Help needed with FX loop tone suck!

For those who are having issues with the FX loop, I would suggest calling Mesa Service.

The TC-50 is quite similar in design to the RA100. The FX loop circuit is always active in both. All signals will pass though V5 in the TC-50 as there is no hard bypass for that circuit. The send level is created with a cathode follower circuit using V5 (12AT7) and gets restored by the other half of the tube. The Send/Return jacks are switched on and off with a relay (relay breaks the circuit path between the Send and Return jacks). For this to take effect you need something plugged into the jacks as I believe the jacks also have an integrated switch. The RA100 only has the integrated switch in the jacks and no means to turn on or off the FX loop with a toggle or footswitch control. Also with the RA100 the tube position is different for the loop (V3).

If you do not believe me, remove V5 from the amp, there will be no signal to the phase inverter if you do this. In the case with the RA100 that would be V3.

If you notice any drop in signal strength (volume) or degradation (tone) it could be something you are using in the loop that is causing the issue. (cables may be the root cause or it could be an effect processor). What I have seen thus far with the test I performed on a few amps, the TC-50 signal is approximately in the range of -4dBu due to signal compression from the higher gain stages and distortion, and the clean channel is capable of spitting out 8.17dBu (with channel master and gain maxed). Master or global volume control as well as the solo boost has no influence on the signal strength at the send jack. In all cases, the send level is a product of the channel master and gain control for each channel. I have not been able to get the CH2 or CH3 output above 0dBu since the signal is distorted and clipped.

If you are thinking this to be BS..... go here... http://forum.grailtone.com/viewtopic.php?f=33&t=74195

I started the test with the Mark V and then followed though with the JP-2C and then the TC-50. Just out of curiosity mainly as the Mark V seems to be more problematic with most devices in the loop than the other two amps. Also I found that the Ebtech LLS-2 works quite well with the TC-50 when used as a step down in the loop send and a step up on the return. No volume drop or tone loss noted. I had good success with a Line6 DL4 using the Ebtech and without. No output loading of the signal like you would get with the Mark V using the Ebtech unit.

Still I would recommend you call Mesa if you are having issues with the FX loop, especially if all you do is place a jumper cable between Send and Return.

Did a tiny bit of testing. Used 18’ cables to and from the El Cap. No tone suck at all that I can tell.

Before testing that, I did notice a very significant volume/tone issue right after building the new pedalboard but I tracked that down to a bad cable (one of my custom cables I remember having a particularly hard time soldering).

Contrary to what I may have stated earlier, the TC-50 loop is not exactly instrument level. I assumed it to be as it worked well with the Line6 DL4 and the TC Flashback X3. Both of which would compress the Mark V completely. The send level is a factor of the gain and channel volume controls. CH1 if you were to max out the gain and channel volume that puts out +8.17dBu. Normally you would not be running the amp like that so typical it remains below 0dBu. So perhaps it is sort of instrument level (there does not seem to be a definitive range or how far a signal can deviate from -10dBu as some pickups can be much hotter than that).

Still the TC-50 Send level is about the same as the JP-2C (could not get a signal higher than -4dBu on any one channel). Note testing was all done with a single frequency at 750Hz and a signal level of 223mVrms. Also was able to use the Ebtech LLS-2 in the TC-50 loop with no ill effects on tone or volume. I was curious to see if it would work with the TC-50 and it did. On the flip side, things were not too favorable for the Mark V using the Ebtech LLS-2 probably due to impedance issues. Moderate signal levels at +5.82 dBu on Tweed voice of CH1 and typical values just shy of +4dBu on CH3 with either voice selected.

Perhaps my hearing has gone as I cannot hear a volume or tone difference on the FX loop of the TC-50 with a jumper cable or 15 ft of cable on both send and return. Also the Ebtech LLS-2 did not make any difference when in the loop either. Most of my effects are good up to +8dBu so no bother to me. However it is good to know what to expect when selecting an effect for use in the loop.

The problem described, becasue it seems to be fixed by using a short cable, sounds like the output impedance of the FX Send is too high. So unless you use a very short cable (with very low capacitance), you will lose high end response (tone suck). We have seen this in one other amp (from Two Rock). These FX sends were made to be used with rack units sitting right under the amp, using very short cables.

In our opinion, this is not a good idea. FX Sends should be designed to also work thru long cables going from amps at the backline out to pedals at the frontline.

To find all you ever wanted to know about tone suck, cable capacitance, output impedance, etc. , see our article Do Guitar Cables Affect Your Sound? http://www.pedalsnake.com/blog/category/guitar-related-stuff/

Anyone using something like a Line 6 Helix in 4CM with the TC-50? Any tone loss?

I only notice it when long cables are used, i threw a buffer right after the send using a shrot cable, the buffer sits on the amp then feeds the signal to my pedals via a 15ft cable. No tone suck at all.

