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Orelle XTC Pre-1 and Pow-1...

Discussion in 'classic' started by Dowser, Sep 12, 2015.

  1. Dowser

    Dowser Learning to bodge again..

    Not sure why I bought these, they were not particularly cheap but I just got interested - Chris Bryant designed I think, XTC were formerly Orelle, or an offshoot of Orelle...not really sure! Anyhow - I need to swap 211 valves on my DIY power amps to GM70s, and want to try different output caps in my Croft Micro (mustards :))...for some stupid reason I bought these to listen to while I'm doing it...

    Picked them up today from a Swiss high end dealer in Kanton Schwyz...my god but what an Alladins cave his place was! He sells the cheap stuff (!) via a local auction site, but has I estimate over half a million CHF worth of decent stock on his shop floor (at his retail prices). The AN Ongaku looked beautiful! I have never seen anywhere like this before.

    Anyhow, get them home, strip off covers to take a look...

    Pow-1 power amp overview - four 175W channels (key switches on rear to switch between 2 & 4 channels)...a very big FO transformer...but look at those tiny smoothing caps, and small bridges...and basic caps used. Wasn't to impressed looking at the design. Its bigger than my Lark Levinson No. 29, and about the same weight.

    Right hand channel component side;

    3 of the 4 output transistors (to provide 2 channels);

    Big FO transformer;

    The pre-1 pre amp - again, not hugely impressed by it at first glance;

    I am hoping this is an add on phono stage - think it is, other pics I find on net do not have it;

    Wildly over spec class A (FET based I think) SE output stage;

    So, all looks good (rev4 board in pre, 1992 on back of phono daughter board) - bolt it all back together and whack it into system;

    First impressions are surprisingly good compared to DIY 211 SE valve hybrid monos & modified Croft Micro II. Mid to top end much more detailled and grabs attention (cymbals are sublime!), not so sure of bottom end yet. Seems muddy, but may only be compared to higher frequency clarity. I can never do quick AB tests - I will live with them for a while and then swap back. So far I have not found anything better than my main system...I am hopeful this can do it...I really like the remote control :)

    One question: I am running it in 1 channel mode, but without what I think should be link plugs on the rear...so suspect I am only getting 175W per channel currently rather than the full 350W. Has anyone who has played with one of these confirm?

  2. Dowser

    Dowser Learning to bodge again..

    Well, that's a phono card - and an MC one at that - I first tried my Linn Asaka via the McKinnie head amp set for Croft MM input, overloaded. Direct into the XTC from Asaka and I need to crank volume to 2-4pm, but it's silent and pretty good.

    I think I need to try the pre into my DIY power amps :)

  3. hifienthusiast

    hifienthusiast Vintage by heart

    Many years ago, I saw a review of the Orelle amps in Hi Fi World, but I can't remember how they were rated.

    Perhaps someone can dig out the review as a reference
  4. Wilson

    Wilson _

    That amplifier topology looks vaguely similar to Steve McCormack's distributed node amplifier, does it not? Small caps and whatnot.

    Interesting components. Are these from the late 90's?

    Thanks for posting.
  5. Dowser

    Dowser Learning to bodge again..

    Would be nice if someone has it :)

    Not familiar with Steve McCormack - I'll check him out. I'm fairly sure Chris Bryant (now HiFi Critic reviewer) did the pre. I think mid 90s - the pre amps seemed to go through a lot of revisions and small changes, so I'm not sure if mine is early or late (phono card has a 1992 date on it, but is a generic item I guess).

    Sounds very nice - I tried the pre into my DIY amps as well last night, too early to really make a judgement, but a very nice sound.

  6. Svein

    Svein pfm Member

    I had XTC Pow-1 in 1996 or 1997 and used it with a Conrad-Johnson PF2 preamplifier. It's a 4-channel amplifier that can be bridged via links for 2 channel operation for more power.
    I am sure this issue Hi-fi World with the review of the XTC pre-power is stored in my attic. I'll scan it and upload here later.
  7. Jowcol

    Jowcol pfm Member

    This XTC combination was highly-rated when reviewed at the time (for whatever that is worth).
    I have never heard one, and only rarely seen them for sale.
    Not many can have been sold, I don't think they were made for long.
  8. Dowser

    Dowser Learning to bodge again..

    That would be great, thanks Svein!
  9. Svein

    Svein pfm Member

  10. Dowser

    Dowser Learning to bodge again..

    You star, thank you :)

  11. Dowser

    Dowser Learning to bodge again..

    An update:

    After happily listening to this combo for 7 or so weeks, I decided to try my modified Croft Micro II into the XTC power amp - I was hoping it wouldn't sound so good, because I love the remote the XTC pre has...however, all I got was distortion! Switching back to XTC pre, same. Connecting XTC pre to my Mark Levinson No. 29 produced music.

