I have finally assembled my DIY Reamp box!!

[Omega_Void]

Are you sure that they can be used for Reamping Boxes? They have all differnt specs from Edcors Transformers, at least for the WSM10K/150 which is being used for Reamp boxes... they are not 1:1 Ratio...

The JT-11P-1 shown in the Jensen schematic is 1:1 ratio.

If you use a step-down Tx the signal out will be attenuated - e.g. a 2:1 ratio will drop the output voltage by 6dB, and you'll have to increase the level in the DAW to get the same level out as you got in, which runs the risk of clipping with high-output pups.

If you use a step-up Tx the signal out will be attenuated - e.g. a 1:2 ratio will increase the output voltage by 6dB, and you'll have to reduce the level in the DAW to get the same level out as you got in, which means the signal-to-noise ratio in the DAW's output devices is now 6dB worse.

A 1:1 ratio is the sensible thing IMO.

 

[diafebus]

and whay are this people usin the edcors Tranformer which has primary of 10000 ohm and secondary 150 ohm which is 8,2:1?
well at that price i'll try both but I'd like to understand why the use of edcors... maybe if you increase the signal to 8,2 you get te possibility to control better the output than 1:1 transformer.. I don't really know...

and if you are looking to my schematic this is an unbalancer, so this is not a reamp box, i'm talking about the first schematic where you can see the 10k primary and 150 ohm secondary

 

[Omega_Void]

and whay are this people usin the edcors Tranformer which has primary of 10000 ohm and secondary 150 ohm which is 8,2:1?

The impedance ratio is the square of the turns ratio - so yes, 10k:150R Z = 8.16:1 voltage step-down. This is fine if you have enough headroom to put out eight times the required signal level without clipping or distorting, but I wouldn't rely on every setup being capable of this.

and if you are looking to my schematic this is an unbalancer, so this is not a reamp box,

By unbalancer you mean it receives a balanced signal and puts out an unbalanced signal? With a varible output impedance? That's what a reamp box is. I see only the Jensen and Melodeath schematics, and both match this description.

This thread is titled "I have finally assembled my DIY Reamp box!!"... isn't it?

A 1:1 transformer, with a 47k resistor across the secondary will provide appropriate loading for a line input to a guitar amp or a standard unbalanced line input. |if you ionly ever intend to plug into hi-Z gear, a 22k resistor will do.

Follow this with a 25k linear pot in the signal path (wired as a variable resistor as shown in the schematics) and you can get as high an output impedance as you would require to match a guitar's Zout for reamping -although the reactances in the reamp box would probably not match the reactances of the pup.

 

[diafebus]

so with a 1:1 transformer of 22k impedance, and then add a volume regulator of 25k will be ok to make my reamp box?
well i'll try to get clearer information about this before buying anything hehe
http://www.edcorusa.com/Products/BrowseSeries.aspx?SeriesID=21 here there are only 15k and 10k 1:1transformers so...what could i do, and something else, in the first schematic sholw you can see that he uses the 10k to 150 ohm transformer and then uses a 50k pot as volume level, so this is like using a 22k 1:1 transformer and then use a 25k pot to regulate the hi z ouput,, right?

i'm not sure about what schematic is better to use, by the way I think that the first schematic it's ok, maybe 10k-150 ohm transformer keeps higher quality, i don't really know.

i wait for an answer
thanks

 

[diafebus]

bump

 

[aortizjr]

You typically want some sort of step-down to happen with the voltage.

A guitar pick-up will typically put out between 100mV and 1V Vpp and a 0dbV line level (unity) is 2.8dBV.

Can't throw any math numbers your way. But with a 1:1 you are just padding the signal with the pot after the isolation of the transformer. But because of non-linear impedance issues with pickups, you would likely get finer control and more pickup like sound out of the 8:1 transformer even though your gain may be maxed all the time. But you want to make sure that the signal out is getting close to the +4dBu.

Mine I built with the Edcor WSM 10k:150 and it works great. I typically have the output full out and I normalize the guitar DI track and keep the fader at unity. I also make sure the outputs are set to +4 and not -10.

 

[Omega_Void]

... a 0dbV line level (unity) is 2.8dBV.

0dBV = 0dBV . Perhaps you meant 0dBV = 2.8V?

Professional (i.e. balanced) line level is +4dBu, which is 1.23Vrms. That's 1.739V peak, so 3.479V peak-to-peak. It will easily accomodate a 1Vp-p signal without clipping. There's no need to step down, and a little headroom if you need to add a bit of gain to make up for losses in the transformer (0.5dB quoted for the Edcors you're looked at) and for the voltage dropped across the "Z-out" pot.

Consumer (i.e. unbalanced) line level is -10dBV, which is 0.316Vrms. That's 0.447V peak, so 0.894V peak-to-peak. If you ever planned to use an unbalanced output for reamping a step-up transformer would be required to avoid clipping and still deliver the necessary signal level to the amp.

...because of non-linear impedance issues with pickups, you would likely get finer control and more pickup like sound out of the 8:1 transformer even though your gain may be maxed all the time. But you want to make sure that the signal out is getting close to the +4dBu.

Why are you recommending an output signal level of 3.479V peak-to-peak? Your 8:1 step-down Xfmr will drop that to 0.435V p-p, a bit shy of the 1V p-p you said the guitar level might achieve.

Bear in mind that the setting of the Gain pot on many (most?) guitar amps will also have an effect on the response of the tonestack, so cranking the gain on the amp to make up for a too-low level input may not be a preferred solution. That's without even considering the SNR implications. And wht happens if you run out of gain before you have enough?

