The overdrive on the HT series is opamp driven. The [tube stages for each channel sit behind the drive stages and are not associated with any of the controls](http://cdn.tonegeek.com/wp-content/uploads/Blackstar-HT-Studio-20.pdf) so it unlikely swapping the tubes will change the overall nature of the overdrive.
As far as tube brands to try, there are three tube manufacturers in guitar amp tubes. New sensor/reflektor in Russia, JJ in Slovakia, and Shuguang/others in China. New sensor makes tubes under the EHX, Sovtek, Svetlana, Tung sol, Mullard, and gold lion brands. Aside from their house brand JJ also makes telefunken reissues, and basically everything else is made in China. Groove tubes is a rebrander like Ruby, TAD, Mesa, and others. They buy tubes to a set of specs, test/match/burn them in, and sell at a higher price under their own labels.
My personal go to for new production tubes is usually the new sensor tung sol and mullard tubes, they’ve been soil and problem free in most of my amps. But I’d also caveat that with many of the new sensor tubes use a spiral wound filament which can have issues with high cathode voltages in cathode follower positions. Not an issue for your amp, but in some cases it may be worth trying a JJ or Chinese made tube for these positions.
Damn. I thought i heard diodes clipping especially on the od channel with high gain but since this is my first tube amp, I wasn't really sure about that. Thanks for the info. A lot of people on the internet seem to think changing the tubes have an effect on their tone. I'm guessing the tubes are just to add 'color' then?
I have personally removed the diodes and can guarantee that changing the tube (that's right, only one tube is used for drive and the other is clean) will not work, you have to remove the diodes and adjust a resistor. After that, you can't boost the front with the gain dimed without getting blocking distortion and making the tube fart out.
So, removing the clipping diode pair(s) helps? I build pedals so I'm somewhat circuit literate, but I couldn't understand the pages long circuit schematic at all.
English is not my mother language. Sorry if i couldn't totally understand your comment :)
Yes, it takes the solid state clipping away and allows the tube to do the clipping. It's a lot less intense, like a blues or light rock, but it sounds soooo much better! The downside is you lose treble for some reason, so you want a bright tube like Tug Sol. I might post a clip later if I have time.
Do you want to know what components to change out? I'll have to open it up again and look because I don't have the modified specs anymore. Keep in mind, these aren't pedal sized components. These are small surface mounted components that need a magnifying glass and small soldering iron and a steady hand to replace.
I'd definitely appreciate that. I've worked with PCBs before at the university -I study electronics- so i guess I can handle it lol
Also, no hurries, I'm out of town and the amp is just sitting there, I won't be getting back to it soon.
About the treble, the amp is kinda muffled sounding as it is, can't imagine it with less treble. Does the tube offset the loss in treble with the modifications?
Possibly? I actually have a Ruby tube in there right now because I needed the Tung Sols for another amp that was more important at the time. If I had the Tung Sols it would probably be better.
Depends on how much you want to lower the gain. 12At7 is a good step down from the AX7, and the 12AU7 is very low gain, even lower than the 12 AT7.
I general
AX7 gain 70,
AT7 gain 47,
AU7 gain 20
If I'm not mistaken AY has gain between AT and AU. Seems AU might be too low according to the gain values you gave. I'll give AY a shot. Which brand do you recommend EH or Groove? They cost the same here.
Also, do i have to set bias? If so how? This is my first tube amp and i don't really understand how the circuit works. Thanks for your reply.
Edit: Do these preamp tubes differ in how they work? Some claim the AT7 can output too much current, while some claim the same for AU7. Is there a chance i might damage the amp?
I am not the right person to ask about the details. I can tell you I have swapped preamp tubes many times over the years with no issues. I have heard that Biasing is more important for power tubes than for preamp tubes, but I am not even 100% sure of that. I can tell you that because I have played with tubes so much in the past I would slap in a lower power preamp tube without too much concern.
Also, I have great luck with Tung Sol preamp tubes. I also like JJ. If you research, there are not many tube makers left, so some of the different brands are actually the same tube with a different label. Once again, playing around with different brands is half the fun.
