Instrument Tube Pre-amps Vs. Microphone 'Toob' Pre-amps

amra

Well-known member
Ok, I have a question here and it is something that I have been wondering about for some while.

People say here all the time, that a pre-amp with tubes in it using a starved plate design is basically worthless, the tubes do not make a difference and basically do not contribute in a positive way to the recording.

Ok, here is my question. Why is it that Mesa Boogie, Marshall and other big names make tube based rack mountable pre-amps for guitar? These are always recommended on this site and most others too as a viable option to get each respective companies "sound". They are used by professional musicians the world over. How is that these can give real tube sound? Are they using high voltage circuits in these pre-amps? Also what type of circuit do most tube amp heads use in their pre-amp sections?

I am asking legitimate questions here, and if the answer is that these well known guitar amp pre-amps are using high voltage or some design drastically different than microphone tube pres, then I have my answer.

However, if they are using starved plate or some other similar low voltage technlogy, then I would like someone to explain how guitar pre-amps are tube pre-amps and held in such high regard for their nice 'natural' tone, and similarly designed mice pre-amps are "toob pre-amps" and considered to be worthless?

thanks
Amra
 
I can answer part of your question -

There are two kinds of tube mic preamps - "toob" - which is the starved plate type, and tube - which is generally pretty expensive, and uses full voltage.

I would imagine, that guitar amps come in both varities. I have a digitech pre that has a "toob" pre in it, and and i would guess that the high end tube amps all have a true tube pre in them.
 
I don't think boxes running starved plate are worthless, it's a good marketing strategy for companies selling tube gear to folks who usually aren't familiar with tube circuits.

For starters, dual triodes were designed for a specific plate voltage. When you change that variable, you end up with less than optimum performance. I've recorded amps that use the starved plate design, most notably the valvestate. But to my ears, they don't compare to what a vintage plexi could kick out, from a sonic stand point. For one thing, having an output section that uses tubes is also a significant factor. Another variable to consider, is that the majority of successful tube circuits use transformers on both ends. They also account for warmt and rich coloration, provided they are properly matched to the circuit.

The only reason I don't care for the starved plate design is because I haven't heard any tube coloration when I use them. There's a lot more to tube coloration than inserting a hybrid tube design in the preamp stage. That's why very few serious recording facilities use them on a daily basis.

Regards.
 
lower voltage means less dynamic range. less headroom so the lower voltage circuits will distort earlier and produce more noise ( hsss ) than circuits running at higher voltages. It is those higher voltage circuits that we call ' high end ' that are the preferable designs for quality mic preamps that need more headroom or dynamic range than guitars and basses. oh that's right, bandwidth (frequency response ) and slew rate also improve at the higher voltages . better for mics not necessarily for guitars.
 
Although I can appreciate your train of logic on this one, Amra ...

You are kind of comparing two different things here. Using your methodology, one could also ask questions like ...

If ketchup is supposed to suck so bad on Rice Crispies, why is it that it tastes so good on hamburgers?

If cheap wine is supposedly inappropriate for an expensive steak or lobster dinner ... then why is it perfectly acceptable to use when mixing Sangria?

If pooping in a toilet is a perfectly acceptable activity, then why is pooping in public frowned upon?
 
Basically nice tube instrument preamps are nice tube preamps that often times impart a great deal of color by being driven into clipping for a distorted sound.

Stuff like the instrument preamps you're thinking of tend to be nicer than their cheap mic pre counterparts, although there surely are some that use starved plate designs, but stuff from mesa and marshall most likely uses "real deal" full voltage tube designs that are designed to be as close to their amps as they can get without the rest of the amp.
 
CCS said:
For starters, dual triodes were designed for a specific plate voltage. When you change that variable, you end up with less than optimum performance. I've recorded amps that use the starved plate design, most notably the valvestate. But to my ears, they don't compare to what a vintage plexi could kick out, from a sonic stand point. For one thing, having an output section that uses tubes is also a significant factor. Another variable to consider, is that the majority of successful tube circuits use transformers on both ends. They also account for warmt and rich coloration, provided they are properly matched to the circuit.

Ok, so to clarify a little. What you guys are saying is:

1. 'All tube' guitar amps like a Marshall JCM800 or a Mesa Boogie Dual Rectifier use full voltage tube pre-amps with transformers.
2. Hybrid amps like the Marshall Valvestate series, use starved plate, transformerless, tube pre-amps, which are the equivelant of low end "toob" pres.
3.Rack mount guitar/instrument pre-amps from top line companies use
full voltage tube pre-amps with transformers.

I always thought I hybrid amp was one that used a full voltage tub pre-amp with a solid state power section. So basically, I thought the power section was the only thing different.

BTW, thanks for all the replies here. You can always count on chessrock's to be er..."colorful"..
lol.
 
In general, the better stuff on the market costs more, but is built and designed better. This is true of both guitar amps and pro audio/recording equipment. Guitar amps utilize some circuits that are similar to those in our outboard hardware, and some that are quite different. It is important to remember that with and instrument amp, often a flat even response and amplification is NOT desired, where as in many ways in recording it is almost mandatory. With guitar amps in particular, taking the top end off of a sound and letting it dramatically break up are often goals, whereas in an outboard mic preamp those are things we strive to avoid.

Full voltage or not, sometimes gear happens to sound good even though it was pretty shoddy in design. There are some cheap outboard preamps that sometimes offer up just the sound we are looking for. This can be true of guitar amps as well. For some players a cheap guitar amp may work better for them than a nicer design. In general however, the expensive stuff really is expensive for a reason. Better designs and implementation just plain old cost more to do. Remember the real Marshall and mesa stuff still aren't that cheap when compared to the really nasty stuff that is out there. Even just a preamp or power amp from Mesa or Marshall still costs more than a lot of your lower budget guitar amps do. Even the so called "tube" ones.
 
xstatic said:
Full voltage or not, sometimes gear happens to sound good even though it was pretty shoddy in design. There are some cheap outboard preamps that sometimes offer up just the sound we are looking for. This can be true of guitar amps as well.

Excellent point.

Many of the old guitar amps were made with budget components and transformers, yet kick out some very decent sound. The Alamo amps are some of my favorites to record. This also applies to other bargain amps that are still in circulation.

Regards.
 
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