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Decky last won the day on June 2 2013

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About Decky

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  1. Easy grasshopper - there is 2h time lag between WA and ACT. They will get there. Eventually...
  2. There is a bit of history around Trams and especially this one. This looks like one of the first Trams I assembled and modified so it can work at 250V Oz voltage. This was way before the Colleman regulators were designed. The issue was with the heater PSU that were overheating due to the insufficient cooling that the original design had. I used to add extra heat sinks but definitely not fans (god forbid). With this mod the amp was working fine with 45 valves while 2A3s were still causing a lot of instability and problems over time (2A3s pull 5A from the heater PSU while 45s use 2.5A). This Tram was fully functional before it was sold by the original owner to someone who decided to do a "better" job in modding it further - hence the fans and the blutac. Mind you, there is nothing wrong in using blutac as long the caps are also supported by copper tape or cable ties. The case temperature gets very high and using hot glue is not possible while silicone is always messy. I can see that Colleman regs were also installed at some stage which is the only way to make these amps work reliably. The final layout and repair looks very clean and functional. Although that this is by far one of the best sounding pre-amps out there, a new owner should know that this baby needs some TLC from time to time to perform at its best. Biasing will eventually drift out of the optimal range since the self-biasing circuit was never designed to be absolutely stable. Re-biasing requires the amp to be open and adjusted by someone who knows how to do it and that is trained to operate 275V HT line inside. BTW - $2K for the whole package is just an insanely low price.
  3. That room is just not big enough for 2 subs - even if they are 10". I would go with a single passive radiator or sealed 10' or max 12" - SVS has some really good ones for sub $1K. Ports do not work well in small bedrooms - but if you have them you can always plug them - so, world is your oyster. Integration is more important than size.
  4. They make all the difference since without them you will not have any sound. Yes, Aussie 99.99% copper is way better than Chinese 99.99% copper 🙄 - even better - just get the ore from SA and refine it yourself - the grassroots DIY all the way! On a serious note - there is a bit of science around cables but there is no need for exotics. I am a fan of high capacitance low inductance speaker cables - see KIMBER 8TC or CAT5 cable conversion (DIY). Also it is very difficult to judge any cable outside the whole system - the cable, once connected becomes part of the signal chain and should be treated like that. Impedance matching is very important and as long as you do not use any exotic amplifiers or speaker or have extremely long cable runs - you should be fine with almost anything. The most of the difference gets generated over time if you allow for the exposed ends to corrode - so using some sort of connectors is always a good idea. Some reading material: https://www.lifewire.com/speaker-cables-make-a-difference-3134902
  5. There is a good example just above my post. It is very difficult to precisely design an isolation platform for equipment without knowing anything about the speakers and their support (i.e. floor). After that I would need to know type of equipment and that being said, I would look into designing anti-vibration platforms only for turntables. CD players are not susceptible to airborne vibration so need somewhat less isolation. SS amps do not need any isolation while tube counterparts are notoriously bad and temperamental. There it really depends on the amp design and the type of tubes one uses. Most of the work should be done on the amps - platforms cannot help as much as isolation from the chassis.
  6. Another misconception - there is no "frequency" as a material property - however, what are you trying to describe is called internal material damping. It is a form of dissipation happening due to a particular meso-structure of the material (meso meaning something in between macro and micro structures). Macro structure is governed solely by the bulk material properties, while micro structure is driven by basic material chemistry/physics. Resonant frequencies are strictly applicable to macro-structures. That drives majority of measurable first and second order effects when we talk about a dynamic response of a structure. Internal material damping exists and can be measured with very precise instruments but its effect is not primary by a great extent. Natural and synthetic composite materials are known to have much higher internal damping coefficient since their properties are largely influenced by meso-scale structural elements. Metals are, for all practical purposes, looked at as isotropic materials where meso-structures are not contributing significantly to their vibration damping. I hope this clears it up a bit.
