Do Pre-Amp Tubes Really Alter Basic Tone?

[Classicplayer]

After reading several threads discussing players' favorite preamp tube brands, I am thinking that the preamp tube swaps produce only minimal tone changes in an amp. The basic tone signature is pretty much incorporated into any particular amp; within the amp circuit design. Am I correct in this regard?

Classicplayer

 

[SWeAT hOg]

I think an amp might behave a bit differently, but in the end, the same tones can largely be dialed in.

 

[wrc73]

Using the right tubes for an amp is similar to pairing the amp with the right speaker, it accentuates the positives of the amp while minimizing negative aspects. You're not going to make the amp into something it's not, but you can make it the best it can be, at least for your ears.

 

[cybermgk]

As mentioned, generally it is eq changes that can usually be adjusted on the amp as well. MOST OF THE TIME. Because there are some crap tubes that just muddy an amp up, that no amount of eq fixes. ALL to often, stock tubes in less expensive price points are exactly that, and they muddy up an amp, make it less clear than it can be, less responsive and less articulate.

Once into good sounding preamp tubes, even new production, then they do emphasize different frequencies. AND, it can vary from tube to tube from same manufacturer.

As mentioned, some tubes just sound good in a particular amp's preamp. And most roll them, because, they will last a good long while.

NOW, if the amp gets a LOT of it's dirt tone from preamp distortion, then darn tootin different preamp tubes will sound different. Once we get into square wave territory and their 1st 2nd and 3rd order harmonics, different tubes will definably sound better in that amp.

JUST as a for instance, say a particular amp is designed with a particular knee frequency for a gain stage(s), and the tube your using emphasixes the same frequencies, the circuit is trying to minimize in that stage. Not going to sound as good, or definitely as designed.

 

[GeeJay]

FWIW I tried a different 12AX7 in V1 of my DSL401 and while it t didn't seem to make a huge difference in tone, it did seem to change the feel/picking response. Somehow the amp felt softer to play. I reverted to the original Marshall tube. YMMV of course.

 

[Classicplayer]

The amp I'm currently honed in on is my newly purchased Orange Micro Dark. It's a hybrid design with only a single 12AX7 for preamp. The power section is all solid state. It's advertised as having 4 gain stages and most probably geared towards much higher gain sounds than I normally have had in any of my amps over the past few years.

I'll most likely form an opinion about the types of 12AX7 that I plan on running through this little tyke. Stock, it arrived with a JJ, but I do have on hand a Sovtek, a Tung-Sol, and Mesa version of the same tube. Most reviews of several branded tubes result in a plethora of options on each. Interesting also, is the fact that tubes that favored by some folks are panned by others. I guess it comes down to personal likes (dislikes) as to just what we expect to hear in the form of distortion coming out of the amp itself. I know that with the amount of gain that is within the Micro Dark's design, I will no doubt, find my own idea of a really a good distorted tone.

Classicplayer

 

[InsertUsernameHere]

To my ears, it's all about small changes in response and gain characteristics. I remember it being really noticeable in my 5F1 clone, maybe due the circuit's simplicity? A Chinese 12AX7 sounded phenomenal in it. Really rich overtones and a certain sizzle that wasn't present in a few NOS 12AX7s I tested including a Blackburn Mullard and a Telefunken smooth plate.

 

[TheX]

Preamp tubes do more for tone than some of the crazy stuff people do to their guitars.

 

[cybermgk]

Preamp tubes do more for tone than some of the crazy stuff people do to their guitars.

And then some

 

[El Pablo]

Rolling pre-amp tubes can be a fairly inexpensive way to adjust your amp. One luxury is not having to re-bias.

An issue I tend to find is that higher quality pre-amp tubes can extend or reduce clean head-room. I personally like to find a tube that will slow down the breakup, while also reducing overdrive fizziness. To my ears, I have a challenge finding the lightly over-driven sounds in an amp. Having an expanded overdrive (before reaching full-on distortion) is the payoff that I seek.

FYI, I have owned two (2) amps that really benefited from Pre-Amp tube swaps - an Orange TH30 and a Hughes and Kettner Grandmeister 36. The effect was just what I described above. I am very happy with the results.

On my old 100 Watt Marshalls, I did not noticed quite the same affect. Each pre-amp change I tried provided only minimum tone change. On the contrary, my old Marshalls did greatly benefit from Power-Amp Tube changes. One of my JCM2000 DSL100 Heads especially loved KT77's. That was a night and day difference.

 

[bulletproof]

Preamp tubes do more for tone than some of the crazy stuff people do to their guitars.

This right here,yes indeed.

 

[SWeAT hOg]

An issue I tend to find is that higher quality pre-amp tubes can extend or reduce clean head-room. I personally like to find a tube that will slow down the breakup, while also reducing overdrive fizziness. To my ears, I have a challenge finding the lightly over-driven sounds in an amp. Having an expanded overdrive (before reaching full-on distortion) is the payoff that I seek.

