Equipment for first build? Scope?

[blinddog]

Hello all. I have ordered the D-lite kit and am seriously gearing up for the build. I have seen posts for meters and soldering stations, so I have a pretty good idea there and already have made some purchases.

My big decision right now is do I need a Oscilloscope ( Silly Scope, if any of my college EE friends who may be here). I know it will help if I need to trouble shoot but if I’m sticking to package builds from Brown note or Nik at Ceiratone, (for now) is it needed?

If so what brands?


Type Analog or Digital? If I’m using a signal generator I’d think analog would be fine, but I’ve been away from this stuff for awhile now.


And what ranges (MHz) should I be looking for?

Any other equipment input would be appreciated

Thanks

[drz400]

Get yourself a Tek 465B on Ebay and make sure it is tested
The Loftech generator is aces TS-1 or TS-2 look and you can find them on ebay as well. A Load resistor as well and some probes and you will have fun.
A Variac would be and excellent idea as well

[sliberty]

You might check these out too.

http://cgi.ebay.com/KIKUSUI-COS5020-COS ... dZViewItem

Maybe not as nice a scope as the Tek, but for a first time builder, it might be more the sort of investment you are ready to make and should be more than adequate. 100mHz is generally not needed for audio applications from what I have been told. I just bought one myself. You will need to buy the probes seperately however. I bought these:

http://cgi.ebay.com/Two-new-100MHZ-Osci ... dZViewItem

and they are rather nice.

[Greg Smith]

A signal generator and a 'scope of minimum 10 MHz bandwidth would be desirable for audio testing, but definitely not a requirement for guitar amp building (unless you're looking for an excuse to buy them, which I can FULLY understand ). All you really need is a DMM to check supply voltages and bias current in the output stage - so that you know the amp is running as expected, and wont overheat/fry components afetr a few days of use.

Beyond that, your ears tell you all you need to know about how your amp is running. Either it sound right, or it doesn't!

If you get into hi-fi or recording gear building, then the signal generator/scope combo become more desirable, so thatt you can do square wave testing, etc.

Greg

[drz400]

A signal generator and a 'scope of minimum 10 MHz bandwidth would be desirable for audio testing, but definitely not a requirement for guitar amp building (unless you're looking for an excuse to buy them, which I can FULLY understand ). All you really need is a DMM to check supply voltages and bias current in the output stage - so that you know the amp is running as expected, and wont overheat/fry components afetr a few days of use.

Beyond that, your ears tell you all you need to know about how your amp is running. Either it sound right, or it doesn't!

If you get into hi-fi or recording gear building, then the signal generator/scope combo become more desirable, so thatt you can do square wave testing, etc.

Greg

I have seen many oscillations that are beyond hearing but visable on a scope, these can cause problems. I have seen this on manufacturers amps as well. Even though the 10mhz is fine I would go at least 20mhz I really recommend a scope if you will make more than one amp mnay problems are way out of the hearing range. You can find a 465B for $350 all tested

[Greg Smith]

I have seen many oscillations that are beyond hearing but visable on a scope, these can cause problems.

Now you've got me all paranoid! Maybe it's time to switch on that old Tek that's been gathering dust on my workbench. Btw. how do you find these oscillations? My knowledge of 'scope usage is pretty much limited to looking at audio waveforms.

Greg

[pila]

I personally think a scope is over-kill for building amps. Like someone above said, it either works/sounds good or it doesnt. Good meters are a must though. I would personally spend money on tools to build chassis' as opposed to in-depth type test equipment. I have all that stuff, this is just my opinion after doing amp builds. I've found that most build problems are small mistakes in wiring and not-too-good grounding schemes.
We can nit-pick what we build, if we really want to. I guess I don't see the point.
But, and that's a big but, if designing and interfacing a pre-amp into a different power amp or other mods like that, or repairing amps, the scope may be justified.

Like I said, just an opinion.

Regards PILA

[Bob-I]

Now you've got me all paranoid! Maybe it's time to switch on that old Tek that's been gathering dust on my workbench. Btw. how do you find these oscillations? My knowledge of 'scope usage is pretty much limited to looking at audio waveforms.

Greg

I thought the scope was overkill too, but recently I fixed a serious oscillation issue with it.

It's really simple, you turn the amp up with no input and look at the output of each stage. The oscillation will show up as a sine wave, or close to sine wave at high frequency. I just put the scope probe on the output of each stage and adjusted the scope from about 8K up until I saw the oscillation. Turned out to be at th ePI caused by interference with the NFB.

[tubetek]

Howdy All-
While a 'scope is really handy for repair/troubleshooting as mentioned above,
it really isn't required for "kit building". A much better initial investment would
be to get the best DMM you can force yourself to afford (FLUKE etc)
I have 3 DMM's (1 top-shelf and 2 cheapies) Using the good meter to measure small values accurately (bias across the 1 ohm cathode resistor in
millivolts/milliamps) and use the cheaper "sacrifice" meter to measure
gross HV B+ (Plate, PS, etc.) at the same time...2 meters makes biasing a breeze. I'm not trying to dissuade you from getting a scope, just saying
that I can do better'n 90% if all my bench work with 2 DMMs and a lightbulb current limiter. Of course YMMV...Hope this helps.
tubetek

[drz400]

I have seen many oscillations that are beyond hearing but visable on a scope, these can cause problems.

Now you've got me all paranoid! Maybe it's time to switch on that old Tek that's been gathering dust on my workbench. Btw. how do you find these oscillations? My knowledge of 'scope usage is pretty much limited to looking at audio waveforms.

Greg

Well a good meter is an absolute necessity
But sometimes ignorance is bliss, other times it prevents the amp from being as good as it could me. I had a look at a friends amp I dont want to mention, but it was a VERY expensive German new amp. On the sine wave there was a very nasty squigle Sideways sine wave) on one side of the sine wave. Had something to do with layout of bundled wires with the NFB and the very low values of the NFB but it wasnt my job to fix it.
I told him to have them fix it. This is an oscillation, as you turn up the presence it went away. You can also look at a square wave and look at a squigly line or ringing. Funny thing about that amp is that it didnt sound great but didnt sound broken either and he liked the amp. I'm sure it wasnt doing the tone any good, You guys can use your ears all day but that doesnt mean everything is OK. I have seen plenty of problems on a scope the ears would never pick up cause they are out of the hearing or speaker range. Some of these oscillations can cause speaker damage as well. At least pay a tech $30 to look at your creation on the scope to make sure it all looks good. To say a Scope is overkill when building an amp is to say doctors should not use Xrays IMO
examples of good and bad
http://www.aoc.nrao.edu/~pharden/hobby/Scope2.pdf
http://www.cs.berkeley.edu/~bh/v2ch13/scope.gif