I want to build a stereo headset valve amplifier

[Don_Zalmrol]

Hello,

A recent topic (here) of mine revealed to me that my valve amplifier kit is not suited to power a headphone.

But being used to the sound created by this amplifier I do not wish to part from it.

So now I'm looking to a way to make my own headset amplifier.

Now some posters advised me to build my own amplifier from scratch, I'm interested in this kind of subjects but am a bit afraid for ruining the project by a huge error/ fault of my own. And thusly the costs will up for buying the new replacements parts or if the sh*t hits the fan that everything would be busted!

I know a thing or two about electronics (mainly kits from Velleman, school, …), but not on the subject on making something like this. I know that home-brewed amps can give extra's to the design. But I'm looking to something straight forward, good quality and durable.

The headset I'm using is an Sennheiser HD558 which works on 50 Ohms of impedance.

I've been looking at some available kits from the internet and came across some interesting kits:

- Bottlehead amplifiers from the US
- Mableaudio

The amplifier (VT-96PP) I currently have is from Mable-audio although the name is nowhere stamped on it (it says Jukebox-Revival from the store I bought the kit) and the ones of interest are the:

- EL84/12AX7
- 6V6 /12AX7

Which give me the option to use my headphones continuously or power a small speaker system, which sometimes would be nice. But mainly I will use my headphones!

So I like to hear from you what is better a kit or home-brewed?

Thanks in advance!

[mrmagnetophon]

Well If your really dead set on putting a valve amplifier together, i would not do a kit, a 6v6/12ax7 schematic is easy enough to put together and give you enough power to supply some rather efficient speakers/ headphones .
-Chris

[Don_Zalmrol]

This is also what Mable-audio suggests to me.

And from some googling, it seems that the 6V6 lives longer than an EL84.
Because the EL84 tends to be more sensitive to overdrive.

Thx!

[murphyv310]

Hi.
The 6V6 is very much an Icon. They were made in droves and powered many speakers in umpteen amps, radios and TV sets etc. Their reliability is legendary! There is no reason why you shouldn't use 6V6's in your headphone amp as they can be run in a leisurely way and last indefinitely. A circuit on the lines of the Mullard 3-3 would be ideal as it is very high quality and low distortion and works very well with a 6V6 and to keep the appearance an EF37A.
Good Luck.

[Herald1360]

I'd say home brew, or at least home build. The EF37A/6V6 3-3 clone sounds good if you fancy a retro look- you have a potential choice in either valve of straight sided cylindrical or classic bottle outline, plus a nice red jacket on the EF37A! In fact that's one of those "now there's an idea" suggestions that might fit my junk box stock (except for the O/P TX)

The original EF86/EL84 3-3 would be more suited to building in the same style as your existing amplifier, though.

[jay_oldstuff]

Both have merits, you will learn much more home brewing an amp. But you will have an easier time constructing a kit.

Jay

[jjl]

You only need a few 10s of milliwatts in order to drive your headphones to deafening levels.
With that in mind, there is no need to build a valve amp that can output several watts to drive your headphones. In order to safely be used, you would still have to waste nearly all of the 3 or 4 watts that a single ended EL84 or 6V6 could provide.

John

[Don_Zalmrol]

Allright I'm starting to get a picture about what to do.

Time is not the problem.
The 6V6/12AX7 kit would be available for delivery in 3months…

So I'm looking at home build system from scratch.

The main properties I want from the home build system is:
- Very good/ Excellent quality sound
- 2 stages or maybe 3
- Simple sturdy construction
- Durable in usage

The headphones amplifier would need to do the following:
- Single input
- Headphones output
- Volume adjustment (notice that I still use the Sennheiser HZR-62 volume controller)

I can get most (practically all) parts from Jukebox-Revival or other stores locally. Chassis is not a problem also, just the design of the circuits is my problem now.

[Don_Zalmrol]

Perhaps something like this?
It's based on a ECC86 design using double triodes

It's derived from the very very very expensive Earmax pro that costs $ 895'

Sorry for the above link, it's in Dutch. But the pricing comes around +- € 100'

Is it difficult to build this one?