It would have been nice to have a buffer built in the loop send maybe but it is what it is, an extra 150bucks for an Area 51 buffer fixed it up for me and in the hindsight its not a big deal. Wouldnt be too hard to add it i side the chasis but for now ill sit the buffer pedal on top and get by, Hope this helps those who cant handle the slight drop.

So I have TC-50 and I grabbed a Boss DD500 and yup, I hear a little bit of top end loss when I use the DD500. With a Mark IV I was getting a BIG tone loss with a Fractal AX8 in 4CM or just in the loop. But a TC Nova system in the loop of the IV worked fine. I don't have the Nova to try on the TC-50. I used short cables and sure enough the DD500 wasn't sucking any tone from the TC-50. Seems the safest route to go is stick a processor back by the amp, which kinda sucks! But, maybe I'll try a Flashback or a Digitech DL8 as those units work great in FX loops.

Bump!

Anyone else still experiencing this issue with the TC 50/100?

I tried a new mini board with new instrument cables (and only one pedal in the loop), and the issue still persists.

I wonder if I could convince Mesa to fix it, since it is bugging the hell out of me.

starbelly said:

Bump!

Anyone else still experiencing this issue with the TC 50/100?

I tried a new mini board with new instrument cables (and only one pedal in the loop), and the issue still persists.

I wonder if I could convince Mesa to fix it, since it is bugging the hell out of me.

Click to expand...

I have definitely experienced it. Dial up a great lead/gain tone, hit the effects loop and it just seems to lose the sizzle (best I can describe). I have noticed a change when reverb is turned on as well. It’s slight, but I can hear it and it’s a buzz kill. Regrettably I have been too lazy to chase it down. I do have “a lot” of cable in the effects loop, so that could definitely play a part. I have DD500 and Mobius (4 cable method) in the loop. I did turn on the buffer in the DD500 and that did not seem to make a difference. I have not noticed it in my Mark V, but maybe it’s because of the adjustment in the level you can make with that amp. Sorry, I can’t help much other than confirm that I have experienced it as well.

For tone suck conclusions at Mesa Triple Crown 100w fx loop, check my recently released experiment here:



100% self-explanatory video

Hope you enjoy,

cheers from Brazil

Mookakian said:

I only notice it when long cables are used, i threw a buffer right after the send using a shrot cable, the buffer sits on the amp then feeds the signal to my pedals via a 15ft cable. No tone suck at all.

It would have been nice to have a buffer built in the loop send maybe but it is what it is, an extra 150bucks for an Area 51 buffer fixed it up for me and in the hindsight its not a big deal. Wouldnt be too hard to add it i side the chasis but for now ill sit the buffer pedal on top and get by, Hope this helps those who cant handle the slight drop.

Click to expand...

I've tested and made a video about it. Please check my last comment.

I'm trying to decipher this on a cellphone with no luck, could you or somebody else explain it even though it’s self explanatory?
I can barely see the text and it seems like settings/variables are changing so quickly that whatever difference in tone there might be is impossible to pin down.

Is the main point that you need a buffer on the send, as the previous poster said?

Hey - super late to the game here, but I've had a TC-50 since they were first available for sale. I've never noticed any fx loop issues at all. When I HAVE experienced problems with my loops (on any of my amps) it's usually been due to one of the components in the chain that the loop is punching out to, or a tube problem.

mkVplayer said:

I'm trying to decipher this on a cellphone with no luck, could you or somebody else explain it even though it’s self explanatory?
I can barely see the text and it seems like settings/variables are changing so quickly that whatever difference in tone there might be is impossible to pin down.

Is the main point that you need a buffer on the send, as the previous poster said?

Click to expand...

Yes, the main conclusion I got is that a buffer right after the fx loop send prevents tone loss.

Yesterday I did another test varying only cable length and the channel master volume (9:00 12:00 15:00) and I concluded that tone suck is lower when the volume is higher, but not as good as when using a buffer that eliminates tone loss.

Please try to watch the video in a bigger screen. For each test I'm changing the track soloing it quickly to let you to listen the tone change but you have to pay attention at the spectrum curves for each combination. Please message me if you get any questions. Cheers

danielpasco said:

Hey - super late to the game here, but I've had a TC-50 since they were first available for sale. I've never noticed any fx loop issues at all. When I HAVE experienced problems with my loops (on any of my amps) it's usually been due to one of the components in the chain that the loop is punching out to, or a tube problem.

Click to expand...

Maybe you have always played using channel master's volume high Iike 15:00 where the tone loss is lower or you used short cables, that is how I don't get any tone suck. Apart from that, when using long cables, in my tests 6ft is already long enough, I got a very audible tone loss which bothered me. Nevertheless, I love my tc100 even more now I can get the high-end and sizzle (placing the buffer right after the fx loop send) that makes it sound much more aggressive.