Audio hardware - headphones

[DrTom]

Hello all

I was just wondering if anybody here is into their sound hardware? I have just finished building my latest CMoy headphone amplifier (if you are laughing, I'm sorry - it's all I can put together - valves, buffers and GOOD op amps are expensive you know!! ) and was wondering if anyone has any design points, tasting notes or critique of these amplifiers they would like to share? For anyone interested, I'm using a dual LF353 op amp - bright and sharp sound, you have to push it to get good bass response.

Happy listening!

[Lambo]

Never built anything or really heard any valve stuff, apart from my phono stage (puresound P10).
Rest of the kit is Rega (P25 with AudioOrigami'd RB250, Radio, Saturn, Cursa and Maia) into Dynaudio 52SEs.

[zix]

Hello, a bit late to this thread I am afraid.
What choice of op-amp do you have? The CMOY uses - what? A buffer IC with high input signal demands, or a high gain IC like the TL072?
Hold on, here: http://tangentsoft.net/audio/cmoy-tutorial/parts.html#op-amp
As you see, it is the OP132/134 amps he recommends, more specifically the OPA2132PA. I would go with that if I was to build the Cmoy, many audio DIY people use these IC:s and say they are good. It seems it is also stable, not prone to oscillation.
An OPA2134 PA costs 4€ at my "expensive-dealer-but-has-a-large-searchable-product-database" (elfa.se). This is with the DIL-8 case, which will fit a standard 8-hole socket. Probably not that hard to find a cheaper one.

Hope you soldered an IC socket in, in that case changing is easy peasy. Just earth yourself before changing.

Second, I would change the volume control to an attenuator. tubecad.com has a good attenuator for a good price, called the "TCJ stepped attenuator". A smart solution for an old problem, most other kits are waaay more expensive. And not as smart of course. http://glass-ware.stores.yahoo.net/netcjstat.html

Third, for low voltage applications, you could get a bunch of OS-CON capacitors to replace the standard caps. They can actually change the sound quite a bit for the better.

Then, fourth, I would try driving the amp with a battery. I like battery PSU:s, and the Cmoy is built to be able to use them.

All these changes will improve the sound

[DrTom]

Not too late at all!

I just finished my (semi) dual-mono headamp recently, using 2 dual opamps, one for each channel. It's based around the Apheared 47 but biased into class A. I say semi dual mono because it shares a common power supply. No buffers on this one, although I have 10 buffer IC's waiting for the next design (BUF634U) which I am rather excited about! (I have read that these buffers will need to be at least doubled in parallel - one on top of the other)

I have used OPA2132PA IC's in both this new design and in the CMoy and find it's nice, but a bit too bassy - maybe that's just how I like to listen I guess. I like to try other IC's out as much as my wallet permits!

http://glass-ware.stores.yahoo.net/netcjstat.html - wow this looks brilliant! I will have to look at these some more! Thank you

You mention OS-CON caps for the low voltage applications - do you mean in the signal path or if I were to use a low voltage power supply and use the OS-CON capacitors to treat the input voltage? I use Vishay MKT's in parallel to reduce the ESR when I'm using a capacitor in a signal path and Rubycon XYF's in the power supply. I'd really like to get my hands on some of these OS-CON capacitors, the low ESR and noise introduction looks very nice!

As for a power supply - when testing an amplifier or listening at home I use my DC benchtop lab supply, I can't hear the difference to be honest, although I understand that I should be able to... I could put it down to a great power supply design on my amplifiers but I doubt it

I'd love to hear any more information you have, it sounds good!

[zix]

OS-CON caps: when using them in IC amps, I have put them as the last pair of power supply decoupling caps, after regulators, as close to the IC as possible. Not too large values if you use a voltage regulator. Max 16-40uF or so. This last decoupling cap is not always drawn in circuit diagrams, but is often used on the cards.
OS-CONs can be used as coupling caps, between input and driver stage in a transistor amp for example. They are a lot better than the other electrolyte caps, but not as good as the best plastic filter caps. But since these can be very expensive and large (as I am sure you know), when the values are in the 4-50 uF range, the OS-CON can be a very smart choice. It will fit in where plastic caps are too large and still deliver a better sound.

