• 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.

my first valve amp

Hi all,

I always loved fixing cars, electrical appliance and DIY in general. So I decided lately to make my own Valve (or tube, in fact is there a difference?) Amplifier after my old hi-fi finally died (an old Amstrad, had it since I was a teenager).
I am not a sound quality specialist (You could probably tell from the brand of my old hi-fi). In fact I am pretty tone depth (can’t tell which key on a piano is lower or higher even 3 tone apart!!). However I once saw a nice Sennheiser headphone amplifier, (Orphuse or Orfuse if I remember well) after listening to it (with the headphone) I was gobsmacked!! So loud yet so clear!!

So I have now decided to make my own tube amplifier, with a Headphone side and also a power side for speaker and the ability to have a CD, and Phono input. I was wondering if I could find anywhere (web site book) a simple method starting from scratch to make my own amplifier. I realise that what I make will might not sound as good as the Sennheiser but anything will be an improvement from my old system.
Also Is there a supplier (in the UK if possible) Where parts can be found.


Thanks for any help

Jerome

:eek:
 
Jerome,

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"I was wondering if I could find anywhere (web site book) a simple method starting from scratch to make my own amplifier. "
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If you do find something, I would be interested as well. I started a thread similar to yours here ( learning, building, testing tube amp) but it is not going anywhere. I am interested in the education and fun of learning-not necessarily gaining an amp. I already have several.

I would be interested in following your thread if you get some interest.

What are your goals? Gaining an amp? Education? Fun?

Aspiring diyer,
Rick
 
IMHO, the best way to learn is by doing. Seriously.

Just find some parts (tubed stereo reel-to reel recorders are a good source of parts), a schematic and you're away.

The physics behind the tube operation will become clear as you are building one.

They are very simple devices, there is not too much to learn unless you go for a complex solution.

I am building a SE amp with just 2 ECL82. The circuit is so simple its ridiculous. I have also built a guitar amp and a PP 6V6 hi-fi amp.

:D
 
I posted some basics over on fragman56's original thread. Also look at the link in that thread to the audioxpress classroom series .

I strongly suggest a kit as a first project. Find one that uses point to point wiring (not circuit boards) as this will help you understand soldering and component layout.

Building or even finding a kit or design with all the features you require (power amp, preamp, phono preamp, headphone amp) will be difficult. Phono preamps are rather tricky in particular. Set your sights a bit lower for a first project.
 
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Set your sights a bit lower for a first project.
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OK, let say I want a headphone amp first with a single input (CD). I assume it is the simplest.
I am confident with soldering (I've done it before)
Where could I find schematics for both the power supply side and the amp side? also tips or guideline for layout (does it actually make much difference?)
Note that I don’t intend to use PCB.

Jerome
 
Hi Jerome,

Just do it! Comes to mind...The only reservation is the high voltages concerned with most tube/valve aplications...!!!! Be careful..I got shocked 4 or 5 times with my first project and am lucky to tell the tale!

Check out

http://headwize.powerpill.org/projects/index.htm

for various projects....pick the simplest and go out and buy the parts...don't go for the boutique stuff.. I would say get normal resistors and you can always go for the good stuff later..

Good Luck!
 
For wiring tips I include an excellent article by Aikenamps..

http://www.aikenamps.com/StarGround.html

and it does make a big difference...however sometimes you'll star earth everything and still get a hum!! (Go figure :)

If and when you do just post your problem here or at headwize or the audioasylum and we'll try to help....

For layout:
a.) Get a larger chassis that you think necessary. Get power transformer and choke (if you are going to use chokes) away from tubes and output transformer ( if you are going to use OT)..
 
I have been having a look at headwize and there is a lot to choose from,

SO far I have three questions:

1-What are the advantages and drawbacks of having a transformer output rather than direct coupling?
(cost, quality of sound....)

2-On the power supply side, Simon Busbridge talk about changing the High voltage supply (from 200VDC to 300VDC) to "increase the drive capability" of his amp (http://headwize.powerpill.org/projects/showproj.php?file=busbridge_prj.htm)
So if one can do that why use a transformer in the first place?
Why not use the 240VAC straight away and just convert it to DC?
I suppose if nobody does it there is a good reason why but I have had a look at transformer suppliers and they can be quite expensive!!
Note: I realise that a transformer is still required for the filament supply

3-Fianlly is an amp built for a specific headphone impedance?
I am only guessing here but from what i have seen speaker are usually 4 or 8 Ohms and headphone a lot more??
My problem being that I will not be able to afford a very good headphone at first, hopefully later I will. Will I have to make sure the headphones impedance match?

Thanks

Jerome
 
1. Advantage of using a transformer is ...

a.) Impedance matching.. tube to headphone..
b.) No capacitor. ie. reputed to sound better than a cap.

Drawback..

a.)Costs.. Frequency bandwith? (Guessing here)


2.) You can easyily do the 230v
(230v in all of europe now, uk came down in voltage and europe came up, or so I am told)

But apparently that is extremely dangerous!! (don't ask me why, don't know... maybe someone more knowledgeable can answer that)


3.) You don't really have to match the impedance..but that is theoretically better.

I would advise to start with a cap coupled amp... then if and when you have more bucks/pounds ...convert to transformer.

