Quiet amps

[Scouser]

I am yet to own an amp which stays silent and doesn't develop a hum or a buzz of some kind over time. Does such a thing exist ?

Admittedly I haven't owned a ton of amps:

Orange
Vox Ad120VT
Fender studio 85
JTM 45
AER Compact 60 ( This may be the exception, but it's early days and not for electrics )

When I was playing in bands, it didn't matter too much, but when you are either playing for your own pleasure, practicing or recording at home, it's real nice to have the silence..

The only amp for electrics I still have is the Vox AD120 which has done 10 years of live work. I have had it serviced a couple of times over the years and once again recently for use at home, the guy changed to tube and serviced it but it's far from quiet, he did say it was in need of a service and sounded a lot better which it did, but it was still far from quiet, I think he mentioned part of the problem is the design, etc, not that I would know.

So do I just get rid and get something better/quieter or see if there is a way of way forward with the vox although my skills in this regard are zero, but maybe ruling out the obvious before giving up ?

[ef37a]

Hi Scouser, if that is the Vox 120'VT' it is a transistorised amp with one valve stage to give a "tooob sound" I have no idea how effective that is. However, in terms of its noise levels it should be quite good. It is not difficult to make very quiet transistor amps and the valve should not add much noise if the design is right. Hum levels should be low to inaudible as the valve should have its filament heated by very clean DC.

I cannot speak for other makes but Blackstar have a bit of a 'thing' about making quiet amplifiers. Do note however that although a guitar amp can(should!) be quiet enough at normal gain levels, cranking gain up for OD effects will inevitably introduce more noise. Hum levels however should always be low. The guitar will likely be the limiting factor there.

Dave.

[Matt Houghton]

Have you checked out Hamstead Soundworks? Very nice valve amps, and very quiet. (Not inexpensive, though!)

[Wonks]

The Fender Studio 85 is solid state, so no valves to go noisy. But it is quite old, late 80s-ish, so I suspect it could probably do with a change of electrolytic caps, especially in the PSU and any directly in the audio path. Fender’s standard choice of IC brand caps isn’t the best and they don’t stay in spec long.

Some of the chips used probably aren’t as quiet as some more modern versions. Someone with a circuit diagram and knowledge of alternatives could probably improve the basic circuit noise.

The valve in the VT120 is a 12AX7 used as a power valve (not a preamp valve as is normal). It produces a maximum of around 1W, which is then amplified further by a solid state power stage. So if that valve is noisy, then that noise is amplified further. The rest of the amp should keep a pretty constant noise level over time, but the circuit design and component choices may be compromised by budget considerations.

With the all-valve amps, most noise will be down to individual valves or electrolytic caps needing replacement, though there are sometimes bad circuit layouts that promote noise.

Most valve noise comes from the pre-amp valves, with the first valve being the main one to check, but any pre-amp calve can add noise and microphonics.

There isn’t an easy way to guarantee buying quiet valves. Some suppliers say they test them, but if they rejected all that weren’t whisper-quiet, they wouldn’t have many to sell. There are low-noise versions of the standard 12AX7 available, and these do seem to be better in general, though they are often not as good here as the original low-noise valve from the 50s/60s.

So it can often be a case of buying a number of valves and trying them out. Swapping the same type of valve around can often change overall hiss noise level.

Hum is normally either bad capacitors or bad wiring layouts, with signal wires too close to other wires carrying AC power signals (either 50Hz mains or 100Hz rectified ripple voltages on a nominal DC supply). Sometimes just moving one wire can make a big difference. Sometimes you need to use a screened cable to replace an unscreened one.

But a lot of classic valve amps were compromised in the hum department by less than optimal grounding arrangements. These are rarely improved by modern reissues in a desire to maintain ‘authenticity’.

But valve amps do require constant attention, especially if you want to keep them as quiet as possible. Get one quiet and it won’t stay that quiet for too long.

What sort of guitar sounds are you after? Clean, slightly broken up, fairly overdriven or insane levels of distortion?

If fairly clean, I see Blackstar have just brought out a 50W non-modelling solid-state amp for £199. The overdrive sounded a bit gritty to me in the Andertons
demo, but the cleans sounded good. As ef37a says, Blackstar do design their amps to be low noise. Might be worth trying one out.