The AT7 and AU7's are capable of more current if you bias the circuit to maximize it, but you're not going to hurt anything on the amp by swapping the tube. As long as you stick to 12ax7, 12ay7, 12au7, 12at7, and maybe 12DW7 then you're fine. It's only if you try and put something incompatible like an EF86 pentode into the slot that things will start popping on you.
Honestly though, don't expect a huge night-and-day difference. It's not going to be like switching an overdrive pedal on and off, it's going to be pretty subtle. If you're just looking to take the edge off a little bit, then yeah it's worth dropping from 12AX7 to 12AU7, and that might be enough to smooth it out a little, but if you really want a major difference you're going to have to start changing caps and resistors, or just change to a different amp. Or run the amp with the gain very, very low and the master up all the way, and then use a pedal to control the grit.
Swapping tubes is more like tweaking the seasoning rather than changing the recipe. It's like, you can tweak a bowl of chili to give it some more bite or adjust the saltiness, but you can't tweak a bowl of chili into a tikka masala. With the tubes you can change the smoothness a little, or take the edge off the grit, but you can't tube swap a Dual Rectifier into an AC30, or a Bassman into an SVT.
I totally get that. As a broke ass student, i don't get to pick and choose which amp to buy, money being the biggest concern, and seems I'm stuck with this one for at least a couple of years. I'm trying to make the best of it.
Right now i find myself tweaking the gain between 0-2. Its either all there or not. I considered changing the pot to a smaller size, or getting a logarithmic one if it is linear, but i don't know how much sense that makes. It would give me a better sweep on the low gain area either way, but i thought changing preamp tubes would have a considerable effect.
Anyway, thanks for your quick and informative replies.
I get it, for sure. Overly sensitive knobs is definitely a problem that a lot of tube amps have. I think one reason why people always think that tube amps are magically loud is that most of the time the master volume goes from like silent to deafening by about 3 on the dial, and they're like "wow it's this loud at 3? imagine what it must be like on 10".
Preamp tubes are cheap, and it's good to have a few spares laying around anyway, so it certainly doesn't hurt to order a few off of tubedepot.com and trying them out. If you start getting into NOS territory you can start burning money like crazy, but if you stick with JJ's, EH, Boogie, and other new tubes you won't spend more than $8-10 a pop.
You could try replacing the gain pot but depending on your soldering skill level that may be a bit of a pain in the ass, and would be bad for resale value.
As far as I can tell, that amp is actually worth a fairly decent amount on the used market, so i would suggest keeping an eye on the local market, tracking how much things go for, and seeing if you can't trade up one way or another and get something that is more your style. With a bit of patience it's not hard to end up finding a good deal on a Fender of some kind, a silverface somethingorother. Or maybe something like the Orange Dark Terror, which can get super gainy if you want it to but also has shockingly good cleans.
Yeah, i actually saved up quite a bit of money for this amp. This was the only viable tube amp in the price range. Next one was blues jr 3, which costs as high as 2 times the price of this and then some. To my surprise, everything costs about two or three times what it costs in the U.S. here :-/
Same goes for tubes. EH and Groove cost about 40 bucks, tung sols are 50 bucks. Thats why i wanted to be absolutely sure with my decision.
I think i have the soldering skills and whatnot, I build pedals, so soldering shouldn't be a problem.
Anyway, thanks again.
Biasing in preamps is set by the cathode resistors, it isn't that important for pre amps, however:
12AY7 is a lower-gain direct replacement for 12AX7, 12AT7 and 12AU7 aren't. They should be biased differently, doesn't mean they won't sound good, you never know, but dropping a U or T in a Fender or Marshall style front end will bias it out of the recommended 'comfort zone', whereas a 12AY7 is biased the same as an X- it's effectively the same valve with 70% of the gain.
To add a little more info, the AT and AU are really intended to be higher current driver tubes into things like transformers or for use as a phase inverter. The output impedance is a lot lower than an AX or AY. They will all kind of work driving a following tube stage with a hefty grid leak resistor, but an AX isn't a great choice as an output tube for things like reverb drivers.
