ECP Audio T4 Headphone Amplifier

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by TomB, Aug 6, 2018.

  1. TomB

    TomB MOT: Beezar

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    I am currently seriously working on parts sources for 4 more T4 amplifiers, perhaps 5. The long lead time is for the metal fabricator. There are two amps in progress right now that are already reserved. After that, I am out of any casework, except that Doug just sent me plenty of wood. The metal fabricator (SwiftAtlanta) is working on a new quote for me as I type this. So assuming that goes well, I expect the T4 will be available again in a couple of months.
     
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  2. TomB

    TomB MOT: Beezar

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    I apologize for this and obviously left many of you in the lurch. We were hopeful, initially, that more T4s could be produced. Unfortunately, SumR went out of business in manufacturing our toroid power transformer used in the T4.

    We've been unable to find a suitable replacement with the same ratings and size. That means a re-design of the PCB and a new round of prototyping and testing. Needless to say, that's an expensive investment and T4s have already been popping up on the used market. So, business-wise, it probably means an entirely new amplifier is a better business decision.

    That means things are probably in limbo for a while, until Doug and I decide what to do next, if anything.
     
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  3. TomB

    TomB MOT: Beezar

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    An issue has come up with a couple of T4 owners. A T4 suddenly fails to turn on and operate, with supposedly no prior warning.

    The power fuse is ALWAYS the first thing to check when this happens. Short of a literal meltdown or a brick falling on the amplifier, it's the only thing that can cause a total failure of the amplifier in every aspect.

    The fuse is closely rated to the T4's normal current draw. So, a burnout is probably no cause for alarm once the fuse is replaced. The idea is to protect the power transformer, first, and given SumR's history and our inability to procure anymore PTs, that's more important than ever.

    There are many variables in play that can cause the fuse to burn out - voltage swings, brownouts resulting in high current draws, even perhaps extended use of higher current tubes such as the 12AZ7 or 5965. Again, it shouldn't be any cause for general alarm once the fuse is replaced.

    We have them sized at 250ma (0.25A) for 110/120VAC and 125ma (0.125A) for 220/230V (international). They are slo-blo fuses. This is important, because the tube heaters and large capacitors in tube amplifiers cause a large current draw upon turning the amp on, but this settles down to a much lower current in regular operation. Again, another reason perhaps that can cause the fuse to simply wear out over time.

    The thing about slo-blo fuses, and especially the ones we selected for the T4, is that the element does not have to be burned in two pieces for the fuse to be bad.

    These are glass fuses, at the common size of 5x20mm. AFAIK, there is a single filament within an outer coil. That filament inside can burn out, but not the coil. I believe they do this because the outer coil wrapped around the inner filament provides some heat transfer to keep the filament from burning out right away. Thus, Slow-Blow. Reports have been consistent, however, that burn marks appear on the glass, regardless of whether it appears the filament is burned in two or not.

    I tried my best to ensure that everyone was shipped an extra fuse. At first, I put the spare in the extra space within the IEC inlet. However, that caused a rattle and made customers think that something was broken as soon as they took the amp out of the box. So, I stopped doing that (no good deed goes unpunished.)

    Bottom line, any T4 owner should probably have some extra fuses handy. Here are some good sources and cheap prices I looked up for a T4 owner this morning:

    Amazon:
    Glass T250mAL250V 5x20mm Slow-Blow for Speakers Fuse 250mA 10PCS 0.25AMP (T250mA): Amazon.com: Industrial & Scientific – 10 fuses for $9.50 (free one-day shipping with Prime!) However, that looks like a foreign source that may not have all the recognized certifications. These might be OK to get you up and running, but maybe you shouldn't depend on them long-term.

    Mouser:
    0239.250HXP Littelfuse | Mouser – definitely buy 10 at $8.20

    DigiKey:
    0239.250HXP Littelfuse Inc. | Circuit Protection | DigiKey – 5 at $7.03 or 10 at $13.15

    Allied Electronics:
    Littelfuse - 0313.250HXP - Cartridge Fuse, T, 250mA, 6.35 x 31.75mm - Allied Electronics & Automation – 5 at $6.35 or 10 at 11.90

    Newark:
    0239.250HXP - Littelfuse - Fuse, Cartridge, Slow Blow (newark.com) – 5 at $5.45 or 10 at $10.90

    Finally, here’s one from ebay that’s as big a mfr as Littelfuse (probably bigger) – BUSS:
    5x BUSS/BELFUSE USA brand 250mA 250V Slow Blow Glass Fuse 5x20mm T250mA GDC250mA 790753160938 | eBay – 5 at $6.38 with free shipping.

    As with any source, lower prices may be offset by higher shipping costs, so choose carefully if you pinch your pennies. ;-)
     
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  4. Armaegis

    Armaegis Friend

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    I did not know SumR was Canadian. Always sad to see another company go out of business :(
    I suppose that means their subsidiary Primrose Audio Transformers is also gone.
     
  5. gepardcv

    gepardcv Almost "Made"

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    I bought several transformers from Toroidy in Poland. Prices were good and no complaints about quality. The only one which has a bit of hum if I bring my face all the way up to it had unusual specs and too many windings (i.e., mostly my fault). Have you tried them?
     
  6. TomB

    TomB MOT: Beezar

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    I've gotten a quote, but haven't pulled the trigger, yet. It's definitely on my Do List.
     
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  7. joyway

    joyway Rando

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    Sorry to bother you guys, my DSHA1 has some problem ( a screw was missing). I need to know its size. If any guy has Doug's email adress, can you send it to me if possible? Thank you !
     
  8. dsavitsk

    dsavitsk Friend

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    PM sent
     
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