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Hoffman Amps Forum image Author Topic: Methods for improving a build  (Read 12721 times)

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Offline HotBluePlates

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Re: Methods for improving a build
« Reply #50 on: March 28, 2016, 05:28:16 pm »
... Reason for this fiasco is these are 12 amp modules. ... and noticed the 12A module has .11mH chokes whereas the 3A module has 2.5mH chokes. In fact the larger the amperage the lower the mH rating for these products. Would it be better to have bigger chokes on the line? ...

How much current does the amplifier draw? Probably 3A or less, right? It seems silly then to try to acquire the higher-amperage models.

I didn't know the cords would be different, but it makes sense if you think about the fact you're going from typical "consumer-size" to a current rating similar to the wiring in your wall.

Assume the people designing those power entry modules know a bit more about the design of their product than you do. I'm sure that whatever value chokes and caps they use will be appropriate to the task. In all likelihood, the values of those parts are scaled to each other, and probably to the line frequency. There's likely a number of other tradeoffs as well.

Reason for this fiasco is these are 12 amp modules. Convinced, right or wrong, that a bigger module would be less likely to have problems when I bought them. ...

Would using 10 gauge wire through the amp in place of hookup wire make it any better? Probably wouldn't be as easy to work with...

I went through a period of this same thought process when I started amp tinkering. "It's gotta be better to use 1w resistors in place of 1/2w, right? If 1w is good, 3w is better, right? What about those 25w aluminum-clad resistor for cathode bias?" Over time, I learned it's cheaper to use just-good-enough parts, and in some places you want the $0.50 resistor to burn up and fail rather than the $150 output transformer.

So Right-Sizing is often better (and cheaper) than over-spec.

Offline Mike_J

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Re: Methods for improving a build
« Reply #51 on: March 28, 2016, 06:36:54 pm »
This would be the cheap option if not for the fact that I won't use them. Mouser wants almost $8.00 for the 3A part. This 12A part was $2.00. The 12A part is commonly used for equipment with heating elements in them. It has a notch in the receptacle so a heavy gauge power cord must be used. Makes all the sense in the world but doesn't work for a guitar amp. Take the amp to a gig and forget the cord and your out of luck. Not out enough money to worry about. Would cost as much to return it as I would get back. Live and learn if this is the most expensive lesson for the year this will be a good year.


Thanks,
Mike

Offline HotBluePlates

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Re: Methods for improving a build
« Reply #52 on: March 28, 2016, 10:44:02 pm »
This would be the cheap option ... almost $8.00 for the 3A part. This 12A part was $2.00. ...

I just found out the same thing buying parts for a 1/3w amp. Was looking for a 1w resistor (maybe even a 1/2w would have worked), but the same thing in 3w was cheaper. Guess it's a higher selling-volume part...

Offline kagliostro

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Re: Methods for improving a build
« Reply #53 on: April 01, 2016, 11:40:43 am »
Diodes to protect OT and Power Tubes was told previously ?

Franco



The world is a nice place if there is health and there are friends

Offline sluckey

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Re: Methods for improving a build
« Reply #54 on: April 02, 2016, 09:18:29 pm »
Good soldering techniques.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline Moonage

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Re: Methods for improving a build
« Reply #55 on: April 02, 2016, 09:27:23 pm »
Here are some things I have done with my amps and not mentioned in this thread so far:
Fast acting fuse (inside EMI power entry module)on the primary of PT, rated just above the max current for transformer  :w2:
Inrush current limiter on the primary of PT (for my amp I used CL90 wich has 120 ohms cold, but goes down to 3 ohms at 1A) :laugh: fast acting fuse does not blow....
Thermal cutoff on the primary of PT, rated 100oC
Every single tube heater wired with separate twisted pair( no daisy chain)that way current through them is much smaller, and EMF they create is also smaller.
Designated cathode resistor (and capacitor) for each output tube in PP configuration.

« Last Edit: April 02, 2016, 10:29:03 pm by Moonage »

 


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