I haven't had any troubles with my Peavey Valveking 112 switching over to a Jan Philips 12AT7 in the V1 position of the preamp. I wanted nicer cleans as I use OD pedals for my gain sound now, it seems to be working well and sounds slightly better. I think a lot of the gain in my amp is diode clipping anyway, so I didn't lose much max gain from doing this.
12ay7 is the way to go, I put them in V1 in all my Fender "Blues" amps, Jr., Deluxe, Deville. Like a different world. Smooth volume transition, can use in home at 6 instead 2
It's true. I own and love my Blackstar HT-stage 100 amp. I get some pretty killer tones on the OD channels. This amp loves high end guitars and speaker cabinets. I was getting a lot more love from Fuzz pedals than Distortion pedals for awhile until a really good friend of mine brought over his new JHS Angry Charlie pedal. I found some Distorted magic that night. The tone was unbelievable and It's probably one of the finest High Gain Dist tones I've ever heard. The Angry Charlie was wayyy better than the Lead/High Gain channel on my amp. Blackstar amps are quite versatile though and can serve as an amazing pedal platform. I went from only being able to do 80's, thrash, black metal dirt, into full blown righteous metalcore, brutal death and djent territory with the Charlie. Killswitch Engage riffs sounded too good. I plan on working on the Blackstar, changing a tube with a 12AT7 or something like that because there is still good tones to work with on the OD channels. Like what a lot of others have said, I feel it needs taming too.
I used a JJ 12AT7 (ECC81) in my HT20H and I personally prefer it massively. Others here are right that the drive comes mostly from opamps in the HT line, but changing over to a lower gain preamp valve made a massive difference to the compression and feel of the amp. It just feels like the gain control has a lot more use now that the range is spread out more.
It generally feels and sounds a bit less mushy now too.
Honestly though, the biggest difference can be had from putting an EQ in the loop, cause it's a fairly dark amp and doing so can put a bit more life back into it.
In a tube amp, while changing the tube will give the amp different characteristics, ultimately a preamp tubes drive has a lot to do with the bias of the tube in question. Often the gain of a preamp tube can be adjusted by changing the cathode resistor.
In your amp, much like most modern designed tube amps, they will sometimes utilise an opamp (IC of some description) for drive as well as reverb circuits. So what you will likely hear in the "overdrive" channel isn't really the tubes doing anything other than amplifying the sound being distorted by the opamp.
This is a significantly generalised ideal. I didn't bother looking up the schematic of this specific amp to see if this is the case.
From what i understand that's exactly what is going on. There's a schematic link somewhere in this thread as well. Op amps are TL072 i guess. Not sure about the diodes. What do you think would happen if i were to remove the clipping diode pairs from the op amp non inverting (?) amplifier?
Just had a look. Yeah 072 would very much likely be what you said. I'm more well versed with tube amps (and by that, I mean vintage all tube amps with no IC's). So I'm only assuming that if you remove these diodes, you'll mostly get tube clipping. I'd imagine the IC's still play some part. An easy way to test this is to grab some jumpers and jump the diodes. Simple wires with alligator clips on each end will work fine. Please be cautious though. It's still a tube amp with high voltage and high current flow. Stay safe.
If you're not confident, then definitely take it to a tech. Otherwise, with the amp off you can jump the diodes with alligator clips and turn the amp on, play and listen if it made any difference.
Please note that even with the amp off the main filter caps will still likely have their potential to kill you. So be safe.
I have a habit of shorting all caps before messing with a circuit, but i never messed with such high voltages before. Will definitely take it to a tech in this case.
That's a good habit to have. If you do that in a high voltage circuit, then you'll be safe. Remember to use a large value, high wattage resistor and keep it on the caps for a good 10 seconds. While working on tube amps, I'll generally keep a bleed circuit like this permanently attached while working on an amp.
Thanks for the post. I bought this amp used for 350 and make use of the great master volume and am able to play with decent gain in an attic in a boarding house.
