Bucking Transformer DIY (Drop 240V to 220V)

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.

Bucking Transformer

Mr Liang 845 SET Tube Amplifier Driver Modification

Before I got back into using Solid State Amplifiers I had already gone through many tube amp kits, various KT style push-pull builds, 2A3 and a 300B Mono-Block SET for example. I eventually got talked into buying a 845 SET. This was my last tube amp before switching to a Nelson Pass F5 Class A. The build quality for a china made amplifer was high and this thing weighed a ton, far better than some of the typical China tube amp junk floating about on eBay. It really is a two man lift.. it is that heavy.

However, as good as the sound was on first use it soon became obvious that it could be easily improved and it had a few flaws, namely being a little rough around the edges.

 

NOS Tube Changes

Mr Liang 845 SET Tube Amplifier

Korsun Dussun V6i Integrated Amplifier Review

The korsun / dussun v6i is a monster of a power amp from china costing around 800 usd. It really is a poor man's krell or Mark Levinson that is built like a tank with dual mono construction in 1 stunning but large aluminium chassis. It is kind of a class A build in that the first few watts are class A were then it slides into class AB mode as it is driven harder; with output powers of 2x300 W into 4Ω and 2x150 W into 8Ω.

Korsun Dussun V6i Integrated Amplifier

Aikido Tube Pre-amp DIY

This was the third and final incarnation of the Basie Vacuum Tube Pre-amplifier from Diy HiFi Supply and it went through a complete re-design both in looks and the circuit it uses. The new circuit was based on John Broskie's famous Aikido design of TubeCAD fame. John kindly gave permission for his circuit to be used in this new kit. John is clearly a talented tube circuit designer, there are not many these days. I certainly don't claim to be. I just build kits and other peoples ideas :)

 

Design Changes

Aikido Tube Pre-amp

Vintage Trio KA Series Amplifier Repair and Re-Cap

I picked up this vintage Trio KA-4000A amplifier to use on my Desktop PC (DAW) to drive a small pair of book shelf speakers. However, the amp had a fault on testing so out came the iron and a box of spares. The fault was noise (hiss) and crackling on one channel. This turned out to be a faulty transistor, namely a 2SC458. This particular transistor is quite well known for failing and is a common part in many amplifiers and other audio equipment of this era. Therefore changing these is a must. If you have a vintage solid state Trio amp with a noise problem and it is not just a simple volume pot cleaning process then check for any of these 2SC458 transistors.

Trio KA-4000A

Joplin 2A3 DHT Push Pull Tube Amplifier DIY

The Joplin tube amplifier was a 2A3 or 45 based unit using 2 DHT power tubes per channel in push-pull configuration from Diy HiFi Supply. The unit featured a pre-amplifier stage and a volume control allowing it to be driven directly from a line level source negating the need for a separate pre-amplifier. I eventually rebuilt my unit to replace the pcb, making it all hardwired to create some space for larger Teflon caps. Below is the original build review in pdf format.

** I have included the circuits which would allow you to build this amp from scratch build as the kit is no longer available **

 

Joplin 2A3 DHT

Basie SRPP And Basie Mk2 Tube Pre-Amplifier DIY

The Consonance Basie Pre-amplifier kits were originally available from Diy HiFi Supply. The Mk1 was a SRPP based unit with a cathode follower output stage that could be modified to use other tubes. In my original build I eventually by-passed the cathode follower and used 2 x Mullard E80CC driver tubes making it an Anode follower.

Basie SRPP And Basie Mk2 Preamp

Billie Ladyday 300B SET Power Amplifier DIY

The Consonance Billie 300B SET amplifier kit was originally available from Diy HiFi Supply. This was a dual mono 300B single ended tube power amplifer with many upgrades and possibilities.

I upgraded this unit over a period of 5 years to incorporate the newer Ladyday 300B features such as the WE91 power supply, Ultrapath caps, MU driver stage and grid chokes. Below are the original various pdf files such as build reviews, tweaks and upgrades.

** I have included the circuits which would allow you to build this amp from scratch build as the kit is no longer available **

 

Billie Ladyday 300B SET Power Amplifier

Easy Super Clamp Mains Filter Clone DIY

It is possible to make a SuperClamp plug like the ones Russ Andrews sells for £20 using a standard UK mains plug and a few parts. Total cost is a few pounds. Simply take any UK mains plug, the MK ones are better since they have more space inside them but I managed with a Volex one. Inside the plug you need to connect a varistor across Live and Neutral. If there is enough space you should use 2 in parallel. That is it !! You can take this a step further and connect a varistor across Live and Earth and one between Neutral and Earth. They are very low capacitance like a typical Y-Class Cap and act as such here until clamping a spike. Blank the cable entry with a rubber grommet or some sealant if you wish.

 

In Use

Easy Super Clamp Mains Filter

Easy Build Audio HiFi Mains Filter DIY

An alternative to the full DIY mains filter build in the previous article is to use a standard chassis filter make by either Roxberg or Schaffner. These are off the shelf parts that come assembled in a metal box with input and output tags for L, N,E. They can be selected based on the current rating you require and have various choke sizes.

Choose a filter with a large inductance choke (10mH) for a source component filter like CD players, DAC, pre-amp or small integrated amplifiers for example. Use a smaller inductance (higher current rating such as 10A) for large dedicated power amp filtering. A mid range inductance (5mH) is fine for a computer based filter or more general audio use. The chassis filters can be bought from RS components, CPC and even on ebay occasionally.

Easy Build Audio HiFi Mains Filter

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