IS THIS OK: guitar-->basshead-->guitarcab ??

[everdrone]

is it a good idea or bad idea to plug a bass-amp into a guitar cab and play guitar through it? (guitar-->basshead-->guitarcab).

Im not sure when Ill buy it but I would like to have a small backup head for gigs for bass and guitar in case a tube blows or amp short circuits. I like the looks of Gallien-Krueger MB200 200-Watt Ultra Light Micro Bass Head.

I might use it at practice too with my Tech 21 Oxford pedal. I just dont want to fry an amp or a cab doing it.

[everdrone]

sometimes with ohm mismatches I read that it is half the wattage, sometimes twice as much

I wanna get a small backup head that is loud enough for gigs and practice with a loud band.

Here are the amps I am interested in:

GUITAR HEAD: Quilter ToneBlock 200 Guitar Amplifier Head (200 watts)

http://www.zzounds.com/item--QUITB200HE ... CWjHw_wcB=" onclick="window.open(this.href);return false;

BASS HEAD:
Gallien-Krueger MB200 200-Watt Ultra Light Micro Bass Head

http://www.sweetwater.com/store/detail/ ... oC7xrw_wcB" onclick="window.open(this.href);return false;

each of these heads can take 16ohm or 8ohm though according to their manufacturers


Im thinking I should save up for the quilter cause I am guitarist in a band currently so there are chances of me using it more

I use Orange 212PPC cabs and they are 120watt handling capacity, so Ill stay away from playing the high wattage bass-heads through it.

My drummer says that because my Orange Thunderverb 50 head is new and I use Furman P-1800 PF power conditioner which is top of the line, that if a tube goes out the other tube will work, and I should not anticipate any issues otherwise.

Here is my Furman:
http://www.furmansound.com/product.php? ... d=P-1800PF" onclick="window.open(this.href);return false;

[Hubaxe]

Give it a try, the worth that can happen will be guitar ==> basshead ==> guitar cab with new speakers

[everdrone]

lol true dat

the Gallien mb200 bass head and the Quilter guitar head both handle anything you throw at them, i.e. 4ohm, 8ohm, 16ohm. the Quilter scales wattage and I am in one band and play guitar in it so I plan on getting the guitar head over the bass head.

I play an Orange thunderverb 50 (50 watter) into 2 of the Orange 212PPC cabs. If one tube blows, does my entire amp shut down? I dont know how to change tubes or trouble shoot to find detect this problem, so maybe it is crucial that I have a backup amp. other backup amps I am considering: Orange Micro Terror, EHX Magnum .44, Orange CR120(maybe too big), maybe a Hovercraft Dwarvenaut but that is an expensive fragile tube amp.

[megalithic]

sometimes with ohm mismatches I read that it is half the wattage, sometimes twice as much

Usually with a bass head you get maximum wattage at 4 ohms, so on a 200 watt amp you get 200W at 4 ohms and something like 120-150 at 8 ohms.

Be careful some bass amps don't work at 16 ohms and many are very loud, maybe above the rating for your guitar cab so you have to watch out not to blow it.

[everdrone]

sometimes with ohm mismatches I read that it is half the wattage, sometimes twice as much

Usually with a bass head you get maximum wattage at 4 ohms, so on a 200 watt amp you get 200W at 4 ohms and something like 120-150 at 8 ohms.

Be careful some bass amps don't work at 16 ohms and many are very loud, maybe above the rating for your guitar cab so you have to watch out not to blow it.

thanks man, ya I plan to stay away from plugging in a bass amp and I might get that quilter if I save up in a month or two. I need more power than an orange micro terror. bass amps seem to be a bad idea, I am concerned about my guitar cab rated at 120 watts

I think that with my 16 ohm cab, there may be issues with the Gallien mb200 bass amp. The quilter definitely is not intuitive and DOUBLES power with 16 ohms. I am worried about the quilter 100 watt setting now...Ill call quilter with my concerns. Here is what folks on the forum reported back:

http://www.thegearpage.net/board/index. ... b.1632580/" onclick="window.open(this.href);return false;

i recently purchased a Quilter Tone Block 200 as an experiment in SS, and as a lightweight backup head in case one of my precious tube amps dies at a gig. The TB wants to run into 8 or 4 ohms, but most of my cabinets are 16 ohm. I contacted the company, and they informed me that running 16 ohms is fine but that the power wattage out to the speaker will be about double from running an 8 ohm cab. So that means that you'll be seeing about 80 watts out when you set the master on the 40 watt setting IF you are using a 16 ohm cabinet.


