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Paul Spencer

DIY audio: what are you building?

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After finishing the Noir HP amp I decided that I didn't like rubber stick on feet.

So I found some rather small screw on spikes and fitted those instead.

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You may have seen I boxed the Altec horns. I was expecting no sonic difference, Boy was I ever wrong. They are more forward than before and transparency and dynamics has jump a huge amount. Trying to guess why it maybe that before the throat sat on small cardboard boxes which may have muffled vibration in it. Also the mouth mount sat on the isolation glass plate on top of the woofer. Could some of the higher frequencies been dampened too much here? 

Regardless if you have similar horns suspend them in (in my case) 5 ply boxes. They are Dacron lined. I have to say once more a massive improvement in sound and hard to explain why! Bonus, I think they look a lot better two which is why I did it in the first place. 

 

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Something like the sound bar I think should be but maybe with bigger drivers or even more. I realise this is centre channel. 

9EA5288F-6BFC-4E97-A512-AC746039D5F5.jpeg

Edited by mwhouston

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S6OCatp.jpg9WKTULL.jpgfcdToV2.jpg

A headphone amplifier design I've been toying with. It's simple (well at least I think so...) but has some unique features that I wanted:
-Powered by 5V USB, produces isolated and voltage regulated +/-9Vdc rails (good enough for 250ohm headphones, most 600ohm headphones)
-Selectable gain +6dB or +20dB
-Selectable bass boost 0dB, +3dB or +6dB
-Selectable RCA pass through - can break the pass through connection while the amp is powered or just have the signal always pass through
-DC offset protection and turn-on delay to eliminate turn-on thump
-Audio signals do not pass through any of the mechanical switches. Instead the switches digitally control analogue multiplexers. The multiplexers only switch virtual ground connections, minimising their distortion impact.  The switches are debounced, so there will never be any pops, thumps or scratching noises when they are operated.
-Up to four DIP8 dual opamps operate in parallel for the output stage, giving a high current drive for low impedance (32ohm) headphones.  

A couple of areas that still need work are that it creates a soft thump at turn-off and when operated on inadequate USB power or a bad power cable it can go into an oscillation. The former can be fixed by adding a graceful turn-off circuit (turn off output relay before turning off amp power), the latter I hope to fix by adding a USB power management IC.

Edited by TMM

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20 hours ago, TMM said:

S6OCatp.jpg9WKTULL.jpgfcdToV2.jpg

A headphone amplifier design I've been toying with. It's simple (well at least I think so...) but has some unique features that I wanted:
-Powered by 5V USB, produces isolated and voltage regulated +/-9Vdc rails (good enough for 250ohm headphones, most 600ohm headphones)
-Selectable gain +6dB or +20dB
-Selectable bass boost 0dB, +3dB or +6dB
-Selectable RCA pass through - can break the pass through connection while the amp is powered or just have the signal always pass through
-DC offset protection and turn-on delay to eliminate turn-on thump
-Audio signals do not pass through any of the mechanical switches. Instead the switches digitally control analogue multiplexers. The multiplexers only switch virtual ground connections, minimising their distortion impact.  The switches are debounced, so there will never be any pops, thumps or scratching noises when they are operated.
-Up to four DIP8 dual opamps operate in parallel for the output stage, giving a high current drive for low impedance (32ohm) headphones.  

A couple of areas that still need work are that it creates a soft thump at turn-off and when operated on inadequate USB power or a bad power cable it can go into an oscillation. The former can be fixed by adding a graceful turn-off circuit (turn off output relay before turning off amp power), the latter I hope to fix by adding a USB power management IC.

Very cool stuff, your design? What did you use as USB - Audio?

 

Cheers,

 

Alberto

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Yes, my own ground-up design. The USB is only used as a power source - input is analogue-only (via RCA jacks). I'm using my PC soundcard as the DAC.

Edited by TMM

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Because I insisted on keeping the massive heatsinks for my two latest Holton builds (300W and 150W) inside the box (should have thought outside the box) I have added silent slow running fans. They employ a special bearing (hydrodynamic) type and blade shape to ensure silent operation. 12V fans which run on 9V run extremely quiet. In the latest addition they are mounted on double layers of thick double sided tape. No hard mechanical mounts. Great isolation.

 

The  fans are exhaust fans so the blades face away from the wind direction. I wanted the fans the other way round. I reverted the polarity so I could turn the fans around. But you try that they don’t run. No biggy they will never been seen. Maybe (I’m assuming) being brushless they may only run in one direction. All good now and even if you hang directly over the top of the amp they can barely be heard. Definitely not from three meters. 

Edited by mwhouston

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On 22/10/2019 at 8:32 PM, Primare Knob said:

Finally started working on my first subs build, using Dayton RSS390HO drivers

The core plan was to keep them small, 410x410x410x18mm, with drivers and bracing that comes down to roughly 44l net.

The baffle is double 18mm, and I did manage to piece together the 3D bracing today.

