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Different classes [message #88462] Wed, 18 July 2018 14:00 Go to next message
Lennix is currently offline  Lennix
Messages: 14
Registered: July 2018
Location: South Carolina
Chancellor
I've come across sites that have conflicting information. Some sites say that classes are important and there is a significant difference between them. Other sites claim that there's no difference whatsoever, that it's all about the individual amp, not their class. What's the truth? How much importance should I be giving to classes when I'm picking out an amp?
Re: Different classes [message #88465 is a reply to message #88462] Wed, 18 July 2018 15:55 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1375
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi, There are differences, but I won't go into them at the moment. There was a few recent threads on this and perhaps someone else can point you to them. (BTW, to be clear, my personal preference is class A push-pull / ultra linear tube gear) However, I have a suggestion....don't so much worry about the class as the sound. Use your ears as the guide. If possible bring some favorite tunes with you to a place that sells gear. Unfortunately this is getting harder and harder to find. So second best is to get something that others like, but only from a source that will allow full returns. IMO one of the better sources is Audio Advisor. They are on the Web and will send a catalog if you ask. Cruchfield used to be good, but I have not seen any adds from them in a while. Needle Doctor is another source. They do tend to specialize in vinyl gear, but also have lots of other stuff. I don't find the big box stores very useful (including Best Buy) as they are limited in what they carry and often in expertise about the gear. However, Fry's Electronics (check the Web for gear and store locations) sometimes can be a good source. One thing to be aware of is the loudness that sample gear being played. Loud is not necessarily better and will often make it seem like is superior to gear set at lower volume levels.

Good Listening
Bruce
Re: Different classes [message #88467 is a reply to message #88465] Wed, 18 July 2018 16:53 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17316
Registered: January 2001
Illuminati (33rd Degree)

I agree with Bruce in this matter, 100%.

I would add that there are some classes that are definitely wrong for hifi audio because they generate a lot of distortion. Examples are Class B and C. Neither are suitable for an audio amplifier.

But nobody would be talking about those types of amps in the context of audio - They're used for different purposes, mainly RF communications and power circuits. Where you will find discussions about audio amp classes, its usually Class A versus Class A/B, and/or Class D versus Classes A and A/B. There are advocates for each type of amplifier.

And with tube amps - where Bruce is an expert - there are a lot of topologies and technologies within each class. There are transformer-coupled, capacitor-coupled and even direct-coupled stage interconnects. There is Parafeed versus output transformer primary-feed. There are even tube amps without output transformers.

Also germane are all the types of negative (distortion cancelling) feedback: No feedback, interstage feedback and global feedback. And ways of achieving it, like grid coupled (presented from the plate), cathode coupled (usually presented as a cathode resistor), and distributed load or Ultra-Linear, using a transformer tap connected to the grid.

Some of those topologies apply to solid state amps too, like some feedback techniques. But many don't apply, like those that use an output transformer. Solid state designs employ different techniques; Some that are wholly different, like digital amps.

Long story short: There's much more to evaluate than just the "class" of the amplifier.

Re: Different classes [message #88539 is a reply to message #88462] Fri, 27 July 2018 22:34 Go to previous message
Lennix is currently offline  Lennix
Messages: 14
Registered: July 2018
Location: South Carolina
Chancellor
I wish I had more places around me where I could actually test the products in person. That's why I was sort of hoping that class would be a good way to narrow down options since I'm unable to listen to them in person prior to buying them. Thanks for the Audio Advisor suggestion. I'll be ordering a catalog from them. I'll make sure to not be swayed by the loudness. I'll also keep in mind all of the information that you gave, Wayne. I really appreciate how you broke down the classes.

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