The HiFi chat, build and modification thread!

[greenstiles]

My little headphone amp is dual mono, i was lucky enough to hear it's earlier version so can appriciate the difference it makes.

 

[greenstiles]

The chap who built my little headphone (was portable) amp is sending one of his lastest for me to try out (he's a great bloke like that )(think this is right) mosfet class A dual mono .....ie 2 seperate power cables. I had an earlier version which was very nice, so should be fun to see how it has changed.

 

[apache]

Given that the BBC worked out (when they were rolling out stereo FM radio) that you only needed something just short of 30dB of separation (crosstalk), and the ridiculously high crosstalk immunity of current decent quality op-amps (it's possible to build 100dB+ of separation quite easily), it's *probably* unnecessary to split L/R power, but as I've said before, why not aim for better if it can be done at reasonable cost?

Let me know how it goes. I can see I'll need to put more work into my h/phone amp - though as it will be a modular part of my pre, it can be improved at leisure.

 

[legrandefromage]

The EU has said that we're all going deaf due to too loud iPods and such like. So the volume output is limited by quitea lot.

There are two cures for this:

1. Change the region in player settings to USA or whatever

2. Install Rockbox (google it - it's alternative firmware you can install for most popular players; its free and plays every codec I've heard of)

I used an older set of late 1980s headphones and they were much louder than my current ones too so maybe there is some limiting going on there too.

Nope. It's just that some headphones provide more decibels per amp than others. This has always been the case and always will be. It's a headphones characteristics thing.

The audio from the bottom of an iPod is much better than the headphone socket and is fixed.

The audio out from iPod varies with the model. On the whole, it is actually damn good - this is not subjective, because you can actually test signal accuracy with standard electronic hardware. The best accuracy of all tends to come from Sansas, weirdly - they are waaaay past the point where anyone with normal hearing and using anything like standard headphones will be able to hear better quality:

http://nwavguy.blogspot.co.uk/2011/02/s ... sured.html

To get a substantial improvement over a $40 Sansa driving $150 HD25-ii phones (this is a model that Sennheiser designed for TV news soundpeople, but which has become standard for DJs too - they have very accurate sound and are extremely hard to destroy) you really have to go to electrostatic headphones and an amp powerful to drive them.

Otoh, you can a big boost to audio quality for free if you tune your headphones using pink noise: most people have a couple of dips in their frequency response, and if you compensate for them using an equalizer you'll have a much more accurate sound.

edited for mood swing - I know most of this but not everybody does hence my pointing it out. Too many people rely on the headphone sockets of iPods which are shite for anything other than headphones. Regarding headphones, apart from working in the industry for a while, I have a lot of old headphones to contrast and compare to new. I find the older (20+ years) to be louder regardless of make (aiwa, JVC, Sony etc). Full size stuff seem to be the same.

 

[apache]

Modular pre-amp prototype taking shape. Top board is low noise input circuit (multipath amplifiers) / variable gain control. Chosen a variable gain control rather than a volume control (attenuator) for several reasons. It enables you to maintain low circuit impedances (for practically unmeasurably low noise) and constant impedance in / out so loading on previous and following stages remains constant. This is important, and also why passive pre-amps (or a pot-in-a-box) are a daft, if very lucrative, idea. Input switching will probably go on this board also and will consist of small signal telecoms relays.

Bottom board is a basic but low (enough) noise PSU. Further boards will include a headphone amplifier and an RIAA card.

Doesn't look too cool on vero, but it's quick to use and has no impact as long as you think about the layout - earth paths in particular.

 

[greenstiles]

Hi Apache, i have sent you a pm, cheers

 

[apache]

Replied

 

[greenstiles]

New neco V3 mosfet home amp arrived today for me to try out before buying, just running it in( as it says to do) ......then will be comparing it to my cheaper neco amp which is battery powered and has diff opamps in than standard. Then with the new tone controls Apache kindly built to see which will work best for me. (Apache can you spot anything in the blurb that sounds suspect electronically speaking ? )

http://www.ebay.co.uk/itm/new-V3-high-s ... 0935950085

https://www.facebook.com/pages/Neco-Sou ... 2363058227

 

[apache]

Yes - 'running in' solid state electronics does naff-all, but as it's been promoted as 'fact' by the hifi press, is has become fact amongst audiophiles - ergo if I sell anything on a serious basis, I will be recommending a run-in period.

Will have a read of the blurb later.

 

[greenstiles]

I've had a theory about this...........do you think it's just the case of.......when you hear a new bit of kit, cos it sounds diff, it's like putting on new clothes, it feels a bit wrong, then the more you wear it, the more comfortable it feels ? ie the amp doesn't run it, but the person just gets more acustomed to the sound over time, but it sounds better to them, because they have just re-ajusted to it after a few listens ?