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PostPosted: Wed Nov 22, 2017 2:06 pm 
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Mark II

Joined: Fri Feb 01, 2013 10:51 am
Posts: 62
Well I made the “mistake” of pretty much finishing my stereo rig. TC-50 + Invective + a handful of pedals. Good lord it’s glorious. Now I don’t know if I’m getting any tone suck at all anymore but if so it’s going down from ungodly to just godly lol. When I get the MIDI functionality up and running I’ll be able to test it out easier but I’ll do so out of curiosity. The rig sounds absolutely immense.

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PostPosted: Sat Nov 25, 2017 10:39 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2988
Location: North Carolina
I have a theory on why some are having issues. for one it could be number of pedals, length of cable runs, type of cable, crappy batteries (some pedals use batteries and even if they are installed and using external power supply, if the battery is weak it may affect the performance of the pedal). As is the case with amps, not all effect pedals are created equal. Sure I am as picky as the rest of you when it comes to the signal chain and want no loss of signal (tone or volume) when using the FX loop. When it becomes amp related, it compounds the issue. However, my theory is simple. How would you know if the pedal in use is not phasing the dry signal from the effect? The obvious would be drop in volume and tone when the effect is active vs set in hard bypass. I would not make any difference to the amp if there was a phase shift on the signal if the amp is using a series loop. Most important is the loading on the send and return lines, so the impedance of the send should be appropriate for the signal being delivered. Send impedance should be low and the return impedance should be high. If you have an impedance miss match the issues will be apparent, the obvious would be trying to drive an instrument level device with line level signal as is the case with the Mark V. I have not had any issues with the following amps using instrument level effects in the loop: JP-2C, TC-50, RA100, Roadster, Mark III, Mark IV. The only black sheep of the heard so far was the Mark V. The effects loop on that amp is not very good and is difficult to manage even with the line level shifter. I have been able to use the line level shifter with the TC-50 without any signal loss which was a surprise as I expected the reduction in signal level would be of concern to the instrument level pedal (test unit was the Line6 DL4, not one of my favorite pedals).

I will attempt another test today if at all possible as I have borrowed some gear from work that will help reveal the truth of the FX loop. Not sure if this will prove anything. Test plan, use a function generator at 1Hz sine wave signal at instrument level, driving the input of the amp. Monitor the FX loop Send signal level as well as the Output to the speaker with a differential probe and a current meter. If there is a change in the output it will be revealed in the current level or voltage amplitude. I was going to do this first with the Mark V as that is the one amp that is more problematic due to its signal levels.

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Sun Nov 26, 2017 2:32 pm 
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Mark III

Joined: Sun Feb 02, 2014 11:51 am
Posts: 161
“The only black sheep of the heard”

Not sure if this was an intended pun or not, but it was a good one.

It will be interesting to see what you find out with the scope on the Mark V and TC50 EFX loops.


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PostPosted: Sun Nov 26, 2017 2:58 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2988
Location: North Carolina
Yes, it was intended to be a pun.

There is some interesting stuff I have measured this weekend. It is obvious that the Mark V send levels are line level. Oh boy are they.... However, the TC-50 has a stout drive on the send level too. The clean channels of the amps I looked at revealed the truth of the signal level ranges. Since the higher gain channels will compress the signal considerably due to distortion my findings on the TC-50 and the JP-2C will remain below 0dBu no matter how hard you drive the gain or channel volume (TC only, JP-2C uses the channel volume as the master and is not linked to the send level anyway). The highest signal level recorded was with the TC-50 clean channel with the channel volume and gain maxed out. Almost nearly enough to clip a strymon pedal in the FX loop at +8.17dBu. Strymon DiG, Brigadier, Big Sky max at or will clip at levels above +8dBu. I doubt I will ever run the clean channel that way but may have to see how it sounds just for kicks. The gain setting maxed out is a definite but not the channel volume.

