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Monkeyboi

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Monkeyboi last won the day on May 17 2014

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About Monkeyboi

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    D.I.Y. Audio Enthusiast

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    Bakers Hill
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    Australia

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  1. Ah, the Stereonet website on the big monitor and those speakers. Good to see the priorities are in order. 👍 Cheers, Alan R.
  2. Good to read that you are doing the best you can not only to keep your community safe but also to keep the wheels moving. We often take these services for granted and don't value them until they are no longer available. Kudos to @colinm1 Thanks for the heads up and suggestions regarding parcel movements at the extremely small LPO in my town of Bakers Hill. I'm expecting things in the town to be very quiet as from Tuesday as most of the activity is because of the passing tourist trade that stop at the famous Bakers Hill Pie Shop (great pastries and cakes, terrible coffee). There is an upside to all of this. There won't be any bus loads of "shoppers" coming into my closest regional centre town of Northam from the city and stripping the supermarket shelves of just about everything. Hopefully things will get back to normal soon by everyone doing the right thing. I would not like to see some of the measures implemented overseas like house lockdowns, curfews and complete bans on been able to get certain supplies and services. Anyhow, in the coming weeks the electronics service workshop in a separate building on the property will be getting a well overdue makeover. Take care everyone. We have a great community here on SNA. Cheers, Alan R.
  3. Western Australia will go into regional lockdown as from midnight on Tuesday. For just about everyone this means no travel is permitted from one region to another except for essential services and medical emergencies AFAIK. As my business basically is face to face lecturing and based in an adjacent region I can no longer service my clients even if I or they wanted to. I can still keep the service workshop for electronic repairs and instrument calibration, but if the device has to come in or out of the region I will be 100% reliant on Australia Post. Obviously practicing physical social distancing as I believe this is a strategy that will ultimately slow the rate of infection and flatten the curve when this insidious virus takes any more hold than it already has. Anyhow, do your best to stop the spread and please stay safe. Cheers, Alan R.
  4. So far I've never had a problem with my Sony. Maybe I'm just lucky. 🤪 Cheers, Alan R.
  5. Pretty poor customer service IMHO on the part of Lehmann. The phono stage is still under warranty? I doubt the ceramic fuses were "bad". Never been a fan of "audiophile" fuses. Cheers, Alan R.
  6. Thanks for the heads up @neweskimo Cheers, Alan R.
  7. The importance of matching depends on the circuit and the degree of differences in transconductance of the valves (tubes). I don't have the schematic for this pre so I'm reluctant to comment further as to what extent matching will affect the performance. However at $10 per you've not got much to lose. Google the datasheets for both the 6933 and the 6N23P to see the differences (if any). Cheers, Alan R.
  8. Welcome Tom, Don't worry it's just part of the journey. The vinyl gear will probably graduate to a $20,000+ turntable and a $10,000+ cartridge. Then comes the very expensive phono stage, the esoteric cables et al. Welcome to the club. 😃 Cheers, Alan R.
  9. You're welcome. If the manufacturer offers say a 5 year warranty, then they probably have designed and expect it to last that long. They don't like having to pay for warranty repairs. Cheers, Alan R.
  10. Agreed. Replacement of the electrolytic caps would be my first move on an old amplifier. I look up the specs for the specific caps and estimate their remaining lifetime. Anything that looks sus (bulging or vented caps get replaced immediately.) Cheers, Alan R.
  11. Unfortunately the answer to your question is "how long is a piece of string" As with any electrical item it depends on so many factors it's impossible to generalise, however here are just some common factors that can have an influence on how long a power amplifier could run trouble free - Design - has the designer chosen parts with some degree of safety margin? If for instance semiconductors, resistors, capacitors and transformers are constantly operating close to their maximum ratings there is a good possibility of failure. Quality of parts. Electrolytic capacitors are a good example. Many have an in service life anywhere between 1,000 to 20,000 hours depending on the manufacturer and type under normal operating conditions. This lifetime is shortened significantly if the ripple current rating is exceeded, the applied voltage is too close to the maximum rating or the temperature is too high. The input voltage of the mains power. If a 220v rated amplifier with a transformer linear PS is operated on say a nominally 240v supply the core of the transformer can become saturated. This causes a significant rise in temperature even if the amplifier isn't driven hard (say Class A/B design as an example). This is only mage worse if the mains voltage drifts up to say 260v which is quite common in WA (see the thread on WA Power). This excessive voltage stresses the components on the secondary and d.c. side of the transformer. Operating in high ambient temperatures. Class A and Class A/B power amplifiers give off a lot of heat. They need adequate ventilation to prevent premature component failure. Just about every operating manual has information about appropriate power amplifier placement in this regard. Inappropriate loudspeaker load impedance. Connecting a loudspeaker of too low an impedance to the output of an amplifier and driving it can damage the amplifier. The lower the impedance the more current flows into the load (loudspeaker). This current has to come from somewhere and its the output devices and the power supply which provide it. This excessive current often exceeds the safe operating margin of the output devices which can lead to failure of the output devices. Lastly, but by no means the final point - tampering, servicing or modification by individuals that think they know everything about the design but in fact are just hacks . I call these people audio alchemists. Some of which even bypass the safety devices in amplifiers to apparently "improve the audio quality". Things like shorting out fuses, bypassing protection relays, in-rush current limiting devices et al. Whilst I recognise that all commercial amplifiers are built to a price and yes it is possible to improve the performance, anyone who doesn't thoroughly understand what they are doing and why they are modifying a piece of equipment should IMHO refrain from doing so. Just my 2c worth. Cheers, Alan R.
