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JoelG

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About JoelG

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    South Melbourne
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    Australia
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    Joel

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  1. Thanks for your reply, hope these photos help.. if needed let me know and Great! Actually Tesla was my thinking too after illiminating tungsram as my second best guess. Yes, no Telefunken diamond underneath. I wasn't sure if Phillips had a connection with Tesla but probably they owned it at some stage.. 😅 Thanks for your help, much appreciated! Oh.. it's labelled 6dj8 ecc88 bit you think it's a e88cc? That's good if it is, I believe they're a better tube..
  2. Hi all Hope this is the right place to ask couldn't find a dedicated section. Underneath the tube in center moulded into glass one tube has has a backwsrdss 7 and the other one I have an 8 Both have a 2 imprinted between the pins Any help would be great and questions welcome. Thanks, Joel
  3. yes, I've never heard of this before watching this video and you would really think it'd be something worth mentioning 😁
  4. I see, so without a load the operating point might be out. A load will just relatively change the relationship based on the starting point... And adjusting this bias will do the trick 👌
  5. Ok, I actually unplugged everything from the amp and ran them to eliminate any variables and one was hot one cold so not sure, does your diagrams depend on having a load , being the speakers or is that the amps internal bias ? Anyway I can see how it can be a variable load. Thanks, Joel
  6. Ok, that's good to know... Hopefully it's an easy fix then. 🤞 Thanks, Joel
  7. Ok, I'm not very tech savvy but I kinda thought class A was just full on all the time so bias doesn't come into it? Happy to be wrong about this and if it's just a simple adjustment I will be stoked 👍
  8. Hi all, just after a good technician to repair one of my vintage marantz mono blocks. One amp is running way hotter than the other... Not sure if it's the hot one or cool one that's the problem though, as both sound fine and they always ran hot. Anyway any recommendations for a amp guru in Melbourne would be much appreciated. Joel
  9. Hi Mike, good to get your message. I was referring to single ended inputs (unbalanced) rca. My amps are class A (30watts) push pull/ MOSFET output stage. They do run pretty hot.(good for cold winters) I'll do some research on single ended class A output stages, sounds interesting. The question originated from the attached video which stated some amps are able can convert a normal single ended signal(unbalanced) (rca) into a differential signal (balanced)using a twisted pair IC to achieve some sort of common mode noise reduction not dissimilar to true balanced gear.. a
  10. Thanks Mike, much appreciate you answer. Yes, sticking with single to single. It's all very interesting stuff, just started scratching the surface. Cheers, Joel
  11. Hi, no, the particular hole was about single ended input(rca) connection that acted like a balanced input but requires a twisted pair IC to work. (Common mode noise reduction) he said that about 25% of amplifiers (usually high end)use this method but it has been overlooked for a long time in the industry. I did find a lot of corroborating evidence and many car amps seem to use twisted pairs to work with this type of input, but as usual also many contrary statements.
  12. I see, well it's good to know, thanks for the information 👍 I watched something on YouTube and fell down a rabbit hole 😂
  13. Excellent, thank you very much for that. Twisted pair going in the dumpster 😉
  14. So apparently my marantz mono blocks have a differential input stage using rca type connection. At the bottom of the attachment there is a diagram of the differential input stage, I've also included the amps schematics. The music link sc-22 preamp that is this models (music link) preamp has two rca outputs, one in phase and one out of phase. Although as the power amp only has a single input I don't see how this is relevant but it might be? ( I don't own this preamp) Also the diagram shows the output coming from a BTL (bridged source) again probably irrelevant. From my limit
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