There is a device called the line level shifter made by Ebtech. I got it for the Mark V but it does not work so well with that amp due to the send level drive impedance. I was able to use the Line6 DL4 with the Mark V and not overdrive or clip the input buffer but the end result was not much effect in the signal. Also the Ebtech LLS-2 reduced or loaded the send output by 23%. Definitely noticeable when turning on or off the FX loop. At least for the case with the TC-50 there was no signal reduction or loading on the send level. I was able to use the Ebtech LLS-2 with the TC-50 with no ill effects on send level or notable change in volume between FX on or off. That was surprising as I expected the level to be closer to instrument than it actually is. However if using a strymon product in the FX loop or even a Boss DD-500, Terra Echo TE-2, you will not be able to overdrive the input buffer. Not sure on signal integrity with the Boss gear (except for the Terra Echo as I have that). The initial focus was on the Mark V but I did include the TC-50 and the JP-2C following the third post or somewhere thereafter.

viewtopic.php?f=33&t=74195

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Sun Nov 26, 2017 4:06 pm 
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Donating Member
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Joined: Mon Jan 24, 2005 4:57 pm
Posts: 4491
Location: South of Heaven
Liquid wrote:
I have the same thing with the fx loop. It sounds like the volume drops a tiny bit or the sharpness. But its nothing raising the presence a smidge wont fix.


This is what I had. Kind of sounded like a volume drop but attempts to adjust the volume back to unity were elusive. Best I can figure out it was a shift in the mids, and volume adjustments won't fix that.

TC-50 -> Strymon El Capistan using two 20 foot cables.

I wound up fixing the problem by putting the delay on top of the head and using a couple of short 18" patch cords.

guitarman3001 wrote:
I posted on another forum and a couple of other people said they were experiencing the same thing with their TC50s, but several others said they weren't noticing any tone loss through their FX loops. The difference seemed to be that those who didn't experience any tone suck were using high end line level processors like Fractal and Line 6 HD units.


The shift in tone is only going to affect those who are using the footswitch to bypass the loop since it's inserting/removing a whole bunch of circuitry/cabling/buffers/etc into the audio path. If you switch the effect on/off at the processor there will be no shift in tone since there's no changes being made to the audio path.

A lot of the guys using multi-effects processors are likely leaving the loop on all the time. Switching the loop on/off will kill their delay/reverb trails and effects spillover when changing presets.

In a way Mesa gets punished for trying to provide a purist option. If they just left the loop on all the time no one would notice the difference. But, because they provide us with bypass options and a way to easily A/B the two sounds people will pick up on the details every time.



Quote:
The biggest mystery for me is why I'm only getting the tone suck with the TC50 and not with any of my other amps, which seem to work perfectly and have no tone suck when using the same setup with their FX loops.


Every Mesa I've ever owned has had a loop that sucked tone, the difference has largely been how perceptible the changes were and how easy it is to A/B the loop against the bypass sound.

My theory is that with the TC-50 being brighter and having more upper midrange than your typical Mesa the small shifts in sound in that part of the frequency spectrum become much more noticeable.

I also suspect it's also a different effects loop design since the master volume/solo are always on and can't be hard bypassed like in previous amps. I don't know what changes that's prompted to their switching and/or design logic.

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Ignore the hype and trust your ears. Play more, buy less = better tone.

|| McCarty | Les Paul | Custom 24 ||
|| Cantrell Wah | Rotovibe | Phase 90 | Grid Slammer ||
|| Triple Crown 50 | Recto 2x12/4x12 ||

|| Jazz Bass | Bass Strategy | PH410 ||


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PostPosted: Mon Nov 27, 2017 6:42 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2988
Location: North Carolina
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... 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.

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Wed Nov 29, 2017 11:49 pm 
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Mark II

Joined: Fri Feb 01, 2013 10:51 am
Posts: 62
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).

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PostPosted: Sun Dec 03, 2017 4:03 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2988
Location: North Carolina
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.

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Tue Feb 13, 2018 4:08 pm 
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Bottle Rocket

Joined: Wed Jul 18, 2012 12:07 pm
Posts: 2
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 ... ted-stuff/


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PostPosted: Sat May 19, 2018 11:13 am 
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Mark IV

Joined: Tue Dec 13, 2005 12:05 am
Posts: 747
Location: Central NJ
Anyone using something like a Line 6 Helix in 4CM with the TC-50? Any tone loss?

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PostPosted: Fri Jun 01, 2018 4:28 am 
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Bottle Rocket

Joined: Thu Jun 09, 2016 6:54 pm
Posts: 19
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.


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PostPosted: Sat Jun 02, 2018 9:16 pm 
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Mark IV

Joined: Tue Dec 13, 2005 12:05 am
Posts: 747
Location: Central NJ
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.

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MarkIIC+,III, IV and V, ED clips here.

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