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View Full Version : Teh vacuum tube amp versus teh solid state amp



Raven
09-18-2005, 12:38 AM
Since it's not a production amp, no need to post anything but the initial impressions of my "new" Vacuum Tube (VT) amp against a solid state (SS) amplifier in what I hope is a controlled environment.

The background story is I got a vintage Westinghouse turntable that was pretty much destroyed. I pulled out the tube amp and made all the necessary repairs to make it make sound. Just stuff like cleaning the tubes with water and soldering a bit here and there. There's moisture damage. Every part on the amplifier is almost undoubtedly older than every member on this forum. (Man it feels good to say that! =)

It's competitor is an SS amp. A Mobile Authority M103A amplifier, which attached to a 1 amp power supply makes quite the headphone amp. I should mention I need more repairs to do to the VT amp. There is a LOT of noise. I continue the test regardless, having no means of correcting this yet.

SOUND QUALITY
The first test is general SQ. I basically just fire up XMMS (Winamp for you Windows users) and play random songs through each amp. The SS amp performs about how I expected. The extra power makes for an improved bass response, snappier midbass, and everything is a little clearer. It also made everything distinct, in a way. I don't know how to describe it, but *everything* stood out. Almost like every instrument was recorded on it's own and they are just being played one on top of the other. The harsh highs were very harsh. Unbearably harsh at times. It also brought out every flaw in any MP3 encoded at less than 96KBPS. The sounded muddy and distant. Like I was listening to them through a piece of cloth.

The VT amp is a little different. It just sounds.. different. The bass is fuller and lower. Nothing like magic, just there enough to take note of. The midbass stands out a little more. It's very difficult to describe just how it sounds, but it's very pleasant. Everything blends together more like I think music should, which was a big disappointment with the SS amp. The mids are very clear. Unlike the SS, the highs were smoothed out a little, and while the harsh highs were still harsh, they were bearable. Going to the low bitrate MP3s almost was like magic. It brought out everything in them. I can hardly tell they the difference between them and normal 128KBPS mp3s with the VT amp, and not in a bad way.

NOISE
The second test is for introduced noise. This is important because headphone amps are usually very close to a PC and CRT monitor (Can you say EMI?). The SS amplifier performs right about where I thought it would. It is very susceptable to noise. Just moving it closer to and away from the monitor causes a big loss and gain of distortion.
The VT amp surprised me. Dispite the large amount of noise created by the amp itself, it is basically impervious to the EMI caused by my monitor and PC. The amp is quite literally touching the monitor as I'm typing this, and the THD could care less.

POWER
No contest. The SS amp takes home the trophy, pushing roughly 6 times the power of the VT amp.

CONCLUSION
Vacuum Tube > Solid State. In a great many aspects I just like the sound of the vacuum tube amp better. The only way I can think of describing it, is that the solid state amp is trying too hard.

NOTES
When I did the SQ test, I kept the SS amp close to the monitor. Enough to keep the noise level about the same as the VT amp. I know someone will want to bring this up and say that having a buzzing problem puts the VT amp at a direct disadvantage (Making the preference a really big deal), but it didn't.

The VT amp was cheaper that the SS amp in my case. Normally VT amps have the worst dollar to watt ratio of any type of amp in existance. I'm sure this would change the review knowing so much money was on the line. Sad but true. The Mobile Authority amp cost me $40, the Westinghouse has $21 in purchase and repairs so far.

If I could have level matched the output between the amps, it would have been a fairer test. I can guarantee you the SS amp was pushing far more power. See it as you want, both amps were overpowering my test headphones by a factor of 10x to 20x. They are, or were, $10 Sony earbuds from Walmart. In the tests the right earbud popped once and now crackles with certain frequencies of midbass. =\

Acidburn
09-18-2005, 12:43 AM
interesting, very interesting

**looks to Frosty**

JimJ
09-18-2005, 12:46 AM
:thumbupw: :word: :yes: :ladysman:


We need more people to do tests like this. Although, frankly I'm surprised with your findings between lower bitrate MP3's and higher ones. My Decware Zen SE84CS was ruthlessly revealing with lower-quality sources...if you weren't feeding it very high bitrate material or original CD's, you would really hear it. Depends on the amp topology, probably.

This is the single-ended EL84/6BQ5 amp, correct?

I actually just bought a pentode-connected EL84 amp off Ebay for my living room system. Around 5.2wpc @ 8ohms.

JimJ
09-18-2005, 12:50 AM
Also...

tube pr0n or ban.

Don't give me that "My camera doesn't work" excuse...:D :naughty:

Raven
09-18-2005, 01:36 AM
No, really, my camera doesn't work. If it did I would post pics of the transformers and capacitor. I think are damaged, and need some opinions on if I should invest in new ones. But it is a neat design. The cover is actually a huge chunk of iron that serves as a common ground. There is no circuit board, just a holy mess of wires under the cover.

JimJ
09-18-2005, 01:38 AM
There is no circuit board, just a holy mess of wires under the cover.