  7. Materials do not have resonant frequencies (sorry) - structures do. Material properties contribute to that but the geometry is important too. The difference between granite and slate I would put at the 9th level of importance. Definitely not the first thing that should concern you when vibration isolation is concerned.
  8. It is always amusing repeatedly reading about various magic methods for equipment vibration isolation on SNA. It is always the same misconceptions and mythical unicorn solutions that are being suggested. Maybe I can shed some light (or not) on the topic: Passive isolation: - spikes are never isolation devices - they are coupling devices. They are used to direct vibration originating from the flat side of the spike into the sharp side of the spike (simplistically speaking) - springs alone are also not (effective) isolation devices but rather frequency shifting devices. Depending on their stiffness they will change the dynamic response of the platform they are supporting. They could indirectly produce an effect of isolation if their resonant frequency is much lower from the disturbance frequency. - vibrational energy can be absorbed only by dissipating elements - rubber mounts, fluid dampers or same other way that will be effective in transforming the input energy into heat. - The most efficient way is to use all three elements above and assign them to the tasks they are designed to perform. Active isolation: - This would require some aspects of passive isolation and a close loop control that can change in real time parameters of the system to counteract the input vibration. For the problem that is presented in the opening post: - isolate your speakers from the shelf - they are the source of vibration - use soft sorbothane/PU rubber half domes (under the speakers - not on top of them - "toppers" and other unicorns are covered elsewhere) - put CD player /turntable on a hard base made out of material that is good in absorbing vibration (slate, wood, composites) or make a custom one with vibration absorption elements (lead shoots, sand, oil etc). Use spikes between the CD player and the base. - Isolate the base from the shelf with rubber or combined spring/rubber legs. Springs should have the first natural frequency of 5-10Hz MAX. They should be in rubber boots or somehow coupled with a viscose dumper of some sort. Finally - try to measure the vibration before you start isolating - do not fix something that is not broken or that does not exist.
  9. Those things are only good for fixing plastic parts on your car, not for any electrical component or wire soldering. Spend around $100 for a basic temperature controlled soldering station if you want to play the DIY game.
  10. If you want to develop your soldering skills do not start with silver solder. Start with regular leaded Sn solder and try to "feel" the right solder flow by adjusting the temperature. After that you will probably never go back to Ag solder since that "feeling" is much more difficult there. Cardas had a very good eutectic Ag solder mix that was better than others but still very "stubborn" compared to a normal solder. In my experience - proper solder penetration and flow is much more important than the solder composition. A properly formed contact area will be much more conductive with a Sn/Pb solder than a problematic droplet-like contact of an Ag solder joint. For very heavy gauge coax cables I usually terminate the shield with an add-on wire instead to try to solder shield braid directly to the connector ground. This is almost the only way with XLRs and light RCAs like Eichmann bullets.
  11. DIY is a path paved with blood sweat and tears. Suck it up and solve your problems yourself - the pot of gold waits for you on the other side. We do DIY work not because it is easy but because it is hard. No one is born with soldering skills - you have to practice to get better.
  12. The reason for that is a very simple one - EI core transformers have primary and secondary windings on opposite sides. It is natural to make connections as close as possible to the windindgs. Nothing to do with "pollution" or RFI - just engineering practicality. The other reason would be just perception of the power flow "through" the transformer. Stepdown transformers are designed and made for general use - not specifically for audio so I very much doubt that designers care about audiophile perception of purity or how our equipment is organised .
  13. A very old one that needs some cleaning
  14. He is not lying - I used to build them myself just using dual filters and tailoring level of filtering for individual output. It is the best way to do that since the performance is measured and the filter is shielded so there is not stray EMI field emission from the filter itself. Belkin used to make a version of that just with discrete components and without shielding on filters but they used to charge arm and a leg for them. Cheaper commercial filtered power boards would have usually one single stage filter for the whole board - still better than nothing.
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