• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Is this worth my time?

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I am looking to improve my audio system. Current equipment includes:

Denon 35 Watt per channel 1980's model amp
Cerwin Vega floor speakers (10" woofer)
5.25" woofer bookshelf speakers

The improvement I am looking for is to increase the mid and bass response when the volume is set at a reasonable background level, as this is how I listen to music most of the time. I am not necessarily looking of lower frequency response; I want to hear a balanced (flat freq. response?) at lower listening levels. Currently, the bass drops out of the music at low levels.

I am considering ordering the S5-Electronics tube amp kit which is advertised as 15Watts w/8ohm output impedance. I have always heard that tube power is not the same as power spec. for your typical low end commercial amps such as mine.

Question:
1. What's the difference between tube power (i.e. 15W) vs. my Denon 35W per channel amp?

2. Will I get more easily get the sound I am looking for from the S5-electronics tube amp at 15W?

I am a mechanical engineering student and know that power is power. In electronics P = I^2 R or P = VI, so what's going on with the numbers provided by manufacturers, if tube power is better at driving speakers?
 

BHD

diyAudio Member
Joined 2004
There are lies, damn lies, and specs... :D

Watts are watts, but like most things, it's just not that simple.

With amps, it can depend on how the measurement was made. Was it a 1 KHz test signal into a resistor, or a reactive load? Speakers are not resistors. Manufacturers are going to tweak their specs and measure them in a way that puts their products in the most positive light. Some even lie.

I think that some of this "tube power" legend comes from the beefier power supplies in some tube amps that allow for more headroom during short peaks. Tube amps also have a more forgiving clipping characteristic when they finally do run out of gas, often people have been running their amps into clipping and didn't even notice. You'll definitely notice clipping with your Denon.

Since Cerwin Vega speakers are pretty efficient anyway, I'd suggest you look at it as a quality upgrade. The CV speakers I've heard (granted a long time ago) were a little on the bright side and I think they'd benefit from a tube amp driving them.

Another thing to consider is that the difference between 15 and 35W is just a little over 3db of sound output, which is almost imperceptible. I'm not familiar with the amp, but I did find an interesting page, though:

http://www.siteswithstyle.com/VoltSecond/K-12M_AMP/K-12M_Push_Pull.html

It seems like it'd be a great first time project.

I guess the bottom line is this; if you find the Denon is running out of gas and you're turning it all the way up, I doubt replacing it with a 15W tube amp is the answer (and I fear for your hearing). If you're not going past 10-11 o'clock on the volume control, you should be fine.

As far as the bass issue goes, I doubt that tube amp has really high quality transformers and you need that for good deep bass. You may want to save up some cash and build something with better iron.
 
The improvement I am looking for is to increase the mid and bass response when the volume is set at a reasonable background level, as this is how I listen to music most of the time. I am not necessarily looking of lower frequency response; I want to hear a balanced (flat freq. response?) at lower listening levels. Currently, the bass drops out of the music at low levels.

Loudness control.

EQ.

Tilt/tone controls.

These are going to get you what you want much more surely than going from a good transistor amp to a good tube amp.
 
diyAudio Senior Member
Joined 2002
Hi,

How about the tube amp compared to my transistor amp?

What I wonder about is what on earth is causing this perceived drop out of bass at low volume levels, assuming it's a-typical??

Human earing responds to the Fletcher-Munson curve, this is why you'll find loudness control on amps/preamps in the first place.
Have you tried that?

If there's a problem with the speaker setup then a tube amp is not going to correct for that either.
Which is the message SY was trying to get across, I s'ppose...

Cheers,;)
 
OK. A couple of things I should clarify.

The bookshelf speakers are in a different room (kitchen) from the floor speakers (Cerwin Vega). I listen to them at separate times. Also, the floor speakers are full-range with woofer, mid and tweeter. Also, I have adjusted the loudness control on the amplifier to the limits (fully flat). I have no doubt that I have cheap equipment, I'm 31 now and I got this stuff when I was 13 or 14 years old (Can you tell I'm cheap? I also drive the car I got when I graduated high school).

What I want to know is whether an inexpensive tube kit like the S5 Electronics amp will be an improvement over my Denon transister amp; and if so, why. You guys are interested in tube amps for a reason. What are the qualities you perceive as superior to other types (sound quality? Ease of assembly? Price? Durability?). The best idea I've heard here is that tube amps are more responsive to short spikes in the music. This seems plausible considering bass is power hungry and often is present in short pulses, as in percussion. Perhaps my transittor amp flattens those spikes out at lower listening levels. Perhaps it is simply how music is mixed and I simply need to crank it up to a level which it was intended to be listened at. Perhaps I need more sensitive speakers.

Can someone give me a sales pitch here? Keep in mind that if I go with a kit, I will most likely do a speaker project with better quality components than my 18-year old Cerwin Vegas or my $200 bookshelf speakers.
 
What are the qualities you perceive as superior to other types (sound quality? Ease of assembly? Price? Durability?).

Tube amps are harder to construct, more expensive, less reliable, and have poorer objective performance compared to decent quality solid state amps. The same can be said for a '57 T-Bird versus an Acura. But which would you rather drive?
 

BHD

diyAudio Member
Joined 2004
Also, I have adjusted the loudness control on the amplifier to the limits (fully flat).

The loudness control is usually off or on. If you have one I'd say make sure you have it on, and use the bass control. If you have both the bass and the treble cranked all the way up, back off on the treble control a bit.

What are the qualities you perceive as superior to other types (sound quality? Ease of assembly? Price? Durability?).

I like tube amps because they sound more like music to my ears. You may not feel the same way. Have you heard a tube amp recently? Tube amps are normally easier to DIY, but there are SS kits like the gainclone that are easy too. Check out the chip amps section of the site.

Can someone give me a sales pitch here? Keep in mind that if I go with a kit, I will most likely do a speaker project with better quality components than my 18-year old Cerwin Vegas or my $200 bookshelf speakers.

I don't think anyone here wants to sell you on tube amps. With tube amps the most important thing is good design, followed by the quality of the output iron. At that kit's price point, you're just not going to get really good output transformers. You'll also be limiting yourself to just a volume control - which is fine, but really inflexible, unless you plan on building or buying a preamp. Also, if you're not sure what speaker you're going to use, buying such a low powered amp could limit your speaker choices quite a bit.

My :2c:
 
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