[Essex Boi]

A silent guitar amp is nigh on impossible. Assuming this is for recording, where an amp’s self noise will be more noticeable, I’d suggest one of the latest modelling amps. I find them infuriating and cannot get on with them, but friends and colleagues speak highly of the Neural Quad Cortex. A plug-in is another option, and on this front my go to is the Scuffham S-Gear, though your DAW may already have something suitable.

[ef37a]

A silent guitar amp is nigh on impossible. Assuming this is for recording, where an amp’s self noise will be more noticeable, I’d suggest one of the latest modelling amps. I find them infuriating and cannot get on with them, but friends and colleagues speak highly of the Neural Quad Cortex. A plug-in is another option, and on this front my go to is the Scuffham S-Gear, though your DAW may already have something suitable.

It is of course impossible to make ANY amplifier noise free. Mr Johnson is always with us but the use of (no so) modern technology can make a huge improvement in guitar amp noise.
The main problem as Wonks pointed out is the first stage which normally produces around 35dB, X60 of gain. Good old Mullard ECC83s were decently quiet even so but modern, low noise samples are rare. Blackstar solved the problem in virtually all their designs by using a jfet op amp front end. This incurred the wrath of many a cork sniffing, valve loving, purist gitist but it has huge advantages.

You get several dBs of very low noise gain* and the signal is now raised to several tens of mV which make the noise of subsequent stages of little impact (this is basic, good low noise amplifier design...e.g mic pres)

The input overload capacity is in fact higher than a triode but in any case very few pickups could drive that first valve stage into distortion so. Nothing changed there then!

There is NO hum because it is easy and cheap to produce low V supply rails with near zero ripple.

The chip input stage never goes wrong. I certainly never had one fail and its performance will not change in 50 years, or ever?

MUCH cheaper than a valve. Valves are used further on in the pre amp stages to deliver the overdrive tones we love but op amps are also used in tone circuits where again their low noise and economy is so useful.
Solid state components are also used to protect valves and make the circuits less 'fussy' of the low QC and imperfections of today's valves. I will not expand on that further, if a certain company has not worked it out yet I am certainly not going to help them!

The first amplifier to embody all these design ideas was the HT-5. It had the IC front end and two stages of valve pre amplification. That drove a solid state PI and finally a double triode output stage. Marketed as a 5W amplifier that was actually a bit of an understatement. The Five could put out just about 5W of clean power but driven hard they hit about 10W and plenty were used with 4X12 cabs for serious gigging.
But the amps were also extremely quiet and I am sure many are found in studios.

*And that was with the venerable TL072. I understand a newer, better op amp is now used?

Dave.

[Essex Boi]

Thanks Dave. I don’t profess to any technical knowledge of the inner workings of my valve amps beyond the rudimentary, so your thorough explanation of what’s going on is most welcome. FWIW I’ve not enjoyed the Blackstar amps I’ve played through - including a couple from their Artisan series - and it’s possibly down to the preamp design you’ve explained, even though I had no idea at the time.

[Wonks]

I doubt it's the op-amp factor. Probably just their general design philosophy and sound. My original batch HT5 still sounds great. The HT5-R I had wasn't so good, much thinner sounding and I never understood why the clean channel didn't go through the EQ as on the HT5. I really don't know why I bought the S1 45 combo.

[ef37a]

I doubt it's the op-amp factor. Probably just their general design philosophy and sound. My original batch HT5 still sounds great. The HT5-R I had wasn't so good, much thinner sounding and I never understood why the clean channel didn't go through the EQ as on the HT5. I really don't know why I bought the S1 45 combo.

I agree Wonks, the OP amp front end is unlikely to affect the 'tone' of the amplifier, it is a very transparent gain stage as indeed is the first valve of a conventional guitar amp. Just adds gain but in the case of a valve usually some hum and hiss. Oh and in my list of op amp goodies I forgot lack of microphony!

However is is a sad fact that Blackstar amps seem to be a bit of a 'marmite' range of products? A lot of people on forums have said they don't like their sound but well over a decade on they are still selling shed loads of amplifiers!

