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Paul Spencer

DIY audio: what are you building?

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8 hours ago, betocool said:

Marc, how did you get 200V out of 24V? A special transformer?

 

Cheers,

 

Alberto

I have using this simple trick for years in all sorts of amps. Easy to implement in preamps where current demand low but I've  used it low power tube power amps also.

 

From the 24VAC wall wart connect it to the secondary of a 24V step down tranni. In other words connect the second tranni backwards. Out of the primary comes 240V. Once rectified 1.4 times this. I use Jaycar 24VAC 1A wall warts and a small step down 150mA 24V tranni as in the image.

 

Because the wall wart is also powering the filaments it tends to load it up - 630mA. With a result instead of 240V out if the now step up tranni a lower voltage is presented. Usually I use this method for small tubes with far less demand on filament current. But 200VDC HT is sufficient for this build.

 

I have two wine box 6L6 power amps (2W pc) and I use two 300VAC 12V toroids in the same way. These I have in an external seperate enclosure. In the wine box I have the rectification (diode bridge) and filtering. Works a treat. Also in this amp I series the filaments (6V each) and run 12V AC to them direct off the first toriod which is driving into the second toriods secondary. 

 

In some preamps, where I have the space, I use bigger step downs (backwards) and 3A step down as the primary tranni. Some may argue regulation but as long as the trannies are scaled to the job at hand and lots of filtering storage caps (the build above has 400uf) and current demand is not high it's not an issues. And you get double mains filtering and isolation you wouldn't get from a single tranni. 

 

Hope that helps.

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On 04/11/2018 at 9:38 AM, CamSemp said:

Yeah the ply on the front of the woofers has a fairly nice face. However I've decided to make things hard for myself and I've got a roll of Silver Wattle veneer to apply to the whole lot. That said, I haven't actually done a cut diagram to see if I've got enough from one sheet to do it all. May do the baffles in black or something.

 

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Looking good Cam.

Silver Wattle should have some nice natural lustre to it like most of the acacia species.Shellac would bring that out nicely.

You might find that angling the top boxes to align the front baffle so it is parallel with the grain direction will give a more interesting look as well as meaning you use a bit less width of the veneer sheet.

I will post pictures of my Kairos boxes when they are finished.Just sprayed the last coat of lacquer today.

 

Jon

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11 hours ago, THOMO said:

Looking good Cam.

Silver Wattle should have some nice natural lustre to it like most of the acacia species.Shellac would bring that out nicely.

You might find that angling the top boxes to align the front baffle so it is parallel with the grain direction will give a more interesting look as well as meaning you use a bit less width of the veneer sheet.

I will post pictures of my Kairos boxes when they are finished.Just sprayed the last coat of lacquer today.

 

Jon

Thanks Jon. Can't wait to see yours! Not quite sure I understand what you're saying with the grain direction? Do you mean having the grain on the sides running at the same angle parallel to the front baffle?

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3 minutes ago, CamSemp said:

Thanks Jon. Can't wait to see yours! Not quite sure I understand what you're saying with the grain direction? Do you mean having the grain on the sides running at the same angle parallel to the front baffle?

Yes.That is how I did mine using solid timber .I guess see which you think look best but if you are struggling to get enough width out of the veneer it will save about 20-25mm across the sheet.It meant I could get the full depth out of the boards I had but I also quite like the look .

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Ordered the PCBs to build a First Watt M2X.

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I made some posts a few weeks back about using wire wound resistors or carbon film resistors for a "L" pad for my Altec 511B horns to work with 12" woofers. I found the wire wounds bright and felt the carbon film pad, of the same value, better sounding. Well here I am weeks later and I haven't changed anything where in the past I would only last a day or two before going back to carbon film resistors.

 

I only just realised I haven't  changed the pad for weeks so it tells me I'm comfortable with the attenuation level and sound. Just raising the level 1db (in 21) and using wire wounds was too bright. Same level with carbon, (though I can tell the level is raised a little) not too bright. I like to think a good balance.

 

And that's the beauty of DIY. Us DIYers are not stuck with what a manufacturer gives us, we are free to try different and many varied alternatives, cheaply, untill we are happy with the result. For me $1 worth of carbon film resistors has given me many hours of music pleasure and a long term satisfying result.

