Tube amp Theater How to test amplifiers via oscilloscope by D-lab
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- Опубликовано: 15 сен 2024
- I have had many requests for testing amplifiers using a dummy load and oscilloscope. The method is pretty straight forward. Not much equipment involved. This is how I bench test all amps. Afterwards, I have one of my demo guys do a live test in my small studio. Hope you enjoy.
I love all the D-Lab episodes. He is the very 2nd one on my subscription.
I ended up watching this video at 1 am for no damn reason other than your great presentation. I know nothing about amps for a jack about the Os-scopes! I think you can be a great example of demonstrating communication skills!
Maybe worth mentioning, older amps with hot chassis and grounded scopes make for some sparky fun and melty probes. Great videos, keep em coming!
Hey Terry, I'd be interested in a schematic of the D Lab Audio Test Set. Please let me know what is cost for the schematic and parts list. From what I see below you made several of these for sale but that was years ago. I'd appreciate any help on this.
I love to see vintage test equipment, I keep an analog oscilloscope still.
Excellent video, this the way to do the test.
Cheers.
Very cool and informative. Glad you are passing on valuable knowledge. I have several of your amps and they are fantastic. Thanks
Thank you Mr Dayton, this info was just what I was looking for. Can you do another video sometime on the correct way to hook up volt meters and amp meters to a variac ?My best regards to you.
Hello Terry everything in order?
This test with the oscilloscope + audio generator and dummy load is very useful for our benches services with amplifiers.
Congratulations on your work and wish much success in its work.
+Sebastião Souza Hello, Thank you my friend. I do my best to share the knowledge with a small twist of humor.
Love your videos Doug, but a word of advice - the red alcoholic juice has a distinct effect on the brain. The brain controls whether or not we get (or avoid) a high voltage shock, which seems to happen to me at the most unexpected times. If I made use of that brain juice at all, I would surely forget to discharge more and more capacitors!
Yes Sir, I had to remove the brain juice box from the bench. Had a mis-hap, it dispensed red stuff into a radio!
I am in electronics for 40 years, this test is for check if you have some distortion or if you want to test the power of an amplifier.
But many other test will be do it if you want to know if the amp is working correctly.
Is very important to test the background noise and some times the bandwidth.
I been fixing Audio Research amps for many years, AR is a High End audio company based in Minessota.
Cheers.
Thanks for all of this Sir.
Hi Terry, have you ever been asked to build a high power test load for 200w or more amplifiers?
Sorry Terry, called you Doug? Any chance of a vid exploring the crossover points of push-pull amps and methods to decrease the possible distortion? If there is one, let me know and I’ll look for it.
You are a legend Terry :)
@ 2:30 Terry said to put the scope's negative lead on the chassis ; but it's on the dummy load . What am I missing here ?
@ 3:05 which knob on the amp did he turn to increase the gain ?
Thanks in advance to anyone who can provide the answers
I would really like to see the inside of the stereo test set. Planning on building something similar.
D-Lab Juice is a requirement!
Thanks Terry, quick question here. If my dummy load isn’t a non inductive how much of a difference would it make when testing?
You’re the man! Cheers!
What adjustment did you do when you said that you're "cranking the jobber up"?? The voltage on the scope went down.
Wine, but no isolation transformer?
I forget to say " Fix tube amplifiers is an art"
Howz about tracing with a sillyscope if the signal isn't passing through? Where NOT to connect the scope? Don
+umajunkcollector Can do man, Love your shocking image. Looks very retro
Hi! I have a 100w tube amp project and I was wondering if I could get 10+ of those resistors and wire them up in a combinations of series parallel circuits that they end up with 8 ohms. Will that work as a dummy load?
Is the schematic available for the D-Lab audio test set?
What if you wanted to do the same test on an 1 kW RMS ampliifier? How would you simulate the speaker? Could you actually use a speaker - or would that hurt the oscilloscope due to impedance?
Many thanks Terry, Just what I was looking for. I'm about to build myself a somewhat more robust 16 ohm dummy load comprising a pair of 50w 8ohm resistors in series on an off cut of 1/2" MDF board. I plan on testing amps up to 100w. I also have a pair of 50w 4 ohm resistors to do the same for an 8 ohm dummy load. I have a few spare jack plug available from other projects. I see you are a Cab Sauv kind of Guy, I'm into Rioja right now. Thanks again.
BTW
Are you still producing the test box? If not, could you release the schematic for a small fee?
+Andy Wragg Hello, I have enough materials to make another box. The cabinet was from a VIZ power supply. I may have a schematic around. Will let you know. TD
I'd be interested in having one. reply here if you can make me one?
Don't use mdf, use a piece of square section Aluminium screw your resisters to the outside with some thermal compound then mount a fan at one end then you make a cooling chimney...
Hello
very interested by you Dummy load "D-Lab electronics Amp test center" I suppose it was you who made it ! the meter tells the RMS watts ? I will want to manufacture the same you have a schema
regards to FRANCE
kriss
Hello Kris, Yes, I built it long ago. I will see if I can locate a schematic.
Hey Terry, I'd appreciate one too.
I know you said the d-lab audio test center. What is the technical name for it?
+Corey Savolainen Hello, It is actually a audio dummy load with wattmeters and L-pads to allow for monitor speakers. So, you can play audio thru it at high wattage and monitor at low volume. I made approx 20 of them years back. This is my shop unit.
+Terry Dayton do you still have any of these laying around, or did you sell them all?
Hey Terry, fantastic video. One question: what kind of probe do you recommend? I understand there are different types for different applications. What specs should I aim for when sourcing a probe for tube amp repair?
Hello, I would recommend standard X1-X10 probes. Probe-Master makes a nice set + older B&K probes are easy to find on ebay. Thanks for being on my channel. TD
Thanks for the reply. I have two HP probes: a 10041A and a 10435A. They both are 10:1. Is this what you mean by X10?
Hello, Yes same type. I prefer probes that can be switched for straight thru or X10 operation.
Could I use a Heathkit SG8 for tube amp testing? It seems that the unit only allows for a 160KHZ signal...did I buy the wrong signal generator?
The SG8 is an RF signal generator that produces signals far above the audio spectrum - it won't work for this application. However, it does have a built-in 400Hz audio generator that you could use, but you won't be able to adjust the audio frequency. An actual audio signal generator that produces audio signals between approximately 20Hz and 20kHz would be best for this sort of work.
Thanks for the help on that Roast! I eventually figured that out and sold the RF sig generator for a Leader audio generator LAG-26...works like a charm with my matching Leader o'scope!
Thanks again!
Vary Good
What is the signal generator? Model brand?
doing the same but stereo can i just combine generator output to left and right channels or does it need any special combining circuit,, one sourct going to both L and R
Hello, yes, you can simply connect the 2 channels in parallel to the signal gen
My brain is missing a few Lego blocks cause I never understand this stuff!
high voltage and alcohol ?
A great mix
I do likewise but instead of boxed wine, I use a bag of weed.
I stick to the wine, so to keep my tweezers clean!
pleximanic I
How would one go about testing a tube radio with an oscilloscope?
+Chase Parten Hello, I will put together a video for this application.
Terry Dayton Thanks a lot! And thanks for all your other videos!
Very carefully.....
Hello
cool
regards
kriss
dont forget the importance of a drunkard to run the equipment
real world,,, use real spkr,,, no dum load