Blackstar HT-5 Tube Swap

Discussion - HT-5 amplifiers.
User avatar
Posts: 1
Joined: Sun Jun 23, 2013 11:49 pm

Wed Jul 31, 2013 12:02 am

I had a HT5. But I sent it back because I can't justify it and the HT-20. But while I had it I noticed RCA gray plates are a much better tube than the New Tung-Sol 12BH7As. There was a big difference in smoothness and harmonic content. I also have some black plate Tung-Sol, RCA and Raytheon 12BH7As. To me the difference between gray and black plates is minimal. They are better and smoother, but only in a minor way.

If you're looking for tubes, radiotinkerer on ebay is a great guy and I recommend him.. He gets $13.95 for NOS gray plates and he has some red and white box as well as red and black box RCAs! The price includes shipping for CONUS. radiotinkerer is NOT me and I am not associated with him in any way. Just sharing my experiences with him.

Posts: 5
Joined: Sun Apr 21, 2013 2:03 pm

Sun Apr 13, 2014 12:29 pm


I've been playing my HT-5 for 3 years now and I was wondering if the sound had deteriorated over time. So I did a tube swap and I figured I'd share my findings.

I recorded some samples into a RC-3 pedal, some clean parts, chords, distorted riffs and palm muting. Then played them back and recorded it all with a SM-57 mic, before and after the change.

The stock tubes in my HT-5 combo were:
preamp: 7025/12AX7WA SOVTEK
poweramp: TAD 12BH7A-STR Selected

I swapped them with:
preamp: TAD 7025 E83CC Highgrade
poweramp: TAD 12BH7A-STR Selected (exact same type)

So now I've been comparing the recordings, and it's hard to hear any difference in sound at all. Perhaps it's a tad bit brighter now, but that may just be the power tube new-ness. But essentially, the amp sounds almost exactly the same as before. Of course different tubes can have different results I guess.

I'm happy I tried this at least and for me it's a comforting thought that the tubes don't seem to go "bad" after some years. :)

Posts: 9
Joined: Tue May 06, 2014 11:22 pm
Location: United Kingdom

Sat Jun 07, 2014 10:52 pm

I received my spare valves this morning; I'd ordered a 12AT7 and a 12AY7 from Voc-Rock on eBay. I put the 12AT7 in which has a mu of 60 compared to the standard 12AX7 (mu 100) and supposedly a higher bandwidth from the data sheets I've found.

In short it's a revelation for me: That abrupt jump from virtually silent to almost full saturation when using the gain control on the dirty channel is now much more linear. I can dial in a clear clean tone with the gain down low and then use the EQ and ISF to tweak it. Much more flexible than the single 'tone' control on the clean channel. Of course it's reduced the output on the clean channel, but it's still loud enough for home playing or recording and a boost pedal would make it back up anyway if I wanted to. There is much more control over setting a sound just on the edge of break up too. Works well with my Tele and LP (looking forward to trying my Strat through it when I get it back from being refinished).

I haven't tried the even lower gain 12AY7 yet, but I suspect it might be too low for my tastes, but it was only £10 and I have another valve based project that I may use it for anyway.

It's been a long time since I played through one, but I think it's now more like the sound I got from an older master volume Marshall amp, ie brighter and less full on saturation. However, the saturation is still available it just comes in much further round the gain control than before.

User avatar
Posts: 601
Joined: Thu Feb 24, 2011 1:00 am

Mon Jun 09, 2014 4:38 am

Try the 12AY7, you might be surprised by the tonal differences. I like it in my HT20.

Posts: 9
Joined: Tue May 06, 2014 11:22 pm
Location: United Kingdom

Tue Jun 10, 2014 10:35 pm

Yes, the 12AY7 is next...Not very rock n roll but I trapped a nerve in my back last week so I'm a bit limited about lifting the amp or even getting down on the floor to open it up again. On the mend a bit now, so it's my next job I think.

