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.

Diy HiFi Supply EZ Preamp Kit

Diy HiFi Supply EZ Preamp Kit

The EZ kit from Diy HiFi Supply is a a linestage pre-amp with an adjustable gain from 6, 12, 18, 22 and 30db. Input impedance is 400k+ depending on the gain setting chosen and consequently measurements vary with different tubes fitted. This is not my own unit but for Val I know who asked me to build this pre-amp with some special custom modifications.

Upgrades :-

Blackgate PSU Caps for HT and Heaters
Calrity Caps for Audio Coupling
Wima FKP Flim PSU By-Pass Caps
Gold Plated Silver Audio Wire in Teflon
Seiden Selector Switch
Japanese Step Attenuator
Silver WBT Style RCA Sockets
Custom Made Wooden Knobs


Nelson Pass F3 Class A Single Ended Amplifer DIY

Nelson Pass F3 Class A

When I was building my Nelson Pass F5 power amplifier, a Friend (Dave H) was building his F3 at the same time. This is the result, using the same Italian Made case as the F5. The F3 is again a class A design like the F5 but that is where the similarity ends, the F3 being 15W single ended were-as the F5 is 25W push pull. The F3 output is Capacitor coupled since it uses a single rail power supply were-as the F5 needs a split rail supply. Also due to the F3 lower power output it better suits an easier load were-as the F5 is a little more forgiving.

Havana PCM56P DAC Upgrade DIY

Havana PCM56P DAC

I was asked by a friend to upgrade his Havana DAC with some better capacitors and non magnetic resistors in key locations which he supplied. This is the result and these are Val's ideas for upgrades. Output coupling is now by Clarity caps with Glass based Russian silver mica and BlackGate caps used elsewhere except the power supply which keep the original Gold Muse caps. This DAC uses a classic Bur Brown PCM56P chip with a simple form of conversion using matched resistors in a ladder configuration. This results in less signal manipulation during the conversion process. Those clarity caps are huge and only just fit in the case and I had to fit them rotated 90 degrees compared to the originals. These would not be my choice for practical reasons of fitting as the unit is very compact.

Nelson Pass F5 Class A Power Amplifier DIY

Nelson Pass F5 Class A Power Amplifier

Recently I have been moving away from vacuum tube power amplifiers and more towards solid state amps capable of driving a pair of Electrostatics, namely an older pair of Martin Logan made around 1995. These speakers have newish panels and rebuilt cross-overs with brand new film caps. However these speakers are a difficult load and quite current hungry. I have also tried these speakers with other power amps, namely a Korsun / Dussun v6i in power amp mode capable of 400W into 4R, an Accuphase P180, a Crown Pro Audio, a few tube amps and finally this F5 which is my main amp at present. This amp was a scratch build using PCB's bought via a group buy. Case is from Italy and other parts from RS and CPC. I used premium parts when available and later upgraded to Aerovox caps for the PSU.

12B4A Tube Pre-amplifier DIY

12B4A Tube Pre-amplifier

If you do a quick search though the forum you will come across an old thread that was once very active. It is based around building a 12B4A based pre-amplifier. The circuit given uses a regulator in the cathode for a constant current design but a resistor can be substituted in its place. The main circuit is very simple, easy to make which I always like. It was also getting quite favourable reviews from those who had built it so I decided to have a go myself. I wanted a pre-amp at the time to test with a 20W Mr Liang 845 SET, which although is an integrated, sometime needs a good pre-amp for a little more gain. I also later tested this pre-amp with the large Korsun (Dussun) V6i transistor power amp from China and a DIY 25W Nelson Pass F5 Class A power amp.

Martin Logan Crossover Upgrade DIY

Martin Logan Crossover Upgrade

My Martin Logan Aerius speakers had been fitted with new panels but the cross-overs had never been touched in 15 years. I replaced the most important original panel capacitors which consisted of 1x10uF Solen film wired in parallel with 1x20uF Non-Polar electrolytic with 1 single large 30uF film cap. I also replaced another 10uF electrolytic with a single film cap. Other caps are a little too large in capacitance for a film cap and they are only used on the Bass unit anyway to shunt high frequencies to ground so less important as no audio passes through that ends up at the panel.

Bucking Transformer DIY (Drop 240V to 220V)

Bucking Transformer Circuit

The problem with many china made tube amplifiers from the likes of eBay is the voltage requirement being 220V. Do not believe the voltage written on the back of most china HiFi. My now sold Mr Liang 845 SET amp was marked as a 240V unit but checking the 6.3V heaters showed them to be running high at 6.85V and the 845 heaters at 11V. This means all the voltages can be 10% higher including that HT !! A problem waiting to happen. A higher voltage may not be an issue for a transistor amplifier or CD player that is well made with over rated components. However with vacuum tube amps the heater voltage can be a problem in that it will shorten the tube life if they are running hot. Also the heat output can be an issue and the HT being higher may stress other parts.


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