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DIY audio: what are you building?


Paul Spencer

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I have also been thinking about a carbon version (of Mimic) with PIO Russian Mil caps on the output. In all builds I have used Metal film resistors and even Vishays. Lately I have built a few tube power amps with all 1W carbon film resistors. They produce a very mellow and rich sound with great musical flow. So I think why not a Mimic in Black Shadow Al enclosure but with all 1/4W carbon film resistors. Also I have a bunch of Russian 4uf PIO Mil. caps. 4.7uf caps are required on the output. In the past I have used Polies, NP electros, Solen and others. 

 

Even if I had a standard Mimic it would be nice to have the carbon version to add some variety to my vinyl listening. Just a thought at the mo but easily achievable.

 

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I'm gong to build a Mimic a "Carbon". I was going to get the parts yesterday but found no 1/4W carbon resistors on the shelf. Then at home remembered they are sold as a pack. Unfortunately I'm going to end up with 90% of the pack I can't use but that's how it is. So now I have more carbon then I ever needed. 

 

Made a start today and have the differential PS (which is built on the same piece of 5cm square veto brd, as the rest of Minic) compete. I'm changing most of the caps from MKT and MKP types to Polyprops and PIO. With carbon film resistors and quite different caps Carbon film resistors should have a much different sound to the standard Mimic. Warmer and smoother. 

 

I going to take this build even further with the enclosure being a much larger cast Al type with large gold sold brass cones for feet. Carbon may be a unique build with an unusually mix of passive compnents. I'm still undecided whether to use an all bipolar LM833 or the high performance jFet\bipolar OPA2134. I kind of like the fast edgy sound of the 833 but I can roll chips 'till the triffids come home. Plug and play design makes it so easy.

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Finished Mimic - Carbon. On a short listen rich and warm. I wanted it to run on one 9V but it distorted. It should have worked. I have managed to cramp to 9V in there and now perfect.

 

1/4W carbon film fine resistors, polypropylene and PIO Russian Mil. caps - should sound different. All in a Black Shadow cast Al enclosure. WBT silver base solder as usual.

P8133627 (800x568).jpg

P8133628 (800x598).jpg

P8133629 (800x570).jpg

P8133630 (800x599).jpg

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What's the big R+L red thingos there Mark @mwhouston?

 

Those enclosures are pretty good to work on, not too hard metal, and you can get a decent finish. The only thing I don't like about them is that the sides are not straight going down, but I can live with that.

 

Cheers,

 

Alberto

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3 hours ago, betocool said:

What's the big R+L red thingos there Mark @mwhouston?

 

Those enclosures are pretty good to work on, not too hard metal, and you can get a decent finish. The only thing I don't like about them is that the sides are not straight going down, but I can live with that.

 

Cheers,

 

Alberto

Being cast Al they have to get them  out somehow and the slope side help. The big red things are Russian Military PIO (paper in oil) 4uf caps. I've snubbed them with 220nf polies to bring them to 4.22uf where 4.7uf is required. Not only that putting a smaller cap (e.g. 0.1uf) across a larger cap provides a HF shortcut and suppresses nose from caps. Not that PIO caps generate any noise but most other caps do. 

Edited by mwhouston
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I wanted to compare the latest Mimic - Carbon with a two stage chip phono preamp I had built a few months earlier. Also I wanted to compare the two 6L6 SE UL power amps I had recently built. And further wanted to know, sonically, how my 250W Class D fared against the two tube amps.

 

A fellow Melbourne Audio Club member had dropped in to talk about some Raspberry Pi issues he was willingly to give an opinion about the A/Bing I was about to do.

 

Result:

  • The new Minic - Carbon was very close sounding to the two stage phono pre with totally different passive and active parts. Maybe the retro-833 (two stage phono pre) had it in the end. I have to agree.
  • The two 6L6 power amps again were close with the Carbon resistor and 1944 military metal tube version just edging out the JJ tubed, Mundorf Silver supreme capped brother. Again had to agree.
  • The Class D amp with the IRS2902 gate controller came in second to the 6L6 2W power amps. My judge and jury felt the tube amps had a better top end than the Class D. All the Class Ds I have built all have quite a warm almost tube sound but with greater detail. I was surprised by the remark the Class D lacked top end. 

 

The retro-6L6 SE UL metal tubed amp stayed in the system over the other amps but I went back to Mimic - Carbon. This is really a great MM phono pre (only a few days old) but I may have to put it up for sale as I have too many DIY phono stages. It is extremely good sounding though. Bass is full bodied and deep and has great clarity in the mid-range.