 

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On 01/10/2018 at 1:29 PM, Muon N' said:

I also wonder how Mal went with that build

He'll be finished by Christmas....    ;) 

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On 11/10/2018 at 9:09 AM, mwhouston said:

12" woofer with a Fo of 25hZ and effcienecy of 96 or better db

You'll likely need to revisit one of these parameters.   As you will need a very high power motor, and very low compliance to ever get the sensitivity up that high, with the Fs staying so low.

 

FWIW, an example of a pretty extreme driver is the Tannoy HPD (dual concentric) woofer.   ~25Hz, ~94dB, 12"

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11 minutes ago, davewantsmoore said:

You'll likely need to revisit one of these parameters.   As you will need a very high power motor, and very low compliance to ever get the sensitivity up that high, with the Fs staying so low.

 

FWIW, an example of a pretty extreme driver is the Tannoy HPD (dual concentric) woofer.   ~25Hz, ~94dB, 12"

I guess what you want and what you need are always at odds. Currently very happy with the Poly cone 12" woofer in sealed 60ltr box with 92db efficiency. The woofer has an fo=25Hz and gives me a 31Hz -3db point. With 150W class D amps driver the woofer and horns plenty of power and dynamics with detail.

 

And I really don't want to spend anymore money on this project though I'm recycling the bass boxes and paid stuff-all for horns and compression drivers.

 

As I have been doing for some months now I'll just enjoy the music and finishing boxing the horns. Wife thinks they are ugly. 

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5 hours ago, mwhouston said:

happy with the Poly cone

Got a link /info to this driver?

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Meniscus Audio Kairos kit speakers in solid curly jarrah.

26mm thick curly jarrah with the sides laminated on to 12mm MDF .

The sides are glued onto the 12mm MDF which is rebated into the sides with a dry joint where the timber meets to allow for movement.

These are 17litre sealed.

The jarrah is quite unusual being more of light brown colour rather than the usual deep red.

Finish is satin 2 pack lacquer.

 

I guess I need to make some matching stands!

Or finish the three way version.

 

The Kairos white paper-

http://meniscus.lightningbasehosted.com/wp-content/uploads/2016/02/Kairos-Write-up.pdf

IMG_0233 (2).JPG

IMG_0224 (2).JPG

IMG_0222 (2).JPG

Edited by THOMO

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1 hour ago, THOMO said:

Meniscus Audio Kairos kit speakers in solid curly jarrah.

26mm thick curly jarrah with the sides laminated on to 12mm MDF .

The sides are glued onto the 12mm MDF which is rebated into the sides with a dry joint where the timber meets to allow for movement.

These are 17litre sealed.

The jarrah is quite unusual being more of light brown colour rather than the usual deep red.

Finish is satin 2 pack lacquer.

 

I guess I need to make some matching stands!

Or finish the three way version.

 

The Kairos white paper-

http://meniscus.lightningbasehosted.com/wp-content/uploads/2016/02/Kairos-Write-up.pdf

IMG_0233 (2).JPG

IMG_0224 (2).JPG

IMG_0222 (2).JPG

 

Looks very, very nice, how do they sound?

 

SS

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18 minutes ago, Sub Sonic said:

 

Looks very, very nice, how do they sound?

 

SS

They sound quite like the Sonus Faber Cremona Auditors I had.That sort of composed and refined sound but probably a bit more weighty sounding.What is nice about these compared to the Sonus Fabers is they sound best closer to the wall whereas the Auditors had to be brought about 1.5 metres out to sound their best -which gets a bit silly in some rooms.The fact they are sealed rather than ported probably helps in this regard.I would say they are a lot better than the Dynaudio Contour 1.3s I had  and also the Lenehan ML1s and Osborn Eos Special Editions which I have also tried [although the Osborns have fantastic treble courtesy of the Seas Millenium tweeter].The Kairos have a better/more natural midrange than those speakers and at least as good as the Sonus Cremona Auditor -which is saying a fair bit because they excel in that area. I reckon they compete with similar commercial speakers in the $4000-$6000 price range.Maybe a fair bit more than that.These Satori drivers would generally be found in pretty expensive speakers.

As I have said elsewhere I prefer 3 ways but as two way stand mounts go these are very good.Dynamics of course are a bit curtailed but that is the nature of the species and a good sub would probably help in that regard.

Edited by THOMO

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Have a thread in speakers and subwoofers section but this is probably the best place for it.

Building a 5 way active speaker with the following drivers:

2 x 15 inch
2 x 8 inch
2 x 6 inch
2 x 4 inch
2 tweeters

That’s each box

Total budget is $5k

Everything has to come from gumtree or eBay

So the drivers with the exception of the 15” are all from VAF speakers courtesy of eBay.

