Single-ended amps - are they all 'harsh'?

Moe_Zambeek

Every single ended amp I've tried - not a lot admittedly; thd univalve, loads of matamps, some others I forget - and I found all of them to be somewhat harsh and metallic sounding when wound up.

Is this a characteristic of single ended designs?

crunchman

I think it depends on the power valve.  I've a got a VHT Special 6 with a 6V6 that sounds good, but I've had other single ended amps with EL84 and 6L6 power valves that did have something nasty and harsh about them.

Edit:  I've also played one or two old Fender champs that were single ended 6V6 that sounded good.

Babones

Some people would argue that most amps sound harsh when fully cranked and in fact, sound better in their sweet spot, ie dialled back a bit.

ESchap

I've an AC4 (EL84)  I built myself to the origin circuit.  I don't find it harsh at all plugged straight in, very sweet amp, even cranked.  However, if using a drive pedal it definitely sounds better with the amp volume rolled back a little.

ecc83

Seeing as how the guitar amp started life as little more than the arse end of a radio set and very few of those were ever push pull, it should be possible to make a decent single ended amp.

The "enemy" is odd harmonics and radios but especially telly OPStages with their puny transformers, used the CR filter across the primary trick to smooth things out.

NFB of course but it does not help much if you drive the bllx off things!

One problem for SE amps is hum which is why Bs' have never made one.

Dave.

Phil_aka_Pip

The Epiphone VJ isn't 'harsh'. Neither is the Vox AC4TV (when the right guitar is plugged into it)

martinw

No.

richardhomer

My LSS sounds noticeably brighter and more 'open' on the 5w single-ended setting, than it does at 15 or 30 watts.

My understanding is that higher order harmonics get cancelled out in a 'push-pull' output stage.

I can't remember where I got that from - someone who properly understands circuitry will no doubt correct me if I'm wrong.

The difference I've described is very clearly audible.

darcym

what's a singled ended amp ?

crunchman

Phil_aka_Pip said:

The Epiphone VJ isn't 'harsh'. Neither is the Vox AC4TV (when the right guitar is plugged into it)

I'd disagree on the VJ.  Not tried the AC4.  Compared with Push Pull or 6V6 amps I definitely find the VJ harsh.  That might just be a characteristic of EL84s though.  I've found some amps with push pull 84s that sound harsh and brittle to me.

ICBM

Phil_aka_Pip said:

The Epiphone VJ isn't 'harsh'. Neither is the Vox AC4TV (when the right guitar is plugged into it)

No, they aren't.

They're both muddy .

My old Centurion SE amp is not harsh, although it is also bordering on muddy - and that's even with an EF86 preamp as well, which I often find harsh.

darcym said:

what's a singled ended amp ?

Any amp which uses only one power valve, or more than one in simple parallel (which is rare), instead of the more usual 'push-pull' arrangement for two or more valves where as the name implies, one valve 'pushes' while the other is 'pulling' to produce a symetrical waveform.

jellybelly

darcym;427235" said:

what's a singled ended amp ?

It's an amp that uses only one valve to produce both 'sides' of the waveform, and therefore is never 'off' - in push pull amps a pair of valves (or pairs of pairs) take it in turns to do the 'top' and the 'bottom' of the waveform (think of a sine graph - one valve does from 0 to 1 and the other kicks in from 0 to -1. This gives a different sound, generally 'harder' and 'tighter' as essentially they have less to do and are 'better' at performing their jobs (electronically) while in single-ended amps the one valve is doing both sides of the wave, working hard and when pushed doesn't do it's 'job' 'correctly. I hope there's no quota on inverted commas. I get confused when 'push pull' etc gets brought into it, I just have a very simplified view if it... Martin @mjw will have a much more accurate description I'm sure!


My opinion - my vht special 6 is sweet as, same with some other single-ended amps I've tried. Depends on the circuit, a lot more is to do with the preamp than the power amp as far as I can tell...

jpfamps

Harshness is the power stage is usually, in my experience, due to asymmetric hard clipping.

In a single ended amp this occurs if the output stage is driven into grid conduction before the other end of the signal is clipped.

EL84s require the least drive of any of the common output valves so are more likely to be driven into clipping.

