rmorris

Following on from Matte_black comment - what is the radius of the neck and is it a compound radius ? Although I thought 12" was quite a flat radius cf a 'vintage' radius. Happy to be corrected as I'm too tired to look it up myself atm !

tbh I didn't know there were 'imitation' Speakons. I'd have thought the potential market share would be too small to be worthwhile. OTOH I've seen more surprising things on counterfeit semiconductor products do what do I know 🤔

+1. For this application it's all about mechanical strength and integrity. As the OP seems to have discovered with the 'Stagg' failures - would be interesting to know where they are breaking physically. Essentially you just need a decent gauge of conductor protected by a robust jacket and properly attached to good quality connectors. I'll say that you don't particularly need audio branded cable though it does no harm. I favour two core stranded mains appliance cable. And preferably the 'Orange' jacket type intended for external appliance use (eg lawnmowers etc) because a) the jacket should be robust enough to survive being trod on etc, b) You can see it easily in the 'cable bag' and less likely to leave it behind 🙂 OP already has the Speakons so just requiring to properly strip to the correct lengths that should be available via Neutrik info'. Personally I tend to 'tin' the exposed copper ends to give the screws something 'solid' to bite into - but I know opinion varies on that. For the jack cable or adaptor piece then I suggest one of those large bodies Neutrik jacks to allow for a good cable diameter and give plenty of room to solder / insulate the connections.

Is this for amp head to speaker cab ? Or a PA ? What sort of length ?

I think you probably already have what you need with the MXR ?

You'll be able to plug it in and get a signal into the desk of course. But that doesn't require any particular level. For a 'DI' output best suited for the task the signal should be balanced (several variants possible) and low impedance - typically <100R for an active signal. Some would also say it should be at a low 'mic' level but that's a slightly different question. Without some form of balanced output you lose the benefit of noise(interference) rejection and breaking any 'Ground Loop' issue. Basically your signal may well be noisier. I also noticed there's one output only. A DI would normally have some form of parallel output so, typically, one output can go to an amp and the other straight into a desk.

It's not a DI output though from the block diagram. It's simply an unbalanced output. Output level is not what defines a DI (in fact they'll often have a low 'mic' level output designed to be the input to a mic channel on a mixer). Primarily a DI out needs to be balanced or 'Ground Cancelling'. And 1K0 output Impedance is rather high. It's a shame that lots of pedals miss a DI out. Passive impedance balancing costs next to nothing.

Interesting stuff. A couple of related queries. You mention notes choking at the first couple of frets. Doesn't this make the instrument as is basically unplayable or was it only when bending etc ? Related to that - unless I missed it - there's no mention of the neck relief or any truss rod adjustment you made. Would be good if you could clarify these points. Thanks again for the review.

It depends on how the circuit operates. If the effect is due to a signal getting 'near' a voltage rail (or something a bit more complex related to the voltage eg affecting the operating point of a transistor) then yes. But if the process is basically independent of the voltage level as long as it doesn't go too low - eg clipping levels defined by diodes - then the controls won't really alter. Although the circuit will probably have a different audio spec performance due to differing voltage rails. Of course, some pedals etc will have internal voltage regulation in which case - to a first level - everything will be the same until the voltage is too low and it starts to go wrong !

Audio specifications can be, let's say, a somewhat confusing area. I know. Been there Done that etc. But basically, depending on the definitions you are using, you don't really get better than 100dB SNR. Yes - a good mic amp may give an Ein of, say -127dBu. But that is typically at a gain of 60db. So actual noise level at the output is -67 dBu. So if you are setting the gain at 60dB to give an output level of +4dBu then your nominal SNR is 71 dBu. As gain decreases the Ein increases a bit. So while the signal may increase by, say, 20dB, thus requiring a gain of 40dB to give the same output level, the noise added at 40dB is a bit more than that added at 60db so the actual SNR wrt the input signal is better than the figure at 60dB gain but not by the full 20dB decrease in gain and noise may have already been added by any preamplification.

Yeah - it's difficult when you don't control the whole signal chain. A live setup isn't the ideal environment to optimise stuff. Cheers.

But what are you taking as "Line Level" ? +4dBu / -10dBu or ???

