Amp sweet-spot v Reliability?

[Balcro]

My inclination is to never turn "Gain/Power/Volume" controls full on. If a use my hi-fi CD player the advice is to turn the output up to max so as to get the best signal-to-noise ratio. I suspect bass to combo-amp settings might be different.
Using an Ashdown 5-15 combo/practice amp.

1. Pick-up volume control set to 70% - above that it tends to boom out. Old simple guitar (Squier like), ordinary pick-ups. That's given. No problem.
2. Single instrument input with variable "Gain" (designed for passive or active and claimed to have lots of headroom). Generally set to about 65% of rotation.
3. Output control/volume control is set variably depending on whether the neighbours are in or I'm listening on headphones.

In order to get the cleanest good sound (that sweet spot), should I turn up the "Gain" to max and reign back on the output control? If I do turn the "Gain" fully up, what are the consequences for the reliability of any part of the amplifier. I'm not looking to create an overdrive sound, just balance the sweet spot against reliability for this equipment or amps in general.

Your guidance please.

[EvilSmile]

The gain needs to be set so the signal is just below clipping level. If the amp starts to clip for prolonged periods this can severely damage to amp and cab.

Most amps have a level indicator so you can set the gain to just below clipping. This gives the best signal to noise ratio afaik.

Hope this helps.

[Welshbassist]

It depends really, some amps have some method of telling you if you're on the sweet spot or not - Ashdown's VU meter, gain lights on the Eden heads etc. But otherwise the only method of telling is your own ears, wether your bass sounds clear or not! I imagine the input gain at full would usually be too much, but it really depends on your bass, how hard you play etc. Oh and another thing, the sweet spot changes all the time, as sometimes you pluck harder, and other times you pluck weaker. I find i play MUCH harder live so I turn my input gain down before the gig! Obviously, a good dose of compression will fix this!

[bennifer]

[quote name='Welshbassist' post='247374' date='Jul 24 2008, 10:57 PM']Oh and another thing, the sweet spot changes all the time, as sometimes you pluck harder, and other times you pluck weaker. I find i play MUCH harder live so I turn my input gain down before the gig! Obviously, a good dose of compression will fix this![/quote]
Just to clarify on that fact. Compression won't help if you're already overloading the input stage - it'll still be distorted! However running the amp at a slightly low preamp gain level and then hitting a compressor will achieve a much more workable result ready for the power amp

[lowhand_mike]

[quote name='bennifer' post='247445' date='Jul 25 2008, 12:32 AM']Just to clarify on that fact. Compression won't help if you're already overloading the input stage - it'll still be distorted! However running the amp at a slightly low preamp gain level and then hitting a compressor will achieve a much more workable result ready for the power amp [/quote]
so use the compressor in the effects loop rather than before the preamp?

generally i set the gain no more than 3/4 but i also have the ashdown VU to check levels don't go over the red too much, the gain will determine how clean your signal is and the health of your amp too. your eq qill have an impact on the gain level though which is what i found with my ashdown. ie turning up the bass level on the eq will push the VU higher so gain has to be reduced.

the 5fifteen doesnt have any clip indication so you will just have to use your ears but you should be able to hear when it start to clip just dont drive the gain too high.

[cheddatom]

If you play so hard that the pre-amp is overdriven, then a compressor infront of the amp will help reduce the input gain and reduce any distortion. - I think that's what Mike meant?

[Welshbassist]

[quote name='lowhand_mike' post='247764' date='Jul 25 2008, 12:58 PM']so use the compressor in the effects loop rather than before the preamp?

generally i set the gain no more than 3/4 but i also have the ashdown VU to check levels don't go over the red too much, the gain will determine how clean your signal is and the health of your amp too. your eq qill have an impact on the gain level though which is what i found with my ashdown. ie turning up the bass level on the eq will push the VU higher so gain has to be reduced.

the 5fifteen doesnt have any clip indication so you will just have to use your ears but you should be able to hear when it start to clip just dont drive the gain too high.[/quote]
No, you put it BEFORE the preamp to keep the signal relatively steady, so you don't get any unwanted peaks. A compressor won't stop your amp from clipping, but it'll keep it the level of signal at the "sweet spot" once you've found it!

