SS mods

hellohello

Hello All,

I have a SS PA (Bogen Challenger 100 mono) amp that im using temporarily as a bass guitar amp. Being solid state it has a lot of grainy distortion when cranked. Sounds great for guitar, but makes a bass sound fuzzed and farty unless i have the amp turned down reaaaal low. I have hotter pickups in the bass than in my guitar so i think that might be one of the culprits. (And the strings are a lot thicker ) I was wondering if there was anything i could do to make the amp a little cleaner. I think it uses germanium transistors, not positive on that, tho. One thing I found that I may try are fast recovery/soft recovery diodes on the power rectifier. I dont want to go really major, otherwise id add tubes Anyone have experience with said diodes or have tried to "clean up" a SS amp?

unc2701

does it has pre- and post- volume controls?

hellohello

it has a "gain" (mic volume) and a master volume, but unless the gain is at 3 and the bass guitars volume is at 1/2 its gonna distort. And even then, if the master volume is high (4+) itll distort. I am using the mic input btw, it has an aux input, but its too weak.

hellohello

I guess what im loking for is more headroom before it starts clipping... if i could have a switch that went from current gaininess to clean(er) and back, that would be most versatile and delicious

unc2701

Ahh... never mind. I was going to tell you to bring down the gain and crank the main more, but you've already discovered that. I think you just need to get a new amp- A lot of PA amps aren't built for the low end- just vocals, so they'll work w/ guitars, but once you go to bass, they just crap out. Keyboard amps work pretty well, though, so if you can pick one up cheap, it's worth a shot.

hellohello

thats kinda what i was afraid of... oh well
I forget where i saw this, which is why i posted here, it was concerning the fast recovery diodes, theyre supposed to be used in the power supply and supposedly help smooth out the signal... am I right? Or am I asking the wrong forum of folks?

jarros

Do you have another bass amp that has a preout on the back? Or maybe even an effects pedal with level control? Try running these into the Line input on the power amp to see if it still distorts. You may just have a bad mic-level input on the power amp. It's worth a shot if it means avoiding getting into the guts of the amp.

Jared

hellohello

ohh... i didnt think of that, some guitar tech i am
It didnt even occur to me that the line in would bypass the preamp... i feel like an idiot because i tell my friends who have 'actual' amps to use that method if they get a lot of feedback or interference.
Ill give that a shot... but im still tempted to tamper with the guts, just cause i got the thing for free I already used some sound dampening on the inside of the cover because sitting on the cabinet the thing would ring like a bell, now its almost as it it was made out of wood. I also took off the old power cord and 'installed' <enlarged a hole with a dremel and bolted it in> an IEC power connector from an old PC power supply, and removed the loose and useless 70V speaker outs to make room for a 1/4 inch input jack. So Im not afraid of tampering, be that good or bad.

hellohello

ok well, i tried the effect pedal into the line in, it still had a lot of fuzziness... so im thinkin maybe its not the amp (or at least not the preamp) So i decided to try something else.
I was using a 10" 4 ohm pioneer car sub, and the amp has a 4 ohm tap, so i figured they were a pretty good match... the sub performs well into 4000 hz, according to the specs. I changed to a 10" 8 ohm fullrange from an old stereo, and it seemed to fair a little better, the low end wasnt as pronounced as with the sub, but the speaker seems to add a little "life" to my fretless. So with that i added the other complementary 10" woofer from the stereo and now i get more volume at the 4 ohm level with 2 10's than with the one sub. It still has a touch of clip, but i get more volume before i have to turn it to clip level. I think im gonna have to get an 8 ohm sub, so i can use that and the fullrange for a little more low end.

jarros

Good stuff. Are you using those subs in any enclosures, or are they just out in the open?

Take it from a fellow bassist (I've been "holding the low end" for five or six years now), you won't want to be using car subs for bass guitar. Those things are designed for a 40hz rumble, and that's about it. While you may get some sound in other frequencies, it most likely won't be pretty.

When you wired in a 8 ohm speaker, you lost some power from the amp because of the higher impedance. With this higher resistance the amp won't have to work as hard (i.e. won't clip as much), but it won't be as loud as a lower impedance load would be. When you added the second 8 ohm speaker you dropped the resistance to 4 ohms (assuming you wired it parallel). It's louder than when you had just the single 4 ohm speaker because you've increased the total speaker surface area.

Where do you hope to use this amp? Will you be jamming with a band, or just practicing at home? Do you have any speakers or cabs at the moment?

Jared

hellohello

Hey Jared,
I knew that the car sub wouldnt make a lot of high end, but it did enough for me at the time. I had them laying around and i thought, they are for Bass right? lol That one sub could really shake the house

Im using some fairly stout PA cabs at the moment, I disconnected the Pizeo tweeters (very evil lil ****) and the cabs are ported. I was hoping to use this amp as a beater, i can practice at home, or jam if the chance arises, so thats why its in 3 small pieces, (amp,and two speakers) so i can easily transport. Ive helped transport some "combo bass amps" and those things weigh tons, dont get me started on stacks... :rolleyes: ( I was going to use a large amount of even smaller speakers 6or8 inch so i have more actual coils moving rather than just one or two with HUGE cones. Needless to say it was going to be expensive and time consuming to go that route.)

