Published January 2017
Tuesday, February 18, 2020
Monday, February 17, 2020
Q. How do I hook up guitar pedals to my synth or keyboard?
When interfacing with guitar pedals, attenuating a digital keyboard’s output externally is less likely to result in reducing the signal-to-noise ratio to an unacceptable degree than simply turning the keyboard’s onboard volume control. If you can solder, this simple cable is a very affordable means of providing that attenuation.
I have a Nord Electro 4HP keyboard, which I’d like to run seamlessly through guitar pedals (namely a Digitech Polara and a TC Electronic Flashback X4) in real time and in stereo. I haven’t had any luck so far; the signal distorts quite badly at higher keyboard and pedal volumes. Can you suggest a device that would remedy this? I’m not too audio-savvy but as far as I know I have to match the impedance of the keyboard and the pedals. I already own a Radial ProD2 if that helps.
Timotej Jerman via email
SOS Technical Editor Hugh Robjohns replies: The fundamental problem is that the guitar pedals expect a typical instrument-level signal such as that from an electric guitar, which is nominally around -20dBu, whereas the Nord is capable of generating a line-level output which will be some 20dB louder. So it’s not really surprising that you are overloading the effects pedals very easily.
Impedance isn’t an issue here at all. The golden rule for voltage-matched interfaces like this is that the destination’s input impedance should be at least five times, and more usually 10 times (or more) greater than the source’s output impedance. Electric guitars are very finicky about the impedance they have to drive, and so most effects pedals and guitar amps will have an input impedance of 250kΩ or higher, and most active DI boxes will present an input impedance of 1MΩ or more (ie. four times higher still).
However, with an active electronic output, such as that from the Nord, the output impedance will be a few hundred Ohms at most, so anything above a few kΩ will be absolutely fine — there really are no impedance concerns when connecting an electronic keyboard like this to an effects pedal, all the issues are related to the signal level alone.
The practical problem, then, comes down to the best way of attenuating the signal level to something that the effects pedals are happy with. Obviously you could just turn down the master output level control of the Nord, and for many situations that will work perfectly well. However, if you need to turn the output level down substantially it’s possible that this simple approach will reduce the signal-to-noise ratio to an unacceptable degree, meaning that the Nord’s output will appear to become excessively noisy when routed through the effects pedals. In such cases, a better solution would be to turn the keyboard’s master level control up to a more conventional setting, and attenuate the signal externally prior to feeding it into the effects pedals, as this approach more or less maintains the Nord’s original signal-to-noise ratio.
If you are competent with a soldering iron then you could simply make up a couple of custom attenuating jack-jack cables to connect the Nord into the effects pedals, with a couple of resistors in the destination jack plug to form a simple voltage attenuator. For example, a suitable configuration would be as shown below, with a 10kΩ series resistor and a 560Ω parallel resistor, giving around 25dB attenuation.
Increasing the parallel resistor to 1kΩ will reduce the attenuation to 20dB, and if you swap it for 330Ω the attenuation will rise to around 30dB. This is certainly the approach I’d take, but you would need to mark the cable in some way to make sure you recognise it as an attenuating cable and know which way to connect it — plugging it in backwards wouldn’t actually damage anything, but it wouldn’t provide the correct attenuation either!
If soldering cables isn’t your thing, then you need a ready-made attenuator. For example, the JBL Nanopatch. While this is intended for passive monitor systems, it would be a perfectly workable solution in this situation. Alternatively, some form of re-amping unit could be used. These are usually passive boxes designed to accept a balanced line-level signal from a mixer or DAW interface and attenuate it to instrument level to feed a guitar amp or guitar effects pedals, while also providing galvanic isolation with a transformer to avoid ground loops. In your case you have an unbalanced source, but the re-amper won’t mind — just use a suitable adapter or cable. My recommendation would be the Orchid Amp Interface (http://sosm.ag/orchid-amp-interface).
