Impedances for re amping

[John_C]

can anyone tell me what is wrong with just shoving a resitor on a line out, in order to re-amp?
or am i misunderstanding what impedance really is?

http://www.jensen-transformers.com/as/as092.pdf as far as i can see from this diagram then only thing actually doing any impedance changing at all is a single resistor..............

 

[Jesse Z]

Transformers isolate the signal.

Otherwise: NOISE

 

[John_C]

mmhmm i get that, but if noise wasn't proving to be an issue (is there any reason why it would be if the line out signal is clean?) then would simply putting a single resistor of the correct value in between a line output and a guitar amp input work as a basic reamp setup?

 

[devouredremains]

You could try the passive DI in reverse trick but there really is no cheap method of proper reamping short of DIY'ing an actual reamp box.

I say pony up the $100 for a Radial ProRMP and don't look back.

http://www.dv247.com/invt/43781/

 

[John_C]

mm i guessed that'd be what i'd have to do...... but what is it in a real DI box that makes it so much better at the job than just say a ground lift, a transformer and a resistor?

 

[Jesse Z]

The transformer isolates the grounds.

If there was a cheaper way to make a Reamp without a transformer using just a resistor, don't you think companies would be capitalizing on it? It will work, but it won't sound good. Even the DIY schematics on the net include a tranny.

If it was any easier, it would be.

Also, from what I understand about amplifiers and from what Jonathan at Little Labs has told me about impedance is that the LEVEL of signal that the amp sees at the input IS the impedance as far the as the amp is concerned. Meaning that any reamp with a trim pot is capable of varying the impedance the amp sees simply by turning the trim up or down. This makes perfect sense when you consider what a trim pot does.

 

[John_C]

has anyone here ever made a DIY reamp circuit? did it turn out well?

 

[aortizjr]

Yes I have made one. It works just great.

I used an Edcor transformer. Way cheaper and sounds great to me.

 

[John_C]

cool, what schematic did you use?

 

[Fox Mulder]

Holy Necro Bump
I take it a 1:1 ratio transformer (isolation) would be sufficient? Or are there experimenters out there?

Blessed be!

 

[GuitarHack]

http://www.diyrecordingequipment.com/store/kits/line2amp-reamping-box-full-kit/

Transformer used
http://www.edcorusa.com/p/121/pc10k-150
1/4W 10K Ohms to 150 Ohms (8.2:1) line level matching transformer.


Quote on webpage by MatrixClaw (from here):
"I'm using my LINE2AMP and it's doing better than [another commercially available reamping box] ever did, at 1/4 the price" -MatrixClaw, UltimateMetal.com Forum Member"

 

[The-Zeronaut]

hey guitarhack
did you have any clip comparisons?

 

[TheWinterSnow]

Holy Necro Bump
I take it a 1:1 ratio transformer (isolation) would be sufficient? Or are there experimenters out there?

Blessed be!

It would work, but without a step up in the voltage, you wouldn't be pushing the amp as hard as a pickup would.

 

[deLuther]

Why? Modified Radial ProRMP almost have 1 to 1 transfer, if interface have +20 dbu (or so) output level, getting pickup level is no hard...

 

[TheWinterSnow]

Almost 1:1, which means it may be 1:1.5 or 1:2. Plus line outs above +4dBu aren't readily available, or exist to my knowledge.

With most DI's you step down to get to proper tracking levels, then you would either have to boost (normalize) the output signal so that the "almost" 1:1 would be at pickup level. Proper tracking in the DAW and then needing to boost the track is not a good practice. The ratio of the Reamp should be the same as the DI being used ad the ratio should be large enough to get on average proper tracking levels in the DAW.

 

[aortizjr]

I have built and use 2 reamp boxes. One with a 1:1 Edcor and another with an 8.2:1 (10k:150) Edcor.

In practice, the 10k:150 works fine, but you pretty much have it wide open all the time and I would have to normalize the DI track to essentially get maximum output from the line outs. That would get me pretty darn close to the same gain settings reamped as I would directly plugged in with a guitar. Sometimes maybe a just a hair more gain on the amp.

The 1:1 as you can imagine is considerably hotter. I never run it over 2:00 or so because then it becomes a boost. Often even around 12:00. And it is full-range boost too, so all kinds of muddy shit, not the same effect as a tube screamer or something.

I agree that the theory makes sense that it wouldn't gain stage properly and all this stuff. I have had that argument before, hence why I built a 1:1 and I couldn't refute it. I also have a clean, full range, op-amp gain booster that I figured I would use just in case. But in practice, the above work just fine.

I recently bought a Little Labs RedEye mkii. So far the DI is pretty solid, haven't reamped with it yet. But that shootout is coming soon with the current band I am recording.

 

[TheWinterSnow]

With the 10K:150 sounds like you had it wired the wrong way, it is supposed to be a step up not a step down, in that configuration a 1:1 would be hotter.

The best solution would be an 8.2:1 DI and then 1:8.2 Reamp. The stepping is high enough where the guitar signal on the DI is at proper tracking levels given the average pickup output and the step up of the reamp would get you back to those levels to the amp. You would not need a gain control at all, no gain guess work.

 

[deLuther]

I`m just record my DIs with zero gain into +20 dbu input (+4 dbu reference), so I`m have unity gain across my chain.

 

[Fox Mulder]

Thanks guys. I have a question:
What's wrong with using a 600:10k ohms (1:4.1) transformer?

 

[Trevoire520]

Almost 1:1, which means it may be 1:1.5 or 1:2. Plus line outs above +4dBu aren't readily available, or exist to my knowledge.

With most DI's you step down to get to proper tracking levels, then you would either have to boost (normalize) the output signal so that the "almost" 1:1 would be at pickup level. Proper tracking in the DAW and then needing to boost the track is not a good practice. The ratio of the Reamp should be the same as the DI being used ad the ratio should be large enough to get on average proper tracking levels in the DAW.

I recorded guitar DI's at a proper level (average -18dBfs) went out of my Profire 2626 and into my modded Pro RMP, back into the same DI input used to record the DI, with the same level of preamp gain, and I had no trouble getting the reamped signal to the same level as the original DI. In fact I could get about 1dB or so louder than the original DI with the RMP's input gain all the way up.