GCKelloch wrote: ↑Sun May 22, 2022 8:15 amef37a wrote: ↑Sat May 21, 2022 10:55 amGCKelloch wrote: ↑Sat May 21, 2022 5:31 amef37a wrote: ↑Wed May 18, 2022 10:45 am I think it is obvious that much will be made of the lightness in terms of all your poor old backs (mine is 76.5 and painful) but making a product that will ship all over the world half the weight of almost all other valve* 50 watters has 'green' credentials as well. There is also surely some saving on Copper?
Also very important I think is the universal mains capability. The debate has raged forever whether amps should just be made for intended destination voltage or have traff taps. The latter adds a cost that is very rarely useful (you watch!) and often they get it a bit wrong 'over there'!
*I have heard, but not had it confirmed, that the amp uses an op amp to get the first stage gain. I do hop we will not go down that daft "not a valve amp" rabbit hole again?
I remember reading that the phase inverter is the Op-amp. Would have been better if it was the first gain stage because that isn't driven hard enough to compress or generate distortion anyway, so it would hardly matter if it is a tube or not. I guess they wanted to have an extra tube stage for high gain sounds. I suppose they apply more high end filtering on the phase inverter op-amp so it's not harsh. Blackstar amps do tend to be a bit dark sounding.
Where, did you read that GC?
Since you need in excess of 130V peak to peak to drive a 25W OP valve into distortion I very much doubt that the PI is an op amp? It is true that the HT series uses a MOSFET LTP PI and that has been criticised, quite unfairly IMO.
The most common valve PI is the cathode coupled LTP and this has massive headroom since half of it is a cathode follower. Consequently it is hardly ever driven into distortion even when seriously hammering the OP valves. The MOSFET circuit is similarly very clean and transparent. (the Series Ones use the circuit but with additions I shall not reveal here).
An op amp front end though makes a deal of sense. Valves hum, hiss and are microphonic and I found it increasingly hard to select good ones for the first stages of the Artisan amps (out of 50 ECC83s I would get perhaps ten good ones). Op amps, even the venerable TL072 have less noise, zero hum (if you get the supply clean!) use far less power, cost SIGNIFICANTLY less (how important is that now?!) have zero microphony, and almost never fail.
They also have at least as high an input headroom as a triode and as said, the first valve stage in an amp cannot usually be driven into distortion by a guitar. There are now even better jfet op amps than the 72 and I bet Blackstar are using one!
What's not to like?
I don't remember the details of where, but I think it was indeed about the HT series. I confused the MOSFET for an Op-Amp. I don't know that much about electronics, but I knew it was some type of SS component. I also read recently that MOSFET's have a smoother S-curve than ECC83's. I see no reason to think these new amps are an entirely different design. Perhaps all the preamp overdrive comes b4 the MOSFET, but I have also heard that most distortion in a Plexi comes from the PI tube. So couldn't the MOSFET be used as an overdrive stage as well?
I recently watched a YT video demo wherein the reviewer showed how cranking the Master vs pre Gain knob yields a substantially brighter sound -- opposite the case with most guitar amps. Perhaps the Master volume is situated post MOSFET PI, and the brightness is then coming from the less-driven preamp tube stages combined with the brightness of the overdriven 6L6GC's? The MOSFET may well generate lower harmonics when driven, yet not compress, and the overdriven preamp section then reduces the high end, yielding the final darker/fatter sound? Interesting approach. My only concern is if something breaks.
Some Blackstar owners report that they can not a find techs to fix them, but that's also true of other PCB amps. Is it really worth ~5x the price of a 60W Line 6 Catalyst considering how Line 6 recently eliminated the digital aliasing issue, and that there are multiple great sounding amps that include response tuning parameters? It may also break and can't be fixed, but you'll only be out ~$300. One could buy two and replace any broken ones to always have a backup. Might be ~$300 every ~5 years.
Replace the speaker if you want a personalized stage tone. The stock speaker does sound a bit midrangy to me. A Weber smooth cone Ceramic 'California' (w/paper dust cap), or a '1230-55' (100W version) might be a nice affordable upgrade. The California has more high end with a bit more 2.3kHz "clarity" than the 1230-55, but it also has a bit more ~3.2kHz "ice pick", so it's a trade off. The 1230-55 has that big warm low end and strong ~5kHz presence. Users say they can hear themselves well on stage and it's not harsh. The WGS WGS12L is a sweeter sounding EVM12L type if you don't mind the 18lbs. Again, the amp section response parameters also make the amp models customizable.
You say you don't kno much about electronics friend but then go on to make some unsupported assumptions about the sonic qualities of various circuits!
For example, there is nothing mystical about a "gain" control that changes the frequency response as it is moved. Usually they don't but a very simple arrangement of suitable capacitors and resistors can give you pretty much any 'rotation v response' characteristic you want. Many controls on amps and guitars have a "bleed cap". Just to note gain was put in " " because in valve pre amps they are not gain controls as an audio engineer would understand them but volume controls, often with a limited range.
MOSFET PI more linear than a triode? Don't know I would have to put them both on the old AP anny! However, both circuits have massive inherent negative feedback so there is likely little audible difference between them. For a given HT voltage the MOSFET will swing closer to ground (and it loses less HT because it uses a constant current 'tail') but the ECC83 version can easily drive either OP valve into cut off and so the matter is rather academic? (once the valve is off it's effin OFF see?)
I get a bit miffed when people on forums make judgements based on very limited technical knowledge. The audio market and especially the guitar gear market is rife with innuendo and misinformation. Products can be dammed by a few ill chosen words in a forum and jobs lost.
Repairability: Depends where you and who you know, same as cars!
Do any of the very large guitar amplifier companies have heavily subsidised service departments in every small town world? In UK this used to be the case for domestic electronics and, to a limited extent for the music shops (I did amp work for one of them for a time) but now, everyone wants cheap and do not want to pay for service so, yer pays yer money?
Blackstar are a relatively small company and so if the biggies can't/won't do it? I CAN tell you that their service is first class in UK. Even people that don't like the sound and design choices of their products will readily admit they give very good service.