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Thread: 6J1 Pre-amp modifications (hum removal)

  1. #61
    Join Date: Nov 2010

    Location: Sheffield/Peak District. UK

    Posts: 368
    I'm Richard.

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    OK; thanks Grant.


    How does one know if one has impedance mis-matching?

    Richard.
    Quote Originally Posted by struth View Post
    Impedence mismatching

  2. #62
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 35,537
    I'm Grant.

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    Ideally you want a very high input impedence and a very low output impedence. It is often mentioned in the specs or can be worked out via math. Sticking a buffer in guarentees this. Alas a poor buffer circuit may also add a rair bit of distortion so you have to be careful there too. If you try one and hear no difference then you dont likely need it. It can be inserted between any 2 components, although most will use it impedence wise between pre and power.
    It will, so im told by some give a valvelike experience to solid state like a cd player. I dont really see it quite that way, but that is how i use mine..ie between cd and amp. Not sure why i like it but it sounds more real to me
    Regards,
    Grant ....

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    DENON DV2900 - TWIN PRO MONOBLOCK AMPLIFIERS - XIANG SHENG DAC\PRE\HEADPHONE AMP - AUDIO TECHNICA ATH-MSR7 & OPPO PM-3 PLANAR HEADPHONES - WIN10 JRIVER23, SPOTIFY PREMIUM - SMSL M6 MINIDAC - FULL RANGE TWIN TELEFUNKEN's - Q ACOUSTIC BT3 actives - CANTON SUB - MAINS REGENERATED AND FILTERED.

  3. #63
    Join Date: Nov 2010

    Location: Sheffield/Peak District. UK

    Posts: 368
    I'm Richard.

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    Thanks Grant.
    BW

    Richard

  4. #64
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,617
    I'm Jez.

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    Bonky. Are you still wishing to try the Arkless phono stage which you put your name down for? I have PM'ed you but had no reply.
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  5. #65
    Join Date: Nov 2010

    Location: Sheffield/Peak District. UK

    Posts: 368
    I'm Richard.

    Default

    Hi, apologies, I didn't pick-up any PM. My fault.

    Yes please ...but I'm on holiday at present and won't be back until mid-April. Perhaps after then?

    Many thanks,

    Richard.
    Quote Originally Posted by Arkless Electronics View Post
    Bonky. Are you still wishing to try the Arkless phono stage which you put your name down for? I have PM'ed you but had no reply.

  6. #66
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,617
    I'm Jez.

    Default

    Quote Originally Posted by Bonky View Post
    Hi, apologies, I didn't pick-up any PM. My fault.

    Yes please ...but I'm on holiday at present and won't be back until mid-April. Perhaps after then?

    Many thanks,

    Richard.
    OK no problem just pm me when you are ready to try it and if it's still in circulation by then you can try it.
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  7. #67
    Join Date: May 2008

    Location: Surrey

    Posts: 5,758
    I'm Rob.

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    Quote Originally Posted by Puffin View Post
    I did the "hum" mod, but the fizz has been replaced with a..........hummmm hm? 50/60hz probably. I have disconnected one side of the 470uf cap (as I hot glued the cap to the board and might need to re-connect it - ?) Oddly the fizz has all but gone and there is only a very feint hum left. The cap has been left connected by it's NEG leg to the join of the 47r resistors only.
    Actually the hum is noticeable without any music playing.
    Buy Bose...And get your parking validated!.

  8. #68
    Join Date: May 2008

    Location: Surrey

    Posts: 5,758
    I'm Rob.

    Default

    Finally got round to boxing this up as I was fed up with it skating across the table when I touched it. Being a cheapskate I used an old Sure amp box. Not too shabby IMO of course.


    Alan, I am now using it with another power amp and the hum has gone (I have also removed the extra cap) Amazed at how completely silent both the pre and a valve power amp are.
    Buy Bose...And get your parking validated!.

  9. #69
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 3,589
    I'm Alan.

    Default

    Excellent

  10. #70
    Join Date: May 2015

    Location: Kent

    Posts: 85
    I'm john.

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    Hello been meaning to post this for ages and ages finally got around to it, All working well, I made a bit of a mess drilling the top of the alu case with not a good enough drill set, but hey ho, am using this after my dac befor the amp, a Technics su-8011, im not great at describing sound but an certainly enjoying it, I have now switched to an old Rotel amp i got 2 days ago which has a 15db pad switch, It seems to all work together better then the Technics Top end now has a really nice clarity to it, things like chimes and bells you can really hear the tone of them rather then just knowing they are there. Thanks for posting all the info about this firebottle, and everyone else who chipped in.

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