proformig amp

The lowdown on the Mississippi Sax. Just for Google, this section is about harmonicas.

proformig amp

Postby bigcat72 » Fri Sep 15, 2006 9:33 pm

hi guys i am looking for a amp for inside gigs and out side to play with aband and i play with just a guitarest i use a mud cat mic thanks happy harpin. t elliott.
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Postby bosco » Mon Sep 18, 2006 1:31 pm

BigCat-

First it has to be a tube amp. The standard place to start these days is the Fender Pro Jr. It has 15 watts and a 10 inch speaker. You'll need to replace the first 12AX7 preamp tube with a 12 AT7 or 12 AY7 to diminish the preamp signal to avoid the feedback common with using a handheld mic with an amp. You should be able to find a used one in the $250.00 range.

The Shaker Madcat harp mic is notorious for having a weak output signal and usually works best with an amp in the 30 to 40 watt range, which of course costs more money. Try it with a Pro Jr, it may work without diminishing the preamp, who knows?

Other amp suggestions would be Peavey Delta Blues- 30 watts, 2x10 and the Pignose G40V, 40 watts 1 x 10. I would avoid entry level tube amps with 5 or 6 watts and 8 inch speaker. They are OK for practice, but you will be disappointed when you play outdoors and will just have to upgrade anyway as your playing progresses.

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Postby angerboy » Tue Sep 19, 2006 6:48 am

I've got a 5F1 clone with one 6V6 that's as loud as a Pro Junior.

Why does it have to be a tube amp?
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Postby bosco » Tue Sep 19, 2006 1:58 pm

Why does it have to be a tube amp?

Because 50 years of amplified harmonica players say so.

If you had to ask that question you probably haven't tried to play a bullet mic through a solid state amp yet. The feedback threshold is so low and the feedback so intense it will melt your brain and your bandmates will never forgive you. For the sake of argument, lets say you always play on a theatre sized stage and have a 40 ft cord that allows you to dodge the proximity induced feedback. You, nor anyone else in the theatre will appreciate the shrill, fingernails on the chalkboard tone of harmonica through solid state. Sure, some of the new hybrid amps have a tube preamp. This may also allow you to dodge the feedback monster, but without a tube rectifier, you won't have the necessary sag qualities, which is a desirable amped harp property seldom discussed these days.

To recap- Solid State;

1. Monster Feedback
2. Shitty tone
3. No sag

Tube Amp;

1. Low Feedback
2. Warm tone
3. Great Sag

Why does it have to be a tube amp? :wink:

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Postby ricochet » Tue Sep 19, 2006 2:17 pm

Class A tube amp = no sag. No matter what sort of rectumfrier it's got.
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Postby bosco » Tue Sep 19, 2006 2:28 pm

Class A tube amp = no sag. No matter what sort of rectumfrier it's got.

What the hell do I know? :roll:

I do know this much...you'll never catch this harpster blowin' through a solid state amp.

For a wide variety of reasons. The least of which is what my ears tell me.
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Postby jeffl » Tue Sep 19, 2006 3:15 pm

I agree with Rico, that you can get by easily without a tube rectifier, Bosco. I know Brian Purdy is building his new higher powered amp with a SS rectifier, and that little Maverick I fell in love with has a SS rectifier on it. I haven't played harp thru a SS amp lately, so I don't know what the new ones are like, but for tone, there's no warmth like that provided by tubes. Maybe a higher powered SS amp, so you don't have to turn the gain up to get acceptible volume levels, would work-- I dunno,but there's plenty of affordable tube amps out there, so why mess with SS? My Peavey Classic 30, downtubed, has been a great gigging amp, and I'm sure those things are available for $200-$250, used, in good condition. There's always Pro Jr.s, or Blues Jrs. available everywhere,too. I agree that 15-20 watts may be ideal, and a 30 can be too much, unless you de-power it a little,with a 12AT7,or to taste. The AT7 is 60% of the AX7;Ay7=45,AV7=41,AU7=20%, with regards to gain. This will allow you to push the amp harder and get it to break up a little more, without hitting feedback issues. Without downtubing, my 30 would be too clean for me at the volume settings I'd have to play it at most of the time. You only need to replace the first tube in the line. There are some excellent discussions about these technical aspects at http://www.fenderforum.com/.
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Postby ricochet » Tue Sep 19, 2006 5:23 pm

