One more 4P1L SE

[regal]

Originally Posted by Pano

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?

Well the Ra of the 4p1L isn't particularly low, so you need quite a bit of inductance, and you need to step down to 38 ohms. So you are looking at a 5k:38 OPT. So 11.5:1 ratio. Two watts into 38 ohms is 288 Vp-p across the primary, no way the 4P1L can swing that without A1/A2 and hitting the ugly portion of the curves, imho anyway you look at it its not a big enough "upgrade" to my 6c4pi/5842 spud amp.

Originally Posted by Pano

Is damping factor really that important with most headphones? Maybe with the ear speaker type, but with more normal headphones

damping factor effect depends on the headphone driver design. Most modern headphone drivers have been "tuned" to modern SS <2 ohm opamp output impedance.

Simple tests which have been done adding resistors in series have been shown to change the frequency reponse. Not saying its black and white, but damping factor is an issue in how the transducer reponds to power.

The biggest issue as a tube guy is all the signal loss with a high DCR windings, its just that much harder the output tube has to "work", more distortion. And headphones reveal it.

[Pano]

Originally Posted by regal

So 11.5:1 ratio. Two watts into 38 ohms is 288 Vp-p across the primary

OK, but I see only ~9V needed for 2W peak into 38 ohms. Or 206V P-P on the primary. That just details. Whatever the output impedance of the OPT, 2W is going to be pushing the 4P1L, agreed. Wavebourn seems to indicate it's OK up there, but I've not pushed it that far yet.

Honestly, I don't want headphones that need two watts to function. My speakers hardly need that! If I did like them, I guess I'd do like you and go for a more powerful amp. My OPT has a 600 ohm winding, might be interesting to hear what that sounds like on 300 ohm cans.

[iko]

Originally Posted by Pano

Honestly, I don't want headphones that need two watts to function.

+1

[Wavebourn]

Originally Posted by regal

no way the 4P1L can swing that without A1/A2 and hitting the ugly portion of the curves, imho anyway you look at it its not a big enough "upgrade" to my 6c4pi/5842 spud amp.

Huh? Which ugly portion of the curves? I'm asking once more: did you ever dare to read the topic from the beginning?

I started this topic to share with you how I got 2.5 W of pristine clean power from one 4P1L tube, and 5W from 2 in parallel, why start again from common musings about common tubes according to common beliefs?

Nobody needs 300 Ohm secondary to drive 300 Ohm headphones that need milliwatts of power. But to drive 50 Ohm 2 W you indeed need 50 Ohm secondary. To drive 32 Ohm 2 W you need exactly 32 Ohm 2W secondary. To drive 5W 50 Ohm headphones you need 2 tubes in parallel and 50 Ohm secondary transformer.

By the way, I found a company in Russia that will make me 32 and 50 Ohm 2 and 5W transformers for headphones. Stay tuned.

[Wavebourn]

I don't see here any "ugly portion of curves". Up to +16V in class AB2 they look nice. As I said, in AB2 driving up to +12V I was getting 2.5V from the tube. In A1 only output power can be obtained around 1.8 W from tube. Why I made the A2 capable, because it's hard not to hit positive voltage on control grid of the output stage on peaks, that means non-linear grid current, rectification of signal, and dynamic change of bias point.

Here again, triode curves that show how nice is the tube when driven in class A2 mode:

[FLT]

Originally Posted by Wavebourn

By the way, I found a company in Russia that will make me 32 and 50 Ohm 2 and 5W transformers for headphones. Stay tuned.

Nice to hear...
What about output transformers for power amps?
I always wanted to build an "all-russian power amp"

regards...

[merlin el mago]

Originally Posted by Wavebourn

Huh? Which ugly portion of the curves? I'm asking once more: did you ever dare to read the topic from the beginning?

I started this topic to share with you how I got 2.5 W of pristine clean power from one 4P1L tube, and 5W from 2 in parallel, why start again from common musings about common tubes according to common beliefs?

Nobody needs 300 Ohm secondary to drive 300 Ohm headphones that need milliwatts of power. But to drive 50 Ohm 2 W you indeed need 50 Ohm secondary. To drive 32 Ohm 2 W you need exactly 32 Ohm 2W secondary. To drive 5W 50 Ohm headphones you need 2 tubes in parallel and 50 Ohm secondary transformer.

By the way, I found a company in Russia that will make me 32 and 50 Ohm 2 and 5W transformers for headphones. Stay tuned.

The Russian company will make 300 ohms transformers?

[regal]

Originally Posted by Wavebourn

Huh? Which ugly portion of the curves? I'm asking once more: did you ever dare to read the topic from the beginning?



By the way, I found a company in Russia that will make me 32 and 50 Ohm 2 and 5W transformers for headphones. Stay tuned.

Ugly is a harsh word, its just that with orthodynamic headphone they have much lower itrinsic THD than speakers so you hear distortion much easier. The 4P1L is extremly linear over all. I just can't seem to explain that its Ra is not low enough to drive an orthodynamic driver 25Vp-p, but thats OK its an unusual situation.

If you find a transformer winder please do share, I too am interested in an all russian tube amp.

[stajo]

Originally Posted by regal

If you find a transformer winder please do share, I too am interested in an all russian tube amp.

200:ish would be my choice as I have a pair of DT 931. Heres a little infosite on headphones. Pretty nifty. Meier Audio

Staffan

[regal]

Originally Posted by stajo

200:ish would be my choice as I have a pair of DT 931. Heres a little infosite on headphones. Pretty nifty. Meier Audio

Staffan

Great summary of what I was trying to comnumicate, now imagine headphones with specs like 32 ohms 98 dB/mw, or 600 ohms 94 dB/mW or 50 ohms 87 db/mW all tuned for different output impedance, all "liars" on their specs, and all offering lower distortion greater transperancy than the most expensive hand crafted speaker.

Then you see that you really need to "customize" your 4P1LE SE OPT to match your headphone of choice.

With the 4P1LE output it would power 90% of the all the high end headphones with the right output transformer. But its lower voltage rules out some orthos like the HE6 with its super strength rare earth magnet,AKG K1000's, and it rules out electrostatic headphones of course.

Senn and Beyer guys are lucky because those headphones match well with preamp configurations.

But as a positive the 4P1LE's lower plate voltage offers the opportunity to parafeed, imagine a nickle permalloy OPT for headphones, I would love to hear such a thing.

There is also the MGM engineered peerless tl404 autoformer, probably the only output iron really designed for headphones. But if anyone finds a pair I get first dib


Amonst all this discussion about impedance matching we mustn't forget that sensitive headphones must have a black background, no 60/120/180hz hum or buzz at all, my rule of thumb for Grados is that stuff has to be -90dB down.