Blackstar HT5-RC Tubes?

[csimic]

Hi I have a Blackstar HT5-RC which is a nice amplifier but I cannot get many different sounds out of it, I cannot get a real clean sound it always has gain in it and when I move the Bass, mid and Treble knobs nothing seems to change much. I spoke to another fellow who had the same problem and he was told to take it to a Blackstar repair agent and have the tubes upgraded and the bias would have to be reset.
Is it true to say that Blackstar only install average tubes in the HT5-RC and that it would be beneficial for me to get some upmarket tubes installed by a technician?

I am a newbie only been playing 12 months - 55 years old - so cut me some slack if I have asked a stupid question.

Also what brand and effect pedals do you think I should buy and use? I mainly play warm clean blues tones. I must admit at this stage I am not real impressed with the HT5-RC's performance but I am happy to pay for some better tubes if it will make a lot of difference.

I play Strats, PRS SE 245, Telecasters, Les Pauls, Gibson SG limited edition and I have just bought a Fender Mustang being vintage it is kind of nice.

Please give me some advice about the amp I always use Mogami Gold Pro leads, I don't know what is going on there.
Cheers, Mick

[thephantum]

The HT5 is a good sounding amp, but out of the box it has a few flaws. Specifically the speaker (in the combo) and the tubes, so changing these can have a big impact. One key thing to keep in mind is that, by design, the HT-5 does not have a lot of headroom. So while tweaks can be made to increase headroom slightly, you will never be able to crank this amp and stay clean. Personally, I like the fact that the clean channel does not have a lot of headroom. I think pushing the clean channel into saturation sounds better than the gain channel. As far as cleans, I also like the fact that it responds almost like a Class A amp. In other words (once you tweak it and get it dialed in), the amp can be extremely clean, but if you dig in harder it gives you a little dirt...

It sounds like you are still under warranty. So unless you are willing to (potentially) void it, you'll need to have an authorized repair center do all the work for you. Since these are upgrades, you will be coming out of pocket...which might get pricey. Having said all that, these would be the tweaks to make, in the order to make them (most to least impact on tone) as well as some reasoning as to why:

• Speaker:
  Upgrading the speaker will give you the biggest tonal improvement for the least amount of work. It's literally a bunch of screws and two clip on wires. While the amp does not have a lot of headroom, a lot of the early breakup you are hearing is the Blackbird speaker. It's very raspy in the upper mids and is most likely the majority of what you don't like about the clean tone. Regardless of the choice (Celestion, Eminence, Jensen, etc), getting rid of that rasp will make the amp seem like it has more headroom. It will also amaze you how much better the amp sounds overall.
  
  I highly recommend doing this before even thinking about the tubes. Mainly because after swapping the speaker out, you might decide not to bother with tubes until the amp needs them.
  
  Tubes:
  This will be much more subtle then the speaker, but still be very noticeable. Again, the amp is actually designed to breakup early...in other words to push the tubes into saturation. So the trick is to get tubes that are more resistant to being knocked over.
  
  Specifically speaking to headroom, changing the preamp tube type is an option here. For example, if you swap the preamp tube (12AX7) for something like a 5751 or a 12AU7, it will give you more headroom (in terms of the knob), but you'll also have slightly less volume....so it's sort of a push. Plus, to my ears, anything but a 12AX7 makes the HT-5 lose it's edge and sound "flat". So I wouldn't go that route...at least not with this amp. It's best to just upgrade.
  
  Keep in mind that the order listed here is not to imply that the preamp tube is more important than the power tube...arguments could be made either way. They are simply listed here in order of signal flow.
  
  • Pre-amp tube: Changing the preamp tube (12AX7) is one of the easiest mods you can make. It is literally plug and play...no adjustments needed. Tubes do wear out, so eventually you'll have to do it anyway. I recommend either a TungSol or Mullard for the HT-5. Both are fairly inexpensive ($15-$20 USD each) and will have more head room than the stock tube. Personally, I run a Genelex Gold Lion, but it's pricey (~$45) and there is not much difference between it and a TungSol when clean (the Gold Lion really shines when overdriven).
    
    Power tube: First of all, contrary to popular belief, the power tube (12BH7A) does require biasing. So it's not just a matter of plug and play here. Mine came with an Electro-Harmonix (EH), but I believe they are coming with TAD's now. In terms of tubes currently being manufactured, those are pretty much your options. The problem is those options are mediocre, at best.
    
    I've found that a brand new EH tube has a fairly low trans-conductance (Gm). Without going into all the math, Gm is one of the factors needed to determine the amplification factor of a tube. In terms of a percentage (1-100), an EH tube measures about 60%. I've bought used 12BH7A tubes from the 50's and 60's on the cheap and they measure 90-95%...way stronger than a brand new EH tube. Not only that, but even a halfway decent used tube blows the EH away in terms of sound as well. You can actually pick up NOS 12BH7A's from online retailers like Tube Depot or The Tube Store for $40 or less. The trick is to make sure you get a decent brand name: GE, RCA, Sylvania, etc. Given the limited options available for this amp, IMHO, it's well worth the money.
  Transformers:
  Now we are getting into doing surgery on the amp. Based on what you are looking for, this is not necessary. But, it is an option, so I figured I would list it. In terms of tone, this is much more subtle and not everyone will notice the change. It can also increase headroom a little since the OT and power tube are part of a system. So, all other things being equal, a better OT can help make the power tube a little more resistant to breaking up.
  
  Unless you know what you are doing, it should go to a tech for this. It also starts getting expensive. Mercury Magnetics makes a specific replacement for the HT-5's output transformer. It doesn't change the tone of the HT-5, it just gives it more clarity and definition. It comes at a price though...almost $200 just for the part. A tech might be able to get it cheaper, but you still have to pay for his/her labor.
  