On the other hand, if it's break up I'm seeking, I believe not all tubes are alike. My crunch preference is JJ's.

 

[dc007]

The simpler the amp circuit, the greater impact tube rolling makes.

 

[JellyOnToast2345]

I don't tend to think that different brands of tubes make THAT much of a difference in sound. I think 99.999% of the "differences" we all hear are psychological. However, a different type of preamp tube (12AX7 vs 12AT7 vs 12AU7 vs...) will make a difference in your preamp gain. Brand will make a big difference in reliability, but no so big in tone. YMMV

 

[freefrog]

IME and IMHO...

Yes, the influence of tubes varies according to the circuit involved.

Yes, the whole circuit is (most) often much more important than tubes. I've recently swapped the unique power tube of a single ended class A amp without noticing much tonal differences between 6V6, 6L6, EL34, 6550...

That said, tubes with a different inner architecture (or old vs new samples) can exhibit largely different characteris when it comes to gain vs headroom...

Do these specs affect the sound?

I post below two pics.

The first shows the frequency response (white line) and THD (green line) of the same preamp excited by a sweeping monophonic signal (in the same basic Fender Hot Rod Deluxe) with various 12AX7's in V1.

The second one shows how two amps react when miked with the same three 12AX7's successively tried in them...
These charts are obtained with a same polyphonic recorded guitar soundtrack played through the amps once the tube swapped. The first amp is the HRD named above. The second one is an "uber-modified-by-me" VHT Special 6 with a single preamp tube in it. The mic used and conditions of recording were of course strictly similar.

Make your own conclusions.

 

[Dolebludger]

If you are using 12AX7s in your re amp (especially in V1 and want a more creamy tone, you could try 12AU7s or 12AT7s. They don't have as much output and may help you get those "in between" gain levels between clean and screaming -- if that is what you want. Maybe not, if the gain adjustments on you amp allow you to get these "in between" gain settings with 12 AX7s, as my amp does. But if you have one of those amps that wants to go from pure clean to screaming, a switch to one of these lower output tubes may help you get the "in betweens".

 

[grayd8]

Putting a 7025WA in v1 of my DSL killed alot of the fizz and excessive brightness in the amp.

From what I've read, you want the best tube you can afford In v1, any noise induced here is only going to get worse in the later gain stages.

 

[grumphh_the_banned_one]

I have a Marshall 6101 combo.

In that particular amp swapping preamp tubes absolutely and undeniably makes a difference.

Different tube designs may actually emphasize different overtones when overdriven, so there is a perfectly rational explanation to as why there are audible differences between various types of ecc83/12ax7 tubes.


However - even though there are fairly obvious differences between tubes, the amp still behaves and sounds like a marshall 6101.
No preamp tube swap is going to make it sound like a bogner or a mesa - or for that matter a DSL, or even a JCM800 which is what one of the channels is supposed to sound like...

...so well, no, an amps "basic tone" is probably not going to be changed by preamp tube swaps.

 

[grumphh_the_banned_one]

Add on, on the subject of tubes.

I have a "Hohner" amp from the late 60's, which is designed to sound clean, and does just that, and sounds nice while doing it

It came with a Telefunken 12ax7 (yay!!) and of course i immediately tried swapping the Telefunken into alternately the clean and the drive channel of my 6101, and of course i put the Marshall branded 12ax7 from the 6101 into the Hohner.

The Telefunken didn't make much of a difference (if any) in either of those positions in the Marshall - but the cleans on the Hohner definitely suffered from the "Marshall" tube, so in the end i put the Telefunken back into the Hohner, where it was the most useful.


What i am trying to say with this, is that my personal experience with tube swapping is that even a well recognized tube such as the Telefunken (that did prove that it sounds nice in one of my amps) may not be the right thing or do much for a different amp - so experimenting yourself rather than reading tube reviews on the net is probably the best way to go

 

[ScottMarlowe]

As mentioned before, it REALLY depends on the amp.

My Fender Ramparte came with I think sovtek 12AX7s, and switched them out for Chinese 12AX7As which are known for high gain and for being very bright. Definitely livened it up a bit. Before that it was a bit too dark for my tastes.

On my Peavey Classics (2 50s and a 30) swapping out the V1 for a GE 5751 made them much more pick / touch sensitive. Chickin' pickin' and rockabilly stuff REALLY sounds a lot better on the clean channels. Replacing V2 (lead channel gain tube) with NOS American GE JAN 12AX7WA made for a much smoother and to my ears a better sounding lead. Before that it was fizzy/harsh/brittle sounding to me.

OTOH, my Vox Lil Night Train seems to sound exactly the same no matter what tubes I roll through it.