New Carvin X100B tech note

[Twitch]

Ok, so if you read my other thread a few lines down I mentioned my X100 not having enough top end volume. Apparently, this is an ailment on every piece with the Series IV branding. The problem is with the effects loop. It apparently buffering the output to the power section. There are multiple fixes for this from ghetto- setting the loop level switch to an "in between" spot on the switch disengaging the switch from the circuit and hoping it will stay there and not cause a short, Solder Jockey- changing the value of a couple of resistors at the ass end of the pre amp circuit, and finally, what I call The Hack Mod-(this I could recommend to anyone with a pair of snips and a sense of directional orientation) take the amp apart, remove the modular board that contains the switch and effect loop jacks( it takes some fenagleing and finesse to get it around the power amp modular board to pull it out***BE CAREFULL NOT TO BREAK THE BOARD***). Once you have the board out, unplug it. There will be 8 legs from the switch to the board. The switch stands about 3/4 of an inch off the board. Pick either the top 2 or the bottom 2 and sever the legs with a pair of snips. Once youve made the cut, use a pair of needle nose pliers to bend the legs up towards the body of the switch to ensure they are no longer gonna touch the board(you could cut them away but I bent cause I couldnt find my small snips). Put the board back in reverse of procedure to remove it **remember "finesse" to get it back in with out damaging it**.

There you have it. The increase in top end volume is roughly 250%. THIS WILL NOT AFFECT THE USEFULNESS OF THE EFFECTS LOOP. The effects loop will still work like normal, you just wont have one of the level correction settings you once had(either the +4 or -4 setting depending on which legs you cut).

Also this Mod seems to have added another tweak to play with. As long as the effects loop level correct switch is in the position of which it makes no contact(the setting on the switch where you made the cut) youll have the true volume potential of the amp. If you flip the switch back into the circuit, the loop will again be buffering the O/P to the power amp(again a roughly 250% reduction in volume). So in addition to the 25/50/100 watt switch you now have the effects loop level correct switch to curtail the volume level for bedroom or apartment practice.

Notes: This Mod will work without the use of the foot switch. However, if you have the foot switch plugged in, you can toggle a 250% volume boost or reduction by pressing the "effect" button on the switch.

I cant wait till practice friday so I can blow the drummers head of with it(that will teach him to not use mute rings).

[MakeAJazzNoiseHere]

I could use a 250% volume boost for solos...

[Cygnus X1]

I could use a 250% volume boost for solos...

Oh fugg.



Sometimes it's the little things.
Humor is all about timing.
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[Twitch]

Suppose you could do that. Guess I should have clarified thats 250% with volume on 1. At some point youll run out of available power and there wont be as much of a boost, its a deffinent curve. Point is, its now as loud as my 900s were. Arter the mod the amp is fuggin loud on 1, almost too loud for my apartment.

[Twitch]

As an example, pre mod with master on 1, you can still hear the guitar strings them selves. Post mod with master on 1, its pushing the line of pissing off the neighbors 2 units over.

[Cygnus X1]

I believe that...good tip Twitch.
Thank you for passing this along.

[Newc]

So, what problem does this fix, and what does it cause?

This "250%" increase you mention, has it been measured at that level of increase? I mean, the amp is 2 and 1/2 times louder than it was before simply by defeating a switch?

I mean, what, you've got a rolloff at 16K or 18K and a max volume of 10dB SPL before the mod, and after the mod you get 250db SPL?

[Twitch]

As written above, with master level at 1, yes there is at least what Id call 2.5 times louder at he same knob setting after the mod(at least) and again as stated before, Im sure the more its turned up the less difference there will be in overall volume. I dont really understand your problem, it goes from very quiet to holy shit at the flick of a switch. I dont know how to explain it any better than that. It worked, Ive got way more top end volume than I had before. Before the mod it would barely be able to be heard over the rest of my band mates with the volume a c%$# hair short of 10, now it cuts right through like a 100w amp should plus some at the 3-4 setting.

[Newc]

You running 4x12 cabs or 2x12? 2x12 should get louder (SPL) and will cut more than a 4x12. My ex-singer and I had the same head - Fender RocPro1000 - and he ran his through a 4x12, me through a 2x12. Even with the same settings, and swapping rigs completely, my 2x12 had more presence and clarity. His had tons of woof but no punch or bite.

[Twitch]

I had tried both cabs at practice, no noticeable difference. This is apparently an issue with the newest models only, the Series IV. I havent heard any complaints about the older models.

[Twitch]

Youve got me curious now though to the actuall numbers. Perhaps Ill bring my multi meter to practice friday and take some peak voltage readings at the cab to determine peak max wattage pre mod and post mod. Im gonna guess that pre mod it was peaking somewhere around 30 watts as I know a 50 watt amp is generaly plenty for practice and gigging. However, due to the double your wattage and gain only 3 db thing, it could be as low as 15-20 VERY clean watts. At the volume level at 1 like Ive been using as reference the difference in db levels seems to be vastly different. Id say just my educated guess(by ear and specualation) would be 12 db difference pre mod to post mod with volume at 1 which would be 4 fold in (say maybe 5 watts pre mod into 20 watts post mod) wattage output. So Id say at that volume level my original statement of 250% or 2 and a half fold, would be conservative.

[Newc]

Have you investigated other mods to smooth out the volume difference? I mean, blasting the walls on 1 sounds brutal and all, but the mod actually sounds more like you've bypassed an internal buffer which regulates output volume more than anything.

Personally I've never liked the fact that an amp could even have the ability to stop getting noticeably louder once the pot reached a certain point before 10 (no detectable increase past 6 or 7). I've always considered that a design flaw - if it can't go louder than 7, why are there 10 numbers?

But I would actually prefer that to "goes from 0 to 10 in one number"

[Twitch]

Yes, thats the concensus written earlier that there was some kind buffering of the final output to the power stage going on, so thats exactly what Ive down, Ive bypassed it. The amp has Channel volumes and a master, so the volume can still be set lower. And why 10 if it wont go past 7? Its the type of pot used, audio taper instead of linear I believe.

[lerxstcat]

Sounds like a possible bug, but I'd contact Carvin about it because it seems that technically you may have violated the warranty by defeating that switch. Maybe there's a reason for it.

On the other hand, if it IS a bug, you might hasten them taking that bug out of subsequent production of the Series IV. And if it ISN'T a bug, you may find out why before you damage your amp.

[Twitch]

Sounds like a possible bug, but I'd contact Carvin about it because it seems that technically you may have violated the warranty by defeating that switch. Maybe there's a reason for it.

On the other hand, if it IS a bug, you might hasten them taking that bug out of subsequent production of the Series IV. And if it ISN'T a bug, you may find out why before you damage your amp.

I bought it second hand, and Carvin is very aware of it and says they have "fixed" it for current production. What Ive done is something thats been done by others with no reported damage(this "fix" is all over the Carvin boards, though I performed mine in a more safe manner). I dont see how this will damage the amp as I have not added anything or removed anything, I have simply bypassed a cicuit. A circuit that is not essential for normal operation. The function of this switch originally was to correct the level of the effects loop for different effect types(ie rack or pedal). The circuit for the leveling while doing its job(correcting the level of the chosen effects) was also reducing the final output to the phase inverter, the mod simply bypasses the level correcting circuit.