    That was a few weeks back, tonight I popped open the XTC to have a look. It's a four channel amp, I was only using 2 channels - their F6.3A fuses had blown. I swapped the good ones from channel 2 on each board, and reconnected - all good. I had a feeling the ML 29 was not as good as the XTC into my ESL63s...I can confirm that now - more air around everything with the XTC, and much faster, harder bass (anyone interested in a vintage & mint Mark Levinson No.29, please let me know...I think!).

    I now need to find out what blew the fuses - the XTC is Mosfet output stage, with no cap on the input; signal goes straight to an Analogue Devices SSM2131P opamp (never heard of these?!). My Croft has output caps though, so no idea why fuses blew?

    Picture of XTC power stage;

    I had been using the Croft Phone stage into an XTC pre line input OK - all I did was switch everything off (ESLs too) and swap cables over - got distortion immediately. I will order a bunch of fast blow 6.3s and then check - I suspect switching on pre first will fix it....XTC pre has a 30 second soft start...

  12. Dowser

    Dowser Learning to bodge again..

    Not done any further testing with the power amp yet, not ordered spare fuses :)

    However, did swap smoothing caps in the Pre over the weekend - nice tightening up of bass a little.

    I am very impressed with the sound quality of this combo - especially given the subjective low quality of some of the caps. I'd like to learn more about its design and see what I can do to improve it, especially the Pre-1. Anyone have contact details for Chris Bryant they'd care to share? :)

    I see internet reference to a few mods of this, including a potential pre-prod run of a Pre-2 design based on this. Details are sketchy - seems they modified the PSU to a never connected one (whatever that means), removed the heatsinks for class A output stage (not really required, they do not get warm in operation) and potentially swapping mosfet output devices for normal bipolar.

    Mine seems to follow the basic design of all the photos I can see online, but still has the heatsinks, and has the only phono stage I have seen in one.

    If anyone has further info - I'd love to know. Thank you!

    Anyhow, pictures;

    Original caps - 2 big ones for +/-30v rails were Samwhas, 6k8 and 85v. 12v rail used a 2k2 - think this is just for digital circuitry, but have not checked yet;

    Untidy motor wiring - I redid this as a tight twisted pair and routed it up towards the top of the case (no after photo, sorry) - I didn't have any issues with sound quality while motor was active, but sometimes it runs slow...tidying the wirng didn't fix it :)

    Kendeil 10k main replacements, plus a spare Rubycon I had for the 12v line;

    The 30v lines feed the regulatros to right of shot - never investigated too far, but there are also +/-15v rails inside the pre.

    These are the input caps to the class A output stage I guess - what is 0u1J for a value in uF or nF? Are Ansar any good - I have seen Google photos where these have been replaced;

    Output stage - el cheapo electrolytics, that should probabaly be replaced? The 2 regulators by the RCA connections and ribbon cable provide a regulated feed for phono stage I think.

    Labelled protection - the red wire is an AC signal feed - I assume (but don't know!) this gives the 20 or 30 second delay from power on to final output relay switching on;

    Phono stage - actually sounds good, but a bit low gain for my Asaka (which I normally use via McKinnie pre-pre, and through my Croft Micro MM stage and out of tape loop;

    Cheers, Richard
  13. PigletsDad

    PigletsDad pfm Member

    The phono daughter board just seems to have a pair of NE5534s on it - industry standard audio op-amp, used by the thousand in recording studios.

    Perfectly respectable part, but it doesn't have a a very low noise floor, so I am surprised it is quiet enough for MC use. Do you get background hiss when using the Asaka?
  14. paskinn

    paskinn pfm Member

    At the time, Chris Bryant was working closely with Martin Colloms, and I suspect that the Meridian SS amps of that period were from the same designers.
    Chris Bryant now lives in East Sussex, on the outskirts of Bexhill, and I understand he still does the occasional repair work.
  15. Dowser

    Dowser Learning to bodge again..

    I only listened to the onboard stage briefly PD - low gain, but it sounded ok... Just tried volume with no cartridge connected - a slight hiss detectable by 1pm on volume, but not too bad.

    Paskin - do you know a way to get a message to him? :)

    Thanks, Richard
  16. paskinn

    paskinn pfm Member

    I think the easiest method of contacting him would be through an e mail to Hi Fi Critic. He still associates a lot with Martin Colloms.
  17. Dowser

    Dowser Learning to bodge again..

    Thanks - I give it a try.

  18. James Evans

    James Evans Bedroom Bodger

    There's a Pre-1 and Pow-2 at 2ndhandhifi at the moment. Never seen a Pow-2 before. The amp boards in the pow-1 look pretty similar to the Orelle sp150 I had for a while (identical in fact).
  19. Sandy

    Sandy pfm Member

    Hi Dowser, did you manage to get in contact with Chris?

    If not, I may be able to help you.
  20. Dowser

    Dowser Learning to bodge again..

    Thanks Sandy - no, I didn't, but while the Pre-1 is an excellent preamp, I still prefer my old Croft, so I will be selling the XTC stuff in due course as is with just the smoothing caps replaced.

    Thanks again, Richard

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