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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups

Help me pick an oscilloscope

Discussion in 'Shock Brother's DIY Amps' started by Outlaws, Jan 1, 2018.

  1. Outlaws

    Outlaws Tele-Meister

    Jan 16, 2007
    The time has come for me to get an oscilloscope. I have witnessed one being used briefly but a lot of it wasn’t for me to ask questions at the time.

    So what features are a must for guitar amp and effects pedal work? What am I looking for?

    I know I want to be able to measure the preclip and clipping wattage (or at least be able to quickly get a reading I can plug into a formula to acquire it)

    I would like to be able to check for high frequency oscillations that I cannot hear and might burn up an amp over time.

    I would like to be able to set the trimmers in a phase pedal. Doing it by ear is nice and all, but i would like the option of seeing it too.

    And I would like to be able to check for noise when probing with a stick that just isn’t loud enough to register to my ears but might be there.

    Anything else I should want it to do? Audio/freq generation or a separate unite for that?

    Is all that available with every scope?

    Ideally my first scope will be cheap and used on Craigslist.
    Last edited: Jan 1, 2018
  2. dunner84

    dunner84 Tele-Meister

    Jul 15, 2014
    Victoria, bc
    Most Oscopes will do what you want. If you are looking for cheap and used, it is hard to make recommendations. If you have any o-scopes on craigslist in your area, you should post them, and we can all chime in.

    New and digital is nice, but an old scope can be very useful, and do all of the things that you want to use it for. You just need a big enough bandwidth to see high frequency oscillations. Dual channel, and 20Mhz is pretty common, perhaps overkill, but I wouldn't go lower than that. 4 channels is nice, but really not necessary.

    I have a separate function generator, and I don't know of any scope/function generator combos, but they may exist...

    I would also look into acquiring/building a dummy load if you don't already have one... there are no single frequencies that are pleasing to your ears when pulsing through your amp!!
    Outlaws likes this.
  3. PinewoodRo

    PinewoodRo Tele-Afflicted

    I use a (free) function generator app on my android tablet if that's any help. Works fine.
    Outlaws likes this.
  4. FenderLover

    FenderLover Friend of Leo's

    Jun 11, 2009
    I had a Leader oscilloscope that had 2-channels and 1MHz bandwidth. Perfectly fine for amp work. I gave it to a friend, but paid less than $100 for it at a music fair.

    Over 90% of what you will be measuring is signal amplitude and frequency below 10KHz. Bandwidth checks can go as high as 100KHz, but a 1MHz scope is still plenty capable.

    An old PC with a sound card and free software is also a good option. Especially for screen capture and documentation.
    Outlaws likes this.
  5. Outlaws

    Outlaws Tele-Meister

    Jan 16, 2007
    Ya i was thinking about making some equipment with rack mount enclosures at some point. One would be a 2/4/8/16 ohm 200 watt load box with a switch so I can dump a dimed 100-120 watt head into it.

    Channel wise is 2 enough? Any example where I would use more than one?

    Any recommendations on audio generators?
  6. FenderLover

    FenderLover Friend of Leo's

    Jun 11, 2009
    Two channels is plenty just to check phase relationships if need be.

    There are audio generators on the used market too. Chances are that wherever you find a scope, you will find other useful things, like an audio generator. I like a generator with a sweep function so you can easily probe from stage to stage is see if/where high frequencies are tanking.
    Outlaws likes this.
  7. Digital Larry

    Digital Larry Tele-Holic

    May 30, 2017
    Silicon Valley, CA
    I got a Hantek 70 MHz dual channel digital scope for about $250. Somewhat overkill for pure audio work but the nice thing is that it has a "measure" mode where it will tell you all sorts of things about the current waveform - peak to peak, average, frequency, etc. It's small and lightweight. I had been using a Velleman USB scope (plugs into your PC) which was "OK" before it up and died but this is not so great for the work bench since you need to hook it to your laptop and all that jazz. It also surprisingly didn't even attempt to use color to improve readability and zero application or driver updates were ever issued in the 5 years I had it.
  8. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    For tube audio, a used Tektronix and a simple signal generator are fine. Personally, I'd rather have a standalone $30 generator over risking a smartphone, but that's just me.

    4 channel is useful for chasing intermittent problems, especially if you don't know where it is coming from. Plug in four probes at various points, crank up the signal, and wait until the issue pops up on one or more traces. If you're not pressed for time though, you can do the same thing with a 2 channel and some patience.

