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beginner forum: for novice and developing blues harp players >
Managing Feedback
Managing Feedback
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MindTheGap
1838 posts
Oct 20, 2016
3:32 AM
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I originally put this on the MF, but it's better here because the grown ups are talking about big amps and stages and pro or semi-pro stuff. But we have to deal with feedback too, and without buying expensive large and harp-friendly amps and vintage mics it's all to easy to run into feedback problems. What I've found helpful is:
1. Putting something like a Harp Break in front of an amp. The Mojo Pad is a fixed attenuator, with the HB you have continuous control.
2. An amp simulator like the Joyo American Sound which has Hi/Med/Lo eq as in an amp. Sometime I can dial out the troublesome frequency. Again, it gives continuous control over the gain and the output into the amp. Mooncat discusses eq on the big amps, and we can do that too.
3. Volume control on the mic. That's the main one really. You can be your own Harp Shield.
4. I've found the Bulletini to be relatively resistant to feedback, and when it does, it tends to at a low frequency which is easier to deal with: it builds slowly and I can catch it.
5. When push comes to shove, compromising on the amount of distortion in the sound. That's an advantage of being an amateur. With a master-volume amp you can do that, if you've a single volume/gain control you can't really - another reason not to use a 5W amp outside the home :) That's where the modelling amps are really good.
I had a look at the anti-feedback boxes, and it all seems very subjective and woolly. If I were a serious player, I could imagine having these anyway as they might work in different situations. There was a recent test on MBH that's worth a look. It suggests there was no significant extra volume to be had. Perhaps some perceived increase. I'd expect the results to vary with different amps and situations.
http://www.modernbluesharmonica.com/board/board_topic/5560960/5493140.htm
Tube swaps. I don't have much experience of tube amps, like Superbee does, but I have tried it and found a benefit. The obvious thing it can do is lower the gain - but actually so will the things I mentioned above. But I believe it had some extra effect on feedback resistance too. The thing about tube amps (having studied the circuits at a simple level) is that you might expect changing components to have a strong effect on the frequency response, and that's likely to affect feedback. Hard to predict, but you can try it, quite simply and cheaply.
Last Edited by MindTheGap on Oct 20, 2016 3:49 AM
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SuperBee
4200 posts
Oct 20, 2016
6:53 AM
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I used to have an amp which had a 'tone-shift' switch. I expect it was just a cap switched in or out of the tone stack. When activated it was like some bass was cut. I was able to turn the volume up. At the time I thought it was cutting a frequency which tended to feedback. Maybe it was. Or maybe it was just reducing the overall volume so I could turn up. And I had less bass so maybe more 'cut'. I don't really know and I sold the amp.
Tube swaps are something to try for sure. I'm wary of it, and usually end up putting 5751 tubes in where the 12ax7 would be, or sometimes a 12AY7 instead of a 12AX7. But in my big amp I kept all the 12AX7s...oh, actually I just did change out V1 to a 5751 a few weeks ago.
But the amp which inspired me to get a hotrod Deville is the one Aki Kumar uses at his Grand Dell Saloon jam nights, and that amp does have a 12AU7 in V1, and I think a 12AT7 in V3 (which is the phase inverter). I was gonna do that but eventually took a different approach to the modifications.
As far as feedback goes generally, I've had a bit to do with it I suppose but my one foray with a specific anti-feedback device was disappointing.
In general, I've taken the approach of trying to use an amp big enough for the job, so I don't have to be right on the limit.
Most of the time that has been a pipe dream. So I've learned to manage life on the edge.
A volume control helps a lot. Dunno how I'd manage without one, but sometimes I do.
Where you position yourself relative to the amp is a big deal. I think you just learn that. Every situation presents different challenges. I've been lucky sometimes to have big stages and that makes life a lot easier. It's rare for me though. Far more common to be in cramped quarters.
Amp off the floor is good.
If your amp is miked to PA, don't have harp in the monitor. At least not in your monitor. If your amp isn't loud enough to hear, you need s bigger amp. You'd be better off going direct to PA, via a pedal perhaps. If you can run a line out from your amp, that's better than a mic and then maybe it's ok to have the pa monitor.
There was some talk about mics. I use bullets. I have a sm58 and I prefer it over a 57 but I'm in the beta corner there. The 57 & 545 are far more popular. For me the 58 is less handling noise and easier to hold with my arthritic hands. And better to sing through. I had a 57 and I swapped it with Indigo for a reverb pedal. I have rarely missed it.
When I had a harp break pedal I found I couldn't get as loud before feedback if I used that. I understood people used that pedal to get a break up in an otherwise clean amp or an amp they didn't want to turn up so loudly.
I bought mine at the same time I had the harp shield and I sold it at the same time too. Probably hasty. But I went down the track of modifying my amps rather than using pedals in front of them. I do use delay and reverb sometimes, and rarely now I use the harp octave but I used to use it a lot, it was a core part of 'my sound' (ha!).
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