Thursday, June 1, 2023




Glen Coleman does not build mass produced equipment, instead he focuses on solutions to problems faced by every audio professional. Is the TC4 something you could use?


The TC4 is the center piece for your monitor speakers, mixing and mastering. In this review we'll be looking at all the functions this box brings to your studio.


Most of the boxes built by Coleman Audio are passive which means no capacitors or semiconductors in the signal path. By eliminating frequency response altering components you're left with the pure audio signal which is what you need to be focused on. 


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The Main Level rotary knob on the front panel controls the speaker output level, it does not affect the signal passing through the inserts. This is a "mastering quality" stereo rotary selector switch with very tiny precision resisters used to control volume level in logical audio increments. This knob feels a little gritty and chunky as you rotate it but rest assured your audio will arrive at your speakers without shifting left or right due to variances in manufacture. 

The headphone amplifier provides plenty of output for low and high impedance headphones. I've used it with a variety of headphones including the Sennheiser HD600, Audio Technica ATH50 and ATH70 and Beyer 770 200-ohm. 


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The really big and unique feature on the TC4 is the four relay-controlled stereo processor inserts. Each insert is selected with a lighted front panel button which shows which loop(s) are selected. Your stereo audio travels through the loops in order, from left to right, 1, 2, 3, and 4. The mastering audio path is all passive to provide you with the truest representation of the final sound. Premium quality relays are used on all the audio insert signal paths and this means you're going to hear exactly what is going on without any distortion being introduced from the TC4.

Loops 1 & 2 are for your mastering EQ and final Bus Compressor. Typically you'll put your master EQ on the first pair of inputs and your Bus Compressor on the second pair. An additional FLIP 1/2 selector button allows the order of the first two loops to be exchanged so you can easily check for sibilance problems. 

How you use the loops is totally up to you and your workflow. 


I connected the four stereo insert loops (inputs and outputs) to a patch bay (not included with the TC4) so I can easily change the processing I'm using on any loop. This allows maximum experimentation as I zero in on a final stereo mix. 


These are my usual processing assignments but I love changing them to hear alternate versions. 

INSERT 1 = Heritage Audio Symph EQ

INSERT 2 = Neve 33609 Bus Comp

INSERT 3 = Pair of EQP Pultec Style EQ with custom output attenuators

INSERT 4 = Prism Sound Overkillers

In my setup the mix output from the TC4 feeds to the input of a TASCAM DA3000 stereo master recorder running at 24/192k to record high quality stereo masters. 

The four insert selector pushbuttons on the front of the TC4 provide you with instant A-B comparisons of your processing. Your ears will love hearing the changes each processor adds (or subtracts). By carefully scrutinizing the IN and OUT characteristics of audio passing through your most vaunted processors you can truly hear their positive and negative characteristics. 

The most surprising thing I've found from using the TC4 is how subtle changes with your processing can improve a mix dramatically. The ease of turning a processor ON or OFF in your final audio can be very enlightening. 

The IN/OUT switch on many pieces of equipment is not a hardwire bypass, this means potential level differences can be present whether the unit is IN circuit or OUT. The TC4, with its bypass relays, eliminates ambiguity by giving you four, switchable stereo hardwire bypass controls for crafting your final stereo mix.


I tried patching my Bricasti M7 reverb into insert #4 and added a nice concert hall ambience to a sweet acoustic guitar performance. The IN and OUT monitoring on the TC4 made it easy to get the reverb adjusted to a very subtle, realistic sounding level. 


The TC4 has a pair of TRS stereo meter output jacks on the rear, I run these to a high resolution JLM stereo bar-graph meter so I can constantly see the output level exiting the TC4.


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The TC4 has an array of other buttons to assist your critical listening. 

PRE/POST INSERTS selects whether the monitor output comes before or after the Insert Loops. Think of this button as a master IN or OUT switch for all the Insert processing. This provides a fast way to hear the effect of all your loops or take them completely out of your signal path for comparison. 

ALT SPK selects an alternate set of powered monitors for listening to the mix. 

MONITOR INPUT 1 / 2 This lets you select the source to hear through the speakers. Monitor 1 Input is where your main stereo mix enters the TC4, it feeds through the Loop Inserts and comes out the Master Output. Monitor Input 2 is fed from a rear pair of TRS inputs. Monitor 2 is where the output from my stereo recorder connects, this selector lets me quickly listen to the recorder without processing. 

MONO converts the main output to mono using an active summing amp stage. 

MUTE L R does what it says, it mutes the Left or Right output depending on which button you press. There are times when it is handy to turn off either the Left or Right speaker, there's a button for that. If you select both L and R to Mute you'll have no output. 

Ø Polarity or sometimes called Phase, this button reverses the wiring on one speaker so you can hear phase cancellation. When you combine Ø with MONO you end up with a simple vocal eliminator (don't buy the TC4 for this effect lol).


This is one of the few active boxes Coleman Audio manufactures. The TC4 has an IEC style power inlet connector on the rear of the steel chassis. 


Connections on the back of TC4

Around back there is a little bit of everything. Most of the outputs are XLR but in the interest of space a few had to be TRS jacks. The loop INSERT audio paths are presented on a pair of 25-pin D-Sub connectors. 


Pricey but priceless is my final verdict on the TC4. If you care about hearing your main bus processors with absolute authority, clarity and transparency there is nothing like the Coleman Audio TC4. Once you truly experience what the TC4 is capable of that $1950 purchase price seems quite reasonable. 

Good Music To You!

©June 1, 2023 Mark King, all rights reserved, it is not ok to quote or copy without the authors written permission. 

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