Comparing Edcor OPTs...

Discussion in 'Tube Audio' started by knockbill, Sep 13, 2018.

  1. knockbill

    knockbill Addicted Member

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    Looking at OPTs on the Edcor site, and can't see the difference, other than Watt rating on these two... Am I missing something, or is the info not accurate? Also,,, I can't find physical dimensions for either of them...
    Sent a message to Edcor, haven't heard back yet...
    Thanks...
    https://www.edcorusa.com/compareproducts
     

     

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  2. primosounds

    primosounds SE KT120 w/ 6J5G drivers. LCLC ps + 2 x 5ar4 Subscriber

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    What kind of info are you needing? I know they have the dimensions listed somewhere in their site. I used it to drill my mounting holes and arrange spacing before the trannys arrived and the listed specs were spot on.
     
  3. Dave451

    Dave451 AK Subscriber Subscriber

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    This compare link doesn't work when you haven't been comparing yourself. What two models are you comparing?
     
  4. knockbill

    knockbill Addicted Member

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    Thanks for replying,,, looking for physical dimensions, mount hole layout, etc... seems it was on the site the last time I ordered, can't find it now... Any thoughts on the 10-15W Tx having same specs?
     
  5. knockbill

    knockbill Addicted Member

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  6. Dave451

    Dave451 AK Subscriber Subscriber

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    Transformers look virtually the same except for power and dimensions. Go to the 'product files' tab for each listing and pull up the pdf file that shows the dimensions.
     

     

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  7. maxhifi

    maxhifi AK Subscriber Subscriber

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    Looks like one is bigger than the other, these are different transformers:

    Wattage 15W
    Max. Current 100mA
    Primary (input) Impedance 5K Ohms
    Primary (input) DCR 90 Ohms
    Primary (input) Inductance 3H
    Screen/Grid Tap 40%
    Secondary (output) Impedance Depends on model.
    Secondary (output) DCR <1 Ohm
    Frequency Response 70~18K Hz., <1dBu
    THD+Noise <0.1% @ 1K Hz.
    Bobbin Material Nylon 6/6 GF-30
    Flamability Rating Class B 130°C
    Core Material M-6 29 ga. grain oriented lamination steel
    Secondary Insulation (transformer) Clear air dry polyester varnish
    Termination 0.187" (3/16") quick disconnects
    Mounting Zinc plated steel channel/frame
    Weight 1.6 lbs.
    Compliance RoHS & REACH

    V.S.

    Wattage 10W
    Max. Current 100mA
    Primary (input) Impedance 5K Ohms
    Screen/Grid Tap 40%
    Secondary (output) Impedance Depends on model.
    Frequency Response 70~18K Hz., <1dBu
    THD+Noise <0.1% @ 1K Hz.
    Bobbin Material Nylon 6/6 GF-30
    Flamability Rating Class B 130°C
    Core Material M-6 29 ga. grain oriented lamination steel
    Secondary Insulation (transformer) Clear air dry polyester varnish
    Termination 0.187" (3/16") quick disconnects
    Mounting Zinc plated steel channel/frame
    Weight 1.2 lbs.
    Compliance RoHS & REACH
     
  8. knockbill

    knockbill Addicted Member

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    Just heard from Edcor,,, seems its under Product File...
     
  9. knockbill

    knockbill Addicted Member

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    Got the dimensions,,, seems that's the only difference tho???
     
  10. maxhifi

    maxhifi AK Subscriber Subscriber

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    The weight and power rating are different. The bigger one will have more iron and copper in it, so can withstand higher magnetic flux, more power, etc. Alternately, the bigger one will have lower distortion at the same power as the smaller one.

    What they share in common, is primary impedance. Aside from this they're different transformers.
     
  11. knockbill

    knockbill Addicted Member

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    Thanks for the comparison,,, I figured all specs being equal. the bigger iron would sound better... 3bux difference, and I haven't laid out the chassis yet so it should work... If something doesn't pop up at Kutztown next week, I'll look into a pair of the 15W OPTs...
     

     

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  12. knockbill

    knockbill Addicted Member

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    One more thought,,, only the 15W Tx has DCR listed... if wire size is the same and there would be more wire on the bigger core,,, wouldn't the bigger Tx have higher DCR? Maybe I should call them and see if there are more specs than posted?
     
