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Posted 6th March 2015 at 07:58 AM by dvb projekt

Dear diyaudio friends,

atm i am not able to to order new batches from the Red Baron and the Tube-I-zator.

The problem is the USD/EURO exchange rate. I must wait till the EURO comes up again,
because i donīt want to adjust the prices for you.

Best regards,

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dantimax (contact information)

Posted 25th February 2015 at 02:56 PM by djg440

Was wondering if any one can help with how to contact...
I have placed a order for three remote boards and three motorized alps pots.
all of the contact links do not go through that is supplied on his sights. Hopefully someone has a email address or contact information that has worked for them and can share it.
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Which is better, Sennheiser HD600 or AKG K702?

Posted 25th February 2015 at 12:24 PM by rjm
Updated 25th February 2015 at 11:41 PM by rjm

The HD600s.

Ok, so why donít you like the K702s?

I didnít say I didnít like them. Just that I think the HD600s are better.

Itís pretty simple really:

The K702s have a strident, hard upper-midrange "bump" that I find disagreeable. Yes, it makes tracks sound more ďliveĒ, but itís also fatiguing and a bit clinical, and - as many others before have noted - makes the sound overall somewhat thin. In direct comparison the HD600s seem full the point of boominess, but I'm willing to accept that midbass plumpness for the Sennheiser's warmer, luxurious midrange. In imaging, the K702s trend to a wide, distant, airy soundstage while the HD600s run towards a closed in, intimate presentation. In that sense the K702 are more like listening to speakers, and I can certainly see people being attracted to that.

These are both top-shelf headphones at the top of their game, I don't mean to imply that the AKGs are bad. The two...
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Random hippie checking out the waffle amp. Er, and his new bass.

Posted 24th February 2015 at 06:21 AM by mlise

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Z-reg II improved simple Zener voltage regulator

Posted 22nd February 2015 at 01:24 AM by rjm
Updated 28th February 2015 at 06:17 AM by rjm

I've added an additional RC filter stage (R3, C4 in the schematic below) before the Zener diode, substantially reducing the amount or ripple on the transistor base by cleaning up the voltage applied to the Zener reference. (The original Z-reg is described here.)

Circuit shows C2 with a value of 300 uF. Typically much larger values are used. I kept the filter capacitance to a minimum here to show circuit working with a reasonably high ripple (1 V p-p) on the input. The rectifier diodes used here are of no particular consequence, I just wanted the simulation to generate a realistic sawtooth for the input.


OK, this doesn't do as much as I originally thought. The improvement is mostly below 100 Hz, whereas the ripple is mostly in the 100Hz-1kHz band. There's perhaps 3 dB less output ripple, but that's about it. You can verify this yourself in LTSpice, just cut the wire between C4 and the junction or R1-R3 and rerun the sim.
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Where I'm standing today, DIY F4's to begin soon.

Posted 17th February 2015 at 09:02 PM by Jeffs
Updated 17th February 2015 at 09:10 PM by Jeffs

Here goes!
This all got rolling after checking CL then picking up some 30+ year old 4 ohm speakers I had wanted since I could drive to a store and drool. Sure, might rather have some old Polk SDA's like the ones briefly owned in 1989, but am happy with what I got and the price.
I started reading DIY Audio a few years ago, and a couple of years ago was sure I was going to build one of the F5 Turbo variations one day. After disappearing for a few hundred hours to read all of the treads I was confused and it was time to buy a new roof, and spend a couple of months in India... so had to quickly forget about the idea.
I should have done an Amp Camp project to learn more about what does what.

