NP I'm listening to Hille Perl play a viola da gamba through that F5 you designed into an old pair of Klipsch Forte speakers and it is just perfect.
I was just listening to Minnie Pearl do a rare solo on an old episode of Hee Haw. You should have seen these Magnepans burn down. Man-I really kinda liked those speakers.
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I follow a rite of passage in the following order.
1. Two say 20 ohm 5 watt resistors in series with the positive and negative rail.
2. Attach a dummy load, lets say a 6 ohm 10 Watt resistor.
3. Remove the two resistors from step 1.
4. Attach a real speaker.
After each step I power it up and check the rails, bias and offset.
1. Two say 20 ohm 5 watt resistors in series with the positive and negative rail.
2. Attach a dummy load, lets say a 6 ohm 10 Watt resistor.
3. Remove the two resistors from step 1.
4. Attach a real speaker.
After each step I power it up and check the rails, bias and offset.
I adjust bias, offset, and measure things first. Then I feed the amp with some very low voltage sinewave... slowly increasing frequency to 20kHz while listening for any strange noises coming from the amp while looking at the oscilloscope. If all is good, I chose a 1kHz signal and then crank the input to see symmetrical clipping (without the load).
Then, repeat the above with a couple of 50W resistors. Once I am happy (mainly looking here for a symmetrical clipping at 1kHz), I try square waves to see if I need to tune the feedback and get it to look nice.. above 15kHz...
Now, I attach the test speakers and play some music.... if all sounds good and sweet, I connect my main speakers and enjoy.
After a week or so, I retighten the output devices (*optional step... but one that I always do). Then, just a quick ohm-meter test to ensure I haven't shorted the collector/emitter drain/source to the heatsink), and then back to listening to music. I believe that the keratherm should be injected into surface imperfections on both the heatsink and transistors cases... which means a fair bit of torque... for the best heat transfer.. but that's me...
The main reason for the above is... I do not like the sound of coupling capacitors (inclusive of any capacitor in the feedback loop - the one going to ground to ensure DC gain is 1) and speaker relays... so the amp has to be performing really well and reliably before it is placed in my main system
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I have a pair of sacrificial speakers that I use to fire up anything I build for the first time. They’ve been with me for like 25 years so I’ve been lucky to have no failed builds! I should have them bronzed for their years of service! I hope I haven’t jinxed my record.
I have a dummy load for the initial tests and measurements, and an old guitar cab that I use for the first sound
After Nelson's multimeter, I would say buy two (for dual) decent PSUs with variable V and I. My chinese PSUs have been my favorite tools after my DMMs and my soldering irons. That way not only you can check your builds with low I and get direct indications that everything is ok, but you can also experiment with different settings.
And then, if you also do your own PSUs, you should build an incandescent lamp limiter.
Alternatively, you can flip the switch crouching to the side squinting your eyes and protecting your face with your arm
After Nelson's multimeter, I would say buy two (for dual) decent PSUs with variable V and I. My chinese PSUs have been my favorite tools after my DMMs and my soldering irons. That way not only you can check your builds with low I and get direct indications that everything is ok, but you can also experiment with different settings.
And then, if you also do your own PSUs, you should build an incandescent lamp limiter.
Alternatively, you can flip the switch crouching to the side squinting your eyes and protecting your face with your arm
Absolutely use cheap speakers. I have two sets on the bench, the really cheap from the tip shop and a quality pair if the first ones survive.
I have some old cheap philips speakers (in a plastic cabinet) for that, i got them for 5€ and others similar speakers did save me a few times as i'm an amateur (and went up in smoke). That kind of speakers are always for sale on local second hand sites down here so there is an endless stock of them... But it's a while now since i burned speakers while testing an amp i repaired (i mostly do easy repairs, i'm not an expert).
I measure everything (rails, DC offset, THD, etc.), let the amp cook for a while (usually a few hours), measure again and if it is OK then I connect to my main and only speakers. Never had any issues so far 🙂
Zen Mod-I am not much of a praying man and do my own speaker repairs but I get your drift. However, I have found my feeble attempts at humor poorly received here. I do my best to remain introspective and not take myself too seriously. Thanks for the chuckle.it's simple, I'm always using my most precious speakers for testing
all I need is just a Prayer
works 50% of cases
and my speaker repairer guy is happy