Edited July 25, 2008 by Welshbassist

[Balcro]

[quote name='Welshbassist' post='247916' date='Jul 25 2008, 04:08 PM']No, you put it BEFORE the preamp to keep the signal relatively steady, so you don't get any unwanted peaks. A compressor won't stop your amp from clipping, but it'll keep it the level of signal at the "sweet spot" once you've found it![/quote]



Good morning and thanks for your advice everybody.

I forgot about the influence of "eq" for the original question, but as I tend to like a deep tone, on a scale of 0 - 100 I set the bass/middle/treble to 45/45/40. I'm going to move "gain" up to 75% and take it from there. Interesting opinions on the use of compressors.

Thanks again.

Balcro.

Edited July 26, 2008 by Balcro

[stevebasshead]

You might also want to read the sticky [b][url="http://basschat.co.uk/index.php?showtopic=3730"]click here[/url][/b] at the top of this forum, there's some very useful info in here which may be of help to you in understanding the interaction between gain and volume controls, what they really do and how best to understand them (despite the misleading labelling some manufacturers use). Very interesting reading.

[Balcro]

[quote name='stevebasshead' post='250680' date='Jul 29 2008, 06:27 PM']You might also want to read the sticky [b][url="http://basschat.co.uk/index.php?showtopic=3730"]click here[/url][/b] at the top of this forum, there's some very useful info in here which may be of help to you in understanding the interaction between gain and volume controls, what they really do and how best to understand them (despite the misleading labelling some manufacturers use). Very interesting reading.[/quote]


Hi Steve,

Thanks for your post. As it turns out I had checked the pinned topic before I posted the original. Didn't want to seem like a plonker. I understood pretty well all of it - the compressor stuff is beyond me at the moment, but alex claber's voltages, no problem. "Welshbassist" and "cheddatom" gave me the point about how hard you play affecting the gain output. Noted.

I've been a bit off colour for a few days so I haven't picked up the bass but I'll perhaps carry out some research tomorrow afternoon.

Balcro.

[Welshbassist]

Let us know how you get on mate!

[Balcro]

[quote name='Welshbassist' post='250894' date='Jul 29 2008, 10:48 PM']Let us know how you get on mate![/quote]

Well here we go.

Well, that was 90 minutes or more of warm work. Equipment re-cap: - Coaster bass, 4-string with passive pups, into an
Ashdown 5-15 practice amp combo. Lots of tweaking with guitar volume level and the tone control. Marked them with tape markers to get a clear indication of placement. Set the guitar tone control to mid-way and likewise the bass, middle and treble on the combo.

I played two-thirds through the headphones (silent practice) and the rest with the combo amp live, so to speak. I confined the single notes to open E and A because the lower notes have the most energy and also used an A octave using the same two strings. The headphones (Sennheiser 450's) which I held slightly off my ears for audio comfort had less reserve than the 15" speaker.
With the guitar volume control set to 80% as per usual, I set both the amp "gain" and "output level" to 75%. I gave the strings a fairly heavy dig. Something rattled on each side of my head.

Again using the headphones I backed the three levels down to 70%. No rattles through the phones. Headphones off and through the cab, the sound was slightly boomy, probably because I was in the hall with the back garden door open. However, there was no clipping or break-up.

About this time I put the headphones back on and started to notice that after hitting E, I could hear an overhang at higher frequency with an incredibly long sustain. I hit the E again, well many times actually, and damped it straight away. Still this overhang persisted.
What was going on? I checked all the tone settings. Everything OK there. I backed of the guitar volume to 60% and the gain/output rotary switches to approx 65% and tried again, from now on holding the guitar flat with one hand, not hanging.
The overhang was much less pronounced but I could stop it instantly, by palm damping the 4 strings. So obviously the source of the overhang was on the guitar. Mostly it occurred on "G" after I hit open "E". Are there any guitar afficionados ahead of me here?