[jjl]

Dat is geen probleem, ik spreek een beetje Nederlands.

Yes, that would give the right sort of power levels for headphones, although the circuit is a little odd looking. The ECC86 is not a common valve, I'd advise look around for circuits using the ECC82 (12AU7) or ECC88 / E88CC (6DJ8) or similar.

John

[Don_Zalmrol]

Haha, leuk om te weten

Is something like this better? It uses two ECC82 valves.

Or this one uses a single ECC82 valve.

@Herald1360 Do you have a link for something similar for powering headphones?

[DangerMan]

Why not just provide your present amplifier with a resistor load, about 8 ohms, and then continue to run your headphones from it, at least for now.
Whatever valve amplifier you build you will need to provide a load resistor anyway (with very few exceptions) unless it is a very low power one.

Just run your 'phones from an attenuator connected to the output as well as the load resistor.
A lot of commercial amplifiers used a simple resistor (about 330 ohms, one per channel) connected in series with the headphones across the 8 ohm outputs.

Pete

[Hunts smoothing bomb]

Hi,

The homebrew route will teach you much where as I've found that building a kit from a set of instructions you just place parts together and don't really understand why, plus with homebrew the only limitations to the design are what you have thrown in the mix! where as with a kit you are tied to the one way that the designer wanted the end product to finish up like. (circuit wise anyway)


I also agree with Pete's comments above about building an attenuator.
Cheers

[Don_Zalmrol]

well that resistor was the problem in my circuit. The amp started acting strangely with overheating the #2 valve (E34L). When I removed the output (with attenuator resistors) for the headphones and "tuned" the bias, the problem was gone.

And with this amp I'm throwing away the capacity of the amp for only powering a headphone and not only speakers. (40Watts powering only a headset, it's like swatting a mosquito with a cannon…)

So I've decided to use this amp for something else and build myself trough a home-made or kit amplifier that only powers a headphone.

[glowinganode]

If you're only running high impedance headphones (50ohm?), you may like to think about OTL (Output TransformerLess) designs, which don't require an output transformer.
Rob.

[Don_Zalmrol]

Ah, that would be the case.
The headphones I'm using is a Sennheiser HD558 which uses the 50 Ohms design

[maninashed]

Hi Don,

Have you had a look on eBay? You can buy a ready built one for £40, roughly €50 and that would do the job perfectly. You could always play about with the circuit, with the help of the chaps on here and save yourself a lot of time and money.

Bill

[Don_Zalmrol]

yes, but most of them are for guitars or just to powerful for headphones…

[Sideband]

Here is one I'm seriously considering building just for fun. I have quite a few ECC82 valves and wanted to use a couple in something useful.....http://webhtb.ro/aygun/otl%20headphone%20amplifier.pdf

I will use a hard-wired chassis rather than a PCB.


Rich.

[murphyv310]

Originally Posted by jjl

You only need a few 10s of milliwatts in order to drive your headphones to deafening levels.
With that in mind, there is no need to build a valve amp that can output several watts to drive your headphones. In order to safely be used, you would still have to waste nearly all of the 3 or 4 watts that a single ended EL84 or 6V6 could provide.

John

Hi John.
I totally agree with you, but I also totally disagree with you. It's the old story that if you let any thing "tick over" it is likely to last a long time and in an amp that is not driven too hard will give extremely low distortion and high quality audio.
I stick to my guns that one of the best amplifiers is the Mullard 3-3 and I would be shocked if anyone said otherwise, I also stick with my EF37A and 6V6 line up, both the 6V6 and EF37A are legendary valves for long life, low noise and aesthetics.
A 3-3 fed into a proper load and attenuator will amaze!

This thread has spurred me on to build my own stereo 3-3 using 2x 6V6G and 2x EF37A. A silicon HT supply (full wave) with output for speakers and headphone. I should have everything here with the exception of some sheet alloy to make the chassis.