I was advised on another forum that the 12AT7 takes more current than the original 12AX7 or the 12AY7. I know there seem to be plenty of users with the 12AT7 in their Blackstars amps though, so I guess it's OK, but it would be a useful benefit if the AY7 sounds as good/better.

Posts: 25
Joined: Wed Apr 10, 2013 2:26 am

Wed Jun 11, 2014 7:07 pm

I actually liked the 12AU7 (the lowest gain).. it made the Ht5 much more of a classic rock, 70s, early 80s sound.

Posts: 9
Joined: Tue May 06, 2014 11:22 pm
Location: United Kingdom

Tue Jun 17, 2014 11:27 pm

I put the 12AY7 in it tonight (mu 45 verses 100 for the original). It's given real control over the gain on the dirty channel, now goes completely clean at the low end adding small amounts of dirt until about 12-1 o'clock where it starts to really saturate. Along with a 4 way switch mod on my Telecaster gives me some useful tone choices from clean through to dirty. The addition of a Tube Screamer adds an extra layer too; tone bliss (for now :twisted: ).

Posts: 7
Joined: Sun Jun 29, 2014 5:57 am

Tue Jul 01, 2014 3:55 pm

After having played through my HT5C for a few months I was not crazy about the heavy gain that others have stated. The stock preamp tube saturated quickly and did have some hiss at higher volumes.

I have a first edition PRS SE Santana and old USA Peavey Predator with Seymour Duncan pickups. I had tried a set of Seymour 1959 PAF SH-1's in the PRS but noticed very little change in the sound with humbuckers. Put the stock humbuckers back in the PRS and the tone was very similar. The single coils on the other hand sounded great with the stock tube. But the sound was still "dark" to my ears. Hendrix and Trower just sounded a bit off, too heavy.

I put in a Groove Tube 12AX7-C and the difference was quite noticeable. This tube cut the overall volume quite a bit. The clean channel was far more usable to almost max volume while remaining pretty darn clean. The gain was now more linear and did not over saturate. The humbuckers now sound much brighter as well as the single coils. This was good for the humbuckers but I liked the tone of the single coils with the stock tube a bit better.

Then I put in a JJ 12AX7/ECC83 S preamp tube. There is no noticeable volume loss and the tone is still brighter than the stock tube but not as bright as the Groove Tube. Liked the tone better for the humbuckers and single coil pickups. The clean channel is also very usable to nearly full volume and the gain does not overly saturate and is also very linear, with almost a clean sound with low gain settings.

To my ear and genre of music the JJ sounds great, no more of the dark tone.

Another tone experiment should arrive today, a 30 watt 12" 16ohm WGS Reaper 75Hz.

Posts: 2
Joined: Sun Sep 14, 2014 4:42 am
Location: Louisville, Kentucky

Sun Sep 14, 2014 4:48 am

I have an HT5TH anniversary 2x10 and I swapped in a tung sol gold pin 12ax7 and it woke my amp up.
On the USA side of the isf it sounds like a killer jcm 800 now. I love this little amp!

Posts: 4
Joined: Wed Nov 19, 2014 12:10 pm

Thu Nov 20, 2014 4:00 am

Hi ... Just got to swap out the year old preamp and power amp tubes to a brand new EH 12ax7 and a EH 12bh7 ... I'm getting a real red grow on the power tube ? Not funny because its burning up some rubber on the rubber ring ...

Replaced the older tubes TAD 12ax7 and 12bh7A back and have a voltage at 311mvdc across R33.

The new tubes had a voltage of 312mvdc ... WoW super high ... did I measure across the wrong resistors with this version of PCA ?

After hours and hours of facts finding on the web ... BS have stated a 46mvdc across R33.

Turn the BIAS voltage all the way anti clockwise and its still growing red hot and voltage is at 286mvdc at R33.

PCA board version is : Blackstar HTRC , 07-03-11 , ISS 1

Checked all components .... no burnt sign (even infamous burning R39)

Is this even normal ?

Any help appreciated ....

Thanks in advance .... 8-)

Billy T.

Post Reply
  • Information
  • Who is online

    Users browsing this forum: No registered users and 35 guests