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DIY audio: what are you building?


Paul Spencer

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6 hours ago, muon* said:

Given what Matty says about his LDR Pre, and my other friends experience with the SC, I'm looking at a ePot Mini with the LDR Module from Tortuga Audio to replace the Comos pot in my EL34 amp.

 

https://tortugaaudio.com/products/diy-preamp-components/electronic-stepped-attenuator-epot-v3-mini/

 

I'll run it without display as my needs are basic, one source is all I need and the ePot mini will have the remote for the basic functions I required.

 

 

That's an intriguing device.    Seems well thought out with the options they offer.

 

The only thing is I would think twice about putting all that digital stuff in my pure analogue all triode preamp.

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9 hours ago, aussievintage said:

 

 

That's an intriguing device.    Seems well thought out with the options they offer.

 

The only thing is I would think twice about putting all that digital stuff in my pure analogue all triode preamp.

I'd like the display so I have access to more features but budget is stretched already, but will be happy with just the Mini with Apple Remote, I think I still have a Sony power brick downstairs I can use for it. I'll just add an input socket to the left side of the amp.

 

I've heard too much good stuff about LDR's from some close to me to not give them a try.

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Guest Old Man Rubber
On 04/11/2020 at 12:49 PM, mwhouston said:

Do a Molly (“do yourself a favour”), bin them. Altronics has good tweeters off the shelf. And make/get a suitable Xovers. 

Went to Jaycar instead and ordered some of these:

Titanium tweeters

 

Now - the description on the Jaycar site isn't quite correct, they are silk/titanium.  I have removed the plastic surround and hacked them into place.  Sadly the mounting holes didn't quite line up with the original ones.  Impedence and frequency response are probably different to the originals as well so I should probably do something with the crossovers.  Now just waiting for some bass reflex ports to arrive from China so I can finish these and start tweaking.  The only original things left are the crossovers and the plastic badges ?

 

 

 

20201123_090716.jpg

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28 minutes ago, Old Man Rubber said:

Went to Jaycar instead and ordered some of these:

Titanium tweeters

 

Now - the description on the Jaycar site isn't quite correct, they are silk/titanium.  I have removed the plastic surround and hacked them into place.  Sadly the mounting holes didn't quite line up with the original ones.  Impedence and frequency response are probably different to the originals as well so I should probably do something with the crossovers.  Now just waiting for some bass reflex ports to arrive from China so I can finish these and start tweaking.  The only original things left are the crossovers and the plastic badges ?

 

 

 

20201123_090716.jpg

I have a pair of those tweeters and they leak. In other words air pressure at the back from the woofers will pump the tweeter diaphragms. At least mine did going back some years.

 

To remedy this either put a sealed chamber behind them In the box to block back pressure or seal around the back of the tweeter. If I remember it is obvious to see where they are assembled at the back. Silicon seal this area. I’d smother the whole back of the tweeter with sealant. One it will stop back pressure and two dampen the tweeters. 

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Guest Old Man Rubber
2 minutes ago, mwhouston said:

I have a pair of those tweeters and they leak. In other words air pressure at the back from the woofers will pump the tweeter diaphragms. At least mine did going back some years.

 

To remedy this either put a sealed chamber behind them In the box to block back pressure or seal around the back of the tweeter. If I remember it is obvious to see where they are assembled at the back. Silicon seal this area. I’d smother the whole back of the tweeter with sealant. One it will stop back pressure and two dampen the tweeters. 

 

OK - I have to admit I didn't look at the backs of them too carefully, the entire back seemed to be magnet.  Without the bass reflex ports installed (they were missing when I got these) I guess I could plug the hole and see if the leakage is significant.

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6 minutes ago, Old Man Rubber said:

 

OK - I have to admit I didn't look at the backs of them too carefully, the entire back seemed to be magnet.  Without the bass reflex ports installed (they were missing when I got these) I guess I could plug the hole and see if the leakage is significant.

You could fill from the magnet down to the plastic mount. Could only improve the tweeter and seal it.  

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Guest Old Man Rubber
1 minute ago, mwhouston said:

You could fill from the magnet down to the plastic mount. Could only improve the tweeter and seal it.  

I didn't test them after re-assembly, have switched them in for the morning in place of the repaired Janssons.  Bass extension without the reflex tubes isn't terrific at the moment but it's fine for a double bass.

 

Streaming "Somethin' Else" (Cannonball Adderley) - the horrible mud from the blown tweeters has disappeared and now they are surprisingly listenable but that piercing brightness might take some getting used to.  Not the greatest recording to test a soundstage (very "stereo" release with solos coming exclusively out one speaker).  They have become very "studio monitor" sounding speakers if that makes sense.  Will disassemble and have a look at the tweeters sealing.

