One more 4P1L SE

[regal]

Originally Posted by merlin el mago

Tango NP-126 can be OK for headphones OPT transformer?

I am a headphone amp transformer pessimist, I don't think any off the shelf OPT's are really suited for headphones, You really have to custome order and it gets expensive, even then there are issues. All depends on your expectation level of course.

Hope is that transformer outfits will see the error in there ways and start offering OPT's designed from scratch for headphones. And then the other issue is the impedances and efficiencies of different model headphones vary exponetially model to model that it turns into a very frustrating dive.

[merlin el mago]

You do not give me very much spirit to do the headphones amp. Transformers are expensive so if I'm not sure I don't wanna lose the money, I will keep wiht my OTL hadphone amp.

[Pano]

I've had the output stage of my amp running for a few days - hoping to finish up the input section this weekend. The output stage sounds great driven by a simple line level signal. Not very loud, of course, but clean and nice. Works great for headphones.

I'll try to get some harmonic distortion plots and post them here.

[regal]

Originally Posted by merlin el mago

You do not give me very much spirit to do the headphones amp. Transformers are expensive so if I'm not sure I don't wanna lose the money, I will keep wiht my OTL hadphone amp.

Well even the basic Electra-Print SET transformer sounds better than a OTL+ cap so I don't mean to be that pessimistic, its just that you must have a pair that you like and want to live with because another model won't work due to impedance mismatch. There is real magic with SET for headphones its just more expensive than building a preamp.

[Pano]

Since headphones need very little power and not a lot of voltage, what sort of output would you want from a headphone specific OPT?

[merlin el mago]

Good question, I have the same question for my Senns HD600 300ohm?

[RajkoM]

Originally Posted by regal

This is why the 4p1l driving another 4p1l is such an attractive proposition. And if you have a balanced source an input transformer can even drive a 2A3 with a 4P1l. Want more? balanced source -input xfomer- 4p1l -1:2 interstage -300B. All DHT two stage tube 300B SET! Its such a fabulous tube.

Yes. 4P1L as a driver have unlimited possibilities. This tube is a miracle.
Pentode driver for 300B you can see in my post no. 396 of this thread.
Will try it in my 300B SET when I get in this tube, and when I have more time.

Rajko

[regal]

Originally Posted by Pano

Since headphones need very little power and not a lot of voltage, what sort of output would you want from a headphone specific OPT?

This is actually a common misconception. For example the hottest high-end headphone right now is an HE-6. It takes a serious 6Watts at 50 ohms. Thats more voltage swing than a 35 watt amplifier. Only a 1000V GM70 SET can deliver that sort of Voltage Swing properly. They are really a ss amp only type of headphone.

For senns they are efficient so you may be able to get away with a 5k:300 preamp OPT. Just watch the secondary DCR, a 300 ohm secodary can kill your damping factor and power transfer.

Even 32 ohm 97db/mw headphones are a problem, I had a pair of custom electraprint 5k:32. Secondary DCR is 12 ohms So I am losing 1/3 of my power down the drain, if I had known that I wouldn't have designed my SET around a we417.

I guess what I am trying to say is make sure you love your headphones cause you have to build the SET amp for the specific model and start with the OPT. Its very difficult to build a one size fits all.

With speakers sometime in the 60's all the manufacturers got together and said "we will make 8 ohms the standard" at the same time headphones were all standardized to a 120 ohm "tap", but the last decade that standard has been thrown out the window. So designing an amp for headphones is really tougher than speakers (if you want the best.)

Main thing is define your scope of work, the beauty of DIY is we can build to match. I definately think the 4P1l would be an ideal output tube for senns, just finding the right OPT will take some legwork, but it should be able to serve double duty as a preamp.

[merlin el mago]

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

[cotdt]

For headphones, you need to figure out how much voltage swing you want and see whether 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.