Vacuum Tube Amplifier Equalization/Settings

I have Audacity 2.0 for Windows Vista and I’m trying to find a good combination. I want my music and voice files to sound as though they are coming from a vacuum tube amplifier. What I’m hunting for is a warm, crisp, hi-fi sound. I’m trying to figure out what equalization curves, compressors, filters to use on my files to make the sound warm as if it were coming out of a tube amplifier or radio console from the 1950s. Here are two you tube videos that demonstrate the kind of sound I‘m looking for:

Any help would much be appreciated.


The top quality Techniques turntable and Shure M44 cartridge may have a lot to say about the sound of the system.

Yes, that robust vacuum tube sound.

You should start combing Google for a VST plugin that already does the transfer curves and characteristics for you. It’s not Move a Slider and you’re done. Tube amplifiers have distortions that are not easily created in Audacity. They have odd sliding relationships between the harmonics, odd and even harmonics (depending on the amplifier), off-center soft clipping and a very gentle transfer curve distortion – again, depending on the amplifier.

I had a pair of MC-60 tube amplifiers (with 6550s)…

See Illustration.

…and their claim to fame was… they didn’t sound like tube amplifiers. They had an active feedback loop through the output transformer and had vanishingly small distortion characteristics.

So you don’t want that.

I suspect you can fake it by dipping the sound response a little at 3KHz and then dropping the overall response starting at 10KHz. That will sound interesting.

Effect > Equalization

Screen shot 2013-05-19 at 9.14.13 PM.png
Screen shot 2013-05-19 at 9.06.20 PM.png

I grew up with the vacuum tube sound as my father would set up an old fashioned stereo system to listen to Christmas music with. A Dynaco amp and I believe a a Fisher pre-Amp. We have a special system that involves a psychedelic color organ, two amps, turntable and cassette deck and a christmas tree.

I will write more later as I have a few things to do before going to work.

Thanks again for the curve, I will have to check that out.

I agree completely with Koz that VST effects are the right way to go about this. There are many excellent free VST plug-ins available that do exactly the job you are after, and I suggest you might start by looking around here where there are some excellent tube simulations like BootEQ, but also plug-ins providing similar saturation effects like Ferric TDS or Thrillseeker LA.

However, if I understand your intention correctly that you want to use these effects with your existing music library, I believe you need to go with an alternative to Audacity.

Foobar2000 is an excellent freeware music player, with numerous add-on components that greatly expand its functionality. One in particular allows you to use VST effects, and if you enable that you can try out and use the various plug-ins much more easily. Foobar itself is somewhat different from other music players and takes a while to get used to, but this is largely because it can be customised so extensively and is IMO an investment well worth making.

A really good amp (such as the McIntosh in Koz’s picture) does not have “a sound” - they are designed so that the output signal is as close as possible to the input signal, just “bigger”. Audacity has a built-in effect that does that perfectly - the “Amplify” effect. The Dynaco amplifiers performed remarkably well in this respect in a much lower price range than the McIntosh.

The “sound” of an amp comes from the distortion (non-linearity) of the amplifier which mostly occurs when the amp is “over-driven” (the input signal is too big to be amplified accurately). This is a common design feature of tube guitar amplifiers and is frequently emulated in solid state guitar amplifiers. It is a feature that hi-fi amplifier designers did their best to avoid. Digital emulations of tube distortion can usually do a reasonable job with “distortion effects” but rarely sound nice when applied to a full mix. Analogue electronics have an advantage here due to their natural high frequency damping effect (limited bandwidth). Digital emulation circuits need to be very carefully designed to avoid aliasing distortion, which is a different type of distortion that generally sounds bad.

What I’m hunting for is a warm, crisp, hi-fi sound. I’m trying to figure out what equalization curves, compressors, filters to use on my files to make the sound warm as if it were coming out of a tube amplifier or radio console from the 1950s.

:wink: There wasn’t anything “high fidelity” about 1950s radio…

Sometimes “warm” means a boost in the lower-mid frequencies. Sometimes it means “soft” distortion. “Crisp” usually means strong high frequencies. AM radio only goes to about 5kHz, and older radios didn’t have tweeters, so there weren’t any real high frequencies. Of course there was no woofer either, just a single “full range” speaker and maybe some wood cabinet resonance to “enhance” the male voice range.

You’ll have to experiment with plug-ins, because there really isn’t one “tube sound”. Every tube amplfier either has a sound of it’s own, or like Koz’ McIntosh amplifers has no sound of its own. The goal of a “high fidelity” amplifier is a “straight wire with gain” (no sound of its own). With solid state electronics that’s easy… It’s very cheap and easy with modern integrated circuits. With tube power amps it’s difficult and expensive, particularly because tube amps require an output transformer, and it 's difficult to make a transformer that’s linear across the full audio frequency range. So, most older tube amps would not be considered high fidelity by today’s standards. I assume most modern tube amps sound as good as solid state amps, because there is little damand for cheap or even “average” tube amps.

Tubes amps do tend to clip softly which means that they don’t sound as harsh when overdriven. But, in a hi-fi application, you shouldn’t be overdriving your amplifier anyway. Guitar tube amps are a different story. They are designed to have a particular sound and to distort the sound of in a pleasing way when overdriven. But, you probably wouldn’t want to listen to regular music through a guitar amp/speaker. And again, different guitar amps sound different… A Marshall guitar amp sounds different from a Fender amp.

Each of those dots on the curve is a control point. Click and drag. Watch the frequencies along the bottom and the gain numbers down the left. The blue/green line is a rubber band. The design center is to make the music less forward and harsh. You might like it.

If you get totally flummoxed, I think I remember how to send you the curve.

We’re working from the idea of recreating the memory of the sound, if not the actual distortion.


I appreciate all the info you guys have given. I’ve found several plug-ins that I think will do the job. I never realized there were so many plug-ins especially for Tube sound. I’ve haven’t had much time to try them out, work is nuts right now. Has anyone tried any plug-ins that you had to pay for? Were they worth it? There was one plug-in that you had to pay for that has a variety of different tube emulating sounds.

Thanks again,

Tube emulation effects are most likely to be “distortion” effects, which from your description does not seem to be the effect that you are looking for. As written in previous posts, a really good tube amplifier does not have a “sound” - a really good amplifier (tube or solid state) should ideally make the signal bigger with no additional distortion or tonal colouration.

Are you playing your recordings through a warm, crisp hi-fi or through crappy computer speakers or through professional audio monitors, or …?