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Old

Tapped Horn

Posted 22nd December 2011 at 02:34 PM by DougL

Found this Discussion and resources:
http://www.cowanaudio.com/th.html
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Old

47 Labs 0247 "Treasure" unboxing

Posted 21st December 2011 at 03:33 AM by rjm (RJM Audio Blog)
Updated 22nd December 2011 at 09:47 PM by rjm

It's here!

It came in a box the size of a small shoe box.

Curious, delightful mix of the mundane and the exotic, outwardly plain but clearly immense thought and effort has gone into the preparation.

The gorgeous hammertone finish, hand-matched transistors, and ultra-high quality machined volume/selector knobs are the little signs that immediately set it apart from the ordinary.
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Old

The cost of hi-end audio: is it worth it?

Posted 20th December 2011 at 05:16 AM by rjm (RJM Audio Blog)
Updated 20th December 2011 at 05:30 AM by rjm

Having recently actually bought some new (not used, not my own design, and relatively expensive) audio gear, and from 47 Labs no less, the following question has been occupying my thoughts of late:

How much would you pay to not have a component installed in the audio equipment you buy?

The traditional price scheme for audio equipment is [BOM-times-X], where BOM is the cost of the parts used to make it, and X is a multiple to cover fabrication and distribution costs, as well as profit for the various parties involved. My understanding is that for consumer audio "X" is about 4, though companies with strong brand recognition can get away with higher multiples. And do.

The basic problem is this: how much it costs to build and how good it sounds are not the same thing. There is some correlation: a large, high quality transformer is pretty much guaranteed to improve the sound quality, but for the rest, stuffing a pretty box with many cheap...
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Old

47 Labs "Treasure" 0247 shipping update

Posted 19th December 2011 at 11:19 PM by rjm (RJM Audio Blog)

Scheduled to be delivered tomorrow evening!
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Old

Zen V4-J

Posted 17th December 2011 at 01:12 PM by alexcp (My DIY projects)
Updated 12th May 2013 at 04:03 PM by alexcp

Now that Nelson Pass published the details of the JFET upgrade to First Watt F2 and that Newark sells power JFETs from Semisouth, there was no excuse not to upgrade my Zen V4 with the new active device.

I replaced Q1 (see the original schematic) with SJEP120R100A; increased R5 to 130 kohm to bias the JFET correctly with Vgs of approx. 1.5V; and reduced R8 to 22 ohm.

The measured result is a nice reduction in THD+N; attached are the graphs for THD+N @ 1W into 8 ohm vs frequency, before and after the upgrade. With IRFP044 as Q1, the distortion was mostly 2nd harmonic (at -65dB), plus some traces of the 3rd harmonic. With the JFET, it is still mostly 2nd harmonic, which is now at -80..85dB, with the 3rd below my measurement floor.

Subjectively, the improvement is remarkable! There is additional detail and depth of the scene.
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Old

Fascinating: SMT attenuator retrofitted into ALPs case

Posted 17th December 2011 at 02:08 AM by rjm (RJM Audio Blog)

http://www.icl.co.jp/audio/att.htm

Less than 3,000 yen, too. Pity it's only available as 100K types, but for tube amps this is a pretty handy little part to have around.
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Old

47 Labs 0647 "Treasure" CD player diy kit

Posted 17th December 2011 at 01:54 AM by rjm (RJM Audio Blog)
Updated 17th December 2011 at 02:01 AM by rjm

Fancy building your own CD player with built in non-oversampling DA converter from a kit?

Look no further.

Based on a TEAC transport and ye olde Philips TDA1543 for the nonoversampling DAC

DAC is basically the Progression DAC (see DAC of ther Klones) reborn.

or salient details:

-top loading, close to the lit to automatically load the TOC.
- isolated digital and analog power supplies
- ATMEL AVR microcontroller, custom program/operating system
- simple, easy to understand display and controls
- standalone or use as a transport with external DAC
- small footprint, B5 size(W250 H65 D175mm)
- comes with a remote!

Although offered as a kit or pre-built, my suspicion is that all the real work has already been done: programming the microcontroller, now that's an area where most DIYers still fear to tread!

Not too many kit/home build CD players...
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Old

47 Labs 0347 "Treasure" stereo amplifier

Posted 15th December 2011 at 11:33 PM by rjm (RJM Audio Blog)
Updated 19th April 2015 at 11:27 PM by rjm

(regarding the Treasure 0347 stereo amplifier)

Well, think of it as a bulked-up headphone amplifier. The design is one of those "ah, I should have thought of that" moments, but the details are quite tricky, as usual.

If the extend the basic "voltage stage + current buffer" topology of the 0147 headphone amplifier out to 40 wpc territory, you end up with the 0347.

The high power means that unlike the headphone amp design you have to run it out of class A, and that means closed loop operation.
While most people might be tempted to wrap the voltage feedback around the whole shebang, this basically ends you up with a big op amp. Op amps, with their massive negative feedback design, are not so happy driving high inductance/capacitance loads like speakers.

The trick 47 labs uses is to have two feedback pathways, with heavy "local" feedback around the op amp and a small secondary global loop from...
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Old

Other options for a headphone amplifier.

Posted 15th December 2011 at 01:02 PM by rjm (RJM Audio Blog)
Updated 15th December 2011 at 01:08 PM by rjm

While I wait for the guys at 47 labs to get the Treasure 0247 together, I took a look around at some of the alternatives.

The Yulong D100 looks quite attractive and for about 2/3 the price of the 0247 kit you get a fully assembled unit!

review at head-fi

Or if you can do without a DAC, HLLY audio has your standard "transistor buffered op amp" implementation in a no-frills case:

HLLY RMK-5

It's listed at $240 but for sale on eBay for only $99 right now.

Of course there are dozens, but I single those two out as being particularly deserving of "honorable mentions". I'm still set on the 0247 though.
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Old

47 Labs "Treasure" Model 0247 DAC/Headphone/Preamplifier

Posted 14th December 2011 at 05:56 AM by rjm (RJM Audio Blog)
Updated 17th December 2011 at 01:36 AM by rjm

Just placed my order for this. I am customer no. 00028!

47 Labs web page

I figure I owed it to them. 47 Labs has been good to me, and the DIY community over the years, one way or another: gainclone, phonoclone, even the DAC-of-the-Klones.

Besides, several reasons:

1. I really want to finally hear 47 labs gear, instead of trying to reverse engineer it all the time!
2. It will be interesting to compare it against the sapphire amp.
3. I'm sure it will be fun to build and examine up close.
4. It's my Christmas present.
5. And hammertone. Finish a audio product in grey, or even better, green hammertone, and its as bees to honey...

Will blog the unboxing, building, and testing right here.
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