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    My guess that what is happening is because the...

    My guess that what is happening is because the ear is not as sensitive to low and high frequencies at low volume. So, when you turn it up you start to hear the less mids and it's more balanced.
    ...
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    You'll notice at full tilt that the transformer...

    You'll notice at full tilt that the transformer RMS current is 1.3A for an output average current of 0.718A. Pretty much the in the same ballpark is I reported earlier, this is why you should not...
  3. Thread: Samson SX2800

    by nickb
    Replies
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    5,818

    See post #6 - it's there.

    See post #6 - it's there.
  4. Isn't the US sending out checks to all taxpayers?...

    Isn't the US sending out checks to all taxpayers? Could that be a lifeline for you?
  5. So very sad to hear about your situation. That's...

    So very sad to hear about your situation. That's a truly amazing collection of gear and I can only imagine how hard it must be to part from it. I hope you can find good homes for it all. The very...
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    Exactly. They typically design using a crest...

    Exactly. They typically design using a crest factor of 10 to 20dB and so can justify an economical transformer. This is is fine 99% of the time. The other 1% of the time you are looking at a charred...
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    ..as is self evident :) But perhaps you should...

    ..as is self evident :) But perhaps you should tell that to Hammond. It's their JCM800 100W transformer 290HX. I'll leave it at that to keep this thread on topic (fuse ratings).
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    I've become very skeptical recently of this rule...

    I've become very skeptical recently of this rule of thumb after meeting the Masters of Doom Metal (fake name) and the Incendiary Power Transformers. They play their amps at full tilt. A 100W amp...
  9. I used a different numbering. The 100K and 20uf...

    I used a different numbering. The 100K and 20uf are a low pass filter to remove audio so only allow near DC to appear on Q1 and Q2. If the voltage there is > 0.7V Q1 will turn on, if < -0.7V Q2 will...
  10. The holes will almost certainly be plated through...

    The holes will almost certainly be plated through so there should be connectivity between the two sides at each one.
  11. Read...

    Read https://music-electronics-forum.com/showthread.php?t=49426&highlight=2n5551
  12. Here are some suggestions that might help you in...

    Here are some suggestions that might help you in the redraw.

    I see that two IN4004's and the 100K go to the amp output, not 0V as drawn.
    D33 is in parallel with the relay coil which needs about...
  13. Can you provide a clear image of both sides of...

    Can you provide a clear image of both sides of the unpopulated board and one of the populated board? Maybe the relay is not a mechanical type. Still if the supply is 48V and the series resistance is...
  14. That cannot be right. The relay probably has a...

    That cannot be right. The relay probably has a diode across it coil. The resistor cannot be 390k, more like 390R if it is in series with the relay. The relay must connect to a transistor collector...
  15. You are correct. Yes, the right thing to do is...

    You are correct. Yes, the right thing to do is use the biggest resistor that give you the pop suppression you need but not so small as to nuke the SSR.
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    Slightly off topic but just to bring some levity....

    Slightly off topic but just to bring some levity. "Mein schatz" ="My precious"

    https://www.telegraph.co.uk/content/dam/PortalPictures/march2020/228202240_Berlin.jpg
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    I'm planning on trying UV sterilization. I've...

    I'm planning on trying UV sterilization. I've cleared an out building and am installing two UV-C tubes, a timer, and a door open safety switch. Pop the items in, push the timer button. I calculate...
  18. The resistor needs to be small enough to ensure...

    The resistor needs to be small enough to ensure the LED lights up, but not so small so at to break it. The cap needs to be big enough to just mute the pop. The original 220uF was just a conservative...
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    Quite so. We need measurements else we're just...

    Quite so. We need measurements else we're just shooting the breeze.
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    I suggest you inject 1KHz (say 100mv RMS) and...

    I suggest you inject 1KHz (say 100mv RMS) and measure the output of each stage in both amps to see where the differences are. Repeat at 200Hz and 2KHz to check for frequency response errors.
  21. I think you're out of lack as they are part of...

    I think you're out of lack as they are part of the rather horrid musictribe aka Berhringer evil empire.
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    Mick removed and bypassed that cap in the first...

    Mick removed and bypassed that cap in the first post so it can't be that.

    I see the focus in on the signal path but I wonder if the noise is getting in the ground side of things. If that is the...
  23. All the above plus don't forget about the huge...

    All the above plus don't forget about the huge effect the speaker has on the waveform. I'll bet the output of that doesn't look very square.
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    Can you please show a scope shot ( with x and y...

    Can you please show a scope shot ( with x and y axis scales specified) with the output driven as hard as you can with a 1Khz sine wave. The idle DCV at the PI plates and 6550 grids will be helpful...
  25. Thread: Mackie SA1530z

    by nickb
    Replies
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    230

    Today I around to yanking the amp module. The...

    Today I around to yanking the amp module. The power amp is just the SA1232z ( which I alrdeay had). So only now do I understand the wisdom of JPB attaching those schematics above - belated thx dude!
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    It's been working for 50 years so I don't see the...

    It's been working for 50 years so I don't see the justification for a redesign unless you are seeing thermal runaway issues with the KT88s. Seems better to solve the known issues which are

    (1)...
  27. Thread: Mackie SA1530z

    by nickb
    Replies
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    230

    No use ..been there already (see OP)

    No use ..been there already (see OP)
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    So... was there a miswire or are the construction...

    So... was there a miswire or are the construction directions in error?
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