Hi. I see your whole post. But quickly on this - cos I'm on mobile and a tediously slow train from London to Brighton 🙄 - the pro line level is nominally +4dBu that does indeed equate to approx 3.5V pk-pk. But any system is expected to handle peak levels in the range of typically 21 to 24 dBu requiring Voltage rails in excess of +/- 9V or 12V. Typical pro audio gear runs OpAmps at minimum +/-15V and typically +/-17V.

Okay. Is that just when it's being switched or constantly ?

A properly engineered balanced output shouldn't have a problem with 48V Phantom Power as it is likely to be capacitively coupled and also the 48V appears in Common Mode. But I'd suggest to contact the manufacturer to confirm 😳 But yeah - it's a good while since I played live - but the SEs often have their way of doing things and don't like to deviate from that even when there's a technical alternative. Eg reduce everything to mic level and all inputs go to desk inputs configured to mic inputs.

But some electronic devices eg OpAmps don't operate to the same spec' at lower voltages. A 9V supply means that an OpAmp is running at only +/-4.5V. Let's say it needs a 1V headroom so a 3.5V peak. This approximates to a 2.5Vrms signal. A transient from a medium to high output passive pickup can exceed this. Plus spec in terms of THD+N etc is likely worse than at higher voltage supply. Then if it's on a battery then that battery voltage will fall a bit over time and make the situation worse. (How it decreases depends on the battery chemistry type). Increasing the voltage to 18V likely more than doubled the signal headroom (because the 1V gap needed to the voltage rail doesn't double) and the audio spec is probably better. Of course, if you are running some high gain "Ultra Shred" pedal it probably doesn't matter and you may prefer the result with lower supply voltage. Hence the thing about "vintage" batteries that 'sag' analogous to voltage sag in some amp designs

Does the Helix DI have a 'Ground Lift' option ? It shouldn't be necessary but sometimes it is due to the way some equipment is configured in a sub optimal manner.

Just to confirm what Nile days here. Passive DIs use transformers in a step down configuration. Basically trading level for a lower impedance output that is also balanced.

Sounds like a paint / varnish stripper type product may be a better option to sanding ?

Impressive !

As it happens I have a similar thing on a Marshall guitar combo' that I recently got free with no loudspeaker (it has one now). Not stopping the amp working but it doesn't short the input as intended with nothing plugged in so it stays a bit noisy. Yes - I can see that while it handles the jack plug okay, it doesn't have enough 'spring' to short when no plug there. It's actually a 'stereo' socket configured to also short some internal points - presumably to stop the OD channel boosting internal noise when there's no input. Obvs not much use when the socket has lost its zing ! Pain to replace because of all the pcb pots etc that mount to the front panel and another socket - 'Aux Input' or similar has the same problem. So I'm thinking to do a bit of metalwork and put in panel mount sockets in parallel.

What degree of volume change are you hearing ? Is the amp very hot (as far as you can tell) when the volume change starts to kick in kicks in. It seems to be time dependent ? So that sort of points toward a thermal issue.

Understood. But the 'driving a 'Fuzz-Face' type circuit with a lowish source impedance is the big thing that arises. Beyond that - yeah - it's all in the circuit details. Amongst other issues a 'box' may be designed with an input impedance more suited to 'line level' sources that is generally regarded as too low for passive Hi-Z pickups - although, of course, sometimes that will be a sound that people like and want as it will, for example, go towards less sustain. At the other extreme a very high input impedance can result in resonances that over emphasise particular frequencies. Would be interesting to hear what differences you found with Ho/Lo Z on specific pedals/boxes. Cheers.

Just a note to say that 600 Ohm is on the high side for a 'Low Impedance' Output although still an order of magnitude below that of a standard Hi-Z pickup. A 'real' low impedance output has an impedance below, say, 100 Ohm. Typically 68 Ohm. In the simplest case simply set by a resistor in series with the OpAmp output. It primarily serves to keep the output stable with a capacitive load - basically cables. It also limits the current if the output is shorted. So in some battery powered pedals etc it can be 1 kOhm or so to protect the battery. But higher resistor value does increase noise. The '600' Ohm standard is something of a legacy thing from old electronic gear where power transfer and hence impedance matching was important. With modern solid state kit it's voltage transfer that is the issue.

If I'm understanding what you propose correctly I'd say: Won't affect the tone since (afaik!) poly' resin has no magnetic characteristics I wouldn't do it since it would appear to prohibit any future height adjustment of pickups (or replacement) ?