I did try my setup with a drummer and you could make it out. That was with the single car sub. Nothing overpowering, which with only one 10" i wasnt suprised.

I was talking to my pop, and he suggested using a capacitor for compression, so that the amp wont distort so much, but i thought that would be more of a frequency limiter.. like i said its a fretless and i kinda want it to sound like an upright, as much as a solidbody can anyway. I just noticed more of the sound i like with these new speakers and i dont want to cap that off... thats why i was thinking of getting a stiffer coned 10" subwoofer to pair up with the paper 10", a lil more punch.

I do think i need to take a look at the wires cause im getting a bit of hum, i think i have a wire thats too long, cause i shielded the entire cavity... at least i think i did. i have 3 guitars and its hard to remember what i did to whom..

Yeah, im all over the place with this post, but i was a drummer, i now took up bass, and i rebuilt a few guitars and amps, so... I may have ADD...

jarros

Yeah, if you've got 'em, you might as well use them until you decide to get something else (if you want). Car subs usually aren't the most efficient speakers, so you'll have to push the amp harder to get your volume. Are the subs in a box right now? If you have the T/S parameters you could always design a box in WinISD and throw a few mdf pieces together to get a box for it. That would make it much more efficient than if it was out in the air.

Smaller speakers will definately work for bass. The only problem is that you'll need more of them to get the cone surface area that you would get from a larger speaker, and as you said that gets expensive. You might want to check out the Eminence Delta 12, if you're looking to get a new speaker to match up with this stuff.

For combos, right now I'm using a Eden Nemesis NC-210. It's a 200W 2x10 combo and it only weighs around 50lbs, and it can throw out some serious lows for 10's. It works excellent for jamming and smaller shows. Plus you get that beautiful Eden tone.

As for the hum, the first thing I'd check would be the ground, or see if the amp has a ground lift. Check around where you installed the new power connection to make sure the ground is connected nicely.

Jared

hellohello

I do have them in enclosures, but not to spec or anything at the moment. Do you think a compression circuit would help the distortion problem?

hellohello

and since i already have cabs cut for 10" speakers, i was thinking of using one of these in cojunction with the stereo speaker i already have set up.
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=295-315

hellohello

ok, im just gonna buy a bass rig...

jarros

hellohello wrote:

ok, im just gonna buy a bass rig...

Good plan

Do you have any ideas as to what you're going to buy?

What kind of music do you play? Where will you be playing? What kind of tone do you like?

Jared

hellohello

well, im looking into something used, ~200 watts, maybe more, but im just gonna be jamming in small spaces for the moment. like i said, i have a fretless, (defretted maple fingerboard) and i like the somewhat buzzy sound i get when i listen to it unamped, so if i could get some of that with a good amount of rumble i think id be happy for a lil while .. as for style of music... i really dont know lol i just mess around a bit, i like jazz, rock, metal, but i dont have a band to really have a focus on a particular style... if u know what i mean... i was looking at ampegs, peaveys, but the GK backline series heads were suprisingly inexpensive, any experience with them?

jarros

I've played through some of the Backline series before, not bad. GK has a pretty clean sound, so you won't get a whole lot of "rumble" out of them.

Are you going to be using the PA cabs you have, or do you want a combo? If you're looking into a combo, I'd check out Yorkville's XM200 and XM200T (the "T" version is a 2x10 as opposed to the 1x15 that the 200 has). They're both really well built, sound great, and are a LOUD 200W. They also weigh around 50lbs each, so they're not bad at all.

Ampegs combos are good too. The tweeters on their 100W combos tend to hiss a lot, so some people just disconnect it all together.

Peavey's are known for reliability. You can throw them out the back of a moving truck and they'll still play for you. They don't have a whole lot in terms of tone, but they do get quite loud.

hellohello

Im not sure what i want to do in terms of combo/stack config. Im thinkin of getting a combo for now, and if it has extension outs, add a cab if necessary. Ill look into the yorkville, havent seen those yet. thanks for the input. And i think I used the wrong term when i said rumble, I mean more like the bottom strings wont sound thin... on the amp i have now they seem overemphasized, so maybe a clean amp wouldnt be a bad thing

hellohello

well, on a complete 180 of what ive been talkin about for the entire thread, ive got another amp in the works for guitar. Its gonna be a fender deluxe clone and i bought a 15" jensen MOD speaker for the cab that im also gonna put together. Let me say this... Ive never seen a speaker this freakin huge!!! lol I almost creamed my pants when I opened the box. Im used to seeing 10's and the occasional 12 but this thing is monstrous, its rated for 150 watts and has 97db efficiency... i hooked it up to my lil 30 watt SS and the sucker is niiiice even tho it isnt broken in... Needless to say this is going to be strictly blues/jazz. I got the amp chassis painted a flat black and am just waiting for the rest of the parts to arrive. (the capacitors, resistors, stuff like that) I already have the trannys and sockets, and tubes of course.

hellohello

Ok, i hooked the speaker up to an old cd player i had, let it play for a few hours, and i think its loosening a bit... but now i have a question about a cab for it. I was thinking of just building an open back cab, with a panel that i can close so i can play with different sounds. I looked online for a guide for building an open back cab, but its all mostly, "build to your own preferences or constraints" ..I was wondering if there was a more definite definition... anyone know?