Capacitors can sometimes be found on ebay and other auction sites. Paper-in-oil, teflon and organic caps (beeswax, for instance) can be fun to try when you have the space and the need for them. People mostly use them in speaker filters and such, finding the right value for sale can be tricky though.

[bruceb]

Wow! I love this thread. These are the electronics I can understand. It reminds me of my days as an amateur radio operator. I built and operated a 400 watt multi-band (80-20 metres) power amplifier with a bank of 6 6L6s.

Transformers, capacitors, resistors, valves, mercury vapour rectifiers...bits you can hold in your hands, not these itsy-bitsy ICs and unrecognisable components that look more like bird droppings or ink smudges.

When I fired up my rig we could turn off the central heating!

[zix]

Oohh 6L6:s. Nice! I agree it feels nicer to handle tubes and tube circuit components. Not always nicer to build though, with B+ voltages typically around 400-500V...
An Aikido line stage and an interstage transformer-coupled 6B4G Push-pull amp are among the not yet finished fun projects in my tool shop...

[DrTom]

Thanks for the great information Zix, really interesting stuff. I have used the same Vishay MKT's to decouple the amp. IC's and I am certain I can hear the difference - I'd love to get some of these more exotic components and try them out.

Tubes are something I would really like to have a go with making a headamp with, but my journey is just beginning and I am at the base of a huge mountain (and I can hear my wallet crying).

Beeswax?! Brilliant!

[zix]

Heh heh, yes, DIY is the real Mad Hatter club of audio... but we are having lots of fun, much more so than the pure high-end consumers who only buy a box and that's it.... we get to spend just as much, only we must make it work, too!
Errr, come to think of it, perhaps the high pitched laughs are more because of that B+ buzz...

I am not quite sure I really should provide the following link for you... "all ye who enter here" and so on, just so you know before you go. The guy (crazy polish DIY audio Mad Hatter) is, on this particular page, among other things, testing out capacitors for a DAC he found on ebay, and ends up liking OS-CONs the best in this application.
http://www.lampizator.eu/LAMPIZATOR/LAMPUCERA/CD%20DAC%20Lampucera%20lampizator.html
You can scroll down to "To evaluate the impact of capacitors", and *do not look at anything else on the page, especially DO NOT FOLLOW ANY LINKS ON THE PAGE*. This is very important. As you may be aware of already, lampizator.eu is one of the big portals to internet DIY Audio Mad Hatter Land.

[DrTom]

Holy mother...

[Aadje]

I was going to say something about my Beyerdymanic headphone and how happy I am with it, but now, I'm think I'm gonna refrain from that . . .

[DrTom]

I only clicked ONCE on that link and honestly it still haunts me

[DrTom]

Well, I'm back on with this project at full power - OSCONS will be getting ordered very soon. I STUPIDLY re-visited Zix's link. Thanks for nothing - my life is now ruined!!

This:

http://www.lampizator.eu/LAMPIZATOR/LAM ... ucera.html

Beautiful... I always wonder why people take so much time and care on the PCB mounted elements but do such a half-arsed job on the raw power and primary power caps?! I know this was just a 'birds nest' setup to try it out but some people box up much worse than this!!

[DrTom]

So, recently I picked out my old amplifier and removed the PSU smoothing capacitors for the positive and negative rails of the amplifier IC's and replaced them with something I cooked up:

http://sphotos.ak.fbcdn.net/hphotos-ak- ... 0072_n.jpg

What a difference...


All capacitors are in parallel configuration and each array is a direct replacement for the dual rail power supply capacitors, originally rated at 3300 uF at 50 V, 85 degrees Celcius.


In each array:

1x Panasonic TSHA series 10000 uF, 63 V, 105 degrees Celcius

1x Panasonic TSHA series 2200 uF, 63 V, 105 degrees Celcius

2x Panasonic NHG series 470 uF, 63 V, 105 degrees Celcius

Each array equivalent rating - 13140 uF, 63 V, 105 degrees Celcius.

Unfortunately I don't have the hardware to measure the ESR but I'm guessing it's MUCH lower than the originals...

[DrTom]

Also, zix, you may have ruined my life with your link above - now I dream of DC biasing circuits to make polarised caps viable in the audio path...