  12. Apologies in advance for the lengthy reply. Most insurance companies will pay out under the "fusion" conditions in the policy, however what actually defines "fusion" must be carefully interpreted as many policies are either vague or ambiguous with this term. Remember insurance is a game or gamble between the insured and the insurer. Their game is to get your premium and hopefully never have to pay out on it. Back to the WA power grid. The nominal grid voltage is supposed to be 240v per phase wrt neutral. Most WA domestic premises are fed with a single phase 70A supply. Some premises may have 3 phase as is my Perth home. My rural property is single phase but 100A supply from its own 25kVA pole mounted transformer that isn't shared with any other property as the original owners had an electric kiln for firing pottery and glass blowing therefore because of their increased supply requirements they purchased the transformer that feeds my property exclusively. Voltage throughout the day and night varies considerably. Western Power say this is normal for single phase rural supplies as the street distribution is done as HV over considerable distances and properties are fed via a stepdown pole mounted transformer the 240v supply will vary with load, which is to be expected. Also grid connected solar / wind inverters will also have an influence on the mains supply voltage inside the premises network whilst feeding back into the grid. Whilst a slightly lower supply voltage may cause problems with some domestic appliances (older non-inverter compressors, pump motors etc.) the effect isn't significant or detrimental to resistive loads such as kettles, electric stoves, heaters and many devices using a switch mode power supply (SMPS). Also most hi-fi equipment won't be damaged or significantly effected if the mains voltage drops a bit. Non-synchronous a.c. induction turntable motors will run a bit slower (but these types are few and far between anyway). Where the danger is in when the mains voltage is too high. Some SMPS will tolerate a higher than nominal input voltage as good SMPS units can handle a wide range of input voltage (within limits of course), but a linear transformer power supply is completely different story. Occasionally I see an amplifier delivered to my workshop for repair. The common comments the customer makes are on the lines of "I could smell this burning type odour, then the device stopped working." On opening up the device one often finds on some units that something has failed in the power supply. A common problem with gear brought over from the EU or parts of SE Asia is the transformer and or some other component in the power supply have failed. In many cases of transformer supplies designed for 220v operation the primary winding has gone open circuit as a common design of EI transformers is to have a thermal fuse imbedded in the primary winding close to the core. This thermal fuse is designed to become open circuit when the internal temperature of the transformer exceeds about 120 deg. C. Unfortunately even if the device hasn't been abused or even if no other component in the device has failed, the transformer can easily overheat due to excessive core saturation. That's why I advise people not to buy transformers with 220v primaries for use on the Australian electricity supply for their DIY projects. So what's wrong with a 220v transformer on a 240v supply? Well if you do the calculation, the 240v is ~ 9% over the nominal 220v voltage rating of the transformer. No big deal as some may say. But what happens when it drifts up to 260v as @jakestar commented? Redoing the calculation this increases the error to ~ 18% too high on a 220v transformer. This in turn translates by the same error to the secondary winding(s), which may stress the other components down the chain. Over voltage is a cause for concern for linear power supplies that use a mains transformers because the increased primary voltage can saturate the core which causes a steep rise in operating temperature even without a load connected. Transformer design is a complicated science and many manufacturers try to do three things - optimise the efficiency of the transformer. This is often done by operating the transformer just below the point of the core saturation, but this makes the transformer less tolerant of overvoltage operation (not talking transient voltage spikes here). keeping the size and weight to a minimum for the VA rating of the transformer. reducing manufacturing costs. So on your next equipment purchase or DIY project don't buy a bit of kit or transformer that has a 220v rating and run it directly from a 240v supply. You're just asking for premature failure of the transformer or other electronic components within the device. Just think about the consequences of a 220v tube amplifier connected to a supply that may drift up to 260v. Elevated HT supply, filaments operating at 18% over their nominal voltage (unless downstream regulated) will contribute to shorter tube lifespan, stress on the other components and increased operating temperatures all working towards reducing the operating life of the equipment. Once again, apologies for the lengthy post but I'm attempting to explain the problems in not so technical terms that hopefully most readers can comprehend. Cheers, Alan R.
  13. The Shibata profile was originally developed to play the CD-4 records (a.k.a Quadradisc etc) which has signals as high as 45kHz. It is an excellent profile to track high frequencies with minimal distortion and groove wear. IMHO it would be a significantly worthwhile improvement over your current conical stylus. Cheers, Alan R.
  14. I agree. It's a warranty issue. I think that there may be any number of possible problems as I eluded to in my previous post. I for one would be interested to find out exactly what the fault is. The only reason I posted some possible contributing issues is that depending on the technician repairing the fault they might declare it all too hard and simply replace the device holus bolus. Often the fault is a simple inexpensive fix but the "tech" doing the fault diagnosis is clueless. Cheers, Alan R.
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