Silverface Fender Princeton Reverb amp. Bottle-o-Blues microphone. Small practice space with band. Carpet on floor only. I'm about 6' from amp. Amp volume only on 3. Mic volume barely cracked. Feedback city.
Therefore, I can't play at a volume lound enough to be heard over the band. Therefore, I wind up bailing and playing through my vocal mic and not getting the amplified sounce. Therefore, I want to quit playing the harmonica.
I would really love to understand feedback and how to eliminate it. I welcome your advice. Thank you.
Agreed. Read Greg's paper. (Which if I'd been smart, I would've used as a topic for a term paper when I was in high school...dammit.) It's a very good resource.
I might go further to ask you though, in the case of the amp....is it a Silverface that has the boost pull-switch on the volume knob? I wanna say those were introduced on the last few years of the SFPR's...maybe in '77 or so. If so, that might be a cause. I can't imagine why a PR would feed back like that at so low a volume. Where is your reverb set at when it feeds back? ----------
Make sure you change the V1 preamp valve to a 12AY7 or 5751, then keep the treble off and the bass up high. Keep the reverb off and stand to one side of the amp, not directly in front of it. If feedback is still an issue at low volume then look into your cupping technique. Also download and read Greg's mic PDF. A silver face Princeton Reverb is a good amp for harp, so with a few simple tube swaps you should be cooking.
It is a 1976, no push-pull switch. The amp can't hardly be heard until the volume gets to 3, so, at 3, it starts feeding back.
I will look at changing that tube like Kingley mentioned.
Now's a good time to tell you that I've never liked the sound of the amp. It's way too clean even at 10. I've been doing a little research on tubes and am awaiting a set of Groove Tube 6V6 power tubes at a low rating of 3. I understand these will distort sooner. Let's see.
Will the change of the V1 preamp valve to a 12AY7 or 5751 give me some more dirt too (in a good way)? And will I have to rebias anything after such changes?
You won't need bias the amp if you're just changing preamp valves. You only need to do that when changing the 6V6 valves (and maybe if you change the rectifier valve too). A 12AY7 or 5751 won't give you any more dirt per se. It will allow you to drive the amp harder though, which in turn will saturate the power valves more. This should in theory make the amp a bit dirtier sounding. If the amp sounds too clean, then I'd look at the mic you're using. A good bullet mic or a good stick mic like a 545SD should sound great with those amps. If it's still too clean sounding then I'd look into your playing and cupping technique. Here's some idea of what a Silverface Princeton Reverb should sound like.
I've just compared my Bottle 'O Blues to my Front 'n Center custom mic on an Excelsior with 5751 pre-amp tube. Feedback is not an issue. Tone, of course, is better with the Front 'n Center, but he BOB is really not bad. I carry it in my case as a conversation piece, but it is really a decent (not great) mic, especially for the $50 price tag. Take Kingley's advice and check your cupping technique. I'm able to get surprisingly good tone even from an SM58, for example, when cupped properly.
So, thanks to you guys, a day that started with total frustration is ending very positively and with improved technique.
On the feedback issue, I believe it is a matter of gain. Learning about that from Greg's article you sent me. My Green Bullet is not feeding back at all, any volume. The BOB, fully open, feeds back at volume 3 on amp.
More importantly, I learned about proper cupping. I was not doing it. Just started tonight and an hearing done really pretty tones for the first time since I've been playing. Really excited to continue that.
Lastly, my Princeton does not sound like the amps in these videos...yet. Perhaps it will as my cupping improves. However in these two videos, I hear nice distortion and crunch, that I do not have. That said, they are using pretty funky mics. Perhaps after a few mods I'll look at a dirtier Mic. Thanks again!
A green bullet will give you more than enough dirt. I'd change the preamp valve to a 12AY7 and then just concentrate on your playing and cupping techniques. Over time you should find that you develop enough skills to make the amp drive. The only other thing I'd do is check that your bullet mic is wired to Hi-Z. It seems strange to me that you say it doesn't feedback at any volume whilst the BOB mic feeds back at 3. What model of Green bullet is it? A 520, 520D or a 520DX ? What element is inside your green bullet mic? If it's a Shure Controlled Magnetic element, what are the number and letters on it?