  You can also install a better power transformer, which will help deliver power faster to the amp when it needs it. In addition, you can install a choke to help level out AC ripples. All of that helps smooth out the sound a little...but again it's extremely subtle and get's expensive.

[csimic]

Thanks so much for your reply you have helped me heaps, I really appreciate it.

Regarding the speakers are they any model numbers that are better than others?

Thanks again.

Michael H
Australia

[thephantum]

It's all going to depend on what kind of sound you are going for. Do you want more emphasis on the upper mids or more emphasis on the lower mids...basically British sound or American sound? Knowing that will narrow down your choices.

Then you can do some searches on YouTube for speaker shootouts, which can give you an idea of the tonal differences between different speakers. Below is just one example. When you hear the stock speaker (Blackbird) followed by the Celestion 70/80 (a "budget" Celestion), it will become clear just how much rasp/fizz is in the stock speaker. Then when you hear the V30, it will become apparent just how much the amp comes to life.

https://www.youtube.com/watch?v=19zSesuHKg0

[Caprica]

Is there a limit to the speaker size? In terms of depth and magnet size?

I hear the celestion greenbacks end up touching the tubes

[thephantum]

Short answer is people have gotten V30's in HT5's, which are slightly deeper than a Greenback. I have heard about speaker magnets coming close to the tubes but, not touching them. If you are talking about Alnico magnets, I can see that as they tend to be much deeper then ceramics.

Bet bet is to measure from the speaker baffle to the edge of the tube and make sure that the speaker you get does not exceed that.

[Caprica]

Thanks. The Alnico is certainly quite deep. I don't know if the alnico chime suits the Marshally Backstar though.

I was more concerned about magnet structure diameter. The v30 is 156mm. The G12M greenback is 150 mm, so should be ok. However, I was eyeing off a heritage greenback with a 168 mm magnet. Do you think it will fit?

btw, what tubes and speaker combo are you using in your HT5?

thanks, Caprica

[Sonofarich]

You may want to look into the G12M-65 Creamback...similar size as the Greenback and a little smoother. I have a Creamback and a Scumback in a 2x12 and it's glorious.

[thephantum]

I have the head, but it has a Gold Lion B759 in the preamp and a NOS TungSol from 1957 in the power amp. I mainly run it with an HT-408 that has Eminence Patriot 820H's in it, but I will occasionally run it with a 2x12 cab that has Patriot Texas Heats.

[Toneconsultant]

Power tube: First of all, contrary to popular belief, the power tube (12BH7A) does require biasing. So it's not just a matter of plug and play here. Mine came with an Electro-Harmonix (EH), but I believe they are coming with TAD's now. In terms of tubes currently being manufactured, those are pretty much your options. The problem is those options are mediocre, at best.

I've found that a brand new EH tube has a fairly low trans-conductance (Gm). Without going into all the math, Gm is one of the factors needed to determine the amplification factor of a tube. In terms of a percentage (1-100), an EH tube measures about 60%. I've bought used 12BH7A tubes from the 50's and 60's on the cheap and they measure 90-95%...way stronger than a brand new EH tube. Not only that, but even a halfway decent used tube blows the EH away in terms of sound as well. You can actually pick up NOS 12BH7A's from online retailers like Tube Depot or The Tube Store for $40 or less. The trick is to make sure you get a decent brand name: GE, RCA, Sylvania, etc. Given the limited options available for this amp, IMHO, it's well worth the money.
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Thephantum,

I'm new to the site and I have a lot of search's to do, but as I'm getting caught up, I had a question for you and anyone that might have an answer. Here it goes:

"The power tube is a 12BH7AEH. I believe that's Electro-Harmonix 12BH7A. What other tubes can I run since this is in a power tube section and not a preamp section?"

Here's my story. I bought a used Blackstar HT-5R. Perfect condtion. I play metal type guitar. I played the same amp in the store and it sounded awesome. This used amp, however, is not so awesome. Apparently, the previous owner made some changes.

-changed speaker to a Celestion
-changed the tubes. It now has an Electro- Harmonix 12BHAEH and a Grooves Tube 12AX7-R

What's it sound like? The used amp has a lot less distortion. As for tone, I just find it having more mids than I prefer. The treble isn't as sizzling as the new amp had either. If I were playing another other type of music, I think it would sound great, but I'm not. The stock new amp had a wonderful "metal" guitar sound. My used amp has a pretty good rock guitar sound. If I run an overdrive pedal through the amp, I'm sure I can get the metal sound, but I don't want to because it should have that sound anyway.

Now there is one factor that could be the culprit. The guy that changed the tubes couldn't even spell "Bias." He didn't bias the power tube and the preamp tube is a EH 12BH7A and not a 12BH7. I don't know if that makes a difference, but as I've been reading, there are a lot of tubes out there so maybe that is the difference. i don't know. So, I have another question.

"How much of a difference could not biasing the power tube make to the tone?"

and

"anyone care to say anything about the difference between a 12BH7A and a 12BH7?"

I plan to bias it, but I was just curious to hear what would happen, tone wise?

Oh, and if anyone knows what the stock tubes were, please share. I'm finding that all tubes are so different. I WANT the stock sound, but I'm FAR from it. Maybe the HT-5R have different wired amps and I got a bad one? That's how different the tone is. Anyone with a bad ear could hear the difference. It's massive.

My fear is after I change tubes & bias, I still won't be able to change the tone that much . . . but I'm hoping you guys will tell me otherwise.

P.S. Oh, and the Celestion change? Now I wonder if he wired it up oddly. Since it's only one speaker, I don't think you can wire it up differently, but I never really thought about it. Yes, I'm desperate. I can't believe I'm questioning the wiring of a speaker. Agh. I need help guys. Please help me.