  13. maxhifi

    maxhifi AK Subscriber Subscriber

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    Don't assume that. The smaller one more than likely uses smaller wire, to accommodate the lower power rating. At 5,000 ohms, 10W gives I = sqrt(p/R) = squrt(10/5000) = 45mA, where at 15W, I = squrt(15/5000) = 55mA.

    The larger core will have a larger window, and enable larger wire to be used to accommodate the higher current. I think this is a no brainer, use the bigger transformer unless you're making something like a Fender Champ clone, or fixing up an old radio, where the better bass performance will be irrelevant.
     
  14. Selmerdave

    Selmerdave Well-Known Member

    Messages:
    767
    Is this true? I know that a given transformer will have lower distortion numbers at lower power levels than the same transformer at higher levels, but can one draw from this that at a given power level a larger transformer will always have lower distortion numbers? Seems to me there aren't a lot of people using 100W transformers in 15W amps, even if high-quality amps do often have somewhat over-sized transformers. In other words, my question is with PPEL84s, for example, with the same primary impedance would 60W or 100W OPTs outperform 25W OPTs necessarily because of their size? I understand to the extent that the 25W OPTs will out perform the 15W OPTs...
     
  15. knockbill

    knockbill Addicted Member

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    Well. that was my thought,, but wanted to confirm... OK, its just confusing when the posted info shows the same specs... I guess the info missing (wire size, length, DCR etc) makes the difference...
    I've read on another forum, where OPTs with the same posted specs from different winders/companies were tested and proved to be not as posted on the data sheets... I am not in a position to buy a bunch of different OPTs to try myself, so I read independent results, and ask here to confirm... Bottom line seems to be bigger is better to a point, at least for Bass response...
    I have a good size trash picked 5K/8R OPT on the test mule now, its probably from an old radio of some kind, but measures (Turns Ratio) proper for the circuit,, however it starts clipping as the Volume is near max... I figure it can't handle the current....
    Thanks again for the discussion...
     
  16. maxhifi

    maxhifi AK Subscriber Subscriber

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    The main mechanism of distortion in a small transformer, will be core saturation at low frequencies. Since these transformers are so small they are only rated to 70Hz, they likely have inadequate magnetic headroom, and are operating close to (or well into, below 70Hz) saturation in the audio band at maximum power. To reduce the distortion, the choices are either a material capable of handling higher flux density, or more core material.

    The question about why not to use 100W OPTs in a 15W amp is simply answered when you consider that transformers are the single most expensive component in an amp. It wouldn't make any sense to pay for a 100W transformer, and then throttle it back by using small tubes and power supply.

    Yes, larger cores do have more hysteresis distortion than small ones, but with small and cheap transformers especially core saturation is far more audible, and will have a much more real impact on the performance of the amp.

    I'm just talking every day applications though, for esoteric stuff like flea power amps, your mileage may vary.
     

     

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  17. maxhifi

    maxhifi AK Subscriber Subscriber

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    Are you sure it's the OPT which is clipping, and not the tube? If it is the OPT, it's simply reached its limit in terms of magnetic flux. This is called core saturation, the magnetic field goes up to a point, and then can go up no more, and clips the peaks. Simply put, you need a heavier transformer to do the job.
     
  18. knockbill

    knockbill Addicted Member

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    Pretty sure its the OPT,, it came from an old radio speaker, I can't think of a SE radio tube from the 30s or so which is good for 10+ Watts... It is approximately the same size as the 15W Edcor, tho... DCR on primary winding is 248R... 15W Edcor is 90R...

    Note,,, Tom B addressed this in post#18 of the build thread...
     
    Last edited: Sep 14, 2018 at 5:37 PM
  19. Selmerdave

    Selmerdave Well-Known Member

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    767
    So it's more an issue of adequate power rating and operating it below the point where distortion begins to suffer, no?

    If there were sonic benefit to using 100W OPTs in a 15W amp that would be a good enough reason to do it, of course one wouldn't find that in a budget amp.
     
  20. BinaryMike

    BinaryMike Pelagic EE Subscriber

    In practice, the evidence (distortion) for core saturation occurs near the zero crossing of the output voltage waveform, not at the peaks. Peak flattening indicates limiting in the output stage, or possibly upstream in a crippled amplifier.
     

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