I believe it is 200mhz but I can't really remember. For audio it is way more than enough. Seems most guys want digital these days. I'm just a hack so it is plenty for my needs. 😀
Thanks Terry. I don't know enough to understand what advantage a digital scope would have over analog. The model you have it seems there are lots of them at surplus prices. I see them from $150.00 to $350.00. There was one that was never used and they were asking $1,200 for that one. Since I am only just starting I'm sure it will be more than adequate for my audio needs.
ps. I guess if you are looking for oscillations at extreme frequencies a higher speed may come in handy but how high is that? What is the max bandwidth we are looking at in an audio application?
ps. I guess if you are looking for oscillations at extreme frequencies a higher speed may come in handy but how high is that? What is the max bandwidth we are looking at in an audio application?
Last edited:
You will need to ask someone who has a digital scope. I see screen shots that show all kinds of information. My scope just shows the sine wave.
We can only hear, 20khz. My signal generator only goes to 150khz. I guess some folks measure all the way up to 200khz. 1mhz is 1000khz. So 200mhz is more than enough AFAICS.
We can only hear, 20khz. My signal generator only goes to 150khz. I guess some folks measure all the way up to 200khz. 1mhz is 1000khz. So 200mhz is more than enough AFAICS.
Thanks again Terry. Yes I have seen Ghz scopes but since I'm not going to do RF design or anything exotic so not so sure what advantage those would be for anything we are doing. I'll look and see if I can see what a digital scope does that you can't do with an analog scope.
A digital scope is nice for getting some measurements displayed as text on the screen with the trace rather than reading off a graticule. An analog scope is still nice in many cases, especially if there is some HF noise / interference; that can make a digital scope display get kinda hairy where in analog scope just blurs a little. I had both (my analog scope died recently, replaced with an inexpensive PC scope) but I generally use my digital Tektronix most of the time anyway.
if you see a Tek 465 or 475 in good shape at a good price, BUY IT.
trust and believe, you will never regret it.
although the 100MHz would be fine, get the 200MHz if you can swing it.
mlloyd1
trust and believe, you will never regret it.
although the 100MHz would be fine, get the 200MHz if you can swing it.
mlloyd1
Thanks Jason.
Mlloyd1. there are so many of those 200mhz Tek 475 scopes they are practically giving them away. Many are even said to be with new calibration papers.
Mlloyd1. there are so many of those 200mhz Tek 475 scopes they are practically giving them away. Many are even said to be with new calibration papers.
The worst case oscillations I had measured were 250MHz (preamplifier output diamond buffer) with harmonics up to 1GHz. I needed Agilent spectrum analyzer to reveal it. And yes, it matters for audio, it worsened S/N and increased distortion.
Thanks Pavel,
I'm afraid that a Ghz scope would more than likely be out of my budget for now, But that is very good information and I will remember that. Hopefully I won't have to look for a problem like that using other proven amplifier circuits rather than my own creations!
I'm afraid that a Ghz scope would more than likely be out of my budget for now, But that is very good information and I will remember that. Hopefully I won't have to look for a problem like that using other proven amplifier circuits rather than my own creations!
On a BJT ? Would not Ft be the limiting factor.
I know of some devices that would ..... RF Transistor, 30V, 300mA, fT=3.5GHz, NPN Single PCP -
But would this hold true for "our" lowly <120mhz Ft BJT's ?
OS
I must say I have enjoyed having this scope. Being a novice, I have very limited experience, so being able to post pictures of what is happening with my amp has been vital to getting good advice from the experts who hang out here. I learn things also that I didn't understand for instance just recently here I learned that my DMM doesn't read AC voltage correctly at high hz. The scope shows the true voltage of a square wave at 100Mhz and the DMM show a pittance of it. I have been burning zobel resistors because I didn't know that. Definitely get a scope. It will make this hobby much more enjoyable.
Blessings, Terry
Blessings, Terry
Yes, BJTs can oscillate past their Ft, especially when cascoded in my understanding.
What was the solution to the oscillation of the diamond buffer Pavel?
What was the solution to the oscillation of the diamond buffer Pavel?
A resistor in series with input (100 ohm) and COG capacitor across one of the c-b junctions. It is here somewhere. It hapenned about 5 or 6 years ago.
Thought I would share my experience this morning. I ordered a couple PSU units from ebay so I could make two identical power supplies for the A/B Slewmaster setup I trying to put together.
4 10000uF 100V High End Power Amplifier Board | eBay
Received them yesterday so I hooked them up one at a time to test them. I hooked them using my light bulb tester just in case. On one of the units the light continued to burn dimly so I felt the caps and one of them was warm. I figured it may need to be reformed so I hooked up a separate bridge and used a 27K resistor and let it charge over night. This morning, I checked it again and the resistor was still discharging about 6V. I tried hooking up the PSU normally and the cap still got warm so I shut it down and discharged it. Then I hooked up the second unit and turned it on. I kept feeling the caps and they were all cool so I decided to let it run for a while and see how it did. Well after about 5 or 10 minutes one of the caps exploded. Fortunately I was a few feet away. I hate to think what might have happened if I was standing right there staring at it. I am attaching some pics for your enjoyment.
Blessings, Terry
4 10000uF 100V High End Power Amplifier Board | eBay
Received them yesterday so I hooked them up one at a time to test them. I hooked them using my light bulb tester just in case. On one of the units the light continued to burn dimly so I felt the caps and one of them was warm. I figured it may need to be reformed so I hooked up a separate bridge and used a 27K resistor and let it charge over night. This morning, I checked it again and the resistor was still discharging about 6V. I tried hooking up the PSU normally and the cap still got warm so I shut it down and discharged it. Then I hooked up the second unit and turned it on. I kept feeling the caps and they were all cool so I decided to let it run for a while and see how it did. Well after about 5 or 10 minutes one of the caps exploded. Fortunately I was a few feet away. I hate to think what might have happened if I was standing right there staring at it. I am attaching some pics for your enjoyment.
Blessings, Terry
Attachments
Last edited: