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RoHo

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About RoHo

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  • Birthday 03/18/1964

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    Melbourne
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    Australia
  1. DIY audio: what are you building?

    Thanks, Owen. I learned a lot from Tomas' blog. More recently he seems to have become a commercial kit supplier and so he doesn't publish schematics. A shame for us DIYers as he had great applications using inexpensive valves like the 6CB5A. I'm only an occasional vinyl listener but my impression of the phono stage is that is in line with Allen Wright's crisp and clear "house sound". "I want speed and I want definition" I remember him stating in a forum way back. So it's all that and with good bass too. On the sound of the amps. I'm still getting a handle on their differences. I hate quick-swap A/B comparisons. My short-term audio memory is poor and find that I listen in a fundamentally different way in this situation. I just end up confused and frustrated. Instead I'll listen to just one amp for ages then swap when I feel like it. ATM all I can say is that they're both good with no marked shortcomings. I should say that my speakers roll off at 70 Hz with below that handled by active subwoofer - probably making it easier for the SE amp. Rod
  2. I note that all NYs early albums have been re-released on CD remastered. Just wondering if anyone has an opinion on the sound of these. I have all his 60/70's albums on vinyl but I tend to listen to CD more because of the convenience. These re-issues on CD are quite cheap so if they sound better than the originals then I'm definitely in.
  3. DIY audio: what are you building?

    Thanks, mwhouston. Sadly I have zero woodworking skills so my amps look particularly daggy next to yours! The open framed Hammonds do look a bit "rugged". It's all about compromise. Having them on top leaves more room underneath for big polypropylene caps and the like. And I like the slim-line chassis which are not deep enough to accomodate them anyway. I would prefer to use those black transformer covers but then that's more expense and more, ugh, drilling. I'll just say it's all part of the new industrial-chic design style.
  4. DIY audio: what are you building?

    Piccie shows several years DIYing. Top is the pre-amp using Allen Wright's FVP5A circuit. Below is the power amp "medley". What we have is the power supply at the bottom. It includes two separate supplies (transformer, valve rectifier, pi filters with chokes). It can power either of the two power amps. First power amp (top middle) is single ended based on Vinylsavor Tomas's 6CB5A design. Lundahl interstage transformers feature in the nude and it can use a number of (cheap!) Russian pentodes on the input. Second power amp below this is push-pull using 6B4G valves for outputs into Lundahl transformers. Input stage is Allen Wright's PP2C which uses 6H30 valves. What have I learnt? Valve amps, especially with multiple transformers and chokes are too heavy. Single ended and push-pull amps both sound good. I hate cutting metal. I probably can't be bothered switching between power amps just for the hell of it. I need a bigger rack, especially as I intend to add a 4P1L pre-amp which is in the component-gathering stage. Under the first amp is a headphone amp which was a recent, just-for -the-heck-of-it build. Uses eBay boards/kit based on a variation of Nelson Pass's Zen design. No valves so not worth talking about
  5. I think you have the process sorted in a very logical fashion. A couple of points- I don't think you'll find much difference in the sound of amps in that price range. In fact, spend as little as you can on the amp. Speakers are where the real action is. Spend a bit more and buy what sounds good to you. Second-hand is good, particularly for amps for the above reason. A "Wanted To Buy" in this little forum may net you a choice bargain. With speakers, auditioning 2nd hand examples adds a layer of complexity.
  6. The signal coupling caps are one of the most influential components, all else being equal. How to define the "best" capacitor is, however, extremely problematic. You can spend hundreds of dollars on a silve foil/ teflon etc capacitor or comparatively little on a still good-quality cap like an Obbligato or Mundorf Zn. Does the super-duper one sound 20 times better? How can you judge such things? I still struggle to have a definitive answer. What I do know is that the coupling caps are only one of many components in your amp. There's only so much improvement possible by upgrading this one component. And so how much is it worth spending on this one component? The 22uF electolytic caps might be the cathode-bypass on the input stage. That's also quite an influential position. The standard ones appear to be Nichicon which are good industrial types. I don't know much about the Jensen's Mike has replaced them with but they are still electrolytic types.
  7. It's the cathodes that are connected to G3, no problem there. 1k resistors are grid-stoppers, should be located close to the grid 1 pin. They prevent oscillation. You're right about the bias being "non-adjustable, fixed bias" shared between the 2 output tubes. Cheap and nasty IMO. There is no way to correctly bias a different type of output tube which may cause BIG problems.
  8. Almost certainly the "odd" tube is shared between channels: two triode gain stages, one for Left and one for Right. Then on to separate tubes for driver/phase inverter duties.
  9. Sounds like an impedance matching issue. Passive pre-amps are very system dependent. Results can vary wildly due to the sensitivity to cable type/length and power amp input impedance.
  10. Neil Young at Foodland

    NY would probably puke if he knew his music was oozing thru the supermarket. Remember "This Notes For You" ? - "Aint singing for Pepsi/Aint singing for Coke/Aint singing for no-one/Makes my music a joke" No respect
  11. It all depends on how much the visual aesthetic bothers you. I don't need a certain style happening but I do need the room to be reasonably neat, I just can't relax and enjoy in a messy room or even a room with too much "stuff" in it. As I said, very personal, but still a genuine issue.
  12. Well.... my experience of exactly one CD player is: My Cd player is a Rotel RSD991, a very well specified and built thing, apart from the generic op-amp output stage. The DACS are PCM 63, current output types. So I disconnected the output stage, put in a simple resistor as the current to voltage converter (I/V) followed by my DIY valve pre-amp for gain. Sounded better, so it stayed that way for a few years. Then I read here and and on DIYaudio of "Lightspeed" George's experience with the AD844 chip used stacked and without feedback (thanks George). Sounded interesting and was simple to implement so I gave it a go. Immediately a more dynamic sound with a larger soundstage, so it has stayed like this since IMO it's all about the design and implementation, tubes or SS. And to do it well with tubes is not simple or cheap.
  13. A frustration of mine is that there are different types of DAC chips with different output stage requirements that can be implemented well or badly by tubes or SS. But we lump them all in either the "tube" camp or the solid-state camp. I repeat myself, and I'm willing to be contradicted, that the typical "tube" CD player, which is probably Chinese, has a delta-sigma DAC that incorporates an op-amp and doesn't really need any further processing. But it will have a chain of op-amps and a tube in there somewhere. Like 12AX7 which has very gain and is useless as an output driver. It's quite reasonable to presume that the tube is there to add "tone" ie pleasant distortion. This is a totally different situation to a current-output DAC with maybe a high quality transformer doing the current-to-voltage conversion and a more sophisticated exclusively tube, gain/output stage. A proper "tube CD player". But this is expensive and so is only found in much more expensive players.
  14. I'd want to know how the tube is implemented in the output stage. From what I've seen/heard in most "tube" CD players there are still op-amps in there doing the main job. For example a 12AX7 just can't properly do one of the tasks required - provide a low output impedance.
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