HT5 power tube distortion and other concerns

[yomutha]

First time post. My apologies if this topic has been discussed (to death) already.

I own an HT-5RS and am learning how to properly manipulate tones. Nevertheless, I'm still pretty clueless about tubes, so please excuse any ignorance on my part.

My HT5's pre-amp distortion sounds friggin' awesome, but the clean channel, in comparison, is quite uninteresting, and my dirt pedals sound crappy on it. On the other hand, when the overdrive volume is cranked up with the gain kept low, I can achieve a very pleasing, dynamic (albeit NOT bedroom-level) "clean" tone, which makes my dirt pedals sound damn good too; however, with this setting, I have to compromise that friggin' awesome pre-amp distortion!

Anyway, TWO things I really want to know:

1) Why do I not get that fabled power tube distortion when my OD volume is cranked? Is it because of the type of tube used in the power section?

2) I'm favoring my second setting (OD volume cranked, gain down) more and more these days for its dynamic tone, but I hate not being able to hear the amp's distortion. So if I get a Blackstar HT pedal, will this do the trick??

[Crunchifyable]

1). On mine, I get output distortion on the OD channel when the volume is between noon and cranked (but depends on the gain setting...noon for high gain and maybe 3 o clock for less gain.)

On the clean channel, there is a very warbly effect when it gets turned up and the output valve is distorting. You can tell its the output valve because u hear it even through a single coil. Like in this recording http://youtu.be/taGZCskUJUo?t=41s


If you want MORE output tube distortion, put an EQ or booster in the FX LOOP. This works for any amp with an effects loop.

Getting a boost pedal and sticking it upfront will only drive the preamp tubes harder, and may get more power amp drive too, but that defeats the purpose.

What you might also try is using a boost to hit the clean channel harder from the front, keeping it on always, and just lowering the gain on the OD channel to compensate.

[thephantum]

Since you are a self-proclaimed "tube newb" let's talk some high level basics about signal routing in the HT-5.

In the HT-5 there are 2 - 12AX7 Sovtek brand tubes in the preamp (called V1 and V2...where V=valve) and 1 - 12BH7 Electo Harminix brand power tube (called V3).

• - On the clean channel, signal is fed through the V1 tube in the preamp and then routed to the power amp.
  - On the OD Channel signal is first fed into V1, then routed to V2 where the signal is overdriven.
  - The gain setting is used to control the signal level (in dBv) sent into V2. The higher the setting the higher the signal level. However, V2 can only send up to a maximum signal level to the power amp. So if V2 can only output -5dBv to the power amp, but it's getting 0dBv on it's input, it starts to clip the signal, which causes it to distort.
  - Conversely you'll notice that if you turn the gain all the way down, you've effectively eliminated the signal going into V2 and the amp is virtually silent.

So, when you are in overdrive with the volume up and the gain way down, you've dropped the signal level going into V2 so low that the output is lower than what would come straight out of the clean channel (V1).

As an example, let's say that the preamp puts out signal of -5dBv. When you turn the gain way down, V2 is only getting say -15dBv and that's what it puts out to the power amp. By doing that you leave the power amp more headroom so it doesn't break up at high volume. However, the power tube is still working hard so you get a great, clean, shimmery tone.

Now, you can manipulate things by trying different brands of 12AX7 (preamp) tubes. Different brands will have different tonal characteristics. The Sovteks that come stock are ok, but not great. The nice thing about preamp tubes is you can change them without having to rebias. So you can pop one in, try it, change it out for another and try it, etc.

It sounds like you are happy with what's coming out of V2, so I would focus on V1. Based on your description, you want some good, pristine, clean tones that you can add some dirt to with pedals. I would recommend either a TungSol 12AX7 or a Preferred Series 7025/12AX7.

Another direction/thing to try is using a lower gain tube in one or both stages of the preamp. So for example, using a 12AT7 in V1 will reduce the gain on the clean channel by about 40%. This would give you a lot more headroom on the clean channel at higher volumes as well as give you some finer grain control of the gain on the OD channel. The drawback in that configuration is that you will reduce the amount of maximum gain the amp can produce.

Going the other way (more gain) is a lot easier...what Crunchifyable said is the best way to go about it.

Hope that helps.
Steve

[peniro0987]

In a lot of these modern 'toy' tube amps most of the gain is coming from the pre-amp section and a lot of new age electronic mojo that has been developed over the years to enhance the pre and power amp section.

The gain in old vintage amps ( e.g. a '60's Marshall 100 watt super lead) came from driving the power tubes and the pre amp tubes were more about tone and harmonics (and most of that came from V1). Back in the old days most guys cranked up just about everything on the amp. (except for the bass... usually set very low or zero, the low end came from the cab).

My HT 5 only has one pre amp tube.... according to 'thephantom' they now have 2 ??? Don't think so!
Remember that the HT 5 is basically an HT drive pedal with a power amp and speaker.

Also, these type of amps don't do well if the input is too hot...e.g booster pedals etc. Even high output p/ups can be too much for the pre amp and will severely shorten the life of the pre amp tube (and won't enhance overall sound). I find that with most humbuckers going into the HT5 the guitars volume needs to be backed off a little. Kinda pointless feeding a drive pedal with a drive pedal.

Most new tubes are junk. Unfortunately most of us don't have access to a source of good NOS tubes but they are they way to go if you can get them. e.g. old RCA's or Mullards.

[thephantum]

I must have conflated my HT20 with my HT5. The HT5 has one tube in the gain stage of the preamp and one tube in the poweramp. The clean stage is purely solid state, although I do think signal still passes through that gain tube. Otherwise changing the preamp tube wouldn't impact the clean channel.

[peniro0987]

Getting a bit off topic re: the OP but solid state means transistors and clearly the HT 5 is not a transistor amp. Replacing the pre amp tube has made a big impact on both channels.

[thephantum]

The term Solid state is inclusive of, but not exclusive to, transistors.

• Solid state:
  1: relating to the properties, structure, or reactivity of solid material; especially : relating to the arrangement or behavior of ions, molecules, nucleons, electrons, and holes in the crystals of a substance (as a semiconductor) or to the effect of crystal imperfections on the properties of a solid substance <solid–state physics>
  2
  a : utilizing the electric, magnetic, or optical properties of solid materials <solid–state circuitry>
  b : using semiconductor devices rather than electron tubes <a solid–state radio>

Technically speaking, even an all tube amp contains solid state components (resistors, capacitors, etc). In this context however, I am referring to the last definition (2b)....the fact that the HT5 is a hybrid amp. What you called "new age electronic mojo", I call solid state.

[shimmilou]

In the HT-5, the guitar signal goes through the preamp tube for both channels, so a preamp tube change will affect both channels.

[yomutha]

Man! I never got any notification about these replies, so I thought no one responded and forgot about this post. Thank you all for your informative comments!

[RCB-CA-USA]

I plug a Zoom G9.2tt into the line of an HT5RH on top of an HT 408 with excellent results. What power tube do you all think would work best for the Zoom into the line in?

In advance, thanks for the replies!