![]() Sometimes there will be some (optional?) resistive components to also lower the level, and perhaps some other features. So we can go from high-impedance and higher voltage to low-impedance and lower voltage at the same time. When using transformers to step down the voltage, we also step down the impedance. It uses a step down transformer to get this impedance transformation that we require and stepping down the voltage a bit as well. To properly interface a guitar with a microphone pre-amp, we need to go from high-impedance to low-impedance and high voltage to lower voltage. Microphones will generally output around -30dBu, so the voltage is lower than the guitar. Microphone inputs expect low voltage and low impedance. Guitar amps expect a signal that conforms to these requirements. We can assume an average of about -20dBu for a guitar output. Guitars have a low voltage output and very high impedance (resistance to rate of change in AC current). So that will mean that impedance mismatches may end up causing changes in frequency response. If the impedance is mis-matched then there will be a difference in how much “resistance” exists between low frequency and high frequency signals. Since our musical signals have a complex set of sines ( see this post for more), there are complex interactions with the impedance of the circuit. The line from -1 to +1 has a lower slope. With a low frequency signal the rate of change is lower. The slope from -1 to the next +1 in the sine is a steep line. When we have a high frequency signal, the rate of change is high. In the graphic above you can see the difference. The rate of change of the current is what we generally call the frequency of change or just frequency. It’s the resistance to change when there’s an alternating current. The concept of resisting current flow show be pretty easy to imagine even if you have no concept of electricity at all. 78.9mb Impedanceīefore we start there’s a concept that needs to be clarified or some of the side-effects that we see happening later won’t make any sense.Įlectrical impedance, not the software development type (which is surprisingly similar!)Įlectrical resistance is pretty easy to grok. These are the test results for the Frequency and part of the Distortion sections. Here’s the REW test files for use with REW. These are the results for the Distortion sections. Here’s the CSF files for use with Voxengo Span Plus. I’m using an old (and reliable) Radioshack SPL meter. I will be primarily using MNoiseGenerator with pink noise then REW and Span Plus for signal measurements. Fender Hotrod Deville 410 that’s been heavily modified.The following pieces of equipment will be used for demonstration: ![]() Pad - A circuit that reduces the signal level.Reamp - A box specifically made to convert an line level signal to something that can be sent to a guitar amp.H-pad + pad means that I use the the H-Pad cable along with the Pad on the Radial JDI direct box.I will be using an H-pad with 4 resistors of 270Ω and a single 47Ω resistor.H-pad - A resistor network built into the cable to reduce the signal level.Reamp with a direct box? What’s the problem?.There’s also another 97.4mb of optional downloads. This post will load up to 105mb of data!!! Let’s find out with some measurements and then real world tests. What IS Reamping? What are these things you do it with? Why do you use them? And can you really do that? There’s all sorts of arguments on the internet on whether you can use a Passive DI in reverse as a Reamp, or go straight out of your amp or maybe use a special cable?
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