Might I aver Wonks that you bought the S1 combo because it is a very sophisticated design? The power control is AFAIK unique in its operation and the amp is very 'well connected'. Even has MIDI. Do you have one of the earliest ones with the Neo speakers? If so you might try it into another cab?
BTW if you ever need to drop the chassis out PM me...tricky! Also, do note it has an ECC8 TWO in it and where it is.

I totally agree about the change of channel routing of the tone controls on the later HT-5s! Just does not make sense to me and my HT-20 is the same. If son were here to use it I would look to mod the bloody thing!

But then~: YCPAOTPAOTT.

Dave.

[Wonks]

My S1 45 had the Neos. I thought it was going to be like a big HT5 but it wasn't. It lacked bass end, but weighed an absolute ton and was a lot bigger when I got it home than it seemed in the shop. Never buy an amp on perceived size when it's right next to a Blackstar 4x12" stack! When playing it clean it really hurt my ears. I don't know if it was very loud transients, but picking a note did make me go 'ouch'!

The power scaling feature was OK, but the 45W to 5W range just wasn't big enough. In theory that's a 9.5dB reduction in SPL. but it never seemed that much.

The MIDI switching was wasted on me, though others would have found it useful.

Had the Club HT20 been out at the time, that would have been a much better choice for me. The other guitarist in my band got one after I left, and he got some really nice tones out of it.

[ef37a]

That's a bit odd Wonks? Most people on forums have said Blackstar amp are rather 'dull' or 'flat' sounding. I don't recall anyone ever saying one was "Ice picky" !

The early HT-20 combos had, as I have said before, the Rocket 50 fitted and nobody, not even otherwise Bstar fans liked those. Maybe they had changed it by the time your pal got one? I also understand the current HT-20 uses a pair of EL84s instead of EL34s. I wonder why?

For the non-technical here, getting 20 watts out of two EL84s means running the beans off them. 20W from two EL34s is beer into water and the valves are running at only about half their design power rating.
But then I was never a fan of the EL84 from my R&TV days, they were never as reliable as the 6V6 which has the same ratings. In fact the (old) 6V6s were just about impossible to kill!

My HT-20 is an original with the big octal bottles and is going nowhere!

Dave.

[SecretSam]

The tiny but very loud Quilter Superblock is very noise-free:

https://www.quilterlabs.com/index.php/p ... erblock-us

Although its predecessor at the Sam Cave was a Peavey 50, which had a fan in it to cool all that authentic glassware, so my benchmark is not challenging.

The Quilter sounds brilliant, has all the I/o you could want, is robust enough* and is ridiculously cheap. Its power switch could be a bit more butch, but the whole unit costs about the same as a valve amp service and new valves, so see if I care.

*One of many good things about small, light amps is that they don't hit the floor as hard when you drop them

[DC-Choppah]

OP don't neglect to check if the noise you hear from the amp is actually generated by guitar!

The instrument or cables can be the source of the noise and that is not the amps fault.

Also, when recording or playing at home, you can find a gain structure where the amp is set to a reasonably low level, and the guitar is buffered with a pedal to bring the signal up. You can find a combination where the noise is very low.

[ef37a]

There is always the noise gate to fall back on. I had a Behringer BCA2000 many years ago and one of its several good features* was an excellent noise gate on the HZ channel. Maybe someone can suggest a software option? I am sure there will be one in Reaper?

*and many bad like dreadful reliability and crap drivers. I got fed up of fixing it and Bherries were no help so it is still relegated to the loft!

Dave.

[Matt Houghton]

For recording (as opposed to on stage), I'd avoid gates — there are better denoising tools now that you can use after the fact, but the gate would limit their success since you need some exposed noise to train them. (Obvs still best to prevent the noise at source wherever possible...)

[Matt Houghton]

P.s. since you ask about Reaper, ReaGate is an excellent gate/expander, and ReaFIR in Subtract mode is a capable denoiser.

[ef37a]

P.s. since you ask about Reaper, ReaGate is an excellent gate/expander, and ReaFIR in Subtract mode is a capable denoiser.

Thanks Matt. I understand there are noise gates that have an adjustment for the attenuation and don't simply smash everything to -80dB?
The amp/guitar combination may be noisy but we can usually live with a bit of hiss?

Dave.