Inserting phono jacks between amp and speakers: safe to do?
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Re: Line outHave a look at this You Tube video. Is it safe for us to do this? https://www.youtube.com/watch?v=QhFI1VkWbFo.
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@mhmercer These are not RCA jacks as you referenced, and this is not line out either. These are special 1/4” jacks and it is speaker level out. In theory what he is doing should work with the Spark (i.e. breaking the connection from internal speaker and sending that to an external speaker), but there may be issues with trying to connect to cabinets that are a different impedance vs the impedance of the internal speakers (causing a different load on the internal amp that may not be compatible with the amp’s design) and doing what he did means you need to connect to two external cabinets (i.e., one external cabinet for each of the internal speakers), or a 2x12 cab that has separate input jacks for each speaker.
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@bschultz8 Thanks for responding. Yes, I should have called them "phono" jacks, not RCA jacks.
I assume that our Sparks have two, 4 ohm speakers.
I do not understand impedance well enough to know the following: if I bought a 2 speaker by 12 inch, each, cabinet with the speakers rated at 16 ohms --2 x 8 ohm speakers wired in series, could I then rewire the speakers in parallel and have the 4 ohm cabinet that the Spark needs? If so, could I do the same with 4, 16 ohm speakers? -
@mhmercer in theory, that would work as you end up with a 2x12 cabinet with a 4 ohm load for ONE of the speakers in the Spark. You would have to do the same to a second cabinet for the other speaker in the Spark.
What hasn’t been discussed is what is the outputs from the amp in the Spark. As I changed the speakers to ones that have more highs, I know they are two 4ohm drivers and each has its own set of wires going to them. What I don’t know is if the Spark is like the Katana Air, which has 4 wires coming of the PCB in the amp. Note that the Boss website says the Katana Air is “a true stereo amplifier”, so by definition, there is a power amp for each speaker (those four wires from the PCB). As the Katana Air has an amp to power each speaker, you can connect a cabinet as per the YouTube video as long as you maintained same impedance.
Now comes the question: is the Spark a stereo amp? There is an FAQ from Positive Grid that says “Yes, Spark has stereo speakers” but there is a forum post from a month ago from shakyaanujman that says “from my conversation with positive grid, Spark is not a stereo amp, but has two separate speakers built-in”. So if this is not a stereo amp with separate amps driving the speakers individually, but just one amp driving the two speakers in parallel, attempting what was done with the Katana Air may put improper load on the Spark amp.
You can try it and let us know how it works out!
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@bschultz8 Much appreciated info. Thanks.
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Instead of doing what the video showed, I purchased from Amazon.com a summing cable with resistors. Headphone Port out --> 3.5mm end Cable --> 1/4" end Cable --> Input on powered, 8", Fender Frontman 15G amp/speaker unit. Had to drop the volume quite a bit; too loud. The sound-out is easily as clear as that from the headphones alone. Much better sound than the 4" Spark speakers IMHO.
At some point, I'll buy an FRFR speaker like the Headrush-112. Until then, I'm very pleased with the result.
