Analog vs digital scope

[nctnico]

Trade-Offs
The probes still have a resistive path to ground - so if a
circuit is sensitive to leakage currents then differential

Well, every probe using whatever isolation method will have some resistive and capacitive leakage to ground. The only way to really avoid having any leakage is to use a probe with an optical interface for both the signal and power. But even then you'll influence the circuit due to the capacitance and inductance of the electrical leads and circuit. In reality most high voltage circuits have a low enough impedance where a bit of leakage to ground doesn't matter.

[Gandalf_Sr]

To all intents and purposes, the high voltage differential probes are very high input impedance (many Meg Ohms) even though not actually isolated.  The OP could use them without worry and that's why I said he was right in his/her summary.

[ToddW]

So no, in general it's safe to assume they're not isolated, and do have a high input impedance (5 Meg + 5 Meg) to provide safety.

Such high resistance values are isolation. It is possible to come up with an 'isolated' circuit (using a transformer for example) which has effectively a lesser degree of isolation due to creepage/clearance paths. The use of a string of high value / high voltage resistors is a well proven technique and most of the high voltage differential probes out there are made this way.

Seems to me that with those high resistance values the whole issue of isolation becomes, while technically true, a bit irrelevant. Other than, as Techtronix says, if the circuit has leakage currents then (non-isolated) diff probes might not be the best choice:

"Differential probes provide a safe method to adapt a
grounded oscilloscope to make floating measurements.
In addition to the safety benefits, the use of these probes
can improve measurement quality. Differential probes
provide balanced measurement input capacitance so
any point in the circuit can be safely probed with either
lead. Differential probes also typically have better CMRR
performance at higher frequencies than voltage
isolators.

Another benefit is the full use of the oscilloscope’s
multiple channels with the simultaneous viewing of
multiple signals, referenced to different voltages.

Trade-Offs
The probes still have a resistive path to ground - so if a
circuit is sensitive to leakage currents then differential
probes may not be the best solution.
Other trade-offs include an added layer of cost -
depending on the oscilloscope capability an independent
power supply may be required, adding cost and bulk.
The gain and offset characteristics must be factored
manually into every measurement."

Just read that too.  But don't know what in a tube amp would be sensitive to leakage currents.

[ToddW]

There goes another perfectly good thread... sigh!

This is the best thread eva! 

[engrguy42]

There goes another perfectly good thread... sigh!

This is the best thread eva!

Okay, but more importantly...

Long ago I had a Fender guitar and electronic amp. We're talkin' late 1970's. And at the time the guitar world scoffed at electronic amps, and said tubes are the only way to go. Kinda like the guys who were conviced that vinyl records were vastly better than all that digital rubbish. But personally I was amazed at how good the electronic guitar amps sounded. I forget the brand...

So does anyone make tubes anymore? Or are they just recycled from old equipment like Ham radios and stuff?

[engrguy42]

Hold on...

It was a Crate G-40C. Beauty.

[0culus]

There goes another perfectly good thread... sigh!

This is the best thread eva!

Okay, but more importantly...

Long ago I had a Fender guitar and electronic amp. We're talkin' late 1970's. And at the time the guitar world scoffed at electronic amps, and said tubes are the only way to go. Kinda like the guys who were conviced that vinyl records were vastly better than all that digital rubbish. But personally I was amazed at how good the electronic guitar amps sounded. I forget the brand...

So does anyone make tubes anymore? Or are they just recycled from old equipment like Ham radios and stuff?

Yes, there are plenty of then still being made. Nowadays the cork sniffers prefer hand wired point to point construction over PCBs. Gotta get them toanzzz! I have an Egnater 15W head (definitely PCB construction) and 1x12 cab. It sounds freakin awesome and it's light enough to carry to a friend's house for jamming without breaking your back.

[edit] I thought you were asking about tube amps...but to answer your question, yes, tubes are still being made. Mostly in China, Russia, and Eastern Europe last I heard. They tend to not be as well made as the stuff made in the golden age of vacuum tubes, but they work fine for guitar amp use where the running parameters tend to shorten their lives anyway, as opposed to say a Tektronix 5xx series oscilloscope where the original tubes often still work fine because they were well made to begin with and are used strictly in a linear regime.

