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Thread: Nobsound 300b Monoblocks - HELP NEEDED!

  1. #21
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,811
    I'm Dennis.

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    Quote Originally Posted by Lawrence001 View Post
    I'm sure I've had amps before that hum if there's no input, doesn't the input provide a ground that might get rid of the hum? Plug in a pre (also plugged into the mains and switched on before powering these up) and see what the hum is like them.
    You could well have; the connection of a pre will put a lowish impedance across the input, tending towards a short circuit.

    It is not possible to develop a voltage across a short circuit.

  2. #22
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 8,679
    I'm Andrew.

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    OK, update, these are going back. I just can't be bothered trying to get these fixed, they should have worked from the beginning. 300b journey over before began.
    SS
    CD Teac VRDS25X(Audiotuned) DAC Caiman SEG+15V PSU+Dorado DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe/Ebony PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10

    VALVE
    PRE
    Croft Epoch(Modified) AMP Sondex S100 (Modified) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Reference XO DECKS Garrard301/401 (Bastin) Mat Teunto Bearings 301/401(Bastin) Plinth Moldovan/Bastin Arms 3009/3012(Ikeda Ag wired) SME V 12 PSU Eagle+Tachometer MC Ag Meister v2 / Royall N SPU's CABLES Arm Yannis 420.5 Litz+ Speaker 10mm Cu + WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostage Paradise(4 Box Modded) / EAR 834 Clone (modded)

    www.facebook.com/wakefieldaudio



  3. #23
    Join Date: Aug 2012

    Location: Eton wick

    Posts: 1,115
    I'm Philip.

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    That's a shame.
    Deserve better after taking a punt.

  4. #24
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 8,679
    I'm Andrew.

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    Shit happens! Lets move on to the next adventure....
    SS
    CD Teac VRDS25X(Audiotuned) DAC Caiman SEG+15V PSU+Dorado DECK 1210 Mat Crystal Audio Mods MN Base/Bearing/Platter+Ebony armboard Feet Isonoe/Ebony PSU Paul Hynes SR7EHD-27XL/DCSXL Ag DC lead/3 Stage Regs/Recap PCB+No Pitch/Strobe/Light ARM SME V(Kondo Ag Rewire&Tags) MC Cadenza Black FGS CABLES Arm Yannis SPD-4 IC Yannis 222 Litz+Ag bullets Power WAR PRE ATC SCA2 SPEAKERS ATC 50ASL STANDS Atacama PHONO Sugden Masterclass PA4 SUT Ortofon ST80SE POWER PSAudio P10

    VALVE
    PRE
    Croft Epoch(Modified) AMP Sondex S100 (Modified) SPEAKERS Tannoy 15"MG+RFC Warwick cabs+ Reference XO DECKS Garrard301/401 (Bastin) Mat Teunto Bearings 301/401(Bastin) Plinth Moldovan/Bastin Arms 3009/3012(Ikeda Ag wired) SME V 12 PSU Eagle+Tachometer MC Ag Meister v2 / Royall N SPU's CABLES Arm Yannis 420.5 Litz+ Speaker 10mm Cu + WBT-0681 Ag IC Oyaide FTVS-510 AgWBT 0110Ag Phonostage Paradise(4 Box Modded) / EAR 834 Clone (modded)

    www.facebook.com/wakefieldaudio



  5. #25
    Join Date: Dec 2008

    Location: East Riding of Yorkshire these days

    Posts: 4,776
    I'm Shaun.

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    My only experience with 300B's was a WAD 300B PP directly heated triode setup and guess what..? It hummed like a bugger. Bloody lovely sound quality but I just couldn't get over the low frequency tinnitus.

  6. #26
    Join Date: Oct 2016

    Location: London

    Posts: 304
    I'm David.

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    A WAD 300b PP properly built and sorted should have no audible hum. I built four clones and hum was inaudible, even with 93db sensitive speakers. DC heaters on the input stages helped, but it was even possible to get hum levels really low with AC heaters. The input stage as standard is very sensitive though at around 300mv for full output. I presume you tried reducing the hum on the output valves with the humbucker adjusters?
    David

  7. #27
    Join Date: Dec 2008

    Location: East Riding of Yorkshire these days

    Posts: 4,776
    I'm Shaun.

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    Quote Originally Posted by AD Audio View Post
    A WAD 300b PP properly built and sorted should have no audible hum. I built four clones and hum was inaudible, even with 93db sensitive speakers. DC heaters on the input stages helped, but it was even possible to get hum levels really low with AC heaters. The input stage as standard is very sensitive though at around 300mv for full output. I presume you tried reducing the hum on the output valves with the humbucker adjusters?
    David
    Yep, the humbucker knobs reduced the hum but never got rid of it. The amp was built by World Audio themselves as was the accompanying KLP1 preamp which was faultless but the power amp, even though the tonal sound quality was stunning never stopped humming. Also, the stereo imaging was pretty suspect. The amp replaced a Musical Fidelity A100X which was staggeringly good at imaging; the 300B was poor in comparison.

  8. #28
    Join Date: Oct 2016

    Location: London

    Posts: 304
    I'm David.

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    Quote Originally Posted by Haselsh1 View Post
    Yep, the humbucker knobs reduced the hum but never got rid of it. The amp was built by World Audio themselves as was the accompanying KLP1 preamp which was faultless but the power amp, even though the tonal sound quality was stunning never stopped humming. Also, the stereo imaging was pretty suspect. The amp replaced a Musical Fidelity A100X which was staggeringly good at imaging; the 300B was poor in comparison.
    That's a real shame. With a pair of sensitive speakers a properly sorted WAD 300b pp is among the very best around. Really sorry yours never was, despite being built by them, and that you never experienced its magic. Of course, I built the clones point to point which meant I could improve the layout over the pcbs WAD used.
    David

  9. #29
    Join Date: Dec 2008

    Location: East Riding of Yorkshire these days

    Posts: 4,776
    I'm Shaun.

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    Quote Originally Posted by AD Audio View Post
    That's a real shame. With a pair of sensitive speakers a properly sorted WAD 300b pp is among the very best around. Really sorry yours never was, despite being built by them, and that you never experienced its magic. Of course, I built the clones point to point which meant I could improve the layout over the pcbs WAD used.
    David
    Yes David with regard to the very best around, the sound of space and air along with the liquid purity was stunning and so much better than I have now so many years later but it was a hugely flawed amp. Yeah OK so it was connected to wholly unsuitable speakers but still gave its best. Had I kept it a year or two longer it would have ended up driving Audio Note AZ-2's but after the A100X I just couldn't forgive its shortcomings. The lack of a huge soundstage was just not good enough and the hum was a big problem but I kept it for a few years before saying goodbye. Years later I used an Audion 300B SET which was every bit as good and better in some respects. These days I have given up on valves

  10. #30
    Join Date: Jun 2015

    Location: London/Durham

    Posts: 5,229
    I'm Lawrence.

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    Quote Originally Posted by Wakefield Turntables View Post
    OK, update, these are going back. I just can't be bothered trying to get these fixed, they should have worked from the beginning. 300b journey over before began.
    When you say they should have worked from the beginning, you did start off by plugging in a source and pre and playing some music didn't you? As you only mention running then with no input and you can't judge a valve amp that way as it's not designed to be used with no input.

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