Power amp is a Yamaha mxa5000

Pre amp is a Yamaha z7 (overkill but I will find an emotiva at some stage for the right $$$$)

Boxes will be made of glass fibre reinforced concrete. 40mm thick. Hand press face coat and spray (structural layers)

53a58eebc637bf98eaa3b675017fed08.jpg



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16 hours ago, THOMO said:

Meniscus Audio Kairos kit speakers in solid curly jarrah.

26mm thick curly jarrah with the sides laminated on to 12mm MDF .

The sides are glued onto the 12mm MDF which is rebated into the sides with a dry joint where the timber meets to allow for movement.

These are 17litre sealed.

The jarrah is quite unusual being more of light brown colour rather than the usual deep red.

Finish is satin 2 pack lacquer.

 

I guess I need to make some matching stands!

Or finish the three way version.

 

The Kairos white paper-

http://meniscus.lightningbasehosted.com/wp-content/uploads/2016/02/Kairos-Write-up.pdf

IMG_0233 (2).JPG

IMG_0224 (2).JPG

IMG_0222 (2).JPG

Beautiful Jon! They came out so nice.

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A few months back I posted pictures of "Grace" a 6SN7-SE preamp based on some Psvane limited edition globes. I love the preamp and find it out performs my other tube preamps.

 

 

Someone  put up their hand and said they'd buy it and I wasnt selling it. Now I have an upgrade replacement. I've named the new preamp "Elite" because this one will use the much more expensive low noise grade A version of the same tube. They come in grade B and A. And there is another $200 the difference making these the most expensive small signal tube I have ever bought.

 

Everything else in Elite is the same as grace. Including the Jesen copper foil PIO caps and the 24 step stepper attenuator. Once more I will use 1W carbon film resistors. I just like there naturalness and warmth. The visual difference is the black chassis to Grace's white. I liked the white but a few members said they would prefer black. I wanted Elite to look different, I think I achieved that.

 

Assembled not wired. A rear image to come. 

image.jpeg

Edited by mwhouston

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There are two selectable inputs on the rear, earthing piont and XLR input for power. Elite, like Grace, uses an external PS. HT and DC filament voltages are supplied through this connection.  Because the PS floats you may need to earth it to the power amp or source this the earthing terminal. 

image.jpeg

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6 minutes ago, danw1million said:

Beautiful work 

This one should be around for AmpFest Downunder 2019 "Quattro". But I'm already planning yet another preamp based on some ruggedised 6SN7s I was given. Not a pretty tube but could sound excellent. Same chassis but with Mundorf silver supremes. 

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This is up and running and bright as. Those big Jensen copper paper and oil caps take about 20 hours to settle. Same with the first one. Tubes need 50hours also.

 

The new super expensive low noise Psvanes do sound even better. Even over the brightness you can hear it. Worth $570 a pair and look cool.

 

Worked at switch on and all voltages correct. Love it.

 

 

image.jpeg

Edited by mwhouston

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I may need to get me that phono pre. Reads very interesting. Maybe try some of the mods re power supply.

 

Cheers,

 

Alberto

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On ‎14‎/‎11‎/‎2018 at 4:46 PM, mwhouston said:

This is up and running and bright as. Those big Jensen copper paper and oil caps take about 20 hours to settle. Same with the first one. Tubes need 50hours also.

 

The new super expensive low noise Psvanes do sound even better. Even over the brightness you can hear it. Worth $570 a pair and look cool.

 

Worked at switch on and all voltages correct. Love it.

 

 

image.jpeg

I used a 250K 24 step stepper attenuator on the output to control volume. This stepper had been in another amp and didn't appear to work properly. I swapped it for a 100K stepper and everything appeared OK. In the last two days the volume, under control of the stepper, appears to jump all over the place. Even going to full volume when turned down to zero. Today I replaced it with another 250K stepper (EIZZ brand same as the other). All better. I think something has come adrift in the original. Hope to get a free replacement. The faulty one is an $80 unit. 

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Much better now with the new stepper. I thought I was going mad.

Edited by mwhouston

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On 11 November 2018 at 7:48 PM, davewantsmoore said:

Got a link /info to this driver?

These are old Jaycar 12" poly cones. If you would like I can provide the specs. They haven't been sold for years. I know two others how have them and love them. One guy has a couple spare. 

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