Bought a router last weekend, as the blade of the jigsaw was warping too much and wasn't creating a perfect circle.

My plan is to finish the outside by using the same bamboo floor boards that are in the cinema room, but I will need the help of a table saw to get that right.

Hopefully my neighbour can be persuaded with some beers.IMG_20191022_123919825.jpegIMG_20191022_123909953.jpegIMG_20191022_194735547.jpegIMG_20191022_194720428.jpeg

I recently had the chance to test my sub build outside, with the mic place 1 meter away. I think the result is pretty decent.

 

Blue line is the Win ISD modelled SPL output with an 800W signal.
Red Line is the measured SPL output with an unknown wattage signal, peaking at 122dB.

RSS390HO.jpg

Edited by Primare Knob

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Ready for testing, when I get up the courage to turn it on :)

 

Still need to modify the Arduino code to accept the new input layout, originally I had 5 inputs but decided to simplify and go back to two.

 

And put the valves in of course, need to check I'm getting the right voltages before that though.

Side 2.jpg

Open With Lid.jpg

Rear.jpg

Side 1.jpg

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31 minutes ago, DQ828 said:

Ready for testing, when I get up the courage to turn it on :)

 

Still need to modify the Arduino code to accept the new input layout, originally I had 5 inputs but decided to simplify and go back to two.

 

And put the valves in of course, need to check I'm getting the right voltages before that though.

Side 2.jpg

Open With Lid.jpg

Rear.jpg

Side 1.jpg

What is it? 

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It's an accident waiting to happen :)

 

But seriously, it's a DAC/Preamp. The DAC is a Twisted Pear Buffulo 3, the output stage is a Broskie Unbalancer. There are two output caps on each side so you can select cap1 or cap2 or both. The Arduino has a touch screen and controls the DAC startup-shutdown, filters, input select, remote control and volume,  it also controls the system startup and shutdown via 2 12v trigger outputs.

 

There's also an Amanero USB Input which is connected to an Acko Reclocker, and there are 2 SPDIF inputs

 

 

 

Edited by DQ828

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Merry Xmas to me. Santa bought me a shiny new replacement for my crappy $2 shop multimeter. 
 

97752FA8-D423-42E2-81B8-9A5539912583.jpeg.f4ee1b12cc96a5006b9815a5254b743a.jpeg

 

Now I just need to learn to use the damn thing properly. 
 

While I think of it, Merry Xmas to you lot, too :) 

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Buy some nicer leads from RS or Element14 and try not to kink them too much.

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1 hour ago, Batty said:

Buy some nicer leads from RS or Element14 and try not to kink them too much.

What difference will nicer leads make? Will a veil be lifted? (Seriously, though, they seem fine)

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33 minutes ago, RankStranger said:

What difference will nicer leads make? Will a veil be lifted? (Seriously, though, they seem fine)

I make all my own. Generally from silver plated fine wire wrap wire. No shielding but two earth wires but only one connected at the destination end. No shielding. 
 

oops. I think we are talking about a meter. If so better leads may last a little longer. 

Edited by mwhouston

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1 minute ago, mwhouston said:

I make all my own. Generally from silver plated fine wire wrap wire. No shielding but two earth wires but only one connected at the destination end. No shielding. 

I can’t tell if you’re being serious. Is it more accurate to have better leads?

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2 minutes ago, RankStranger said:

I can’t tell if you’re being serious. Is it more accurate to have better leads?

Yes, if they are of good quality and are looked after (not bunched up) they will be safer, have less chances of getting breaks in the wire and insulation and will hopefully last you a long trouble free time.

I treat all of my test equipment as if it is audio equipment, especially leads.

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30 minutes ago, MarcAL said:

Yes, if they are of good quality and are looked after (not bunched up) they will be safer, have less chances of getting breaks in the wire and insulation and will hopefully last you a long trouble free time.

I treat all of my test equipment as if it is audio equipment, especially leads.

Cool. Thanks!

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2 hours ago, RankStranger said:

I can’t tell if you’re being serious. Is it more accurate to have better leads?

Silly me, I thought we were talking hifi interconnects. Any fair quality leads will work. Jaycar have a reasonable set quite cheap but will last. I use hem myself. 

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Hugh Dean has come up with a new Class A amp - the Alpha Nirvana ... 40w into 8R (with +/-27v DC rails).  There is also a 4R version (with +/-20v DC rails), which I  am going to build - to see whether it sounds better driving my mids & ribbons than my current NAKSA 80s.  (Mids are 3.2 ohms; ribbons are 2 ohms.)

 

He has made the design open-source ... so you can buy the PCBs from the guy who started this thread on DIYAudio:  https://www.diyaudio.com/forums/solid-state/344540-alpha-nirvana-39w-8ohm-class-amp.html

 

Hugh has also further developed the design ... this will be his next commercial amp (the 'Omega'), with slightly more power.

 

Andy

 

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XRK971 does some nice work.

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