DIY Headphone Amplifier

[PJPro]

OK. I've decided to try and make my own headphone amplifier. Why?

1) I've read on numerous occasions in various threads that the hifi manufacturers are overcharging for their products. This will give me a chance to more accurately assess this claim. I will be using someone else's design, so I will be unable to factor in the research and development costs. Still, it should give me a bit of an idea.

2) I've been looking at headphone amps for a while now. I was primarily interested in the Stello HP100, the offerings from Creek and Graham Slee, the Sugden Headmaster, etc. I tried to audition a model from Creek at the recent show.....but couldn't really hear it over the din from Nintendo's Guitar Hero stand. I also liked the look of the Little Dot V (dual mono).

It was the Stello which interested me most, but with the drop in the pound against the dollar, the risks of buying from abroad, my lack of success with brokering a recent deal with the single UK reatiler and Russ Andrews simply charging too much, I just couldn't bring myself to spend the money.

3) I like tinkering and understanding how things work. I really liked Ray Palmer's Speaker cobbling thread (whatever happened to those speakers Ray?).

So, I've taken the plunge, bought the tools and ordered the parts. I intend to update this thread to record how I get on.

 

[PJPro]

I am going to make the Tangent variant of the CMoy headphone amplifier. This is a relatively simple design, should be easy to make and should provide relatvely good results (apparently the Grado RA1 is a CMoy variant).

The Tangent website provides parts lists from various suppliers. He also provides lots of alternative parts for the builder to select. I aim to simplify this by providing a single definitive list and limit the number of suppliers. I'll also provide a fairly accurate view on costs for a UK builder of this amp using the parts I define.

I also intend to capture all the issues I encounter to help anyone who decides to have a go themselves.

The Tangent site can be found here and the CMoy tutorial can be found here.

 

[PJPro]

You may be wondering why I have posted this thread in the Computer-based Music forum. Well, for me, a headphone amp is a critical part of my PC based system ie PC->DAC->Headpone Amp->Headphones.

Currently, a Beresford DAC is performing the role of DAC and Headphone Amp. I am hoping that a dedicated headphone amp will improve sound quality.

 

[lonely boy]

This looks interesting PJ Pro, going to keep an eye on this to see how it develops. Do you have much experience with electronics, or is this all new to you?

 

[Olli1324]

This seriously interests me. I too currently use the Beresford as my headphone amp, and have recently been interested in building a headphone amp (after reading claims that manufacturer-built ones are grossly over-priced). I have the electronics experience and the necessary equipment, so I look forward to seeing your results.

What 'phones are you using?

What is your estimated time-span for this project?ÿ

 

[Anonymous]

Sorry I didn't find this post sooner PJ. Very interesting. Of course this is how everyone starts, I have never attempted anything like this but the idea takes you everywhere. Let us know how you get on.

By the way, the Beresford headphone output is not anywhere near as good as everyone seems to think it is in my opinion, but if you build something that beats it my hat is off to you.ÿ

 

[PJPro]

lonely boy:This looks interesting PJ Pro, going to keep an eye on this to see how it develops. Do you have much experience with electronics, or is this all new to you?
Err no. No experience at all really.

 

[PJPro]

Olli1324:[snip]....What 'phones are you using?
What is your estimated time-span for this project?

I use Grado SR80s

Time-span? Hmmmmmm. Tangent gives an estimate to complete each section. But I'll be surprised if I can match it due to unforeseen issues cropping up. Moreover, the elapsed time will be greater than the effort required....due to getting additional parts (I still need a box), family commitments, screw-ups, etc.

Given all that I reckon two weeks max. But it should take a few hours!

 

[Olli1324]

Well I'll let you amke all the errors the first time. Make sure you record everything you do

 

[chebby]

PJPro:...but with the drop in the pound against the dollar, the risks of buying from abroad, my lack of success with brokering a recent deal with the single UK reatiler and Russ Andrews simply charging too much, I just couldn't bring myself to spend the money.

Indeed. I ordered a Fubar II USB DAC for £105 just over a week ago from RA.

Just checked today and they are now charging £126. I got there just in time.

However the dollar/pound exchange rate has plummetted and Firestone Audio are an American company so it is not that suprising. Pound is currently 1.49 dollars (has gone down to 1.42 and lower in recent days) so I don't think there is rampant profiteering going on. It will be a long time (maybe never) that we will see the 1.98 dollar/pound rate back again.

If I had ordered direct from Firestone's official ebay dealer (in Canada) it could cost me £87 + 17.5 percent VAT + import duty + $32 delivery and I would have no UK backup/warranty/return policy etc. (+ Russ Andrews delivery is free.)