    I use a Rigol 1052, if you're looking for specific recommendations on models that work well for tech use.
    dogmeat and Outlaws like this.
  9. CV Jee Beez

    CV Jee Beez Tele-Holic

    Nov 24, 2016
    Duarte, CA
    I got a really old HP scope that a business could not use any more. I've only used it to see the wave form when biasing. Any scope should do. I remember a person trying to take issue with the calibration of my scope. This is silly because, most of the time you're not really looking to obtain numerical data.
    Outlaws likes this.
  10. akuster777

    akuster777 TDPRI Member

    Jun 20, 2017
    Ann Arbor, Michigan
  11. Andy B

    Andy B Tele-Afflicted Gold Supporter

    Mar 16, 2003
    My main scope is a GW GOS-622G 2 channel, 20Mhz. Simple straight forward scope. My backup is a B&W 1474. In looking for a scope I'd recommend you look for ease of operation. For example there are some high end scope out there that have so many controls and adjustments that you need to be a rocket scientist to use it. I have an old Knight audio generator which is fine for amp work.
  12. Piggy Stu

    Piggy Stu Friend of Leo's

    Feb 26, 2017
    Name of app?
  13. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    Found my Tektronix 2247A on eBay, at that time there were a lot of nice used Tek scopes.

    Got a great (in my opinion anyway) deal on this... these sold for $3000 in 1995, got it for $275, very clean and calibrated. Even came with 4 probes.

    Omiewise65 and dogmeat like this.
  14. jvin248

    jvin248 Poster Extraordinaire

    Apr 18, 2014
    Near Detroit, MI

    I have been curious about this same question.

    Picked up one of these last summer at a sale "tektronix oscilloscope 502A". I need to find some leads. It powered up and lighted the screen. Beyond that I need to study up.

    dogmeat, xafinity and The Guy like this.
  15. archetype

    archetype Fiend of Leo's Silver Supporter

    Jun 4, 2005
    Williamsville NY
    If you're buying old audio generators and scopes, and old ones should do the trick...

    1. Buy cheap. They're not made of gold and low-frequency ones that will handle the audio range are both plentiful and obsolete.
    2. Look at the schematic before you buy. Be sure that the AC cable is polarized, switched correctly, and doesn't have any capacitor nonsense going on for polarity switching. If it doesn't meet those criteria, be sure you can modify it so it can. If you get electrocuted you can't play guitar any more.
  16. archetype

    archetype Fiend of Leo's Silver Supporter

    Jun 4, 2005
    Williamsville NY
    ^ This. Better to smoke an old sig generator than your phone.
  17. CK Dexter Haven

    CK Dexter Haven Friend of Leo's

    Jun 7, 2017
    Mine is a Tektronics 900 series, these were produced in the thousands (10s of thousands?) for schools, if you have a university near by see if they have surplus warehouse, mine came from such a place and was $30 with a bag of probes. The nice thing about the 900's is there was a self guided user course done by IIRC Illinois Tech, that I believe is still posted on line. Those big beasts like j248 showed are often available at hamfests for free at the end of the day when loading them up to unload them at home one more time is just too much work. There were two sitting by the trash can at the last one I attended, of course you would need to have such a thing checked out.
    Last edited: Jan 2, 2018
    Wobbles likes this.
  18. dsutton24

    dsutton24 Doctor of Teleocity Ad Free Member

    Dec 29, 2010
    I've had several over the years, the current workhorse is a Tektronix 465B:


    I got it for forty bucks, and it came with about $800 worth of probes and manuals. I was glad to get it.

    Analog 'scopes are dirt cheap. A 'scope that would have set you back $4000 in the 80s or 90s can be had for well under $100.

    Ever been to a Hamfest? Google it, there's probably one close to you. They're primarily geared toward radio amateurs, but they're great places to pick up parts, tubes and measuring equipment.

    Look for B&K, HP, Philips, Tektronix. These guys also built a lot of specialized test equipment for communications and television, so buy something that specifically says 'oscilloscope' on it.

    On the upper left corner of the picture, see the knob that says Volts/Div? That's important. Older and cheaper 'scopes didn't have that switch, you don't want one of those. They are usable, but you have to recalibrate the thing every time you change scales. I did it for years, trust me on this one... That old Dumont you see for ten bucks will make you crazy.

    Other than that, newer is (probably) better. I much prefer CRTs over LCD displays... I've got a Fluke Scopemeter, the only times it gets used is when portability is a big deal. If you have two scopes side by side, opt for the one with fewer controls.
    kafka, Omiewise65, Speedy454 and 3 others like this.
  19. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    The Tek 465 was/is a great old venerable standard, spent a lot of time at work with those many years ago. Nearly got one just because it was like a familiar old friend, then I spotted the 2247 and decided to go with the newer model with frequency / voltage readouts on screen.

    Regarding sig generators… I didn't have much luck finding usable used analog ones when I was looking, surprisingly enough. They were either digital and sketchy-looking, or too much cash for what they were, so I'm using a decent generator app on my iPad. Still looking for a decent one with analog sweep output so I can drive scope horiz. to make easy freq. response plots.
  20. PinewoodRo

    PinewoodRo Tele-Afflicted

    It's called 'function generator'.
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