Saturday, February 15, 2020
Friday, February 14, 2020
Q. What should I use to clean connectors?
Caig Deoxit is recommended for cleaning connections, though it’s worth noting that there are variants for different metals, including for gold connectors.I have recently been reorganising my equipment and making new cables. Most of my connectors and cables were bought second-hand, and I’m going through them all to make sure they are as they should be. The connectors are all Neutrik-branded, so I expect they were well built, but some are blemished and I wonder if you could give a little advice as to what would be the best way to clean the connectors. If you could recommend any particular solvents that would also be appreciated.
Additionally, the manual for the Millennia HV 3D recommends that one uses gold-plated connectors with the gold-plated connectors fitted in the machine. I don’t have many gold-plated connectors — is this important?
SOS Forum post
SOS Technical Editor Hugh Robjohns replies: Deoxit from Caig Laboratories is the best cleaner for audio connections — the D5 version is the usual recommendation, but G5 may be better for gold connectors. Regarding the question about gold connectors, note that gold is a very soft metal and thus it can be eroded through friction. For that reason, it is recommended — and a good idea — to use gold-plated connectors to interface with a product’s gold-plated sockets. And if you can afford a Millennia HV3, then there’s really no excuse for not being able to afford some new gold-plated XLRs!
Published April 2017
Thursday, February 13, 2020
Wednesday, February 12, 2020
Q. Which DB25 cable do I need?
Any cable with a DB25 D-sub connector on one end and eight balanced jacks on the other should be fine for analogue interfacing.
I recently acquired a Focusrite Control 2802 analogue mixer/DAW controller. There are numerous connections on the back, including three female DB25 interfaces. These are labelled ‘DAW Inputs (1-8)’, ‘Direct Outputs (1-8)’ and ‘Summing Inputs (1-8)’. The manual says: “These interfaces are wired to the Tascam DA-88 25-pin D-sub standard”. To these, I am trying to connect to a Focusrite Scarlett 18i20 (first edition) USB audio interface which uses TRS jacks for both inputs and outputs. The next step is to obtain two DB25 (male) to eight TRS jack looms. This is proving more difficult than it looks, as ads for some of the cheaper brands specifically say “not suitable for TDIF”. And TDIF is Tascam, right? I seem to remember the Tascam DA-88 as being a distinctly digital recording device, so I don’t understand why Focusrite are using a digitally-inspired wiring convention to execute what seems to be conventional analogue in/out? There are more expensive ‘pro’ looms available, but they are about $35 more each, and they don’t say anything about Tascam one way or the other. Can I assume they will ‘just work’?
SOS Forum post
Technical Editor Hugh Robjohns replies: I see the source of your confusion, but the answer really is simpler than you think — and the short answer is that if it has a DB25 D-sub connector on one end and eight TRS jacks on the other, then yes, it should work. I say that because while DB25 connectors are used for both analogue and digital audio interfacing, the digital ones won’t be terminated in TRS jacks!
TDIF was a Tascam digital interface — in fact, it stands for ‘Tascam Digital InterFace’! — but it used a proprietary digital format and is now largely obsolete.
Tascam also conceived an analogue interface using 25-way D-subs carrying eight balanced analogue channels, first used on the DA-88 (because even digital recording devices usually require analogue inputs and outputs!). This interface has become ubiquitous — it is used in the Focusrite Control 2802 and various other pro-audio devices with multiple channels (multitrack recorders, consoles, audio interfaces, 500-series chassis and so on). In fact, it’s such a common format that the AES have adopted it as an industry standard (AES59); it is now the only wiring format for eight channels of balanced analogue on a 25-pin D-sub.
For digital (AES3) connections on 25-pin D-sub connectors, there are two current formats: the Tascam/AES59 format and the Yamaha YGDAI format. But the digital connections will have either another D-Sub on the other end, or four male and four female XLRs. Hence my suggestion at the outset that any 25-pin D-sub to TRS loom will be suitable — because it will be wired according to the Tascam/AES59 format.
Published June 2017
Tuesday, February 11, 2020
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