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About Juancho

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  • Birthday 01/04/1956

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Wigwam Info

  • Digital Source 1
  • Digital Source 2
  • DAC
    Customised DDDac
  • Pre-Amp
    Blue Velvet based
  • Power Amp/s
    Mastersound 845 mono
  • My Speakers
    Wilmslow Prestige

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  1. Do you mean sound/construction/electrical characteristics? On the latter, the anode and screen voltage ratings are way, way lower, so without a fundamental re-design there's no way you can use them in these amps. But for me it all goes to the resulting sound. This amp was designed around the Radford circuit with a few improvements, one being speccing it for KT120s which can far better stand the high 630v HT and screen voltages the STA100 uses. When I first decided to build these, I always said that it was a shoot out sound quality between these and the Leben cs1000p which also uses KT120s (or EL34s, KT88s etc) and this amp won, hence I went to sell the Leben but ended up swapping it for the two Silvercore monoblocks. So comparing it to the Silvercore 833 valved Class A amps and my wife's Mastersound 845 PSE monoblocks, those that have heard the comparison all agree the Radford monos are the best of the bunch across a wide range of music. All very subjective I know but an indication of how well the amp performs with its KT120s.
  2. To clarify, the principle reason for preferring the KT120 is its ability to stand the high 630v HT anode and screen voltage. Others experience is that JJ KT88s stand the pace, but other makes don't. GE KT88s run reliably and sound great, despite being on the margin /over their original specs, but cost a fortune. That's the way the amp was designed.........With KT120s we've tweaked things to voice the amp in a particular way, that sounds great, and guarantees reliability and decent valve life. Because of the way Radford uses feedback, different valves in any event make less difference than in other designs.
  3. I'm using KT120s which I much prefer to kt88s. Also, there's quite a few circuit changes from the original sta100. Firstly I'm using the choke PSU on the output valves taken from the later TT100. Secondly I've added choke regulation to the driver stage. I'd have to check if kt66s would stand the HT / screen voltage. Kt90s are no problem An sta25 owner said the following: Had the pleasure of a dem on these yesterday. I run an STA25 at home and these have the sweetness of the original STA range but have the power and effortless push in abundance. These are very exciting amplifiers indeed.indeed
  4. Can I suggest anyone interested in a price sends me their e mail address by pm and then I'll reply to the group
  5. There's certainly a bit of 'if it's less than 100 watts they're a bit short on power' but believe me they do sound supremely effortless! Here's what it looked like inside pre a general tidy up. Twin chokes, Black Gate caps, Audyn True Copper and Silver Mica caps all visisble to the keen eye.
  6. It's been a while coming but I took a week off my regular audio work to build myself a Radford sta100 as a pair of monoblocks. These are signature amps with a lot of foo inside including Black gate capacitors and Audyn true copper caps. They are point to point wired and the transformers are specced to take KT150s or KT120s, both of which thrive off the high HT of 630v and high screen voltage. The KT120s sound much better to my ears, suiting the output transformers better. So how do they sound? I'm fortunate enough to own a pair of Silvercore 833 monoblocks and my wife has a pair of Mastersound 845 monoblocks and this amp shows both of these a clean pair of heels. It's got effortless scale and majesty, and sounds very sweet across the whole frequency range. I'd like to thank Will at Radford Revival for help and advice along the way and for speccing and supplying the transformer sets. The output transformers are rated at 100 watts continuous output. Now here's a pair of amps that will drive any Tannoys! I'm open to building some more of these or even a stereo version......
  7. I think there are valve amp options but you'll be moving away from 845s and /or the single ended sound. Designing decent and safe amps for 845s and similar with their high voltage requirements is not cheap, and single ended output transformers need to be bigger and well made-ergo expensive-to sound good. So for single ended and /or 845s you're really limited to Chi Fi, some of which like Ming Da and a select few others is decent kit. Go push pull and there's many more economical alternatives available. It's worth having a listen to some push pulls to see what you think. I currently have three amps around the house: Mastersound 845 PSE monoblocks, Silvercore Class A single ended 833 amps, and a pair of Radford STA 100s I've just made as monoblocks. The first two amps have no feedback, the Radford has feedback and is push pull. Guess which amp I would take to the proverbial desert island if push came to shove? It would be the Radfords as they have the best overall blend of sound quality and specced at over 100 watts continuous with KT120s, they've got superb scale and majesty to spare. And my tastes are very catholic: lieder through baroque and classical, jazz to fusion and rock.
  8. I tried adding a Nord Class D amp to my 845 monos but nuch preferred the 845s full range on their own YMMV
  9. Bear in mind these Icons will be push pull not the SE you're used to. Mastersound do PSEs at 50 watts per monoblock but they may be out of your range. One of the best amps I've ever heard was a Ming Da 805 amp I tweaked at 50 watts SE per monoblock
  10. Turn it off when not in use and leave your dog in peace[emoji16]. Warm up time on a T Amp is a few minutes. Sent from my ONEPLUS A5000 using Tapatalk
  11. And the A and R A60 can be upgraded at reasonable cost to be a real giant-killer...........you don't need to spend loads to get great sound. Although like many others I have😀
  12. I've got stuff coming from Japan, Germany, France, Spain and the US along with the UK and I take my hat off to courier companies who are delivering the stuff with amazing efficiency. They are also delivering foodstuff, medical supplies and other important items so they are a very essential part of the coronavirus ecosystem. The ones I mainly use-Parcelforce, DPD or UPS-either make sure I see them on answering the door before putting then item down before I open the door, or take a photo of the item having seen me come to the door. So I've nothing but praise for them. Postal services from all countries and within the UK are very slow tho IME
  13. No too much mention of valve amps yet.......I have now serviced /restored around 30 Radford and Audio Innovations amps now and properly fettled these amps will stand any comparison with modern gear. A couple of weeks ago I restored some JR149s with new drivers and crossovers and these driven by a Radford sta25 and one of my DACs or my Oppo Sonica reference produced astonishing sound quality and substantial bass and left me wondering what more would you want? On the solid state side, I would add various Quad amps, some Pioneers, the aforementioned A and R 60 and some NAD amps that all stand out as offering a very satisfying musical experience. So yes, if I was starting again I'd definitely look to a classic amp driven by a modern DAC or deck with some decent speakers. David
  14. Juancho

    Done at last

    Hi Richard, there's at least one commercial design that runs 5670s in series and with no reported problems, so you're probably safe enough there. I used 0.01uf on the output of a BB1794 DAC in NOS mode to reduce quantisation hiss, as it theoretically did not affect audio frequencies but removed it in the end as I felt it dulled the HF response, so may be worth experimenting with. David
  15. Juancho

    Done at last

    Great work Richard! Glad it's working! You could always series your two 5670s for 12.6v heater v. Not sure why you want 0.1 uf across your i/v resistors? There's not normally any quantisation hiss with AD1865 and that value is likely to give some treble cut...... David