on the transformer specs:

7k:300 ohm
60mA (in case you want to use 300B later on)
10W
30Hz to 50kHz (-3dB points into 1W)
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Old 18th January 2013, 04:11 PM   #445
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Many thanks
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Old 18th January 2013, 05:40 PM   #446
regal is offline regal  United States
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Quote:
Originally Posted by merlin el mago View Post
regal how many mA needs the Senns?

Wich one Sowter is more suitable for HD600?

TRANSFORMERS FOR HEADPHONE AMPLIFIERS

For preamp I will need other transformer like the Lundhal LL1660 that I have purchased for #26 preamp, right?

Summarizing what are the necessary best spec for HD600:
-application SE
-ratio
-primary impedance in ohms
-secondary impedance in ohms
-primary inductance in Henry
-power in watts at 50Hz
-DC mA
-core
For sowter and senns you can specify a transformer that could meet both preamp and headphone with one secondary winding. They seem one of the few transformer companies I have corrosponded with who understand headphones. You can fill out their request form and be generic, let them know you want minimal primary loss (small core) and minimum secondary dcr/inductance. I would go with a 7k:300. Then they will work with you from there. Bud at Onetics is also good.




Quote:
Originally Posted by cotdt View Post
For headphones, you need to figure out how much voltage swing you want and see wether a custom transformer is necessary. If you need less than 12Vrms, then a standard speaker transformer is the way to go. Some have 16 ohm taps.

Part of the tube sound comes from the transformer. It fattens up the waveform slightly, which gives warmth and soundstage expansion (very desireable for headphones), while being much quicker-sounding than a big electrolytic cap. I would describe a transformer as transparent but slightly colored, while capacitors are neutral but not transparent. For preamps and headphone amps, I much prefer transformer-coupled.
A 16 ohm tap with senns (300 ohm) would be a real compromise, remember your load is reflected to the secondary so you end up with a crazy damping factor, and transformer quality is inversely related to winding ratio, so you can do much better than running a 300 ohm headphone on a 16 om tap. Not only that but you get into ringing and all sorts of non-linearity with a mismatched impedance.

Don't forget that the less voltage the output tube swings the less distortion, another argument for a smaller step-down ratio. Headphones really reveal when the tube is swinging into the non-linear portion of the load-line (where the tube curves are compressed.)

I agree fully that a transformer coupled SET sounds better than a 470uf electrolytic cap couped OTL, especially with digital, there is "something" about a transformer that just fits. Good headphones can be incredibly revealing and down-right superior to speakers if you are into listening to soloist midrange like female vocals, strings, and brass, there is nothing lke it, it is very rewarding.

Off topic but I did have good luck with a fuuterman OTL using big 100uf oil can caps for 300 ohm senns but I always missed that SET sound (too much stuff in the single path.) And I'm not I senn guy.

My conudrum with the 4p1l is I basically have two headphones I like: Grados (32 ohms, need only 30 mW of power and require the most absolute quiet noise level) and HifiMan HE5LE's that are 38 ohms but need 1W to 2W of power. The 4P1LE doesn't quite operate at a high enough voltage to deliver 2W peaks into 38 ohms. I am a big fan of NOS russian tubes, a 4p1l-2c4c (or 6c4c) is what I am leaning toward. I regulator like the SSHV is almost a requirement for a black background with the Grados, as is a coleman for the filaments.

One other gotcha that is same for preamps is the power transformers have to be 3 ft away from the output transformers else you get mains hum pickup.

I still haven't pictured how one can do that and have coleman filament regs, almost need three chassis which is sort of a grounding nigtmare. But this is fun stuff
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Old 18th January 2013, 06:01 PM   #447
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Yes, I would use 3 chassis for such a project.
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Old 18th January 2013, 06:03 PM   #448
iko is offline iko  Canada
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My 26 preamp uses the Coleman regs but the transformer for them and for HT is in a separate chassis, a meter away. Yes, can be done.
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Old 18th January 2013, 06:16 PM   #449
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Quote:
Originally Posted by regal View Post
The 4P1LE doesn't quite operate at a high enough voltage to deliver 2W peaks into 38 ohms.
It does if the transformer has the right ratio, which is (I suppose) what you meant. The voltage out of the 4P1L is going to be stepped down thru the transformer anyway. Might as well step it down to the ratio you need, right?

Is damping factor really that important with most headphones? Maybe with the ear speaker type, but with more normal headphones?
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Old 18th January 2013, 06:28 PM   #450
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Hey, has anyone compared 3A5 with 4P1L? Andy?
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