Last Edited by Kingley on Apr 23, 2013 10:24 PM
@Pauly21: Another thing: you said that you rehearse in a small room. Take care not to pick up the sound from other amps (guitar, bass). My amp, that never feeds back, went totally apeshit when on a really small stage next to a loud guitarist... My mic picked up guitar.... As soon as I turned my mic sideways, away from the guitar amp, it went well. ---------- Skinny Dog
re: " My Green Bullet is not feeding back at all, any volume. "
If your green bullet doesn't feed back at any volume setting on the amp - something is wrong with your green bullet. Perhaps it is set up for low impedance? ---------- ---------- /Greg
A mic feeds back "at rest", that is when you are not playing through it. Usually. So if you have a volume pot on the mic, turn it way down or off until it's time to solo or accent and then turn it off immediately after as well. I don't use a Princeton but more or less a copy of one. My pre amp stage has 3 tube slots and I have in p1 a 12ax7, in p2 and p3 I have 12au7's. This works very well for me. Full signal going in and then it gets massaged in p2 and p3 to a more manageable signal with less feedback issues. I use a hot dynamic or cm mic or a crystal. Lately a Shure 585 has been in the mix and I am about to get an Astatic 332 mic to try out. Thar setup seems to work pretty well with most mics I've used including a 545s. ---------- http://www.reverbnation.com/jawboneandjolene
99S556 HG is the model number of the element on my Green Bullet. It is a 1985 or 1986 520D. it has a 1/4"Jack and the cable is hard wired. I'm the original owner. I bought it back then when I taught myself to play, but then put the instrument down for 20 years while life happened.
I never had dirt back then either, with same amp and Mic...but, nor did i have the internet. flash forward to today and i have you guys to teach me cupping.
I plugged my acoustic guitar into the amp and it distorts as soon as 4 or 5, so i don't think that is my issue. This week i changed the preamp tubes to 12U7's. That has helped with the feedback on the BOB. I have a little dirt now with the BOB and the Princeton. To get more, I guess I have to keep practicing my cupping.
That said, I'm interested in diagnosing the Green Bullet with you guys. Right from the start, the cord would pull out of the Mic. I can see the copper shielding "hair" peeking out from under the spring that protrudes from the bottom of the shell. I've opened the mic before and found there's only a wad of glue poured into the bottom of the shell to prevent the cord from pulling out of the shell and detaching the wires from the element.
I'd take out the 12AU7 and put a 12AY7 in. The 12AU will take too much of the gain away from the amp and make it lifeless. The 12AY retains the liveliness and gives a far, far better tone.
The 99S556 is a good element. Just concentrate on working at that cupping technique and keep the treble rolled off on the amp. Put the bass high (around 7 or higher) and keep the reverb off. Keep the amp on the floor and stand a few feet away from it, preferably to one side. You shouldn't have any real feedback issues then. You should be able to run the amp around 6 on the volume (which is pretty loud). In this video I'm using a JT30 with a Shure CM element inside it, into a Princeton Reverb with the settings as I describe and volume around 5-6. You can see the amp on the floor behind me at the back of the stage.
Took it to a guitar shop to get fixed. Big mistake. He took out the wad of glue and replaced it with a little piece of electrical tape. He put the blue wire, I assume the ground, through one of the screw holes and is holding it in place with one of the screws. Is that right?
Black and red seem to be well soldered to the element. Currently, mic is barely playing, meaning I'm barely getting a signal from it, with the amp on 10.
No that's not right. It sounds like he's tried wiring it to lo-z and doesn't really know what he's doing. If the blue wire is connected to the element, snip it out. That should solve the issue. Just make sure that the wiring at the jack plug is correct too. For it to be wired Hi-Z you only need two wires. Just make sure that the positive wire is connected both to the positive of the element and also the tip of the jack plug (the small prong the sticks out) and the negative is connected to the element properly and the jack plug too. Then everything should be hunky dory. If it still has problems after that, I'd recommend sending it to Greg Heumann and having him wire it up and also get him to fit a screw on connector whilst he's at it. Much more reliable than the built in cable. Greg has all the tooling to do the job properly and his work is superb. He charges a very reasonable price too. Here's how my 520D is wired for hi-z.
Thanks, Kingley...and thanks for the vid too. You sound great. Hope to get to that point. Greg has been very helpful, but I don't think I'll put any more money into this Mic. I'm going to put it toward a custom wood mic from him instead.
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