Point to point wiring is vintage electronics at its best...and worst :D

PV Audio
09-18-2005, 04:09 PM
as i told jimmy poo, i enjoy the sound of tubes, but they aren't practical for those with either:

1. lots of $$$
2. lots of experience
3. people who can build hella efficient loudspeakers

i fit into all 3 :)

JimJ
09-18-2005, 04:19 PM
as i told jimmy poo, i enjoy the sound of tubes, but they aren't practical for those with either:

1. lots of $$$
2. lots of experience
3. people who can build hella efficient loudspeakers

i fit into all 3 :)

Let me break that apart.

1. Lots of money - The EL84 pentode-connected amp I bought on Ebay cost $175 shipped to my door. I'll probably end up doing some work on it, so it'll end up costing around $200. Alright, so that's still $40 per watt, but there are plenty of people on here that spend more than two Benjamins for amplifiers. Plenty.

2. Lots of experience - Experience comes with time. Sure, they might not be the best beginning amps to start with, but anyone with at least a cursory knowledge of electronics can use one properly...

3. Efficient Loudspeakers - Yeah, you need them...but you don't have to build them :) Klipsch Heresy's and the Forte II's I bought are perfect for a small tube amp, and they aren't DIY at all. If you want to save money, DIY is the best way to go...but isn't it like that with everything? My Fostex cabinets were well in the reach of anyone who could build a regular subwoofer enclosure. Or, you could go the headphone route.

And as far as point #2 goes...is this a changed Lemans we see? :D

PV Audio
09-18-2005, 04:23 PM
Let me break that apart.

1. Lots of money - The EL84 pentode-connected amp I bought on Ebay cost $175 shipped to my door. I'll probably end up doing some work on it, so it'll end up costing around $200. Alright, so that's still $40 per watt, but there are plenty of people on here that spend more than two Benjamins for amplifiers. Plenty.

2. Lots of experience - Experience comes with time. Sure, they might not be the best beginning amps to start with, but anyone with at least a cursory knowledge of electronics can use one properly...

3. Efficient Loudspeakers - Yeah, you need them...but you don't have to build them :) Klipsch Heresy's and the Forte II's I bought are perfect for a small tube amp, and they aren't DIY at all. If you want to save money, DIY is the best way to go...but isn't it like that with everything? My Fostex cabinets were well in the reach of anyone who could build a regular subwoofer enclosure. Or, you could go the headphone route.

And as far as point #2 goes...is this a changed Lemans we see? :D
Yes indeed :)

The reason why i said money is because without the other two, you are gonna have to drop some CASH to get enough power to power ur 85 db/w speakers with VTs

JimJ
09-18-2005, 04:25 PM
Yeah, but who would be idiotic enough to do that?

*looks around forum*

*opens e-mouth, inserts e-foot.*

Raven
09-18-2005, 11:36 PM
Hahaha. Well, in my case it's going to be powering some ~108dB/w 16 ohm headphones. If that's not efficient, don't tell me what is.

I'm still having a lot of difficulty with noise issues. I'm arguing against the potentiometers. I turn them and more than one directly affect the noise levels. Also after it gets nice and warm the noise dies off, which I'm told is a common capacitor issue. So this $20 project just got a lot more expensive than I want it to be.

JimJ
09-19-2005, 12:21 AM
Throw in some ALPS pots and Auricaps or Black Gates...:D

Raven
09-19-2005, 12:57 AM
Ok... sometimes I think you're crazy, Jack Frost.

Today I lost the left channel of the amp. I'm really considering just giving this project up right now. It's not worth the effort involved to repair it anymore.

JimJ
09-19-2005, 12:58 AM
Ok... sometimes I think you're crazy, Jack Frost.

Today I lost the left channel of the amp. I'm really considering just giving this project up right now. It's not worth the effort involved to repair it anymore.

:(

From the condition you described the transformers, they might have been beyond saving...if the windings were damaged.

Raven
09-22-2005, 09:31 PM
Well, here's the update.

I took the "cover" that I made for the bottom of it off, and realized when I screwed it down two wires had shorted together. I fixed the problem, the amp works again.

Right now I'm in the process of correcting the noise again. I've discovered that I'll need to replace all 4 potentiometers and possibly the main power capacitor. The problems as follows.

I panic whenever I look at that capacitor. It's a 40/40/30/30uf @ 350v.d.c. How does that work? Does it share a common ground? Do the 30uf sections and 40uf sections share grounds seperately?
Also, the potentiometers have 6 wires attached. Most pots I've dealt with have 2. It's not a matter of how to wire them, I'll just mimic what's there. It's a matter of finding them the right physical size with 6 pins. Radioshack isn't helping...

JimJ
09-22-2005, 10:34 PM
Take detailed pics...post it over on the Decware forums.

I can almost guarantee you somebody will answer your question :)

I wish I could, but I've never seen a cap like that before :D

As for parts, http://www.tubesandmore.com might be a handy place to look.

PV Audio
09-22-2005, 10:41 PM
tubes for teh lose

:D

JimJ
09-22-2005, 10:42 PM
Did I ask for your opinion?

:)

PV Audio
09-22-2005, 11:06 PM
:(

*goes back into leather swing*

Raven
09-22-2005, 11:20 PM
You can always go back to SS amps, Lemans. I really like the fact that this proved the amp is short circuit stable. Wire your sub amp at 1/16ohm and see where you get. =)

Anyway, THANK YOU for that link. It took me all of two minutes to find the pots I need. Now all that's left is to decide what to do for capacitance.