I'd heard it before on odd occasions but never thought much about it, usually when I was just practising. It could have been the headphone lead dragging across a string. This time it wasn't. I checked. Anyway what I think I've found is low level "crosstalk" between the strings emphasised by a high-ish level on the guitar volume control. The problem with the one-piece bridge on this bass is that string resonance is picked up through the brass saddles and transmitted across the steel bridge, up the steel allen-key adjusters, into the brass saddles and on to a sensitive string!

Redesign all bridges to be isolated for each string?
Cut the bridge into 4 slices or try raising the action of the "G" away from the pick-up?
I think I'll try the latter first. If I ever buy another bass then I'll take account of an individual bridge per string design. It just makes sense. Even if it does nothing else on this bass, the crosstalk could muddy the sound at high volume levels.

Anyway, to conclude. Accounting for the "crosstalk", I've backed the guitar volume control down to 60%. With this level, the combo pre-amp "gain" is more than happy at 65% and the same for the "output level". A bit like motoring at 70mph; sort of comfortable. I think there's still a fair bit of headroom to go, so 70%/70% is quite practicable. I'll raise the "G" action tomorrow and re-test.

Balcro.

[Welshbassist]

So you played about for ages to end up with basically the same settings as you had when you started? Typical, that is!

Edited July 30, 2008 by Welshbassist

[Balcro]

[quote name='Welshbassist' post='251763' date='Jul 30 2008, 11:56 PM']So you played about for ages to end up with basically the same settings as you had when you started? Typical, that is! :lol:[/quote]

Well, that's the way it is sometime with scientific inquiry. Two steps forward, one step back. Yesterday will just have to stand as the interim report.

Balcro.

[bass_ferret]

Dont forget that backing the guitar volume is the same as reducing the input level on the amp as that is usually the first thing in the amp. Always best to keep the guitar volume up.

As for vibration being transferred though the bridge - it does happen with cheaper bridges.

[alexclaber]

[quote name='Balcro' post='251749' date='Jul 30 2008, 11:41 PM']Even if it does nothing else on this bass, the crosstalk could muddy the sound at high volume levels.[/quote]

You could of course mute all the unplayed strings...

Remember a bass guitar and amp system is far more like a cello than a hi-fi. Knob positions and so on mean very little because your hands have the ultimate control. When I was changing my preamp for one with switched positions I was worried that having my gain only adjustable in 3dB steps would be a problem because I wouldn't be able to get the exact right volume - I was SO wrong, I simply pluck harder if I needed to be louder, or more softly if I need to be quieter.

Alex

[cheddatom]

[quote name='alexclaber' post='252135' date='Jul 31 2008, 04:03 PM']You could of course mute all the unplayed strings...
Alex[/quote]

Yeh this is the obvious solution. Certain strings will resonate if left open and you play another note that corresponds to it somehow (harmonics and fundamental and all that balls?) so if you don't want them resonating, mute the other strings.

[Balcro]

[quote name='cheddatom' post='252143' date='Jul 31 2008, 04:20 PM']Yeh this is the obvious solution. Certain strings will resonate if left open and you play another note that corresponds to it somehow (harmonics and fundamental and all that balls?) so if you don't want them resonating, mute the other strings.[/quote]


Thank you for you replies today, everybody.

I raised the action on G and D, but it didn't make any difference. Putting my ear to the unamplified guitar p/ups I can still hear the ringing harmonic. I even tried a few isolation tweaks between the p/up covers and or between the p/ups & the body, but no change. So for the time being I'll work away at muting technique.

Maybe more tomorrow.

Cheers,

Balcro.

[Welshbassist]

It's better that you learn correct muting technique anyway, you'll be glad you did!