SE amps can be made to sound very good, however you need to pay attention to the operating conditions.

Phil_aka_Pip

ICBM said:

Phil_aka_Pip said:

The Epiphone VJ isn't 'harsh'. Neither is the Vox AC4TV (when the right guitar is plugged into it)

No, they aren't.

They're both muddy .

Oh no, they're not!

jpfamps

One problem for SE amps is hum which is why Bs' have never made one.

Dave.

Of course.

ICBM

Phil_aka_Pip said:

Oh no, they're not!

The ones I've tried most certainly were - both muddy *and* slightly harsh in fact, but the mud dominates. No top-end at all with either of them - you can get a bit out of the AC4, but only with a very thin/bright guitar. The VJ just didn't have any with anything I tried - or any bottom end. Nothing but midrange, and very boxy midrange at that.

Actually come to think of it now, it's possible that most or all singe-ended amps I've played are like this to at least some extent… so Moe may be right.

ecc83

richardhomer said:

My LSS sounds noticeably brighter and more 'open' on the 5w single-ended setting, than it does at 15 or 30 watts.

My understanding is that higher order harmonics get cancelled out in a 'push-pull' output stage.

I can't remember where I got that from - someone who properly understands circuitry will no doubt correct me if I'm wrong.

The difference I've described is very clearly audible.

Push-pull operation does indeed cancel EVEN harmonic distortion but only to the degree that the OP valves are balanced both in terms of current and individual "gain". Then the drive has to be perfectly balanced. All in all, guitar amps rarely take much trouble to balance either static* or dynamic balance so the effect on distortion is minimal.

The main benefits of PP are, as I said before reduced hum , greater power and, perhaps the biggest one, PP allows the use of a much smaller OP traff for a given power output. Saves weight and OF COURSE money!

"We" do that on most models.

JusFort! Has anyone taken a particularly harsh single ender and swapped the OPT for a "hi fi" jobby? The EL84 design for the Mullard 3-3 could be interesting?

Dave.

martinw

ecc83 said:

JusFort! Has anyone taken a particularly harsh single ender and swapped the OPT for a "hi fi" jobby? The EL84 design for the Mullard 3-3 could be interesting?

I've fitted a very expensive Sowter hi-fi OT on an amp that I perceived as a little harsh - an EL84 based single ended 5 watter.

It made it worse.

Interestingly, the amp in question started life as a Mullard 3-3 amp that I built. The 3-3 was quite nice as a clean amp, but the transition to crunch and overdrive wasn't very nice IMO, so I made various changes, including the OT, and eventually ended up with something like the AX84 P1, using Ampmaker parts including the Danbury guitar style OT, which sounded much better.

Personally, I'm not found of EL84 based single-ended amps, which is why my Goldstar uses either an EL34 or a 6V6.

ecc83

martinw said:

ecc83 said:

JusFort! Has anyone taken a particularly harsh single ender and swapped the OPT for a "hi fi" jobby? The EL84 design for the Mullard 3-3 could be interesting?

I've fitted a very expensive Sowter hi-fi OT on an amp that I perceived as a little harsh - an EL84 based single ended 5 watter.

It made it worse.

Interestingly, the amp in question started life as a Mullard 3-3 amp that I built. The 3-3 was quite nice as a clean amp, but the transition to crunch and overdrive wasn't very nice IMO, so I made various changes, including the OT, and eventually ended up with something like the AX84 P1, using Ampmaker parts including the Danbury guitar style OT, which sounded much better.

Personally, I'm not found of EL84 based single-ended amps, which is why my Goldstar uses either an EL34 or a 6V6.

Ha! I had just looked up Sowters! OOOF! £123 for a 3-3 traff.

I found another supplier that wanted £38. Better but still a lot for 5.7 measly watts!

On the 3-3 p'typ did you mod it back from the direct coupling?

Dave.

martinw

ecc83 said:

On the 3-3 p'typ did you mod it back from the direct coupling?

No. I went for a preamp with more gain, as that was what I wanted at the time. My OT was the £123 one!

lespaulcustom68

THD Univalve through a 4x12 ( putting in some of the 'perceived'  lack of bass) and dialing back on the attitude gets rid of too much top end. With many single enders falling into the low wattage amp scenario - speaker choice becomes significant.