What's the best choice to get more gain out of a tube amplifier

Question

The story behind this question:

I got myself a nice little combo for my bedroom-workouts (related to playing guitar, of course :D ), a Blackstar HT1-R which is a lovely little 1 watt 2 channel amplifier. My only problem is, that the overdrive-channel sometimes hasn't enough gain for my needs. (Since I love to play metal.)

My goal is to use some sort of overdrive/distortion pedal in the already overdriven channel to keep it warm and tube'y (is that an word?), but with more gain.

1. Is this possible? (I tried something like this with an old transister amplifier quite a while ago and it sounded awful... maybe my choice of pedal wasn't good? It was some kind of a high-gain distortion pedal...)
2. If yes, what kind of pedal is recommended? (Vintage overdrive-pedal, like a tube-screamer or blues-overdrive?)

I hope someone can answer this, cause I couldn't find a clear answer in this matter on the net.

Answer 1

You have two options. You can try to simply push the preamp harder, or you can try to put a separate distortion unit in front.

The first option involves using a booster pedal. It does not have to be a dedicated one - I know folks who simply use an OD pedal, such as the Boss SD-1 or OD-3, roll down the drive and turn up the level. The idea is that the higher-level signal you send to the preamp tube, the more it will distort. Since you aren't introducing a lot of break-up from the pedal itself, you'll get more juice, while preserving the tone of your preamp.

The other option creates your distorted tone up-front and you mainly use the preamp as a further amplification stage. Since a lot more of your tone will come from the pedal, you'll have to look around for one that suits your needs. Great-sounding distortion units can get pricy, too, especially if they are tube units.

My suggestion would be to hit your local music shops and simply test-drive a number of pedals on the HT1 - if the store doesn't have one available, ask if you can bring in your own. Try both options: rolling the pedal drive down and turning up the preamp gain and turning up the pedal drive and rolling down gain on the preamp. Ultimately, getting a good distorted tone requires some experimentation and only you can ultimately say what works for you.

If, for whatever reason, this isn't practical, check out some pedal manufacturers' sites and listen to audio samples of their range. You already have a good sounding amp, so if you find a tone you like, odds are it will sound good on your amp too.

Answer 2

Faza covered the conventional stuff pretty well. I have a few things to add that wouldn't fit in a comment.

This amp uses all preamp tubes so no matter what it may sound buzzy or fizzy. The ones I sampled reminded me of Neal Schon with Journey in the 80s. Very much a preamp distortion.

1) If your amp has a master volume, turn it all the way up and use the preamp controls for changing the volume.

2) Try to find an older MXR Dynacomp compression pedal. Keep the sensitivity low and crank the output knob.

3) A tube screamer with the drive turned down low and the output cranked.

4) Try to figure out what the output tube is and change it to a higher gain tube. The ECC82 (12AU7) is a lower gain tube than the ECC83 (12AX7). Make sure you get competent advice from an amp tech if you decide to do this. In some cases its ok to substitute tubes (fender all tube amps, typically) in others it is BAD (Crate tube amps, Older tube ampegs in some slots)

Otherwise, let your ears be your guide.

Answer 3

The other guys have covered the bases, but I wanted to chime in with some additional points, one very important caution and some other clarifications.

The HT1R sports an ECC82 (12AU7) + ECC83 (12AX7), and for the life of me I cannot find anything that says which tube lives where in the circuit. If I find anything I'll update this answer to be more factual instead of conjectural. Typically in an amplifier of this configuration the 12AU7 would be a reverb tube and the 12AX7 the preamp tube--but even on the HT1 (which has no reverb) that tube combination is listed so I can't even make an educated guess. Most high gain tube based amplifiers have two to four preamp tubes--and all of them are usually the ubiquitous 12AX7--but the HT1R only lists two tubes with very different impedances and gain ratings, which could be responsible for a lack of gain in the circuit.

I absolutely do not recommend that you attempt to toss a 12AX7 into the spot where the 12AU7 lives on the HT1R. The impedance mismatch could cause some serious damage and at a minimum cause the circuit to run out of range and not operate optimally. Since we're dealing with electricity here, when something doesn't run in tolerance you have two options: release any excess energy in the form of heat and burn up or sag--both of which are not ideal. Push-pull amp circuits with preamplifier stages designed for 12AX7's can usually take a lower gain rating preamp tube (such as a 5751 or a 12AU7), but it hardly works right the other way around.

Another thing to consider is that the HT1R doesn't list any power amp tubes. One of the wonderful things about vacuum tubes is that they clip (or distort) when they get too much signal--and lots of amplifier designs have additional power amp stages that you can overdrive with enough signal. My Orange gets exponentially louder as I roll up the volume and boost the input signal with a pedal--a factor of the preamp stage being overloaded and the power amp stage being overloaded. So, the HT1R will not get as loud as a Mesa Boogie triple rectifier which sports a large array of preamp and power tubes for example but since the power stage in the HT1R is likely solid state it can still produce a good bit gain and definitely phenomenal cleans.