As far as non-linear impedance goes, the DI from the guitar should have captured the output of the pup being operated into a high-impedance load. The soundcard will faithfully reproduce that into the amp/pedal on playback through a reamp box. Some additional colouration from the transformer may or may not be a good thing, but it's not something I'd shoot for.

If you're getting results you like with your box, that's cool. but if I was building from scratch I'd aim for a gain structure a bit less... wonky.

I'm still recommending 1:1 ratio.

 

[Omega_Void]

@ Diafebus, sorry it took a while to get back to you, it's been real hectic for me the past few days. i only been online once and I just didn't have time to post.

so with a 1:1 transformer of 22k impedance, and then add a volume regulator of 25k will be ok to make my reamp box?

The impedance of 22k is not provided by the transformer. The transformer itself doesn't in theory present any impedance, and in real life just a tiny influence.

The difference in the 10k, 15k and also the 600ohm 1:1 transformers in the catalogue is how much current they can handle. All are rated 0.5W, so the 10k Xfmr will accept ~7mA (@ ~70V), the 600ohm ~28mA (@ ~17V) etc... Any of them should do fine.

The transformer reflects the impedance on one side over to the other, and the impedance is increased or decreased by the impedance ratio, which is the turns ratio squared.

E.g. If there is 10k connected across the secondary...

... if the Xfmr is 1:1 turns ratio, whatever is connected to the primary will see 10k impedance, and the signal level remains the same.

... if it is 6:1 turns ratio, it will see 360k impedance and the signal level on the secondary sidedrops to a sixth of what it was on the primary.

... if it is 1:8 turns ratio, it will see 156ohms impedance, and the signal level increases to 8 times what it was on the primary.

Hence why the 8.2:1 transformer is listed as 10k:150...
8.2 squared = 67.24
67.24 times 150 ohms = ~10k

something else, in the first schematic sholw you can see that he uses the 10k to 150 ohm transformer and then uses a 50k pot as volume level, so this is like using a 22k 1:1 transformer and then use a 25k pot to regulate the hi z ouput, right?

The volume level is the 1k pot in that schematic. As stated in my last post, if anything the level out would need to be increased a bit to make up for losses in the reamp box, which a passive pot can't do.

So if I were you I'd build like in the schematic Melodeath posted, but...

...replace the transformer with a 1:1
...use 22k for R1
...VR2 really only needs to be 25k, but 50k is fine

...you can leave out VR1 and just connect the top of R1 to the "Z-out" pot, or use 250k to 500k for R1

Hope this helps.

 

[aortizjr]

Hmm... yep makes sense. Thanks for the very detailed explanation. That cleared a few things up for me.

Some more reading material:

Guitar pickup output levels.
http://www.muzique.com/lab/pick.htm

Also a bit I found on the NYDave schematic:
http://messageboard.tapeop.com/viewtopic.php?t=6981

Looks like his design was based on the assumption that guitar pickups put out 150mV RMS which is right in the range of the 0.4 Vpp.

I have been trying to find a great debate between the designer of the real ReAmp, NYDave, and the Little Labs guy. It was pretty interesting.

 

[ttrentt]

Anybody ever get one of these DIY boxes working correctly?

 

[Norris-wf]

Yup, they do indeed work. I havent done a comparison between a bought one, but it certainly does what its meant to and cut out all that horrible noise I was getting due to mismatching

 

[Wolfeman]

Yes they work fine. The problems you may read about are solely 'builder' error.

 

[ttrentt]

Yes they work fine. The problems you may read about are solely 'builder' error.

Thanks to you and Norris for the reply. I know my next project. Having modded too many pedals this should be hopefully easy.

Trent

 

[dp1228]

EDIT: It's always the stupidest thing...Total coincidence here, but a speaker terminal clip came loose in my cab at the exact time I decided to test my reamp box. It really tricked me good because the connection made good contact when I plugged the guitar straight into the amp after the failed reamp attempt! Turns out the reamp box is completely fine! My reamp is basically the NewYorkDave design using the Edcor 10k:150 transformer. It's working like a charm. The signal is plenty hot and the impedance pot makes a noticeable difference in high frequency response - higher impedance makes more high frequency and slightly increased output, just like guitar pickups. Rock on.

ORIGINAL: So, I bought my DIY reamp parts last summer and finally got around to doing the build last weekend. I'm hopeful that some of you following this thread can help out with some troubleshooting. This seems like the most recently active thread on DIY reamp boxes. I used a very slightly modified version of the NYDave design, so it's based on the 10k:150 Edcor transformer. Changes from NYDave plan - I used a Neutrik combo jack for the input and I used the Jensen ground lift (51 ohm resistor and 10 nF cap in series between sleeve/XLR pin 1 and the ground).

A bit on my construction - I used the output jack (1/4" TS Switchcraft) sleeve tab as my grounding point to the chassis, and the input jack is isolated from the chassis (so, no ground loop when the lift switch is open). I "floated" the ground point by joining all the ground wires at a common point, soldering them, and covering with heat shrink. The ground wires are (1) off the ground lift switch, (2) off the transformer secondary negative (pin 8, aka pin 4 bottom), and off of VR1 (volume pot). These are all wired to the output jack sleeve. I wired R1 across the secondary tabs (pins 5 and 8). The transformer is fixed to the chassis with double sided tape.

My problem is that the output from the reamp box is very distorted and quiet (low level). It sounds like Omega Void's solution (post #28) of using a 1:1 transformer could be the fix. However, others have had success with the NYDave design. Has anyone else run into this issue and found a fix?

My troubleshooting so far - I have tried normalizing my DI guitar signal on my DAW and checked to be sure that the output it balanced +4dB. The peaks are hitting -0.1 on my DAW and soundcard, which is not clipping.

Any advice is greatly appreciated, especially if you have made a working box based on the NYDave design. Thanks!