• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Ultimate Tube head phone amp.

Hi all,

recently I buy one AKG K-1000 headphone amp & test in very good sound. But this headphone was 74db, 120Ohm. Not such tube headphone amp in market can support this headphone. I try several one but still not performance well. So I decide to build one perfect/Ultimate tube headphone amp for my AKG K-1000.

Any circuits or tubes advise.

BTW, I can call Japan OEM for the OPT for this Headphone amp.
Price still attractive, but I hope to get the best for this headphone.


thx

thomas
 
Hi all,

thanks for your advise.

I agreed that many tube head amp in the markets were very good one.

But the K-1000 work perfect in the matching impendance.

K-1000 Spec was 120Ohm & 74db. I hope to use same 120Ohm out tube head amp for it.

This is the circuit that I considerate was use 5965 directly couple with 12B4. it approx had 1.8W class A Output.

Any advise???

thx

thomas
 
K1000 and Zo

One note about the K1000... even though it has a 120 ohm impedance, it really does not sound good at all if you drive it with a "normal" headphone amp, with an output impedance that is very high at all.

AKG designed this to be driven by a very low Zo solid state amp. So, it relies on the amp's damping factor. A high Zo amp makes it sound bright in the highs and weak and flabby in the bass.

Actually, one of the best sounding drivers for a K1000 is a 300B SE amp, driven off of the 8 ohm output tap! Kinda pricey for a headphone amp, bu then again, the K1000 is kinda pricey for headphones!

I've driven my K1000's from the SRPP amp I designed for it (see my web page), and also from my 6B4G P-P amp and my KT88 SE E-linear amp. Actually, the KT88 amp sounded the best to me.

I also tried it on Gary Pimm's 47 P-P pentode amps. It did not sound good there, probably because the pentode amps have a high Zo. Might have been OK if it were placed in parallel with some 8 ohm dummy load resistors.

But whatever you do, make sure you drive it with an output impedance that is very low. Below 8 ohms source impedance is best.

Pete
www.pmillett.com
 
Hi,

I prepare use the tube rectifier circuit.

use EZ80, 5965/E180CC/12av7 to push the 12B4 SE. It will had high purity 1.8W output.

The rectifier circuit will use C-L(10H)-C.

Can anyone suggest me that the filament of the 5965 & 12B4 use AC or DC? headphone need every low noise will increase the s/n ratio.

Hi, I would like to collect some advise that anyone can suggest me use Directly couple between 5965 to 12B4 or use capacitor couple.

The OPT I order to japan already. It will had 0~3K~5K in primary 90ma. Sec will special for me. 0~4~8~16~39~120( AKG K1000)~150~300~600 Ohm. Core will use 0.22mm Hi-B laminations.
The band width was 70~65K -2db.
3K was test in 13H, 5K was test in 20H.
But the DCR looks a little bit high. had 350ohm. I will test & can japan try to lower the DCR otherwise the efficiency will decrease.
is the volumn of the core increase will lower the DCR???

I prepare to private print the PCB. any suggestions???

thx

thomas
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> the DCR looks a little bit high. had 350ohm.

Do not worry about it. That is normal for a transformer that has to carry DC current and also low-distortion bass. To get the DCR lower, you have to accept worse bass. Or a much bigger core with more core loss.

I think you have more than enough power even for those very low efficiency headphones.

In line with Pete's remarks about output impedance, you might want to connect your 120 ohm phones to your 39 ohm tap. On the 120 ohm tap, the headphones see about 60 ohm source. I believe that should be low enough, but Pete thinks it should be lower. On the 39 ohm tap, the source impedance (even including the "high" DCR) is about 20 ohms, surely low enough for 120 ohm phones. Maximum output voltage is about 10 or 11 volts RMS, or about 1 Watt, or 104dB SPL in your 74dB SPL/mW phones.
 
Ultimate Tube head phone amp

hi PRR,

thanks for your opinions. But if the OPT had same output impendence which same as the headphone. will it really better???


Pls see my headphone circuit!!

I tailor made some parts already. I trusted that the volumn control is very important. So I tailor made a 24 steps Ladder type volumn control. They all use 1/4 watts 0.5% accurate metal film resisters.

I was waiting for japan call back! may be the OPT can improve more!

any comment for the circuit?

The dotted line on the circuit means 5965 to 12B4 choose direct couple or cap coupled.

Filament of the 5965 I suggest use DC & regulator by LT1085 the noise may be lower & 12B4 filament was float up but still choose ac filament the sound will more active!

thx

thomas
 

Attachments

  • f3466357.jpg
    f3466357.jpg
    16.8 KB · Views: 321