[engrguy42]

Wow, I never dreamed that tubes were still around, much less tube amps. Is Marshall still a big player?

So who uses tubes now? I assumed that the Ham radio world had pretty much dried up long ago (?), and the only folks using tubes would be the hobbyists fixing old scopes and radios and amps and stuff.

[0culus]

Audiophiles and guitar players mostly. The former annoy me because they rape classic test equipment for tubes. 

Marshall is still around, yes.

[WattsThat]

Where can you find the “The technology the 1900’s meets the the technology of the 2000’s”?

That’s where you can buy overpriced vacuum tubes from an online store.

https://tubedepot.com/

A matched pair of old stock 300b’s will only set you back $10,000.00. But hey, they’re good for 40 watts each.

https://tubedepot.com/products/nos-western-electric-300b-black-plate-1961-matched-pair

They don’t call ‘em audiofools fur nuttin. With my apologies for helping to drag the thread off topic.

[ToddW]

Tell me your not jealous.
[ Specified attachment is not available ]

[james_s]

Wow, I never dreamed that tubes were still around, much less tube amps. Is Marshall still a big player?

So who uses tubes now? I assumed that the Ham radio world had pretty much dried up long ago (?), and the only folks using tubes would be the hobbyists fixing old scopes and radios and amps and stuff.

Have you been living under a rock? There are many thousands of tube amplifiers in service, a mix of vintage stuff and modern boutique equipment, both hifi and guitar amplifiers, they're as popular today as they've been any time in the past 40 years if not more so. Not all of the old types are still made but modern versions of many of the popular audio tubes are still manufactured. There are even high end $$$ audiophile tubes hand made in small quantities. Musicians and audiophiles are the primary users, then of course there are millions of vintage items out there. I have at least 3 vintage tube radios.

A quick google search for "tube amplifier" comes up with dozens and dozens of sites.

[Cubdriver]

Wow, I never dreamed that tubes were still around, much less tube amps. Is Marshall still a big player?

So who uses tubes now? I assumed that the Ham radio world had pretty much dried up long ago (?), and the only folks using tubes would be the hobbyists fixing old scopes and radios and amps and stuff.

Tubes are definitely still around and popular.  I've built several tube-type audio and guitar amp kits over the past several years.

Dynaco ST 70 clone:


Transcendent T-16 Output Transformerless amplifier:



Encore and LF guitar amp kits from Allan Amplification and a tweed 5F1 kit from Tube Depot.  Also have a pair of VTA M-125s in the build queue.

As for differential scope probes, over a few years I bought a pair of Dave's EEVBlog HVP-70s.  The don't come out to play too often, but are very useful when they do.


-Pat

[engrguy42]

Wow, I never dreamed that tubes were still around, much less tube amps. Is Marshall still a big player?

So who uses tubes now? I assumed that the Ham radio world had pretty much dried up long ago (?), and the only folks using tubes would be the hobbyists fixing old scopes and radios and amps and stuff.

Have you been living under a rock?

Living under a rock?? How the hell would anyone know that tubes are still used without going out of their way to investigate? Y'know, like going to a club or concert where some guy happens to be using a tube amp and go up on stage and say "hey, are those tubes in there?" 

Or spending time, as you say, searching google asking "hey, do tubes still exist?".

Most/all of my limited youtube time is looking at tech stuff, and the only thing I've stumbled on about tubes is the guy who does these 50 year old tube radios and stuff, which, honestly, is a big yawn for me. I never had any interest in tubes.

So back to the basic question: WHY? Why does anyone care about or use tubes? Is it just a boomer hobbyist or "I love old stuff" thing, or do people actually think there's a benefit?

[nctnico]

Probably the same reason people collect old cars, telephones, home computers, etc, etc.

[Gandalf_Sr]

...So back to the basic question: WHY? Why does anyone care about or use tubes? Is it just a boomer hobbyist or "I love old stuff" thing, or do people actually think there's a benefit?

Apparently, musicians think that the sound of tube amplifiers is better than silicon.  I didn't realize until recently that the sound we associated with stars such as Jimmy Hendrix was where they had a specific effects pedal combined with a specific (almost always tube in the 'good' old days) amplifier. Such as the Fuzz Face.

[Fungus]

Living under a rock?? How the hell would anyone know that tubes are still used without going out of their way to investigate?

You know CRT oscilloscopes are still around, even though they're "worse".

So back to the basic question: WHY? Why does anyone care about or use tubes? Is it just a boomer hobbyist or "I love old stuff" thing, or do people actually think there's a benefit?

They give a different sound. Audiophiles call it "warmer" but really it's just noise/distortion.

Why would you want that? Depends on who you are.

Using a tube amp if you're a musician/guitar player it's no different then using a distortion pedal. It overdrives, it distorts, it gives you the sound you want.

If you're an "audiophile" it's usually a sign that you grew up in the 1970s when amplifiers were crap and that's what your ears are accustomed to hearing. Amplifiers without "warmth" sound cold and clinical to you, despite being better.

nb. A similar thing is happening in the younger generation. Their "warmth" is the all nasty artifacts caused by audio compression.  Audio sounds worse to them without it.

https://www.google.com/search?q=youngsters+prefer+mp3+to+lossless

[Fungus]

Apparently, musicians think that the sound of tube amplifiers is better than silicon.

It is better when you're a musician.  Using a distorted amplifier is no different than turning a knob on a synthesizer, putting a mute in the end of a trumpet, pressing a pedal on a piano, etc., etc. It's what gives you your particular sound.

[nctnico]

...So back to the basic question: WHY? Why does anyone care about or use tubes? Is it just a boomer hobbyist or "I love old stuff" thing, or do people actually think there's a benefit?

Apparently, musicians think that the sound of tube amplifiers is better than silicon.  I didn't realize until recently that the sound we associated with stars such as Jimmy Hendrix was where they had a specific effects pedal combined with a specific (almost always tube in the 'good' old days) amplifier. Such as the Fuzz Face.

You are seeing this wrong. The 'amplifier' together with the guitar is the musical instrument. Not just the guitar.

[engrguy42]

I guess I assumed that whatever people believe sounds "better", at the end of the day it's pretty much just a waveform. And presumably you can reproduce that with newer electronics.

I was never sure if the "tubes sound better" thing was an actual thing or just what people want to believe. Like I said, way back when there were those who were convinced that vinyl records sounded better than CD's and all that digital stuff.

I recall reading that Van Halen (a rock guitar god, IMO) never used any distortion effects to get his "brown sound". I suppose it's one of those things that's so difficult to prove that people can argue about it until the end of time. Like they've been doing since when I was a kid decades ago.

[nctnico]

I guess I assumed that whatever people believe sounds "better", at the end of the day it's pretty much just a waveform. And presumably you can reproduce that with newer electronics.

Ofcourse you can reproduce that with newer electronics. Tubes tend to clip softer resulting in even harmonics which are more pleasant to listen to.

[engrguy42]

I guess I assumed that whatever people believe sounds "better", at the end of the day it's pretty much just a waveform. And presumably you can reproduce that with newer electronics.

Ofcourse you can reproduce that with newer electronics. Tubes tend to clip softer resulting in even harmonics which are more pleasant to listen to.

So all the audio tube amp afficionados are wasting their time? 

Uh oh....

[nctnico]

I guess I assumed that whatever people believe sounds "better", at the end of the day it's pretty much just a waveform. And presumably you can reproduce that with newer electronics.

Ofcourse you can reproduce that with newer electronics. Tubes tend to clip softer resulting in even harmonics which are more pleasant to listen to.

So all the audio tube amp afficionados are wasting their time? 

This is getting wildly off-topic...

It can be a great hobby. Years ago I bought a piece of test equipment from an electronics enthousiast. He had build two huge horn loudspeakers (the size of a big fridge) which where extremely efficient. According to him this meant that the voice coils (self wound!) where operating in a very linear area so distortion from the speakers was minimal. He drove these from a (self build) class-A tube amplifier able of delivering just a few Watts. And yet he could crank the volume up to club-like sound levels. He also build his own turn table in which he used the ball from a ball-point-pen as a bearing for the arm. All in all very impressive!

[Gandalf_Sr]

As nctnico said...

This is getting wildly off-topic...

[exe]

the gremlin called aliasing

Peak detect to the rescue.