Speaking of Peavey amps, have you harpers tried the Delta Blues 115 model? I really like the mellow tone of the 15" speaker for guitar. I'd think it'd be well suited to a harp's frequency range, too. Otherwise the amp's rather similar to the Classic 30.
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Postby jeffl » Tue Sep 19, 2006 5:40 pm

Rico, I haven't tried that 115. My favorite local music store is a Peavey dealer,but I haven't noticed any of those for sale in his joint. My equipment buyin' days are over until I start makin' some money again with my hobby anyway. My Classic 30 is as heavy as I wanna lug,and I'll bet that 115 has a few pounds on the one I got.
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Postby ricochet » Tue Sep 19, 2006 8:18 pm

I 'spect you're right.
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Postby jeffl » Tue Sep 19, 2006 9:37 pm

There's a great article on rectifiers,comparing SS to various tube systems at http://www.guitaramplifierblueprinting. ... fiers.html I think I'll download that one and put it in the notebook I started when I joined this forum. I need to start organizing those articles so I can reference 'em easier when I need to. This article on rectifiers is a great one for amp shopping,especially vintage amps.
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thanks

Postby bigcat72 » Tue Sep 19, 2006 11:50 pm

thanks guys great help i was looking at that pro and pro jr bosco do you think i should go back to the green bullet i like the mud cat for the hand effects but you are right about the sound level i have to blow my brains out .and you deont get that dirty sound as much i have been thinking about changing may be to a jt30 or somthing . happy harpin.-
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Postby ricochet » Wed Sep 20, 2006 1:42 am

Bubba, the only information of importance on that page on rectifiers is the varying voltage drop at the rated current levels of the different tubes. The voltage rise time graphs simply reflect the effective resistance across the rectifier that's also the reason for the voltage drop. The graphs don't tell you much, as there'd be a different rise time with different filter capacitors.

The four and five pin information he gave is bogus. These tubes can come either way, and whether they have a directly heated filament or an indirectly heated cathode sleeve, Pin 8 of the tube is the cathode connection. The tube type is what tells you which type of cathode you have, and you can look with your own eyeballs into the tube and see. 5AR4/GZ34 types have indirect cathodes, as do Sovtek 5Y3GTs, which are really Russian-made 5Z4s in a glass bottle. They have less voltage drop and sag than "real" 5Y3 types with directly heated filaments.

The sonic influence of rectifiers has been VASTLY overstated. There is an effect of voltage sag when a Class AB amp is pushed really hard. The dropping voltage causes the preamp tubes to go into distortion earlier and clip harder. The same thing is seen when the overall voltage to the amp is dropped, whether from using a tube with a greater voltage drop (as shown on the page you linked), or from a lower line voltage. Boost the voltage and you get a bit more clean headroom. Drop it, and you get more distortion. As Eddie Van Halen did with his Marshalls, dropping voltage with a Variac.

You shouldn't use lower current rated tubes than the maximum current draw of your amp. Putting a 5Y3 into an amp designed for a 5U4 will lead to very short tube life. Using too big a filter capacitor will greatly shorten rectifier tube life, unless it's combined with a series resistor to limit the peak cathode current. For a 5Y3, the maximum filter capacitor size is 20 uF. For a 5U4, it's 40-50 uF.

A rectifier with less voltage drop will cause the voltage on the filter capacitors to be higher, so putting such a tube in an old amp with marginal caps may cause them to blow.

A tube with a directly heated filament will heat up quickly and charge the filter capacitors to full voltage before the indirectly heated power tubes have started conducting current. This stresses the filter capacitors, if they're not suitably rated for the peak voltage. Solid state rectifiers produce an even faster voltage rise. Indirectly heated cathodes are kinder in this regard, warming at about the same rate as the power tubes so there's no voltage surge on turnon.
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Postby jeffl » Wed Sep 20, 2006 2:46 am

Well,I don't wanna flaunt my ignorance Rico,but the only part of that page that I really understood- or even tried to understand- was the part about the voltage drop. That gave me a cue to "cherry pickin'" different rectifiers if I spotted 'em in some old amp I'd never considered buyin' before. I'd still have to go by my ear, but the reference page might give me a clue to characteristics that I should be listenin' for, and also any clues that the rectifier isn't behaving normally,i.e., may be wearing out. I appreciate your clarification,too,me bucko,aargh. Ye be a horry fine mate.
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Postby ricochet » Wed Sep 20, 2006 3:03 am

ARRRRR, dontcha be lettin' me wench know how horry I be!
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