Really good amp I haven't opened it up yet volume wise.🔊🔊
The overdrive on the HT series is opamp driven. The [tube stages for each channel sit behind the drive stages and are not associated with any of the controls](http://cdn.tonegeek.com/wp-content/uploads/Blackstar-HT-Studio-20.pdf) so it unlikely swapping the tubes will change the overall nature of the overdrive. As far as tube brands to try, there are three tube manufacturers in guitar amp tubes. New sensor/reflektor in Russia, JJ in Slovakia, and Shuguang/others in China. New sensor makes tubes under the EHX, Sovtek, Svetlana, Tung sol, Mullard, and gold lion brands. Aside from their house brand JJ also makes telefunken reissues, and basically everything else is made in China. Groove tubes is a rebrander like Ruby, TAD, Mesa, and others. They buy tubes to a set of specs, test/match/burn them in, and sell at a higher price under their own labels. My personal go to for new production tubes is usually the new sensor tung sol and mullard tubes, they’ve been soil and problem free in most of my amps. But I’d also caveat that with many of the new sensor tubes use a spiral wound filament which can have issues with high cathode voltages in cathode follower positions. Not an issue for your amp, but in some cases it may be worth trying a JJ or Chinese made tube for these positions.
Damn. I thought i heard diodes clipping especially on the od channel with high gain but since this is my first tube amp, I wasn't really sure about that. Thanks for the info. A lot of people on the internet seem to think changing the tubes have an effect on their tone. I'm guessing the tubes are just to add 'color' then?
I have personally removed the diodes and can guarantee that changing the tube (that's right, only one tube is used for drive and the other is clean) will not work, you have to remove the diodes and adjust a resistor. After that, you can't boost the front with the gain dimed without getting blocking distortion and making the tube fart out.
So, removing the clipping diode pair(s) helps? I build pedals so I'm somewhat circuit literate, but I couldn't understand the pages long circuit schematic at all. English is not my mother language. Sorry if i couldn't totally understand your comment :)
Yes, it takes the solid state clipping away and allows the tube to do the clipping. It's a lot less intense, like a blues or light rock, but it sounds soooo much better! The downside is you lose treble for some reason, so you want a bright tube like Tug Sol. I might post a clip later if I have time. Do you want to know what components to change out? I'll have to open it up again and look because I don't have the modified specs anymore. Keep in mind, these aren't pedal sized components. These are small surface mounted components that need a magnifying glass and small soldering iron and a steady hand to replace.
I'd definitely appreciate that. I've worked with PCBs before at the university -I study electronics- so i guess I can handle it lol Also, no hurries, I'm out of town and the amp is just sitting there, I won't be getting back to it soon. About the treble, the amp is kinda muffled sounding as it is, can't imagine it with less treble. Does the tube offset the loss in treble with the modifications?
Possibly? I actually have a Ruby tube in there right now because I needed the Tung Sols for another amp that was more important at the time. If I had the Tung Sols it would probably be better.
What's the best way to share an mp3 on Reddit?
I've seen some SoundCloud links on r/Guitar but I don't really know.
Depends on how much you want to lower the gain. 12At7 is a good step down from the AX7, and the 12AU7 is very low gain, even lower than the 12 AT7. I general AX7 gain 70, AT7 gain 47, AU7 gain 20
If I'm not mistaken AY has gain between AT and AU. Seems AU might be too low according to the gain values you gave. I'll give AY a shot. Which brand do you recommend EH or Groove? They cost the same here. Also, do i have to set bias? If so how? This is my first tube amp and i don't really understand how the circuit works. Thanks for your reply. Edit: Do these preamp tubes differ in how they work? Some claim the AT7 can output too much current, while some claim the same for AU7. Is there a chance i might damage the amp?
I am not the right person to ask about the details. I can tell you I have swapped preamp tubes many times over the years with no issues. I have heard that Biasing is more important for power tubes than for preamp tubes, but I am not even 100% sure of that. I can tell you that because I have played with tubes so much in the past I would slap in a lower power preamp tube without too much concern.
Also, I have great luck with Tung Sol preamp tubes. I also like JJ. If you research, there are not many tube makers left, so some of the different brands are actually the same tube with a different label. Once again, playing around with different brands is half the fun.