Another typical feature on a metal amplifier is the presence of more than one rectifier tube in the circuit (made famous by none other than Mesa Boogie). A rectifier simply converts AC current to DC current--but these magical little components are responsible for the tightened bass tones you hear on many metal records. A reliable rectifier circuit will keep the amplifier from sagging during playing--which results in a tighter, fuller response as the circuit gets the current it needs to run at full capacity quickly. The HT1R looks like it uses a single, solid state rectifier circuit (silicon diode based); that's perfectly fine for you applications--so no complaints there.

The final point I want to make is that the HT1R only has a single 8" speaker. That's hardly enough to push the blinding tight bass tones that lots of metal guru's are known for. Smaller speakers will have a harder time reproducing lower tones (just like in a car stereo) unless you happen to own an amplifier built by Bose ;D. Picking up a closed back 2x12 cabinet that your amplifier can run will definitely help it, but I don't know of many 1 watt amplifiers with the juice to push a pair of 12's at the correct impedance. If you get one, use it at your own risk.

So what can you do?

Well, you can most definitely help your amplifier out a little bit with pedals--but they'll need to be overdrive pedals. A boost will only do so much, and likely push the gain rating on the preamp stage about as far as it will go. Note that you will need to experiment as Faza suggests when mixing overdrives with stock amplifier distortion unless you are always playing the pedals clean. I don't really recommend doing that though because it will really kill the usefulness of the drive stage on the amp and whack most of the tube amp warmth that most of us are in love with. Most distortions sound very sterile unless they are tube based, germanium fuzzes, or hardcore algorithms on a complex modeling unit like AxeFX. There are definitely some awesome JFET based units out there that will fool you though--but the list is very short in my experience.

I have gone through countless overdrives (I recommend you buy used :D) and finally settled on a two overdrive + one boost configuration that I fell completely in love with, so it may take you some time. Be patient. Keep experimenting, and keep playing. My amp doesn't gain out that much either--it's a dual 12AX7 + 4xEL84 configuration, but after discovering a pattern of pedals that I liked and grabbing a closed-back* 2x12 speaker cabinet I can sound like most vintage and some modern metal gurus.

I'm not trying to be a downer here and say you bought a bad amp--but I definitely think that you should understand the shortcomings of the amplifier you purchased versus what you want it to do. Based on my one hour plus of research on the little guy it sounds like you have a really solid practice amp that will last you for a good while--but if you really want to sound like a metal god then you're going to have to pony up and get something louder, larger, and with a power amp stage :D.

*A closed back cabinet is also helpful in recovering some tightness and bass response

Answer 4

I just got a blackstar ht-5r combo tube amp and it sounds great with my distortion pedal, it's a Biyang Metal End King pedal. If you like playing heavy metal then this pedal will give you any type metal sound you want, very heavy, fat tones and not muddy like a lot of pedals! Cheap too, only $79. I play anything from black metal, thrash, or death metal and it's plenty heavy enough for any of it. That's my recommendation

Answer 5

My advice, and not to be terse about it, get an amp with some decent wattage. These little watt amps do not have the depth and headroom because there is no wattage to push the sound. Wattage is not about loudness, as so much marketing hype crap suggests. Wattage is headroom, punch, power and low end body. The distortion is tinny and thin in these amps and that is that. There is no power amp "power".

Get at least a 40 watter going on a clean channel and use a good high end distortion pedal if you want metal gain that sounds good. Most cannot afford a $3000 head and fry the tubes creating a gain level. Just just a decent size amp, metal is best served with a closed back cab and 12" speakers. More depth and punch. Wattage is not loudness. The basic rule of sound engineering is there is only a +3db potential of loudness for every doubling of watts. A 10watt is 3db louder than a 5watt, a 20watt only 3db louder than a 10watt. So a massive 100watt head is really only like 10db in potential loudness than a small 10watt amp. 10db is not much and all the removal of watts does is remove the heart and soul out of an amp. That is just the hard truth. Those who disagree are just wrong and their tone shows it. It's not about your ears or ones opinion it is simply a matter of sonic engineering law. There is no low end without wattage to push it.

Answer 6

The HT1-R is using a dual triode ECC82 pre-amp tube in push pull as a low wattage output tube. ECC83 has higher voltage gain but lower power output than an ECC82 so I don't recommend substituting the output tube!!! You could try nodding the amp by altering cathode resistor and bypass capacitor and anode resistance.