DMS Tech and Audio

Audio DIY

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Lightspeed Attenuator Rebuild

Fri, 24/02/2012 - 05:00 — admin

I have slowly been working on building another light-speed attenuator but in a much nicer case matching the chassis type used in the Nelson Pass F5 and F3 builds. This again is a scratch build rather than a kit. As usual I have built it with parts I already had to save cost but needed to buy the case from Italy and the 4 x Silonex NSL-32SR2 LED-LDR's from buildanamp.com in the states.

The circuit is simple so I built it on proto-board with hard-wire links on the copper side with the shortest routing possible esp on the audio links. I used some left over silver wire I had on the links that carry audio signals and these are situated at the back of the unit very close to the RCA sockets. I also avoided fitting a selector switch so it is 1 pair RCA in and 1 pair RCA out for the most direct signal route. That way we don't lose the advantage of using the LDR's to eliminate the usual audio carrying volume pot and its contacts and spoil that by routing audio through a selector switch or relay.

F5 Power Amp Headphone Adapter

Sat, 28/05/2011 - 19:05 — admin

I was wondering if it was possible to drive a pair of regular dynamic headphones from a power amp such as my Class A F5. Sometimes I have periods of time without a pair of speakers such as if I have sold them and looking for something new to replace them with. In the meantime it would be nice to use a pair of headphones which quite frankly are hard to beat with most speakers. It seems that you need to spend quite a few more in pennies on the speakers to match even a modest pair of cans and once you are in the realms of higher end headphones then most speakers don't come close to the same levels of enjoyment and immersion in the music.

I found a neat little project over at ESP. It is nothing more than a 6 resistors, 3 per side to give the correct voltage levels and impedance to the headphones. You could probably solder these resistors in-line with the headphone to speaker banana leads and heatshrink them but I used a small box, proto-board to hold the resistors and some nice nylon sleeving.

Pass Labs F5 New Power Supply

Mon, 21/02/2011 - 22:11 — admin

Upgraded Pass Labs F5 PSU

I decided to upgrade the standard build power supply in my Pass Labs F5 with some large screw terminal Aerovox caps from CPC. My original build used 4 x 22,000uF snap-in caps shared between both channels L+R on the PCB which is the recommended minimum. Some have used 2 of these PSU PCB boards, 1 per side which is the next step up. My late friend Dave Hewitt used 4 large caps in his F3 so I eventually followed and bought 4. This provided 47,000uF per cap so more than double the original capacitance and storage. I also by-passed each side of the supply lines with 10uF film caps.

The picture of the amp without the front fitted and test leads shows the original power supply PCB and snap-in caps. The new caps are about the size of a Red Bull can.

Sound and Aerovox Caps

Grado RA1 Headphone Amplifier Clone

Tue, 21/12/2010 - 00:14 — admin

Grado RA1 Headphone Amplifier Clone

Fancy making your own Grado RA1 amplifier clone. Well the circuit below is all you need. About £10 worth of electronic parts minus the case and regulated supply. Also very easy to make on veroboard or protoboard. The original circuit came from diyaudioprojects.com who I understand reverse engineered an original RA1. The design can be easily altered to use other better quality op-amps and more importantly E24 series preferred resistor and cap values.

The opamp used is the LM4562 or better still the OPA2134. You can use the cheaper original JR4556 but the OPA2134 should be easier to buy and is much higher quality than the JR4556.

Put it in a nice case with a power supply like Grado do and you have neat little headphone amp for little cost. Probably one of the simplest circuits to make based around an op-amp as it is a standard non inverting circuit.

Battery or Regulated Supply

Teac VRDS T1 / Copland 288 - CMK-4 Mechanism (Broken Gears)

Sun, 05/12/2010 - 02:31 — admin

CMK-4

The teac CMK-4 mechanism is used in :-

Copland 288
Copland 277
TEAC VRDS-7
TEAC VRDS-T1
WADIA 6
WADIA 8
WADIA 21
WADIA 850 (Version a mech)

Assembly and Part identification drawings are attached for replacement nylon gears.

My Copland CDP

Kondo - Audio Note M7 Tube Pre-amp Clone

Fri, 24/09/2010 - 21:03 — admin

DIY Audio Note M77 Clone

I have just converted my 12B4 tube pre-amp to this Audio Note M77 Clone. The 12B4 / 12B4A circuit was my reference bettering all other tube pre-amps I have owned in the past but this just betters it in so many ways. The circuit was linked from another overseas forum over at DiyAudio. Someone had opened up a real Kondo M77, took photos and traced the circuit plus measuring all voltages sketching this onto lined paper. I have re-drawn the circuit in X-Circuit and the supply I use. The M77 is built to such as high standard using quite special parts, with an equal special price that most of us could never afford or justify. Dave H as usual built this first in a few variations / tube types.

Tubes

Yamaha A-S1000 Retro Integrated

Thu, 24/06/2010 - 22:53 — admin

Reto Style

I managed to pick up one of the retro styled Yamaha A-S1000 integrated amps at a good price off eBay. I first spotted these in the windows of Practical HiFi and Sevenoaks and was taken back by the build quality and looks for the price. Furthermore I wanted an amp with tone controls and an headphone output. Yes... you read right... 'Tone controls'. Even in my narrow music tastes of Berlin School, Electronic and Ambient etc there is a wide range of mixes in that some sound lean and others the opposite; so I thought tone controls could be useful. Also the Radio seems to vary widely especially between daytime and night-time shows. Most daytime shows on Radio 2 sound more compressed and lacklustre compared to later shows at night so another reason for trying tone controls out.

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