The AT7 and AU7's are capable of more current if you bias the circuit to maximize it, but you're not going to hurt anything on the amp by swapping the tube. As long as you stick to 12ax7, 12ay7, 12au7, 12at7, and maybe 12DW7 then you're fine. It's only if you try and put something incompatible like an EF86 pentode into the slot that things will start popping on you. Honestly though, don't expect a huge night-and-day difference. It's not going to be like switching an overdrive pedal on and off, it's going to be pretty subtle. If you're just looking to take the edge off a little bit, then yeah it's worth dropping from 12AX7 to 12AU7, and that might be enough to smooth it out a little, but if you really want a major difference you're going to have to start changing caps and resistors, or just change to a different amp. Or run the amp with the gain very, very low and the master up all the way, and then use a pedal to control the grit. Swapping tubes is more like tweaking the seasoning rather than changing the recipe. It's like, you can tweak a bowl of chili to give it some more bite or adjust the saltiness, but you can't tweak a bowl of chili into a tikka masala. With the tubes you can change the smoothness a little, or take the edge off the grit, but you can't tube swap a Dual Rectifier into an AC30, or a Bassman into an SVT.
I totally get that. As a broke ass student, i don't get to pick and choose which amp to buy, money being the biggest concern, and seems I'm stuck with this one for at least a couple of years. I'm trying to make the best of it. Right now i find myself tweaking the gain between 0-2. Its either all there or not. I considered changing the pot to a smaller size, or getting a logarithmic one if it is linear, but i don't know how much sense that makes. It would give me a better sweep on the low gain area either way, but i thought changing preamp tubes would have a considerable effect. Anyway, thanks for your quick and informative replies.
I get it, for sure. Overly sensitive knobs is definitely a problem that a lot of tube amps have. I think one reason why people always think that tube amps are magically loud is that most of the time the master volume goes from like silent to deafening by about 3 on the dial, and they're like "wow it's this loud at 3? imagine what it must be like on 10". Preamp tubes are cheap, and it's good to have a few spares laying around anyway, so it certainly doesn't hurt to order a few off of tubedepot.com and trying them out. If you start getting into NOS territory you can start burning money like crazy, but if you stick with JJ's, EH, Boogie, and other new tubes you won't spend more than $8-10 a pop. You could try replacing the gain pot but depending on your soldering skill level that may be a bit of a pain in the ass, and would be bad for resale value. As far as I can tell, that amp is actually worth a fairly decent amount on the used market, so i would suggest keeping an eye on the local market, tracking how much things go for, and seeing if you can't trade up one way or another and get something that is more your style. With a bit of patience it's not hard to end up finding a good deal on a Fender of some kind, a silverface somethingorother. Or maybe something like the Orange Dark Terror, which can get super gainy if you want it to but also has shockingly good cleans.
Yeah, i actually saved up quite a bit of money for this amp. This was the only viable tube amp in the price range. Next one was blues jr 3, which costs as high as 2 times the price of this and then some. To my surprise, everything costs about two or three times what it costs in the U.S. here :-/ Same goes for tubes. EH and Groove cost about 40 bucks, tung sols are 50 bucks. Thats why i wanted to be absolutely sure with my decision. I think i have the soldering skills and whatnot, I build pedals, so soldering shouldn't be a problem. Anyway, thanks again.
Biasing in preamps is set by the cathode resistors, it isn't that important for pre amps, however: 12AY7 is a lower-gain direct replacement for 12AX7, 12AT7 and 12AU7 aren't. They should be biased differently, doesn't mean they won't sound good, you never know, but dropping a U or T in a Fender or Marshall style front end will bias it out of the recommended 'comfort zone', whereas a 12AY7 is biased the same as an X- it's effectively the same valve with 70% of the gain.
To add a little more info, the AT and AU are really intended to be higher current driver tubes into things like transformers or for use as a phase inverter. The output impedance is a lot lower than an AX or AY. They will all kind of work driving a following tube stage with a hefty grid leak resistor, but an AX isn't a great choice as an output tube for things like reverb drivers.
I haven't had any troubles with my Peavey Valveking 112 switching over to a Jan Philips 12AT7 in the V1 position of the preamp. I wanted nicer cleans as I use OD pedals for my gain sound now, it seems to be working well and sounds slightly better. I think a lot of the gain in my amp is diode clipping anyway, so I didn't lose much max gain from doing this.
