The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Gear for sale  Search Gearslutz Go Advanced
Any tips on mixer sends, routing please!
Old 13th July 2018
Gear Nut

Any tips on mixer sends, routing please!

Could anyone point me to some discussions, circuit fragments/blocks &c. about signal routing? Things like sends, where a signal might be split several times. I've seen great resources on summing amplifiers and EQs that show levels of complexity with associated trade-offs. I think it might be as simple as multing, or using an output buffer with a load resistor (not sure if that's the right term) per path, but there must be so much I haven't considered!
Old 15th July 2018
Lives for gear
ruffrecords's Avatar
I assume you are thinking about the internals of mixers. In simple terms it is all about the load an amplifier can drive. Most mixers have an amplifier pre-fader and one post fader. These drive AUX sends and buses. Each AUX send is little more than a potentiometer connected to a bus feed resistor. All the post fader AUX send pots are connected in parallel and driven form the post fader amplifier. The pre-fade AUX sends pots are similarly connected in parallel. The channel pan pot is also connected to the post fader amplifier and can feed a number of buses via selection switches. As you can see, the post fader amplifier tends to have a heavier load than the pre-fader one.

A typical TL072 op amp, often used in cheap mixers, can drive a 2K load. If you use 10K AUX send pots it can only drive five of them. If you want to drive more you have to use higher value pots; perhaps 47K. A better op amp like the NE5532 can drive a 600 ohm load so it can drive over 16 10K pots.

In practice, the numbers are smaller because we have not considered the bus resistors, which also are part of the load, and the pan pot and all its bus resistors also represents quite a heavy load. Here's a link to a doc I wrote on this subject for my EZTubeMixer project:

EZTubeMixerRoutingandMixing.pdf - Google Drive


Old 15th July 2018
Gear Nut

That is what I had in mind, although I'm interested in general at this stage. And your explanation and doc are exactly what I needed! Cool project. Thank you!

"Bus resistor": roger!
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.

Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump