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Class D vs Class A or A/B

#162
fdeck said:
In particular, you won't get agreement from me. :D

We've been through this. Work out the input sensitivity of the SVT power amp circuit, from the schematic, and compare it to the forward voltage of the diodes.
Click to expand...

Believe only what you measured by yourself.

A very lot of components in the original svt schematic drawings do not reflect the real component values.

I remember that I myself needed a lot of time to fix the "point" from where the svt typical output waveform comes from.

I trusted in the original schematic drawing too much, that was the error I did.

The only one specs you can trust in are the transformer specs.


Btw these diodes are obsolete in the CL version.
If the diodes provide only a safety function to V1?
Then I try to ask the question why is all the time only the SVT and SVT-II and SVT II pro and SVT VR prodected ???
 
#163
ThisBass said:
Believe only what you measured by yourself.

A very lot of components in the original svt schematic drawings do not reflect the real component values.

I remember that I myself needed a lot of time to fix the "point" from where the svt typical output waveform comes from.

I trusted in the original schematic drawing too much, that was the error I did.

The only one specs you can trust in are the transformer specs.


Btw these diodes are obsolete in the CL version.
If the diodes provide only a safety function to V1?
Then I try to ask the question why is all the time only the SVT and SVT-II and SVT II pro and SVT VR prodected ???
Click to expand...

My estimates were based on the schematics that were available online. This is what I posted, last time the topic came up:

http://www.talkbass.com/forum/f15/all-tube-worth-768084/index7.html#post10872918

I don't have access to a SVT to test, and I don't have a dummy load that can sink that much power. At the time, I wasn't doubting the benefits of tube amps, but just happened to post in a thread with that title.

Up until now, in these threads, we have all suffered from a lack of measured data. I was making the best of available information in the form of the schematics plus some common sense about how the components work.

If you are making measurements, please be careful. This isn't worth risking your life or your test equipment.
 
#164
fdeck said:
I don't have access to a SVT to test, and I don't have a dummy load that can sink that much power. At the time, I wasn't doubting the benefits of tube amps, but just happened to post in a thread with that title.

Up until now, in these threads, we have all suffered from a lack of measured data. I was making the best of available information in the form of the schematics plus some common sense about how the components work.

If you are making measurements, please be careful. This isn't worth risking your life or your test equipment.
Click to expand...

I'm not sure if we would have tested for the data you are looking for or not, but we did feature a [Invalid or Expired Link Removed]. Unfortunately, this older flipbook format does not let me link directly to the page.
 
#165
Assigning a particular characteristic to a single cause is ignoring everything else that goes into how an amplifier performs and feels. Almost never is a single feature responsible for the overall sound, feel, texture, playability of an amp like this. Otherwise, why would we go to so much effort on all the hundreds of (important) aspects in the design of an amp?
 
#166
Duke21 said:
This question about matching power supply to a power amp is very interesting. Almost all class D amps have SMPS while only a few like Markbass II and III are class AB with SMPS.
Click to expand...

You are overlooking the vast majority of QSC power amps that have SMPS with class AB/H power amps. Crown also has (and mostly had) some like this, as well as Crest.

The migration to SMPS/class D is for improved power density and weight savings as the technology matures and the performance envelope widens.
 
#167
ThisBass said:
Here in Germany some other well skilled tube amp tecs/engineers know it all.
But there is normally no big discussion about it.
Because it is as it is, and it is therefore no need to raise discussions for nothing.

The power amp "grunge" sound can be simulated a bit when silizium diodes are combined with z-diodes.
However the result of the simulated sound will never be exactly the same like the svt. The whole svt power amp is needed if it shall sound like svt power amp. No doubt about it here.
But the relationship is audible.

I used an improved schematic of it in a SS amp for a couple of years.
I was often asked if the SS has tubes inside.
Click to expand...

Well we are then almost neighbors as I'm from Norway. Anyway nice to know about these diodes in the SVT. Is it an hand build amp you use?
 
#168
ThisBass said:
Promised.;)

But it will take some time (a couple of days) due to some circumstances I don't want to tell.

Do a recall if I forget ...
I'm an over 40 years old people :p
Click to expand...

So what, I'm almost 42..... :)

Anyway, the closest thing I own to a serious amp (beside my Ibanez 20W bass combo) is this little orange dude. The Carot One is an HiFi amp which utilizes a tube preamp/ headphone amp with class D power section. Really cool little amp with great open tone and the damn thing is so small.... thanks to the class D poweramp.
2012-10-15.png


As you can see it is much smaller then my Centrance DACmini which is a DAC and headphone amp.
 
#169
Duke21 said:
So what, I'm almost 42..... :)

Anyway, the closest thing I own to a serious amp (beside my Ibanez 20W bass combo) is this little orange due. The Carot One is an HiFi amp which utilizes a tube preamp/ headphone amp with class D power section. Really cool little amp with great open tone and the damn thing is so small.... thanks to the class D poweramp.
2012-10-15.png


As you can see it is much smaller then my Centrance DACmini which is a DAC and headphone amp.
Click to expand...

I like it! Very cool! :cool:
 
#171
seamonkey said:
You will not get agreement on this forum about the svt solid state components.

If you have oscilloscope traces, and spectrum analysis I'd like to see them.
Click to expand...

Most people like the SVT for how it sounds and performs, not because of the topology or to further the tube vs. SS debate or some other agenda.

The more these excellent threads detail the amount of work and the minutae that go into designing amps tht work well in relation to how musicians use them and to how they respond to real musical situations, the more I understand that I am not crazy for preferring some amps over others in spite of similar specs and the like. Thanks to everone here for their input, it's fascinating even though I can only follow on a limited technical basis.
 
#172
One Drop said:
Most people like the SVT for how it sounds and performs, not because of the topology or to further the tube vs. SS debate or some other agenda.

The more these excellent threads detail the amount of work and the minutae that go into designing amps tht work well in relation to how musicians use them and to how they respond to real musical situations, the more I understand that I am not crazy for preferring some amps over others in spite of similar specs and the like. Thanks to everone here for their input, it's fascinating even though I can only follow on a limited technical basis.
Click to expand...

+1 That is why so much of this very limited 'test data' makes most integrated bass amps 'look like they should sound very similar'. That, of course, is far from the truth, and there is no one on earth who can listen to a sampling of class D amps and a sampling of class A/B amps on a blind basis and identify amp topology beyond chance levels.

Every integrated bass amp sounds quite different from every other one, due to a huge number of non-linear component interactions that are not at all covered in simple preamp frequency slope graphs and 'power delivery and THD' graphs at different frequencies.

A little bit of data (even relatively accurate data) can actually be more confusing and misleading than none at all:smug:
 
#173
agedhorse said:
You are overlooking the vast majority of QSC power amps that have SMPS with class AB/H power amps. Crown also has (and mostly had) some like this, as well as Crest.

The migration to SMPS/class D is for improved power density and weight savings as the technology matures and the performance envelope widens.
Click to expand...

+1 Also, many forget the 'transition' type designs, using a class D power amp but a toroidal power supply back when the SMPS thing was not quite 'there' yet. Examples are the iAmp800 and the Epifani502. Class D to reduce size and weight, but the more traditional power supply to provide full, open low end. These companies have now gone SMPS with their amps, since that limitation no longer exists.
 
#174
tombowlus said:
I'm not sure if we would have tested for the data you are looking for or not, but we did feature a [Invalid or Expired Link Removed]. Unfortunately, this older flipbook format does not let me link directly to the page.
Click to expand...

Thank you for the link to the svt story.
A very exiting story.
Maybe the diodes took part in the schematic when the voltage for the 12BH7 was lowered to reduce the voltage amplifier headroom.
It is a very thrilling thing to read how Keith Richard's playing fashion was able to bring one half of the 6146B tubes to glow cherry.
I heard sometimes about this story. But have never known what was going on under the hood.
 
#176
KJung said:
+1 Also, many forget the 'transition' type designs, using a class D power amp but a toroidal power supply back when the SMPS thing was not quite 'there' yet. Examples are the iAmp800 and the Epifani502. Class D to reduce size and weight, but the more traditional power supply to provide full, open low end. These companies have now gone SMPS with their amps, since that limitation no longer exists.
Click to expand...

+1

Ken,
As I recall you owned both of those amplifiers, and although you liked them there, were and are other amps that you preferred. The Markbass F500 would be an example. Over in my camp, the two Woods amps that I own (a MI-400-8 and a Electroacoustic Ultra) sound very different, with a design that's coming from a different direction than the first iAMP 800 or the Epifani 502.
Walter's original amps were analog amplifiers with "switch mode power supplies. Those amps IMHO, IME sound a lot like a tube amplifier, while the Electroacoustic's are closer to the sound of a tube pre, with a solid state power amp. A good designer like the folks at Genz Benz or Markbass, can create an amp from scratch that has everything you want, regardless of the technology employed.


Ric
 
#177
One Drop said:
Most people like the SVT for how it sounds and performs, not because of the topology or to further the tube vs. SS debate or some other agenda.
Click to expand...
The SVT was my very first amp. Purchased in 1978.
I still own the amp, I'm proud and very lucky to own this amp.
On stage I don't consider any specs or schematic designs.
On stage I like the feeling of the amp. I like how the amp sounds and performs.
It was never a claim/intention of reducing the overall sound and feeling and performance down to some $cent components.

It is highest respect to the engineers work how the svt was approved at the Rolling Stones tour.

One Drop said:
The more these excellent threads detail the amount of work and the minutae that go into designing amps tht work well in relation to how musicians use them and to how they respond to real musical situations, the more I understand that I am not crazy for preferring some amps over others in spite of similar specs and the like. Thanks to everone here for their input, it's fascinating even though I can only follow on a limited technical basis.
Click to expand...
 
#178
agedhorse said:
IMO, I don't think there is anybody here on this forum (me included) who could tell the difference between a class H amp and any other equiv. powered amp (assuming well designed products.) By far and away, the preamp is responsable for the characteristic or signature tones of their various amp lines IMO. I have done enough double-blind listening tests between power amps to be quite confident of this. Bob (Lee) has no doubt done more than his fair share of listening tests, with their otherwise identical class AB and H models as well, it would be interesting to hear his opinion on this.
Click to expand...

This is worthy of repeating.
+1
The "amp" part doesn't matter much. The pre-amp is where the tone is from. I'd rather the pre-amp does this so I get the same tone at any volume level I need it at.

There are design criteria to get amps to behave differently at extremes. The power of today's SS amps for the price, cranking doesn't need to be everyone's concern.
 
#179
KJung said:
+1 Also, many forget the 'transition' type designs, using a class D power amp but a toroidal power supply back when the SMPS thing was not quite 'there' yet. Examples are the iAmp800 and the Epifani502. Class D to reduce size and weight, but the more traditional power supply to provide full, open low end. These companies have now gone SMPS with their amps, since that limitation no longer exists.
Click to expand...

In the power amp world, the Crown K Series was an example of a combining class D outputs with line-frequency power supplies.
 

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