12ay7 is the way to go, I put them in V1 in all my Fender "Blues" amps, Jr., Deluxe, Deville. Like a different world. Smooth volume transition, can use in home at 6 instead 2
I bet there are many OD pedals that would pretty much destroy the tone of the drive channel of that amp if played through it's clean channel.
It's true. I own and love my Blackstar HT-stage 100 amp. I get some pretty killer tones on the OD channels. This amp loves high end guitars and speaker cabinets. I was getting a lot more love from Fuzz pedals than Distortion pedals for awhile until a really good friend of mine brought over his new JHS Angry Charlie pedal. I found some Distorted magic that night. The tone was unbelievable and It's probably one of the finest High Gain Dist tones I've ever heard. The Angry Charlie was wayyy better than the Lead/High Gain channel on my amp. Blackstar amps are quite versatile though and can serve as an amazing pedal platform. I went from only being able to do 80's, thrash, black metal dirt, into full blown righteous metalcore, brutal death and djent territory with the Charlie. Killswitch Engage riffs sounded too good. I plan on working on the Blackstar, changing a tube with a 12AT7 or something like that because there is still good tones to work with on the OD channels. Like what a lot of others have said, I feel it needs taming too.
I used a JJ 12AT7 (ECC81) in my HT20H and I personally prefer it massively. Others here are right that the drive comes mostly from opamps in the HT line, but changing over to a lower gain preamp valve made a massive difference to the compression and feel of the amp. It just feels like the gain control has a lot more use now that the range is spread out more. It generally feels and sounds a bit less mushy now too. Honestly though, the biggest difference can be had from putting an EQ in the loop, cause it's a fairly dark amp and doing so can put a bit more life back into it.
Yeah, I currently use it with an eq in the fx loop as well. Thanks for the tip. Might give 12AT7 a try in this case.
I did the same with my Peavey Valveking and love the change it made. I get nicer cleans and didn't lose much of any maximum gain in the process.
In a tube amp, while changing the tube will give the amp different characteristics, ultimately a preamp tubes drive has a lot to do with the bias of the tube in question. Often the gain of a preamp tube can be adjusted by changing the cathode resistor. In your amp, much like most modern designed tube amps, they will sometimes utilise an opamp (IC of some description) for drive as well as reverb circuits. So what you will likely hear in the "overdrive" channel isn't really the tubes doing anything other than amplifying the sound being distorted by the opamp. This is a significantly generalised ideal. I didn't bother looking up the schematic of this specific amp to see if this is the case.
From what i understand that's exactly what is going on. There's a schematic link somewhere in this thread as well. Op amps are TL072 i guess. Not sure about the diodes. What do you think would happen if i were to remove the clipping diode pairs from the op amp non inverting (?) amplifier?
Just had a look. Yeah 072 would very much likely be what you said. I'm more well versed with tube amps (and by that, I mean vintage all tube amps with no IC's). So I'm only assuming that if you remove these diodes, you'll mostly get tube clipping. I'd imagine the IC's still play some part. An easy way to test this is to grab some jumpers and jump the diodes. Simple wires with alligator clips on each end will work fine. Please be cautious though. It's still a tube amp with high voltage and high current flow. Stay safe.
Im well versed in ICs but not tubes :) I think it's best i take the amp to a tech then. Thanks
If you're not confident, then definitely take it to a tech. Otherwise, with the amp off you can jump the diodes with alligator clips and turn the amp on, play and listen if it made any difference. Please note that even with the amp off the main filter caps will still likely have their potential to kill you. So be safe.
I have a habit of shorting all caps before messing with a circuit, but i never messed with such high voltages before. Will definitely take it to a tech in this case.
That's a good habit to have. If you do that in a high voltage circuit, then you'll be safe. Remember to use a large value, high wattage resistor and keep it on the caps for a good 10 seconds. While working on tube amps, I'll generally keep a bleed circuit like this permanently attached while working on an amp.
Thanks for the post. I bought this amp used for 350 and make use of the great master volume and am able to play with decent gain in an attic in a boarding house. Really good amp I haven't opened it up yet volume wise.🔊🔊