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Blackstar HT-5R


the dog

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I've had this amp for nearly 2 years.

It seems that lately it is not sounding good anymore...It seems like it is a slow progression to bad sounding...

To my ears it sounds more fuzzy than overdriven.

 

This past summer on more than one occasion I would play in clean channel and turn volume all the way up to overdrive channel.

It would stop getting louder at a certain point and just overdrive.

I liked it and would play a while like that.

I also played it at full volume in the overdrive channel.

I was just putting it through some extremes to hear the results...

 

Any way I am thinking of replacing the tubes with these I saw on Amazon.

http://www.amazon.com/Tube-Complement-for-Blackstar-HT-5/dp/B00DJA6VTW/ref=sr_1_2?ie=UTF8&qid=1417308252&sr=8-2&keywords=12bh7+tube

 

Any feedback would be appreciated one way or another.....new tubes....different tubes....anything else....etc...

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Definitely sounds like tube symptoms. Generally 12AX7 last a good while. Not sure about the 12BH7A. Most likely they used a poor set to begin with. You don't get a lot of choices for the 12BH7A as not many people make them. The set on Amazon should serve. If it were me though, I'd go with a Tung-Sol 12AX7 instead of the JJ.

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Definitely sounds like tube symptoms. Generally 12AX7 last a good while. Not sure about the 12BH7A. Most likely they used a poor set to begin with. You don't get a lot of choices for the 12BH7A as not many people make them. The set on Amazon should serve. If it were me though, I'd go with a Tung-Sol 12AX7 instead of the JJ.

 

surfpup

 

Thank you very much for your help....

Here is what I bought on Amazon...

What do you think? I got the Tung-Sol....What about the other one? Electro - Harmonix

tube1_zps91744071.jpg

 

tube_zpsfaceb6bc.jpg

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Both those should be great. [thumbup] None of my amps use that particular power tube, but I have used other EH tubes with fine results. I think they are made in the New Sensor plant in Russia. The Tung-Sols are about the only 12AX7 I buy anymore.

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Both those should be great. [thumbup] None of my amps use that particular power tube, but I have used other EH tubes with fine results. I think they are made in the New Sensor plant in Russia. The Tung-Sols are about the only 12AX7 I buy anymore.

 

If you can find them, the NOS 12AX7M (Mullard) are some of the fattest sounding 12AX7's I've ever heard...going to pick up a set of the reissues for my JCM800 when it needs a retube...

 

-Ryan

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One other question...

Do I have to worry about biasing?

And what is it?

 

You do not. Single ended amps do not need biasing like many larger/louder amps do. One of their many advantages. You will be able to pop in the new tubes and rock out.

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Thanks for that Ryan...Too late now though....

One other question...

Do I have to worry about biasing?

And what is it?

 

You will need to have the amp biased..it isn't self-biasing (cathode biased).

 

Biasing is effectively setting the current flowing through the tubes at idle. Think of it like a fuel/air mixture in a car. Too much or too little and it'll either run inefficiently or not at all. With tube amps, if the tubes are biased "hot" (more current than optimal), the amp might sound "better", but tube life will be reduced, sometimes dramatically. Biasing the tubes "cold" can preserve tube life, but can have some undesirable tonal consequences.

 

Since no two tube manufacturers follow the same spec, and even tubes of the same brand and model can be inconsistent..the optimal bias could change each time you change tubes.

 

It's recommended you bring it to a qualified amp tech, since biasing an amp requires measuring current flow inside the amp while it's powered on, which is extremely dangerous if you don't know what you're doing. 300V+ at a couple ampheres isn't fun...

 

-Ryan

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You do not. Single ended amps do not need biasing like many larger/louder amps do. One of their many advantages. You will be able to pop in the new tubes and rock out.

 

Not according to every forum post I've read. Everyone who owns this amp has needed a rebias when changing tubes, according to the forums.

 

-Ryan

 

Edit: And here's a direct quote from Blackstar on the issue of biasing...

 

"It uses fixed bias.

 

The bias is internally adjustable, but unfortunately we can't assist or encourage non Blackstar authorised service techs to do this, no matter how qualified they are to do the job."

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Not according to every forum post I've read. Everyone who owns this amp has needed a rebias when changing tubes, according to the forums.

 

-Ryan

 

Edit: And here's a direct quote from Blackstar on the issue of biasing...

 

"It uses fixed bias.

 

The bias is internally adjustable, but unfortunately we can't assist or encourage non Blackstar authorised service techs to do this, no matter how qualified they are to do the job."

 

Ryan thanks for that...I did some research myself on the Blackstar forum....It seems just the power tube need to be biased....I will figure it out....

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This is going to be my next amp. I spent a day with the GC "exclusive" (BAHAHAHA) 1 watt non-reverb model, but it was enough to convince me of the sound. When I plugged my Les Paul into it, that was "the sound", I had been looking for. It was perfect. Sublime...

 

The SGJ and Kramer. Sounded good, but I just couldn't get past, having just a single input/output and no phones. I know we're guitarist and play it LOUD, but in my house... right now especially, that ain't going to fly.

 

But, I'm going to get that HT-5R, some of the nicest sounding amps, I've come across. I'm digging the ID: Core 40, I ended up trading the "HT1GC" (not the HT-1, you think it is) for it. But, its a big step up, from the 10 and at least settled my underwhelming feelings on the small sound of the 10, compared to my Flextone. Plus, that stereo is wide and really does sound sweet, especially when you throw a little reverb in there (another reason to dislike the HT1GC). Blackstar has nailed digital reverb, I'll give them major props for that.

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Guest Farnsbarns

You will need to have the amp biased..it isn't self-biasing (cathode biased).

 

Biasing is effectively setting the current flowing through the tubes at idle. Think of it like a fuel/air mixture in a car. Too much or too little and it'll either run inefficiently or not at all. With tube amps, if the tubes are biased "hot" (more current than optimal), the amp might sound "better", but tube life will be reduced, sometimes dramatically. Biasing the tubes "cold" can preserve tube life, but can have some undesirable tonal consequences.

 

Since no two tube manufacturers follow the same spec, and even tubes of the same brand and model can be inconsistent..the optimal bias could change each time you change tubes.

 

It's recommended you bring it to a qualified amp tech, since biasing an amp requires measuring current flow inside the amp while it's powered on, which is extremely dangerous if you don't know what you're doing. 300V+ at a couple ampheres isn't fun...

 

-Ryan

 

Ryan is absolutely right. It is arguable that all valves should have bias set every time a valve is replaced. Need is a tricky word, fixed bias is OK but will generally be on the low side to avoid killing a weak valve.

 

Coincidentally, I've just posted in my build thread about my intention to fit trim pots in my amp for this very reason.

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Ryan is absolutely right. It is arguable that all valves should have bias set every time a valve is replaced.

 

Maybe I need to sell one of my fixed bias amps then to pay for re-biasing the others that have had the same resistor values in them for like 45 years. [scared]

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I forgot to add something important: always keep one hand free when working on a tube amplifier. If you complete the circuit the voltage can stop your heart.

 

Yup...preferably keep it behind your back or in your pocket. Electricity that can't find ground, can't hurt you.

 

And if ever opening up an amp, drain the filter caps first. An easy first step is to turn your amp on, plug in your guitar, start strumming the strings hard, and unplug the power cord of the amp, still strumming. The sound will gradually die...that's your filter caps draining.

 

At that point, there should only be about 20-30 volts left in those caps...much safer than 300V+.

 

Now you're going to need a few things...

 

A piece of wire, 22AWG minimum, about 12" long or so.

Two insulated alligator clips. The ones with the rubber/vinyl sleeves.

A 10 Ohm 1-watt or higher resistor (just to be safe).

 

Cut the piece of wire in the middle, solder the resistor between the two pieces, then heatshrink or electrical tape. Solder the alligator clips to each end.

 

Now the important part...clip one alligator clip to the chassis of the amp (this is your ground). Always connect ground before hot. Then, with one hand behind your back or in your pocket, clip the other alligator clip to Pin 1 of the first preamp tube.

 

Walk away for a few minutes, then come back and check each filter cap with a multimeter (ground probe to chassis first, hot probe to any pin of the cap).

 

You're probably safe under 10V, but I always let it drain down to 1-2V max before I start working...

 

Just thought that was some good information for those less experienced with working inside their tube amps...

 

-Ryan

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Oh... what the hell. Some may find humor in this...

 

When I was in the Navy... I was a Fire Controlman. Weapons Guidance. I worked on an old analog/digital gunfire control system, for the 5" gun (main battery).

 

The radar portion was digital, however the computer was an old analog giant, that worked on synchros and servos. The amp that ran huge motor/generators that moved the director (big box the radar was sitting on top of, it could be manned - by up to 3)... was in our regular workspace. It stood about 6' tall, 2 1/2' wide, 6 drawers, all holding a bunch of warm, glowing tubes.

 

We had this period, where everything was breaking. It was like we were jinxed. We'd fix one thing, another would break. We had a problem with the director drifting. If you had it in manual mode, it would drift to the right. If you were in auto and trying to track, it would pull off. We could not find the problem (and we never did... it just went away). We got to the point, we were actually testing the tube sockets themselves. Continuity, from one side of the socket, to the other. If you know electronics, you know how bad its got to be, when you're to that point.

 

So, by this time, we're all very frustrated... sitting in the Persian Gulf with a radar that won't track. I'm trying to explain to another tech, no experience with tubes... how you test a tube socket. Its actually very easy. You take a multimeter (oh yeah... did I mention NO POWER ANYWHERE CLOSE TO THE CIRCUIT?) and set it to diode mode put one lead on one side (you plug the tube into) and the other lead on the bottom side, where the connections are made. If your little meter makes that nice high pitched whistle, its good to go. Not enough resistance, to impede the circuit.

 

I'm trying to explain this, this guy isn't getting it. At this particular time, the amp was up, running and we had this one particular tube out, that to the positive side of the tube was +300 volts and of course was complemented with -300 on negative side. He's scratching his head. I grab the drawer, yank it out... and as I explain, I lift my arms up and with my index fingers pointed and moving towards that socket, said... "LOOK! I took a lead and put it HERE! and the I took the other and put it HEZZZAARGHARGHAMPLEARGH!" as I completed +300/-300 volts where a tube should be.

 

They had to kick me off it. Luckily, no permanent damage. I think.

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Yup...preferably keep it behind your back or in your pocket. Electricity that can't find ground, can't hurt you.

 

And if ever opening up an amp, drain the filter caps first. An easy first step is to turn your amp on, plug in your guitar, start strumming the strings hard, and unplug the power cord of the amp, still strumming. The sound will gradually die...that's your filter caps draining.

 

At that point, there should only be about 20-30 volts left in those caps...much safer than 300V+.

 

Now you're going to need a few things...

 

A piece of wire, 22AWG minimum, about 12" long or so.

Two insulated alligator clips. The ones with the rubber/vinyl sleeves.

A 10 Ohm 1-watt or higher resistor (just to be safe).

 

Cut the piece of wire in the middle, solder the resistor between the two pieces, then heatshrink or electrical tape. Solder the alligator clips to each end.

 

Now the important part...clip one alligator clip to the chassis of the amp (this is your ground). Always connect ground before hot. Then, with one hand behind your back or in your pocket, clip the other alligator clip to Pin 1 of the first preamp tube.

 

Walk away for a few minutes, then come back and check each filter cap with a multimeter (ground probe to chassis first, hot probe to any pin of the cap).

 

You're probably safe under 10V, but I always let it drain down to 1-2V max before I start working...

 

Just thought that was some good information for those less experienced with working inside their tube amps...

 

-Ryan

 

 

good information......you gotta be kidding me.....that was great, thank you so much......maybe with your help I can do this by myself......

 

I called Sam Ash (closest authorized tech) and they directed me to the shop that they would send it to...the shop is about 17 miles from my house and he wants $40.00 dollars to bias tube....

I would drop it off in the morning and pick it up late afternoon....because of the shops schedule I'll be driving 70 miles.....I asked him if I could wait when I called and got the "no sir"....

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Guest Farnsbarns

Maybe I need to sell one of my fixed bias amps then to pay for re-biasing the others that have had the same resistor values in them for like 45 years. [scared]

 

Possibly a tad extreme. I'm sure you could replace the relevant fixed resistors with variable ones and set it yourself if you were bothered by fixed bias enough to motivate you. Or you could leave it, of course. My post was intended to be technical, I said it was arguable that all valves should have the bias set, not that every fixed bias amp in the world should be modded post haste. :D

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Possibly a tad extreme. I'm sure you could replace the relevant fixed resistors with variable ones and set it yourself if you were bothered by fixed bias enough to motivate you. Or you could leave it, of course. My post was intended to be technical, I said it was arguable that all valves should have the bias set, not that every fixed bias amp in the world should be modded post haste. :D

 

Fair enough. But it sounds like my assumptions that "fixed bias" amps would be okay as long as similar spec tubes were used is at the very least questionable. If nothing else I'm going to use my bias probe to check my old Princetons. I see also that quite a few people make bias pot kits for them. Perhaps a wise investment.

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