Strange volume problem using rack effect in passive loop

[TomWalsh]

Hi all, I believe this is my first post on here, been a long time lurker.

I am using a TC M300 in the loop of my ceriatone bluesmaster (that's technically a low plate non-hrm into a bluesmaster PI now) without a dumbleator (my band already think having a head and cab is too much gear!) And I'm having a problem with the master volume on the amp. When I turn the dial from about 9 o'clock to 2 o clock there seems to be little volume difference when using the m300 in the loop. I don't get this problem with a boss dd3 or tc hall of fame.

I was wondering whether it was to do with the preamp output impedance changing as I turn up the volume?

I had the idea of swapping the master volume leads over (themiddle and outer lug) so that the preamp output sees a more consistent resistance to ground as the master volume is turned up and then putting a resistor connected to ground to give a more appropriate output impedance.

The M300 input impedance is 13k ohms, so an output impedance of 1.3k ohms would be cool, I figured that putting a 1.3k-ish ohm resistor to ground before the output Jack would sort out the impedance after modifying the master volume. However, will I be loosing a lot of signal by doing this?

Getting another unit to carry around and run isn't ideal but I understand a buffer would make all these problems go away.

Thanks!
Tom

[jcsifu]

Hi all, I believe this is my first post on here, been a long time lurker.

I am using a TC M300 in the loop of my ceriatone bluesmaster (that's technically a low plate non-hrm into a bluesmaster PI now) without a dumbleator (my band already think having a head and cab is too much gear!) And I'm having a problem with the master volume on the amp. When I turn the dial from about 9 o'clock to 2 o clock there seems to be little volume difference when using the m300 in the loop. I don't get this problem with a boss dd3 or tc hall of fame.

I was wondering whether it was to do with the preamp output impedance changing as I turn up the volume?

I had the idea of swapping the master volume leads over (themiddle and outer lug) so that the preamp output sees a more consistent resistance to ground as the master volume is turned up and then putting a resistor connected to ground to give a more appropriate output impedance.

The M300 input impedance is 13k ohms, so an output impedance of 1.3k ohms would be cool, I figured that putting a 1.3k-ish ohm resistor to ground before the output Jack would sort out the impedance after modifying the master volume. However, will I be loosing a lot of signal by doing this?

Getting another unit to carry around and run isn't ideal but I understand a buffer would make all these problems go away.

Thanks!
Tom

Might be a routing issue of serial vs. parallel. I would try just using the reverb engine in parallel mode.

Also, are you returning to the amp with the mono output from the TC?

from web:

There are two available routing configurations: serial or dual send/return. The serial mode places the multi-effects processor engine before the reverberation processor, without any facility to change the order -- so no phased reverbs. This isn't really a limitation for 99 percent of applications, but worth pointing out. The latter mode, indicated by a green LED on the front panel, configures the M300 as two independent processors. The left input feeds the multi-effects processor, while the right input feeds the reverb processor, the outputs of both stereo effects being summed to a common stereo output. If only the left input is connected, this signal is normalled through to the reverb processor as well, providing a mono-in, stereo-out dual-effect unit.

[Teleguy61]

jcsifu is exactly correct.
I have a M300, and you have to use it in serial mode for it to function at all well in the loop.
FWIW, the M300 particularly is greatly improved with a D-lator. I didn't feel it worked that well without it.

[rob@tele]

The TC has a low impedance input circuit that is way too low for the high impedance passive loop and the TC will load the output of the preamp. The standard boss pedals have a high impedance input as you are also able to use them in front of the amp. You could try to put a boss pedal in front (in series) of the TC in the passive loop.

[jcsifu]

FWIW, the M300 particularly is greatly improved with a D-lator. I didn't feel it worked that well without it.

I use a D-lator in every amp I own that has a passive loop. Everything's better with D-lator on it.

[TomWalsh]

Thanks for all the replies! I will try the switch on the back of the M300 and report back. As well as trying a boss type pedal first in the chain.

Realising a buffered effects loop would be best I had a look around and I stumbled across this fx loop that can be installed in an existing tube amp, what do you reckon it'll be like in a dumble amp?

https://www.tube-town.net/ttstore/produ ... ts_id=5973

There's also a tube version with parallel option but I've never heard of the tube used

Tom

[Structo]

Tom are you in Europe?

Please put your location in your profile so we can better help you with products.

[Teleguy61]

It's not very hard to build a D-lator, and it works.
I built one into a D-Lite type build, that is in a Weber chassis that is sized for a 45 watt Marshall. Tight but can be done.
https://tubeamparchive.com/viewtopic.ph ... ght=dlator

[rogb]

Thanks for all the replies! I will try the switch on the back of the M300 and report back. As well as trying a boss type pedal first in the chain.

Realising a buffered effects loop would be best I had a look around and I stumbled across this fx loop that can be installed in an existing tube amp, what do you reckon it'll be like in a dumble amp?

https://www.tube-town.net/ttstore/produ ... ts_id=5973

There's also a tube version with parallel option but I've never heard of the tube used

Tom

Build a dlator if you can and adding a line mixer like a Suhr Minimix is the icing on the cake

[TomWalsh]

Using the serial/dual input mode didn't solve anything with the volume problem however putting a boss pedal in front solve everything, plus I realised I can use the boss dd3 delays and use other effects (tremolo, chorus) at the same time so that's cool.

As to fitting the d-lator inside the chassis, I have a ceriatone bluesmaster (http://www.ceriatone.com/images/layoutP ... BM-50W.jpg) if I built a d-lator do you reckon I could fit all the components in between the PI and power tubes? Would I get excessive noise by running wires past the PI?

Tom

[Teleguy61]

I got one in here:

It was crowded but it got done.
The tube and related circuitry are under the speaker jacks, middle rear.

[jcsifu]

Using the serial/dual input mode didn't solve anything with the volume problem however putting a boss pedal in front solve everything, plus I realised I can use the boss dd3 delays and use other effects (tremolo, chorus) at the same time so that's cool.

As to fitting the d-lator inside the chassis, I have a ceriatone bluesmaster (http://www.ceriatone.com/images/layoutP ... BM-50W.jpg) if I built a d-lator do you reckon I could fit all the components in between the PI and power tubes? Would I get excessive noise by running wires past the PI?

Tom

I don't know if I would try to do it just yet bro, you have things sorted out as is. Maybe play it for a while and see if it continues to meet your needs.

On the other hand...
Would be a very cool thing if I had built mine in my D-style. Would be cool to see you do it and post pics and updates...

[jcsifu]

I got one in here:

It was crowded but it got done.
The tube and related circuitry are under the speaker jacks, middle rear.

Holy crap bro! That is some major roadways in there.

Got any more pics of the whole project? I would like to see more.

[Teleguy61]

Here are some more.
No relays, OD and PAB switches, also switches for Midboost, Fat/Thin mid, and three step OD entrance.
Full/half power switch on rear panel.
Kitchen sink probably in there somewhere.

[jcsifu]

Here are some more.
No relays, OD and PAB switches, also switches for Midboost, Fat/Thin mid, and three step OD entrance.
Full/half power switch on rear panel.
Kitchen sink probably in there somewhere.

So do you have a channel foot switch?

What's the LMH switch? I can't make out the 2 resistors wired into it but they look like two 270k's split.

Props to you for jamming that in there and making it still quiet. That would scare me,

Thanks for the pics bro!