By the way headphones can be very good at decent prices...I used to have a sennheiser 480 or something and it was pretty good!!!
 

fdegrove

diyAudio Senior Member
2002-08-21 1:20 am
Belgium
Headphone amp.

Hi Jerome,

Re yr first post: the Sennheiser combo (Orpheus) you once heard is still being sold if you have a spare 15.000 USD ?
It's an electrostatic headphone + amp.
I'm not surprised you liked it.

1/An OTL approach would bring down cost and up sound quality as well (theoretically).
Using an OTP will up the cost surely and you're quite right most headphones are rather high impedance devices which makes them suited for OTL designs,to be on the safe side I'd still use a coupling cap in the output.
The difference in quality in both caps and OTP's can surely be heard.
I know OTP's can be abused by design so mismatched impedances can yield higher output impedance on the secundary windings.
(I know it can be confusing.)
To make a long story short I'd go for the OTL sollution and choose a low impedance tube such as 6AS7G.Cheap and cheerful.

2/You could go for the direct AC approach,but you would still need to observe mains polarity and as you said there's still the heaters to consider.It was once done for an OTL amp on 115 AC mains.

3/I'd say it can be made for a range of headphones.Electrostatic earphones being a topic apart.

All in all my advise to you would be: see what you can afford now,then see what you would like to buy later then see if a headphone amp can be built to suit both ?

Hope this was helpful,
 
I would never consider building a headphone amplifer without a power supply transformer. The shock hazard is just too great! .:dead: :ghost: Some kind of isolation from the AC line is needed to protect the user from the possibility of an incorrectly wired power outlet. I don't think I want 230VAC connected to my ears. :yikes: It just seams like a bad idea to me.

later
Bruce:geezer:
 

fdegrove

diyAudio Senior Member
2002-08-21 1:20 am
Belgium
HEADPHONE AMP

Hi everyone,

You all got scared wittless ?
It is technically possible though.You would need some automatic AC line phase detection circuitry.
I confess this is not for the beginning DIY audiophile.
And for the record:you won't get any voltage whatsoever on your body.The circuit would just burn out,some caps may explode and
on a general note:don't do this kind of thing unless you want someone to collect on your life insurance.:D

See you,;)
 
Ok, now I understand that the power supply transformer is a must, I have a few more questions. I have decided to make Aren van Waarde 's Single-Ended OTL Amplifier for Dynamic headphones. (http://headwize.powerpill.org/projects/showproj.php?file=waarde1_prj.htm)
I look fairly simple for a first project.

1-What are the advantage and drawback of having the power supply as separate unit? More specifically does the fact of having cables between the two affect the sound quality

2-I am not going to use a PCB. so What type of cable (monocore, multicore...) should I use. Also to make the think look tidier I would like to avoid soldering Resistor directly between other components. I would prefer to secure the resistor to the box and then use wire to connect everything. Again which wire shall I use? And will the fact of having more wire affect the sound?

3-I have managed to find supplier for most of the part except for the Stereo Potentiometer. Does anyone know manufacturer names or supplier in the UK?

Thanks

Jerome
 

fdegrove

diyAudio Senior Member
2002-08-21 1:20 am
Belgium
Headphone AMP

Jerome,

I haven't looked at the circuit of yr. choice yet but here goes on a general note:

1/Advantage: -you can use a star ground for the PSU in its own box.
- you will have more space to work with.
-less prone to hum since you keep the trannies away from the amp as such.
-you could also make for a stiffer PSU given the gain in real estate.
-provided your PSU has good regulation I see no disadvantage.(put some decoupling caps in the AMP's box so immediate current demands are taken from those.)

Disadvantage:-an other box + umbillical.
-probably added cost.
-cable length shouldn't be too long,say 3ft otherwise you may see a B+ voltage drop due to cable resistance.
Also use shielded cable where you connect the shield to the AMP's
box star ground.

2/I always use solid core cable of say 22AWG,depending on current demands.There's no point in going for heavy cable where it's not needed.
You'll probably like to use soldering tags. (see RS components catalog for those,other sources exist.)
I use common PVC insulated tinned copper wire for anything carrying DC votages (not directly signal related.) and good quality audio cable wherever needed.Again the smallest gauge for the task is easier to work with.
Whenever you need signal carrying cable inside your box I find single strand (not coaxial) cable both better sounding and easier to work with.

3/Pots:you'll need a logarithmic stereopot a la ALPS.Do a websearch on the item.I'm not sure RS carries it but I'm positive other UK vendors sell it.
http:///rswww.com/

Better still is a resistive stepped attenuator but I would consider that a high-end upgrade already.

I'll have a look at yr chosen circuit soon.

Good luck,
 

fdegrove

diyAudio Senior Member
2002-08-21 1:20 am
Belgium
Headphone Amp

Jerome,

As promised I had a look at this circuit.
Go for it,I remember Rudy as a down to earth designer from the days of the Dutch Audio&Techniek mag.
One last word on the PSU:if you can afford it go for the valve rectified circuit.Your ears AND valves will love you for it.

Rgds,
 
jerome said:
2-On the power supply side, Simon Busbridge talk about changing the High voltage supply

A smart guy that one -- Dr. Busbridge designed the Lumley Metrolpolis a 100w, single sube, single ended triode amp -- one big monster

[IMGDEAD]http://www.metropolis-music.co.uk/pictures/lumley/lumley_metropolis_1(w200).jpg[/IMGDEAD]

dave