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With daughter STILL studying for uni I'm STILL listening to a lot of music on headphones. I have Pi2B setup with HDMI audio extractor. This combo plays DSD64. But yesterday I tried something I have wanted to do for a long time.; listen to vinyl over phones. 

 

I have a Audio-Technica TT with a  number of MM carts which I use for cart rolling. The new Mimic Carbon as the MM stage and an Oatley K272C portable triode headphone amp and three (really four)pairs of headphones. To spice it up a little I replaced the OPA2134 in the HP amp with a Burson V5i-D high performance OPAMP. With a Stanton 881s cart (with new stylus) and Sennheiser  700s the sound was glorious. After a few hours I swapped to the Audio-Technica AD700 Airs. Way too much hiss. I have no idea where this came from. So I went onto the Beyerdynamic 250ohm DT770 pros. This was combo was now 100% perfect and I spent the next few hours with it..

 

I also tried a new Garrott K2 cart but there was some distortion coming from somewhere so back to the Stanton. 

 

 

 

K272C with Burson V5i-D.jpg

TT setup (449x800).jpg

Edited by mwhouston
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  • 2 weeks later...
  • 2 weeks later...

This weekend has been spent designing and building a pair of 2 way active crossovers/amplifiers that I can use in several upcoming projects

 

The amp IC is the TDA7297, which seems to output enough for most home applications and is fairly well regarded among other low power amps

 

IMG_20170909_130937_HDR.thumb.jpg.dbf18eff25ca7e397331391f811e5c8f.jpg

 

IMG_20170910_122127_HDR.thumb.jpg.8ff27c90bca91aa0c078c3aebbc57b17.jpg

 

IMG_20170910_205917.thumb.jpg.69ce60b292eb93490a562403dccd9f1a.jpg

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16 hours ago, oohms said:

This weekend has been spent designing and building a pair of 2 way active crossovers/amplifiers that I can use in several upcoming projects

 

The amp IC is the TDA7297, which seems to output enough for most home applications and is fairly well regarded among other low power amps

 

Great stuff, I have a TDA7297 amp I use as the HF component in my active system sometimes, its a great little amp for a handful of dollars. Very low idle power use as well. I'm using one of those cheapo PCBs from ebay though. I did buy some better designed boards but have yet to get around tuit (plus I'm over supplied in small amps).

 

I have just decided to jump back into some light semi DIY audio hobbying and have purchased a Texas Instruments evaluation board for the TPA3255 chip (there is a special on right now), which is newer Class D chip to replace my IRS2092 based L.F. amp in my active system. Not completely DIY as the board is already assembled, but I do have to sort out the wiring and power supply and stuff.

 

 

 

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1 hour ago, mwhouston said:

@zog I think I bought a valve amp out to your place one hot night for a listen. Correct?

 

Do you have a link to where you bought your bass driver for your speakers? And specs.

@mwhouston Yes - that was me! fun night.

 

I got the bass drivers from ebay second hand, they would have been out of my budget otherwise.

 

But they are Lorantz 15″ C390X B1 drivers (made in Dandenong)

 

Manufacturers specs here: http://www.tubeaudio.com.au/content/lorantz/A-C390X-B1-8.pdf

 

My measurements (which were close) https://minirig.org.au/2013/06/02/cabinet-ideas-for-the-lorantz-c390x-b1-8-woofer

 

 

 

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17 hours ago, zog said:

@mwhouston Yes - that was me! fun night.

 

I got the bass drivers from ebay second hand, they would have been out of my budget otherwise.

 

But they are Lorantz 15″ C390X B1 drivers (made in Dandenong)

 

Manufacturers specs here: http://www.tubeaudio.com.au/content/lorantz/A-C390X-B1-8.pdf

 

My measurements (which were close) https://minirig.org.au/2013/06/02/cabinet-ideas-for-the-lorantz-c390x-b1-8-woofer

 

 

 

Just got a price. They are $420 each. You have speaker test gear what is the -3db point for the lowest frequency in your room?

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6 hours ago, mwhouston said:

Just got a price. They are $420 each. You have speaker test gear what is the -3db point for the lowest frequency in your room?

That's better than the price I found online years ago! I dug up some RoomEQWizard files done with my mic and 27Hz from inroom measurements.

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21 hours ago, mwhouston said:

So you measured 27Hz at -3db? Do you have your box specifications?

I may have to revise that, I am using quite a bit of miniDSP EQ on my regular settings, I have a no EQ measurement here https://pix.minirig.org.au/main.php?g2_itemId=6442 and I just added a whole bunch of links about the enclosure to the "main thread" where I discussed this system a while back.....

 

There's a fairly long thread at

it doesn't have all the cabinet info but I'll add it to the end, plus some other links (I have quite a lot!)

Edited by zog
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