Ok, it does make sense to me .
Earlier I wrote the standard answer, which applies to 98% SS amps out there (the "normal" ones).

There is one SS amp design when Quilter answer is true, and that is that they limit power amp output by limiting power amp *current* to a preset maximum level, instead of conventional *voltage* limiting/clipping.

Or: they limit voltage, (say, a couple clipping diodes), then they feed that to a constant current power amp.
Both amount to the same end result.

Which is easy to calculate:
P=I squared * R so I=sqrt(P/R)
I=sqrt (40W/8 ohms)= sqrt 5 A = 2.24 A RMS which in practice means setting the limiter to 3.16A which would be the current peak .
Call it 3.2A limit and we're fine

That very same current setting will provide exactly twice that power into 16 ohms:
2.24A*2.24A*16ohms=5*16W=80W <-- in this case we used RMS values

Same result if we used peak values , we'd get 160W peak, which again translates to 80W RMS .

That said, the "power doubling with impedance doubling" effect will stay while we are still *within* the rated amp power, which seems to be 200W into 8 ohms (or 100W into 16 ohms) .

So the 40W setting will translate into effective 80W into 16 ohms, but, say, a 120W setting (into 8 ohms) will not translate into 240W into 16 ohms and so on.
Not a defect, quite the contrary, simply that load would be asking for a peak voltage beyond what is available at the Power Supply.

That said, a very clever design.
And I bet there must be a dozen other cool design tricks under the hood, that's for sure

[megalithic]

I contacted the company, and they informed me that running 16 ohms is fine but that the power wattage out to the speaker will be about double from running an 8 ohm cab. So that means that you'll be seeing about 80 watts out when you set the master on the 40 watt setting IF you are using a 16 ohm cabinet.


Ok, it does make sense to me .

Uh, the first sentence is in stark contradiction with the second.

Are you sure it's not the other way around? I have never heard of an amp which gives out more power at a higher impedance, but I guess it possible they could have developed such an oddball circuit. I'm not sure though, it sounds pretty crazy.

[a.hun]

Haven't a clue what is going on here. I'm keeping out of this one...


Andy.

[everdrone]

I contacted the company, and they informed me that running 16 ohms is fine but that the power wattage out to the speaker will be about double from running an 8 ohm cab. So that means that you'll be seeing about 80 watts out when you set the master on the 40 watt setting IF you are using a 16 ohm cabinet.


Ok, it does make sense to me .

Uh, the first sentence is in stark contradiction with the second.

Are you sure it's not the other way around? I have never heard of an amp which gives out more power at a higher impedance, but I guess it possible they could have developed such an oddball circuit. I'm not sure though, it sounds pretty crazy.

I agree, Im not sure. that is someone elses words not mine. I need to call quilter before buying, maybe the wattage is more incremental too.

[Mystic38]

provided you have the impedance matched, having a 200W or more into a PPC212 does not mean that there will be any issues...

So, say you are gigging with a TH50 and can get the volume you need, then you can plug even a 900W amp into that cab and at the same gigging volume you are not producing any more power than the TH50 is....

Additionally, with any solid state or class D amp, i would rather have MORE power than i need available as it will prevent the output stage clipping, and while most modern designs do have soft clipping, I would rather not fry speakers by discovering a smaller amp doesnt.

Again.. since you KNOW what volume you gig at... using a larger amp does not present any issues at that same volume..

[everdrone]

provided you have the impedance matched, having a 200W or more into a PPC212 does not mean that there will be any issues...

So, say you are gigging with a TH50 and can get the volume you need, then you can plug even a 900W amp into that cab and at the same gigging volume you are not producing any more power than the TH50 is....

Additionally, with any solid state or class D amp, i would rather have MORE power than i need available as it will prevent the output stage clipping, and while most modern designs do have soft clipping, I would rather not fry speakers by discovering a smaller amp doesnt.

Again.. since you KNOW what volume you gig at... using a larger amp does not present any issues at that same volume..

cool thanks man, I called Quilter and they confirmed they have a super awesome amp!

it matches whatever ohm you throw at it automatically. so it can handle my orange 212PPC or both of my 212PPC cabs.

also, the wattage is variable at any watt! so if you want 20 watts, it does that. or 40, or 50 or 55 or 56... he said that it does not double power or go down in power, it just matches power to the attenuator knob automatically. so if I dial in 20 watts at my 16ohms then it gives me 20 watts and so on.

pure genius! WANT

[misterfolkertsma]

Haven't a clue what is going on here. I'm keeping out of this one...


Andy.

I did NOT expect this