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View Full Version : Attn: Booli; T-amp interface



CactusWren
09-29-2015, 06:31 AM
Booli,
thought I'd ask your advice on this, it's something I've wondered about from time to time, but since I'm not very tech-savvy, never acted on it.

I have a T-amp powering two Infinity bookshelf monitors, attached to my external soundcard via a 1/8" plug. I would like to be able to plug in a guitar or a drum machine to the T-amp for playing around at my computer. What's the easiest way to do this?

I would prefer not having to get anything extra to plug in if possible--thanks!

pbagley
09-29-2015, 07:17 AM
I am not Booli, but I do have a tiny bit of experience with making sound equipment work.

Do you know what the input impedance is for the T-amp? Do you know if it is expecting a line level signal? Is the input mono or stereo?

If your guitar has a pre-amp then it could be sending a signal that is approaching line level and able to drive a lower impedance input with less signal degradation. The drum machine output is possibly at line level - I think my old drum machine was anyway (sold it many years ago).
You could get by with a 1/4" to 1/8" adapter and your regular guitar cord (1/4" to 1/4") if you are careful not to put any strain on the T-amp input. If the T-amp input is stereo you probably should use an adapter with two 1/4" mono inputs (female) and a stereo 1/8" output (male).
Or if you have a little mixer with RCA outputs (recording outs) you could get an inexpensive RCA (x2) to 1/8" stereo cord. I have them for taking the output from a MP3 player into the mixer at gigs. The mixer will give you some ability to adjust levels between the sources too.

Good luck!

CactusWren
09-30-2015, 07:29 AM
You know, I think it would be best to get a little mixer for my desktop. That way I could plug in the 1/4"s and not have to worry about fiddly adapters and the cord pulling the T-amp to the floor! It would make it easy for me to plug in my tablet as well. Thanks for the ideas!

Booli
09-30-2015, 01:17 PM
Hmm. Why not send a PM?

Anyway sorry for the late reply as my internet connection was down and I could not get online.

As fellow UU brother pbagley has said, you main issue is going to be impedance mismatch, and that is going to manifest primarily as the output of your guitar or uke preamp likely not having enough gain for the input of the T-AMP, or anything else that expects a 'line-level' input.

He has some good suggestions, and if what you want is a mini-PA or practice amp kind of setup, and also be able to plug in other devices, you can usually find a cheap 4-channel mixer that will be more versatile than using a dedicated preamp such as an ART MP Studio ($59) or Behringer MIC-200 ($39), both of which will correct the impedance issue, while giving you around 80db of clean gain to play with to adjust a proper input level for the T-AMP, but the disadvantage is that you will have to unplug/replug each time, in order to use the T-AMP with other devices, unless you get an A/B/C-type of input switchbox ($25) that lets you plug everything together and then just push a button to select the source to feed the T-AMP.

Having said all that, for bookshelf speakers, I'd be cautious about running an instrument directly into them without a compressor or limiter inline before the amp, because of the percussive nature of fretted instruments you will likely damage the tweeter and woofer components if they 'bottom out' too often in their excursion (also called X-max in tech specs) when moving to produce the sound.

Instrument amplifiers are made with speaker elements inside that are designed to handle extreme excursion much more so than home stereo speakers.

Also, keep in mind that most home stereo speakers are designed to handle 'program music', meaning mixed and mastered with a somewhat consistent relative maximum volume level (also often called 'normalized'), whereas playing an instrument like guitar, bass or uke is typically anything but a consistent maximum volume.

So one thing to consider is if you just want a cheap amp, to just get a cheap amp and not worry about all the above. I've seen them range from $50 (used) to like $150 (new) for a little 15-watt Fender Princeton or Peavey, Line6, Vox and others.

Also, Miguel, in one of your videos I saw you playing your guitar into a large amplifier, sitting on the ground (I think it was at the entrance of a Winery or art gallery) - if that guitar amplifier has a headphone jack, you can probably run that into the T-AMP input, just start with the amp's headphone volume VERY low at first so you dont blow the input circuit of the T-AMP, and you can use the controls on your amplifier to even out the sound so as to mitigate damage to the bookshelf speakers hooked up to the T-AMP as mentioned above.

Hope this helps. Please let me know how you make out. :)

CactusWren
09-30-2015, 06:42 PM
Hey Booli! I just wrote it in the forum in case others could benefit from the knowledge.

So I can either get a mixer+switchbox+limiter or a cheap amp and forget hooking up to the T-amp. Cheap amp sounds like a good option. Actually I have a couple lying around. Thanks for the info, Booli.

Booli
09-30-2015, 07:04 PM
Hey Booli! I just wrote it in the forum in case others could benefit from the knowledge.

No problem. That's kinda what I figured.


So I can either get a mixer+switchbox+limiter or a cheap amp and forget hooking up to the T-amp. Cheap amp sounds like a good option. Actually I have a couple lying around. Thanks for the info, Booli.

Actually I was thinking you could use ONE of the following options to feed the T-AMP:

1. preamp that has limiter such as ART Tube MP or Behringer MIC-200
2. mixer that has limiter or compressor effect built-in
3. mixer without effects but using a preamp w/limiter or compressor on the inserts (send/return effects loop)
4. mixer without effects but using a limiter or compressor on the inserts (send/return effects loop)
5. preamp going into mixer that has no effects, using a limiter or compressor on the inserts (send/return effects loop)
6. preamp such as in #1 above, going into switchbox, and other devices (computer, iPad, drum machine) going into switchbox
7. using an existing small amp, or your bigger amp, any with headphones output, that maybe has a limiter, and feeding the LINE OUT or headphone out to the T-AMP
8. just getting a small guitar amp, like a 15-watt practice amp, of which there's got to be nearly a hundred different items available at a reasonable price from all kinds of brands

Sorry if my previous post was a mumble-jumble - hopefully this list above is a but more clear.

In any case - Rock On, Miguel! :music: :)

Please report back, and/or if I can offer any other crazy ideas :P I'd be happy to help in any way I can.