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Thread: Nobsound 300b Monoblocks - HELP NEEDED!

  1. #1
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 8,679
    I'm Andrew.

    Default Nobsound 300b Monoblocks - HELP NEEDED!

    A pair of these monoblocks landed in the listening room. They each have three valves to each monobloc. 300b x1 6H8C ×1 Soviet Union 5U4C ×1. Now the problems start. Douk audio in their wisdom left no markings for the position of the 6H8C or the 5U4C, so I could very easily plug them in the wrong way around. There are no markings on the amp. To add insult to injury my allen keys are worn down and useless and I don't have the right drill bit to have a look at the PCB. You couldn't make it up! . So my question dear AOSer's, do any of you own a pair or know the correct position of the 6H8C or 5U4C valves? The 300b just sits in the middle, that's the easy bit. So, basically, HELP!
    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)

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  2. #2
    Join Date: Mar 2017

    Location: West Sūžsēaxe

    Posts: 1,971
    I'm Edward.

    Default

    Judging from the ebay listing the taller valves (the 5U4C) sit at the rear and the shorter valves (the 6H8C) sit to the front of the 300b. Download the 7th image of the listing so you can zoom in on the valve type. The other images show the orientation.

    I hasten to add I don't have this amp nor direct knowledge - just going on the ebay listing.
    Current: [P20] Roon/Tidal > Custom PC> Metrum Hex > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)


  3. #3
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 8,679
    I'm Andrew.

    Default

    I did just as you said several hours ago. They are now working, nothing has blown up yet. Thanks for your reply.
    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



  4. #4
    Join Date: Mar 2017

    Location: West Sūžsēaxe

    Posts: 1,971
    I'm Edward.

    Default

    Interested to know what your impressions are once you have tuned into them.

    §
    Current: [P20] Roon/Tidal > Custom PC> Metrum Hex > Phast Pre > Neuro. 686 > Tannoy Berkley (RFC tweaks)


  5. #5
    Join Date: Mar 2014

    Location: West Wales

    Posts: 735
    I'm malcolm.

    Default

    Quote Originally Posted by Edward View Post
    Interested to know what your impressions are once you have tuned into them.

    §
    +1
    Audiophile Tosher

  6. #6
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 8,679
    I'm Andrew.

    Default

    Might write a few words tonight if I get time from decorating today.
    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



  7. #7
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 8,679
    I'm Andrew.

    Default

    These 300b are off back to China. These amps hum like a complete bugger. So, I've got the valves in the correct positions. The amps exhibit no hum from the Tx when fired up but as hum like a complete bugger when you attach them to a passive speaker, this is with no pre-amp connected. I've had several different mains leads from cheap walwart jobbies to some expensive Furutech foo shielded monsters. All hum. Both units work, I've had them playing music. This is a HUGE disappointment. Any ideas why they should hum so badly? I'm going to wait to see if any forum members can come up a quick fix, else, it's reboxing them and back to nobsound. I'm very very annoyed.
    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



  8. #8
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,812
    I'm Dennis.

    Default

    Short the I/P to make sure that you are not putting hum into them. (Short = 0V.)

  9. #9
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 8,679
    I'm Andrew.

    Default

    I've powered one amp up (altough this phenomen happens with both units) and just attached the speaker cable from the speaker to the amp. No other cables. I've just tried powering up from the wall socket and still same old hum, I thought it might be the extension I was using.I'm not sure what I/P means Dennis.
    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



  10. #10
    Join Date: Nov 2010

    Location: Yorkshire

    Posts: 8,679
    I'm Andrew.

    Default

    Here's a little video demonstrating the problems. I'm beginning to think it might be an internal grounding problem, but on BOTH amps . The hum is a hell of a lot louder than on the video. I'm certain it's not Tx hum.


    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



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