Audio HiFi

Linn Turntable Valhalla Power Supply Repair

Linn Turntable Valhalla Power Supply

I recently helped a friend to repair a Linn Valhalla power supply pcb. It would seem that these are prone to particular failures and a common one is low motor torque in which the motor buzzes or vibrates since it is too weak to drive the platter. This turned out to be R32 (560k) on the board. R33 had also deteriorated with the ceramic body breaking up. I have uploaded the circuit as a png and pdf file which some may find useful.

If you are having motor problems I would first replace these 2 resistors R32 and R33. Failing that then the next step is to replace the small orange caps around the logic chips if the motor does not turn at all.

Passive Lightspeed Attenuator Pre-Amplifier DIY

Lightspeed Attenuator Pre-Amplifier

I have been working on building a light-speed attenuator pre-amp in a nice case matching to match the chassis used in the Nelson Pass F5 and F3 power amplifier builds. This is a scratch build rather than a kit. I needed to buy the case from Italy and 4 quad matched Silonex NSL-32SR2 from the states. Matched LDR's can be difficult to get hold of and to match these yourself requires buying a large quantity and constructing a matching circuit to test them all across the working range. Quite costly and time consuming.

Power Amplifier Speaker Output Headphone Adapter DIY

Speaker Output Headphone Adapter

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.

Grado RA1 Headphone Amplifier Clone DIY

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.

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

VRDS Copland 288 - CMK-4 Mechanism

The Teac VDRS CMK-4 mechanism is used in the following CD Players :-

Copland 288
Copland 277
TEAC VRDS-7
TEAC VRDS-T1
WADIA 6
WADIA 8
WADIA 21
WADIA 850 (Version a mech)
Krell KAV-300
 

My Copland CDP

My Copland 288 started to shred teeth on gear B. I needed these assembly drawings to work out that is was called gear B and what to order from CHS. Emailing absolute sounds proved to be useless as I expected from past experience regarding their support. Anyhow, not too difficult to replace both gear A and B once you know how to. The original gear had turned very yellow and soft. A common fault with some Teac mechanisms.

Audio Note Kondo M77 Tube Pre-amplifier Clone DIY

Audio Note Kondo M77 Tube Pre-amplifier

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 original circuit in X-Circuit and the supply I used. 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.

 

Tubes (Single or Parallel)

Yamaha A-S1000 Integrated Amplifier Review

Yamaha A-S1000 Integrated Amplifier

I first spotted these in the windows of the long gone 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 BBC Radio sound more compressed and lacklustre compared to later shows at night so another reason for trying tone controls out.

Mains Spike Clamp DIY

MegaClamp Clone

It is possible to make something similar to a Russ Andrews Mega Clamp or the Super Clamp at a lower cost. The purpose of any clamping device such as this is to clamp very high voltage spikes on the mains to limit them entering equipment. A typical spike protector power strip or plug in box is built using Metal Oxide Varistor's (MOV). The cheapest kind use just one clamping device, usually a single varistor between L-N. A better protector will use at least three MOV's, between L-N, L-E and N-E. However, varistor's degrade over time with repeated clamping of spikes, therefore rather than using just 1 or 3 components I have used a bank of 10 in this build, you can use more if you wish.

Symphonies Plus Tube Pre-amp Review and Upgrades

Symphonies Plus Tube Pre-amp

The Symphonies Plus Vacuum Tube Pre-amp is made and sold by YS audio as a level 2 product for around £490 + duty and taxes in the UK. YSA have a scale of 1 to 4 for their products and they sell a number of pre-amps and power amps at various levels of internal parts quality and upgrades.

Nelson Pass B1 Buffer Pre-Amplifier DIY

Nelson Pass B1 Buffer Pre-Amplifier

I decided to make a B1 buffer for my Nelson Pass F5 power amp after listening to a friends version. The B1 is a no feedback JFet buffer that offers low distortion and noise with a very wide bandwidth. Being a buffer it has no gain and just acts as an impedance matching device with a volume control. It is really a source follower and outputs less than its input at less than full volume. It can be used between any source component and power amplifier and even used with another active stage. For example I have used it between my tube pre-amp and the power amp with the volume on the B1 set at maximum so it just acts as the impedance matcher. It is fairly easy to make and if you wish can be run off 2 x 9v batteries in series or a simple brick wall power supply that outputs 18 to 24V.

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