Yulong A100 Headphone Amplifier Review and Capacitor Upgrade

The Yulong A100 is a class A headphone amplifier from the far east. They are not a well known brand in the west but produce some higher end models along with this reasonably priced unit. I have used tube headphone amplifiers in the past and wanted to try a class A solid state. It is a compact well made unit with a brushed black metal chassis, thick aluminium front plate and nice vintage style VU meters. The knob is plastic however but it still looks very good and not particularly plastic looking. Phono sockets are again good quality gold plated but it does not have an audio pass through facility which is an opportunity missed I feel. An audio pass though would make it a little more system friendly since it could be daisy chained with the system main amplifier from the source.

Yulong A100 Headphone Amplifier

Teac VRDS Copland 288 Rubber Tray Repair

The Teac VRDS mechanism used in many high end players does not age well. The gears go soft and start to perish making the unit skip on playback or the tray fail to open and close. These gears are very hard to find now and expensive if you do manage to find some. Therefore unless you have a 3D printer and a good set of gears as a template then I would avoid paying too much for any Teac based cd player.

 

Removing The Tray Rubber

Copland 288

Nelson Pass Labs B1 Buffer Pre-Amplifier Update DIY

Having sold the last B1 buffer I built I ended up building another. I had a spare pcb sitting around for a while and since it is such a good pre-amp, easy to build and the fact I had 90% of the parts already it was a situation of... might as well. It also meant I could use one of those nice aluminium cases from modshop in Italy to match my copland cd player and the lightspeed pre-amp case. Solid state builds such as this simple design do not have much to go wrong and testing is safe unlike tube gear. A big difference working on 18V here rather than 300V plus.

 

Matched Vs Unmatched

Nelson Pass Labs B1 Buffer

Grado PS500 Headphone Review

For the past year I have been using a pair of stax lambda pro electrostatic headphones with my Copland 288 cd player in one of my setups. I sold my Martin Logan speakers and wanted something as good but more suited to a small room, able to be used any time of day or night and as loud as I wanted with minimal external noise. Quality headphones are very hard to better with similar priced loudspeakers. They also provide a highly involving listening experience. Their diaphragms are much lighter than typical dynamic speakers and so have timing and pace unmatched bar the very best speakers. Electrostatic speakers do try to overcome this problem by the use of lightweight film which only weigh a few mg.

Grado PS500 Headphones

Linn Turntable Valhalla Power Supply Repair

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.

Linn Turntable Valhalla Power Supply

Passive Lightspeed Attenuator Pre-Amplifier DIY

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.

Lightspeed Attenuator Pre-Amplifier

Power Amplifier Speaker Output Headphone Adapter DIY

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.

Speaker Output Headphone Adapter

Grado RA1 Headphone Amplifier Clone DIY

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.

Grado RA1 Headphone Amplifier Clone

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

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.

VRDS Copland 288 - CMK-4 Mechanism

Audio Note Kondo M77 Tube Pre-amplifier Clone DIY

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 or justify.

 

Tubes (Single or Parallel)

Audio Note Kondo M77 Tube Pre-amplifier

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