The Stello HP100 is $595 (according to April Music's own website) and the RA HP-1 version is £499 so allowing for the p@ss poor dollar pound exchange rate and the VAT + import duty charges (and free delivery) and the 1 year UK warranty it isnt that bad.

 

[PJPro]

OK. But I thought this might be a little fun too.....although I'll probably just end up losing my rag.

 

[Dave_]

saw your post and this got me thinking about building one.... i know in one of your posts you mentioned trying to narrow it down to one supplier, not sure if you have researched this but it seems you can get all the components from rs components, although they only sell most of the components in packs of ten,,,

 

[PJPro]

Protoboard arrived today. Shocked at how small it is, especially as I will only be using half a board for a single amplifier!

Also got some difficulties with my order for my components (don't know how they will all fit on that tiny board). Seems my credit card had been rejected for some or other reason. Had to ring up the States. Just to make sure I wasn't ringing while they were in bed I checked out where the company is based. Turns out it's Texas...in a place just north of Waco!

Have to say the whole episode was somewhat bizarre. I was put on hold and was listening to american voices advertising who knows what on the phone. I sort of drifted off and was unable to remember my own phone number when the telephonist returned and asked me for it! I laughed. She didn't. Humourless? I was disappointed when she didn't say "Missing you already".

Bottom line is that they were still having difficulty with my card/order (exchange rates this time) and promised to ring me back or email me. They haven't. It's been nearly an hour. They said 10 minutes. This project is starting to hack me off already!

 

[PJPro]

daveh75:[snip].....you can get all the components from rs components, although they only sell most of the components in packs of ten,,,
Not so. I've gone for the high quality precision resistors which they do not appear to stock.

And, yes. I do have the list of component part numbers from a single supplier. It took quite a lot of effort going to multiple suppliers (using Tangents parts numbers) to narrow down the manufacturer part number and then going back to my preferred single supplier to identify the part and get their stock number.

Actually went through a number of single suppliers until I found one that did the lot. Major hassle!

 

[Dave_]

nice one... be interesting to see how you get on

 

[PJPro]

One good bit of news is that I've managed to secure the use of an oscilliscope? Might be useful for diagnostics when it all goes wrong!

A number of people on the forum often bleat about the lack of technical measure of equipment. So, I'd thought I would test the amplifier using the oscilliscope. That's great. But I don't actually know what needs to be done or what represents a good result! My technical friend reckons pumping a sine wave through the amp would probably be the way to go. But what would a good result look like? I haven't a clue. Any ideas/advice?

Incidently, I have other ideas for normal testing using one's ears.

 

[Anonymous]

PJPro:So, I'd thought I would test the amplifier using the oscilliscope. That's great. But I don't actually know what needs to be done or what represents a good result! My technical friend reckons pumping a sine wave through the amp would probably be the way to go. But what would a good result look like? I haven't a clue. Any ideas/advice?.

This is a hard one. From the engineering point of view, you want the amplifier to reproduce the input sine wave as much as possible.

But now let me quote my electro-acustics teacher: "you may spend ages designing the most accurate system just to find out that people loves its imperfections". And example of this would be the Fender Stratocaster, people loved it because of its distorsion... which is a fault from the tech point of view ÿ

ÿ

ÿ

 

[Anonymous]

By the way,

the basics to characterize an amplifier are the Gain Vs Frequency and Phase Vs Frequency charts.

You want the gain to be the same for all the audible frequencies (don't check every single frequency, but some of them, for instance10Hz, ÿ100Hz, 1KHz, 10KHz, 20KHz)

I guess it's the same for phase but to be honest I hardly remember all the electronics I learnt... shame on me! ÿ

 

[PJPro]

Sorry Waldo, I haven't a clue what your talking about!

I had a chat with a colleague at our smoking shelter today and essentially he said that the sine wave going into the amp should look the same coming out? Or something like that.

Apparently, we have an diy audio whiz at work.....but I haven't had chance to have a chat to him yet. Hopefully, he'll come up with something appropriate. But I'm still keen for ideas from the forum.

 

[PJPro]

OK. Here are the list of parts. It is not fully complete. The outstanding item is the hook-up wire. All of the parts in the table were obtained from Mouser.

I will update the list of parts as required. I do know the cost but need to factor in VAT etc.
The ID column relates to the schema, which is available here but note the comments on the virtual earth enhancements below.

There's a large gap to the table of parts for some reason.....keep scrolling and you'll find it below!

