De-Mystifying Sovtek 12AX7 WA WB WC Variants I thought it worth the time De-Mystifying Sovtek 12AX7 WA WB WC Variants. Why are there three versions of the Sovtek 12AX7 and why use one versus the other? One common characteristic of all three types is that they are very low in microphonics. The “W” in the part number is there to tell us its a ruggedised valve. Ruggedised valves are made to withstand more vibration than […]
A Marshall JCM900 100 Watt Combo arrived in the workshop. This version is the 4102 It was very poorly. The first issues seen were : 10 amp fuse in the plug!! Low power output and VERY loud mains hum Pots noisy Amp plays a dying gasp when amp switched off Pops / crackles and very low volume. The valves were tested on an AVO MkII and CT160 tester. The preamp valves were down to a lot
The early (1997-2003) Marshall JCM2000 DSL50, DSL100, TSL100 and TSL122 amps are often troubled by an unstable bias (drifting bias). These are nice amps and I have one myself This can be difficult to diagnose correctly, as it can take half an hour or more of testing and/or playing before this Marshall JCM200 bias drift shows up. . Due to this drift the bias current of the output valves will gradually increase, and keep increasing,
Here are Things learned about Tube Amps in 2018 . They are in no particular order. Perhaps some useful info about your amp. I thought I would share them before they faded out of my head Loudness Your ears respond to sound like a compressor. So when you ears hear the sound from a 10 watt amp and a 100 watt amp, you don’t hear an amp that is ten times louder. Your ears hear
A friend has an ACOM 1000 amplifier. It is used on the HF bands( short wave bands) . It uses one valve for the output and the valve is a Svetlana 4Cx800A. It produces 700-800 watts from a 30 watt input. The valve runs on 3000 volts. You can imagine if something goes wrong in the amp the bang would be BIG ! The designers built a whole load of monitoring circuitry around the valve
Here are a few things to watch out for when buying second hand valve amps. Valves are very old technology and so valve amps inherit the unreliability of old tech. Keep in mind the 6L6 output valve was launched on the market in 1937. Just think about driving a car today that was designed in 1937 and is unchanged today. Cars back then broke down all the time and dissolved in the rain. So don’t
While we do our day to day the day to day work, we find some interesting useful websites and some we just like.. I thought I would be brief and share some things them. They are in no particular order. Honeyboy amps make some really nice looking amps. They are based on the early Fender Tweed designs and are hand wired. Andy makes a lovely 5 watt amp and if you are a harp player