This morning I ordered JFET's and MOSFET's from Alex (Alweit), has an eBay store and is a member on the forums.
I picked up the F4 boards from the DIYAudio store a few months ago, probably after Jim (6L6 on the boards) initially read about my ideas of...
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Supercapacitor b*ll*cks

Posted 15th February 2015 at 11:50 PM by abraxalito
Updated 16th March 2015 at 03:25 AM by abraxalito (Red Wine it isn't, just the same designer)

Here's something very misleading in the 6moons preview of Vinni Rossi's (of Red Wine Audio fame) latest supercapacitor powered kit. They have 18 * 350F supercaps in the box and they say '...the total rating becomes a whopping 6300F'. However each capacitor is only 2.7V so presumably to get any audio signal at all out, they need to operate these caps in series. Caps in series don't multiply, they divide so the total capacitance drops by a factor of 18. Hence only 19.4F. Not a small difference from 6300F or did I miss something? (the text at this link has since been updated to remove the 'total rating...whopping' remark).

I think I may have missed something - they aren't using all the supercaps all the time, rather there are 9 discharging and 9 charging. So the total capacitance in the audio circuit at any time is 350/9 = 39F. Still an impressive amount of capacitance but the problem is that the ESRs add too....
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Gustard H10 Headphone Amplifier

Posted 14th February 2015 at 11:47 AM by rjm
Updated 12th April 2015 at 02:59 AM by rjm

Technical Specifications:

Signal Input : 2x XLR female , balance
2x RCA, unbalanced
Maximum input level : +21 dBu, impedance 10kΩ
Input impedance : XLR: 10kΩ, RCA: 68kΩ
Input Sensitivity : +6 dBu
Main amplifier gain : +8 dB
Main amplifier gain adjustment range : -4 / +2 / +8 / +14 / +20 dB
Frequency response : 0-55kHz (-0.5dB)
Damping Factor :> 400 @ 50Ω
Dynamic range :> 128dB (A -weighted )

THD + N (1kHz 1W @ 100Ω): <0.00035%
THD + N (1kHz 0.5W @ 32Ω): <0.0007%
Crosstalk :-110db (1kHz)

Each channel has a BB OPA134PA - socketed - for voltage amplification and an eight transistor discrete buffer with 2 ea. 2SA1837. 2SC4793, C546B, C556B. Dual mono layout - more or less ... the circuit board itself is shared and not completely symmetric. There's a pair of NE5532s at back for balanced-unbalanced...
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Reference Music Server Finally Making Music

Posted 13th February 2015 at 04:16 PM by wlowes
Updated 22nd August 2015 at 01:24 AM by wlowes (Next tweek.. CLCLC supply to -15v and DC blocker circuit)

Disclaimer that this entry is just a scrap book of my personal journey with a build. No fresh engineering here, so those seeking engineering insights can save the read.

That said, my new music server is now fully burned in, and for me its a delight. It is a collage of ideas developed by diyaudio members and by Lukas Fikus, aka Lampizator. Thanks to all who contributed. I hope these notes pass on some ideas for others.

Basic Approach
My approach is heavily influenced by Lukas of Lampizator fame. I have enjoyed his tube output amp design in my previous DAC, and several cd players. He got me interested in the TDA1541a, and I have had many years of happlily tweaking it for best sound. This server has a clone of his level 6 DAC with tube rectifiers, dual mono supply and film caps in CLCLC configuration.

Also, my digital evolution came via CICS CMP which taught me to appreciate a minimalist PC processor with network attached storage...
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Eltax Liberty 5+ modification

Posted 10th February 2015 at 08:22 PM by Maciej Czerwinski

I bought these speakers in 2000. I was unhappy with the way they reproduce low frequencies. I decided to add a subwoofer. I used the fact that the lower part of the housing of the speaker is empty and isolated from the upper part in which the speakers operate. I cut a hole in the side of the bottom part and installed a 25 cm driver.
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It is Vestra PW-250-2154 woofer.
It has a 19 cm coated-paper membrane, foam external suspension, extruded metal sheet basket, ventilated 4.5 cm coil, the diameter of the magnet is 12 cm, 80 W, 4 ohms, the self-resonance (Fs) at 27 Hz.
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I damped the interior of this newly created enclosure space with bitumen mat and felt glued to the walls and filled it with fleece. I cut out the rear wall from the top part of the enclosure. Inserted a reinforcing crossbars into the lower and upper housing. The upper part of the housing is entirely filled with a damping material (with fleece filled pillow, which...
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