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Thread: Marco's 'tube rolling' and valve power amp adventure

  1. #21
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    Yep, that's the fellow!

    And as you can see from the second picture, there's a lot of circuit boards in there to rip out and replace with point-to-point wiring like there is in a proper all-valve design.

    It sounds fantastic just now, used in conjunction with the Croft, particularly since upgrading the valves, but I think when the above mentioned modifications have been carried out it will sound truly amazing.

    Do you think there would be any mileage in also upgrading the transformers, say with Sowters? They'll have to be changed anyway I would guess when the unit is altered to take 240V.

    Marco.

  2. #22
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    Quote Originally Posted by Marco View Post

    Do you think there would be any mileage in also upgrading the transformers, say with Sowters? They'll have to be changed anyway I would guess when the unit is altered to take 240V.
    http://www.hificollective.co.uk/tran...ransformer.php

  3. #23
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    If your willing to spend on this thing I'd certainly upgrade the iron, especially the output transformers, although not cheap theres no way I'd go back to the supplied ones in my amp.
    Of course its all down to the quality of the originals being used regarding performance boost.
    Double C cores are reported to be the best but these can be mega expensive

    You could always try some simple component changes on the pcb circuit to start with, most of those components look to be bog standard including what looks like polyester coupling caps, grid stopper resistors look like metal films and the electrolytics for the cathode bypasses look to be standard lytics, you could go nuts if you wanted
    Then theres the rectification which looks to be silicon based, could try some ultra fast diodes or the Cree high voltage schottkies before trying valve rectification

  4. #24
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    BTW I'd certainly play about with the existing PSU first before upgrading the PSU traffo, if you decide to go for valve rectification you'd probably need a different traffo anyway than whats used with solid state rectification
    Theres a chance you may not like valve rectification in the amp

  5. #25
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    Interesting, Leo - particularly about the valve rectification. Does that have the tendency to make the sound 'softer'?

    One of the things I like about the Yaqin is that it has the 'drive' and 'dynamic impact', for want of better expressions, of a solid-state amp, and yet also the subtleties and magical sounding midrange of valves. Maybe that's because there's a fair bit of solid-state in the Yaqin!

    I can tell you though that simply upgrading the Chinese valves to Russian ones, from Electro Harmonix and Svetlana, significantly elevates its (already excellent) performance. As it is with the new valves it's easily as good as most £3k designs, which is remarkable when you consider that even with upgrading the valves I've spent no more than £500 including its original purchase value!

    So ok, let's say you were modifying the Yaqin and had £1500 to upgrade it (which is the most I'd spend) which aspects of its design would you target first for modifying/upgrading?

    I definitely want to do away with the internal circuit boards and fit point-to-point wiring, as I believe there is a 'signature' with printed circuit boards that you don't get with hard wiring, so apart from that, what else would you suggest doing?

    Marco.

  6. #26
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    Quote Originally Posted by Marco View Post

    I definitely want to do away with the internal circuit boards and fit point-to-point wiring, as I believe that there is a 'signature' with printed circuit boards that you don't get with hard wiring
    That's easier said than done, i hope you know what your doing, infact if your going to the trouble of that & replacing all the iron, why not just build another amp based on the circuit.

  7. #27
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    Yeah I know, you're right, but trust me I have enlisted the help of an expert, or at least I will be doing so in due course... There's no rush though at the moment as it sounds superb and I'm enjoying my music very much

    Let's see what Leo has to say about things.

    Marco.

  8. #28
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    Quote Originally Posted by Marco View Post
    Interesting, Leo - particularly about the valve rectification. Does that have the tendency to make the sound 'softer'?

    One of the things I like about the Yaquin is that it has the 'drive' and 'dynamic impact', for want of better expressions, of a solid-state amp, and yet also the subtleties and magical sounding midrange of valves. Maybe that's because there's a fair bit of solid-state in the Yaquin!

    I can tell you though that simply upgrading the Chinese valves to Russian ones, from Electro Harmonix and Svetlana, significantly elevates its (already excellent) performance. As it is with the new valves it's easily as good as most £3k designs, which is remarkable when you consider that even with upgrading the valves I've spent no more than £500 including its original purchase value!

    So ok, let's say you were modifying the Yaquin and had £1500 to upgrade it (which is the most I'd spend) which aspects of its design would you target first for modifying/upgrading?

    I definitely want to do away with the internal circuit boards and fit point-to-point wiring, as I believe there is a 'signature' with printed circuit boards that you don't get with hard wiring, so apart from that, what else would you suggest doing?

    Marco.
    So far and my honest opinion yes, I've always found valve rectification to sound softer in the bass than solid state rectification, pre-amps and lower current devices can be different but with a power amp I think valve rectification takes things too far , I've always found that deep and tight control of the speakers missing.
    Others may disagree of course;-)

    If I had 1500 to spend what would I upgrade, I can't comment on the output transformers as I don't know how good the standard ones are, if they was cheaply wound I'd certainly upgrade them, the improvement in sound I got with the Sowters in my system was not subtle, mainly noticed in the bass and dynamics, jmore effortless.
    If the output transformers are already decent quality in the Yaquin then the benefits would be more subtle

    Any valves that uses low voltage DC for the heaters is something worth looking at , ditching the standard rectifiers for high current schottkies is worthwhile doing, improve the decoupling as much as you can to lower noise, Guido Tent is supposed to sell some nice heater supplies if you don't fancy building something from scratch


    Do the same with the HT supplies but obviously you need rectification and smoothing thats suitable for high voltage, lots of choice from the ultra fast type diodes to high voltage scottkies from Cree

    Cathode bypass caps, anode resistors, grid stopper resistors, coupling caps, if it uses feedback then the components there are all parts that effect performance, if any of the parts especially capacitors look to be cheapo branded I'd change them to better quality, not just to improve the sound but mainly the reliability too, nothing worse than having crappy capacitors that go leaky inside a warm valve amp, poor quality parts tend to deteriorate quicker and this can be heard in the sound after a while

    I tend not to recommend particular brands of capacitors and resistors as there is so many options and most of the boutique types like Blackgates can add signature, I'll let others comment on those, some swear that blackgates sound fantastic as cathode bypass caps.
    I personally try to stick with reliable longer life, higher temp industry grade types

    You'll certainly be able to hard wire this beastie although it will take some work, a handful of tag boards, good quality wire in there should sort it, just plan and draw it all out first, hopefully you can get a schematic which is really needed before doing anything anyway tbh, could even try different input valves if you are going to hardwire it although if the existing valves sound ok I wouldn't bother

    With your current budget you have a huge amount of options

  9. #29
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    Interesting stuff, Leo.

    I had a feeling that valve rectification might soften the sound - that is definitely not what I want, so unless someone knowledgeable can give me a good reason to go down this route then that particular part of the amp will remain solid-state.

    Regarding the output transformers, would they need to be changed if the unit was converted to 240V? If not, then I might leave them as they are.

    So apart from that, I'll probably just go for internal hard-wiring and having certain key components upgraded, which I will take advice on.

    If anyone else who's knowledgeable about electronics would like to comment, please feel free. All input is welcomed!

    Marco.

  10. #30
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    Hi Marco
    Funny things you're doing there! Mind you Mullard was the brandname for Philips products in the UK.
    You're not using an ECC83 in the amplifying chain I hope? That one has far too big input capacitance and you'll have a roll off at higher frequencies. In the past it was only used at phono input (that's where a roll off is needed). Nowadays a 6N1P (at 3 mA) does a better job there.
    Oh and I love the Svetlana 6550!

    Have fun
    John
    Music is an emotional experience. Without it, living would be a dull habit...

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