ID
Description
Qty
Mouser Part Number
Cost (£)

C1*

220 æF 35V electrolytic capacitor, radial leads

1

647-UVR1V221MPA

C1*

Alt: 470 æF 35V electrolytic capacitor, radial leads

1

647-UVR1V471MPD

C1*

Alt: 1000 æF 35V electrolytic capacitor, radial leads

1

647-UVR1V102MHD

C2

0.47 æF 50-plus volt full-size film capacitor

2

75-715P200V0.47

RLED

10 KO 1/4W metal film resistor

1

71-RN55D-F-10K

D1

Power indicator LED, red diffused, 3mm

1

859-LTL-1CHE

R1

4.7 KO 1/4W metal film resistor

2

71-RN55D-F-4.75K

R2

100 KO 1/4W metal film resistor

2

71-RN55D-F-100K

R3

1 KO 1/4W metal film resistor, gain 11

2

71-RN55D-F-1.0K

R3

Alt: 2 KO 1/4W metal film resistor, gain 6

2

71-RN55D-F-2.0K

R3

Alt: 2.5 KO 1/4W metal film resistor, gain 5

2

71-RN55D-F-2.55K

R3

Alt: 3.3 KO 1/4W metal film resistor, gain 4

2

71-RN55D-F-3.32K

R3

Alt: 4.7 KO 1/4W metal film resistor, gain 3

2

71-RN55D-F-4.75K

R3

Alt: 10 KO 1/4W metal film resistor, gain 2

2

71-RN55D-F-10K

R4

10 KO 1/4W metal film resistor

2

71-RN55D-F-10K

R5

47 KO 1/4W metal film resistor

2

71-RN55D-F-47.5K

OPA

Dual op-amp OPA2132PA

1

595-OPA2132PA

OPA

DIP-8 IC sockets, gold contacts

1

575-113308

IN/OUT

Phone Jacks 3.5MM STEREO JACK

2

502-35RAPC4BH3

POT

Volume control, Alps 10K (RK097)

1

688-RK0971221Z05

POT

Volume knob (aluminium, black anodized & silver)

1

450-7015

GRD*

TLE2426IP Application Specific Multi-Output Solutions Rail Virtual Ground

1

595-TLE2426IP

GRD*

1uF 50-plus volts electrolytic capacitor

1

647-UMJ1H010MDL

CASE

Plastic Enclosures 2.75X4.94X.94 BK

1

635-H-659V-B

* These parts reflect the quantities required to construct a Buffered TLE2426-Based Virtual Ground Driver (Noise Reducing Version). Ooooh. That sounds cool. Wonder what it does?

"Alt" indicates that there is a choice to be made. For C1 apparently the larger the capacitor, the more bass you get. For R3, the higher the gain, the louder the amp....and louder is not necessarily better as more gain equals more background noise.

I have to say I ordered much larger quantities than specified above. Firstly, if you spend over £50 you get free shipping. Secondly, I wanted to make sure I had ample of everything to allow for the inevitable cockup.

I've also gone for high quality resistors (Vishay). I intent to pair match these by hand. For the quantities we're talking about here, the increase in cost is minimal.

The only other part is the protoboard which I ordered from T2 Retail.

ID
Description
Qty
T2 Retail Part Number
Cost (£)

BOARD

Protoboard

1

2760150

 

[PJPro]

No idea how those big gaps got in there. Looks like the site uses some "funny" stylesheet settings on the table element!

 

[Anonymous]

PJPro:Sorry Waldo, I haven't a clue what your talking about!I had a chat with a colleague at our smoking shelter today and essentially he said that the sine wave going into the amp should look the same coming out? Or something like that.Apparently, we have an diy audio whiz at work.....but I haven't had chance to have a chat to him yet. Hopefully, he'll come up with something appropriate. But I'm still keen for ideas from the forum.

OK, putting it simple, you'll input a sine wave into your amplifier and got and output wich is "x" times larger at the output. The value "x" is dependeant on the frquency of the sine wave; since sound is composed of different frequencies (sorry, cannot recall the audible frequency range), you need each frequency to be amplified by the same value "x".

Phase is the relative position of the output wave compared to the input. This may vary with the frequency of the sine, too. You won't want the different sines that form sound to have different positions between them at the output.

Anyway, don't worry too much if you are working on an existing design.ÿ

 

[PJPro]

OK. So what you're saying is use different sine waves as inputs and see if they look the same coming out....only bigger.

 

[PJPro]

Just looked at the FedEx parcel tracking site and my components are at Standstead already! Not bad considering I only finalised the payment last night at about 8 o'clock.

Also happened to be visiting a subcontractor's site in Brighton today and squeezed in a visit to Maplins to buy some hookup wire, some wire clipers and a few crocodile clip test leads.

 

[Anonymous]

Keep up the good work. I hope to give this a try myself. Parts list/numbers and supplier very useful thanks for the leg work. Shame that there is no macro which can add all components to a suppliers shopping basket.