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Haven’t made one of theses for quite a while. Mimic chip based phono preamp. I’m happy with the layout which changes every time I make one. As long as they work and run dead silent I’m happy.


All carbon 1/4W Rs and a mix of MKT, polyester and low ESR cap. Differential  PS is on the brd. Output cap will be a Russian PIO.

 

Compact Al enclosure is sprayed gloss black and now ready for assembly. 

E5ABF64C-6280-4127-8313-79B904D5A33E.jpeg

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3 hours ago, barbz127 said:

Nothing overly unique but about to start wiring up a bottlehead crack

PXL_20201122_235541051.jpg

 

Post some more photos as it progresses.  I would like to see how  a kit like this goes together.  I have never actually built a valve based kit, all my stuff is my own ad hoc ideas :) 

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My transformer has forgotten the words...

 

56E44786-67BC-48DD-BC40-FCD17B65A235.thumb.jpeg.dad6c5b612367b32bef70a5c83516cb8.jpeg
 

I just put a new transformer in my Studer900-based dual linear power supply and it’s working but it’s humming. I had it custom-made on AliExpress so I don’t know if there’s something wrong with it or I’ve just wired something up wrong somewhere, the latter being the most likely explanation on account of me being an idiot. I guess it’s an earthing problem but, while my previous transformer had an “SCN" lead that I connected to the earth pin on my iec socket, this one does not. 
 

I’d appreciate any guidance or even exclamations of haughty derision, as long as it’s constructive. 
 

thanks in advance :) 

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Finally complete with only one little stuff up that was soon fixed. As said in an earlier post a mix of MKT, Polyester and low ESR electro caps. All carbon film Rs through. Differential PS onboard. Genuine OPA2134 from RS and machined milspec socket. Two 9V batteries for about 50 to 100 hours play depending on battery type. I often use eBay lithium’s first 100 hours.
 

Cast Al enclosure with bituminised heavy Al in the bottom for resonance and vibration control. Paint is Epoxy Enamel with an etching primer. The finish is gloss and tough. This one is also called “Carbon” for obvious reasons. 
 

Some don’t like carbon film resistors but I find they produce a very smooth sound but still let instruments shine in their own space. The preamp is new and requires about 50 hours to burn in. Listening to it now with late model Rega P3 and Gerrott P77i cart. Very nice and to think it will improve. 

AAFC19C3-A040-4DF8-8E9C-59F8793D377B.jpeg

8E9B20C4-33D9-4F8C-B5C4-74E82E0F4E5A.jpeg

8004B1D3-3782-49B0-9459-7D978C5206E3.jpeg

3BCFC25D-9473-4EB1-9F87-BB752FF1E4F8.jpeg

922DB436-F829-4E5D-AD64-4229F24E7AB2.jpeg

D86F2C43-C41F-4539-A8B5-85A875EB148D.jpeg

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Guest Old Man Rubber

Anyone used these kits for making speaker grilles or have suggestions for making frames to suit some speaker grille cloth?  Looking to cover up the faces of the grandfather's axe Dauphins

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On 23/11/2020 at 6:41 PM, RankStranger said:

My transformer has forgotten the words...

 

56E44786-67BC-48DD-BC40-FCD17B65A235.thumb.jpeg.dad6c5b612367b32bef70a5c83516cb8.jpeg
 

I just put a new transformer in my Studer900-based dual linear power supply and it’s working but it’s humming. I had it custom-made on AliExpress so I don’t know if there’s something wrong with it or I’ve just wired something up wrong somewhere, the latter being the most likely explanation on account of me being an idiot. I guess it’s an earthing problem but, while my previous transformer had an “SCN" lead that I connected to the earth pin on my iec socket, this one does not. 
 

I’d appreciate any guidance or even exclamations of haughty derision, as long as it’s constructive. 
 

thanks in advance :) 

The secondaries could be out of phase?

AC lines close to the one IC?

Edited by Ihearmusic
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Sounds good so far.

 

I've only listened to a couple of tracks to confirm its working; waiting for the oil on the base to dry properly before I bring it inside from the shed.

 

Glad I sprayed the top plate but If I was to do it again I would try and anodise it or something else that has a cleaner finish and less prone to scratching... Assuming such a finish is still conductive for the underside.

 

Bottlehead have a 15% off sale on at the moment for black Friday... Might have to queue up a follow on project.

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