Valve upgrade for original HT5-H

[Adam-T]

I`ve just picked up a used HT5-H head ... basically the HT5 Metal I had briefly (bought because it was the only game in town used HT5 Combo wise at the time) didn`t suit, the gain channel was way too gainy and ther clean channel didn`t have access to the tone shaping .. so as I`d got a cab with a V30 in, decided on a head to replace it

Anyway the old HT5 models (C and H without reverb) have full tone shaping on the clean channel and a bonus of the Drive/clean footswitch only requiring a keyboard sustain pedal (momentary latch) rather than a locking switch of the right polarity (woohoo) both being far bigger plusses than the digital reverb chip in the new models .

Anyway the Amp was made in 2009 and is running the original EH valves and it`s sounding rather unrefined - as in harsh midrange and lacking in top and bottom end compared to my HT1R or Laney CUB-10 despite neither of which having proper EQ (only the Cub`s treble cut and the 1R`s ISF) running through the same speaker (the V30) . I`ve searched again and I still can`t find a concensus as to the best valves to swap to .. so a pointer towards the magic forumula for this amp valve wise would be appreciated

BTW this has had a Preamp out socket fitted at some stage - I`ve not read about that mod on these forums, could this be an issue ? I`m adept at electronics so could remove it easily I`m sure

[Adam-T]

Opened the amp and The Pre-Out was taken straight off the speaker outs (where the OP-T connects to the jack board) divided down with resistors on the added on jack socket so I`ve removed it

[thephantum]

I'm not a fan of the EH 12BH7 currently being manufactured. I could get into all the technical reasons why as well as the testing I've done...but I'll just say that my own recommendation is to buy a NOS 12BH7 from a reputable dealer. You can usually pick up decent NOS 12BH7's for under $40 USD. Yea, that's about twice the cost of an EH...but it's going to sound 10x better. So it's well worth the extra money. Just make sure to get a good name brand, Sylvania, GE, etc. and bias the amp correctly (the HT5 like to be biased very warm to hot).

Also, I would change the preamp tube as well. I recommend either a Tungsol or a Mullard but, if your wallet can afford it, get a Genalex Gold Lion ECC83/B759. (make sure to get the B759 version, it is not the same as the plain Genalex ECC83). The only thing that will sound better are NOS 12AX7's that cost hundreds of dollars.

Personally, I'm running a 1957 Tungsol 12BH7 and a B759 in my HT5 and it sounds beyond fantastic.

[Adam-T]

Thanks -
I thought they were using TAD thesedays in HT5s, the Metal Combo had one in anyway, was hoping the OEM EH would be better .. I`ll check what NOS Valves I can get here , I`ll see If there are any GEs or mullards kicking about . Re the preamp - Tungsols are readily available here so thanks for that ..

I don`t know how "pre-out" mods are usually done on valve amps but I didn't like the look of taking the feed from where the Output-Transformer goes into the Jack panel and then using resistors on the extra jack socket to drop the level so removed it - tested that the amp is OK (and it is) and it may have been either my imagination or where the cab was but the thing sounded more open after .. Dunno

Pic of the Mod before I removed it, the added in socket on the left with the resistors on - the green wires running down to the Op-T connection

Blackstar-HT5H-i.JPG (80.51 KiB) Viewed 13806 times

[thephantum]

Yea, that mod was using the resistor as a power soak....but it looks like a total hack job.

Here's the thing, TAD is not a manufacturer of tubes. They just test and rebrand tubes (they sell a lot of other items as well). As far as I know, there are only two companies manufacturing new 12BH7's: EH and JJ (JJ calls their's an ECC99, but it's specs are almost identical).

So, TAD's are just one of those two brands that are tested for certain qualities. I personally believe they are JJ's but I have no direct evidence of that. However, shortly after JJ released the ECC99, TAD's showed up on the market with their 12BH7. Yea, that's very indirect and circumstantial....but I don't believe in coincidence.

To my ears, both the JJ and EH sound very similar...OK, but not great. When compared to a NOS 12BH7, well, there's no comparison...even just a decent NOS tube blows the new tubes away. Couple that with the high availability and (relatively) low cost of quality NOS 12BH7's, and it's really a no brainier...just go NOS.

It's very different from something like the 12AX7 market. Prices for decent NOS 12AX7's are in the stratosphere. Over the last decade or so, that's driven lots of competition among the tube manufacturers in Eastern Europe to develop better sounding 12AX7's. That in turn has driven Chinese manufactures to start raising their game as well.

[Adam-T]

The mod used resistors down to earth as well as in line , as you say a hack and instantly removed ..

I didn`t realise that EH actually made tubes (EH the maker of the famous Big-muff pedal at least) - I thought they were simply re-branding & selecting like GT or Ruby .. as for NOS, depends on the maker greatly surely, I`d have thought that just because something is new old stock doesn`t automatically make it good, there must have been crap / budget tubes back then too ? .. I`ll have to get a bias probe if I`m going to mess with the output valve,

the Preamp one being cathode baised won`t be an issue, that`ll need changing too and hopefully make the most difference . Tung Sols are easy to get here - I can get Brimar and Mazda (Both british made) at sensible prices in used vintage / NOS

[Adam-T]

Did some research and Electro-Harmonix is the same company (had to be really with that name) and is still a New york company which doesn't and never has manufactured Tubes - they just re-brand .. Which tubes they re-brand is another matter , probably why quality varies ..

Anyway I doubt 7yr old ones in a 5W amp are likely to be at their best .. Any Thoughts on Mazda UK made NOS for the Preamp ?

Thanks

[thephantum]

Some of the Mazda branded tubes can be gems, especially if it was truly made in the UK (it's probably a Mullard), Germany (RFT) or Holland (Phillips). So if it's authentic (which is always the trick) and the price is right, it might be worth a try.

As far as branding, yes and no. It's true that the brand names EH, Tungsol, Mullard, etc are all owned by a company called New Sensor Corp. However, those tubes all come from different manufacturers in Eastern Europe. So Tungsols come from one factory, Mullards from another, etc, etc. So, they are different tubes and each one has it's own distinctive sound.

I actually have a number of NOS 12AX7 tubes from the 70's. Mainly Sylvania's, Ratheons and TungSols. In my modern amps (more on that in a minute), most of the tubes coming out of New Sensor sound just as good (but no better). But get your hands on a vintage RCA or Mullard from the 50's and all bets are off. There's no comparison...you will pay for that though.

A lot of it has to do with the fact that these are modern amps that were made to work with modern tubes. So unless you get a really choice NOS tube, you are better off going with newly manufactured ones in a modern amp. The flip side of that argument is if you have an older, more vintage amp, it will respond much better to a mediocre NOS tube than a newly manufactured one.

The difference with the HT5 is that it uses a 12BH7. Like I stated before, the NOS market there hasn't reached a saturation point yet, so quality NOS tubes are still available at decent prices. So new tubes are only being manufactured to the bare minimum of the specs.

[Adam-T]

Got that, thanks ...... the Mazdas carry the BVA markings which means the UK Blackburn factory (mullard) if I`m right, they do say made in England on them and they look like they`ve been around for a while (not crisp fresh lettering etc) , was thinking of getting one for the HT1`s preamp as well, the preamp ones are supposed to make the most difference (though the HT1 uses a preamp valve for the output as well only a less gainy one, an ECC82, both are cathode baised) . I`ll not mess with the power valve in the HT5 until I get a bias probe.

I don`t know who New Sensor Corp are but the EH name is owned by EH the pedal manufacturer in New York ..

[Adam-T]

Pics of the Mazdas - I quickly and crudely made one pic from two