RSE TS508 Review: 500 Series Tube Saturator
What's Included in This RSE TS508 Review?
This breakdown walks through the RSE Audio TS508, a stereo tube saturator for a 500 series rack, first on a drum bus and then in a full mix. It's a double-wide module with triode and pentode circuits, a wet/dry blend, and a three-band EQ that can sit before or after the tubes. The drums under it are only lightly EQed with no other compression, so what you're hearing is the TS508 alone.
No TS508? The concepts still apply to any saturator with a pre/post EQ option or dual saturation circuits.
This session comes from the Home Recording Made Easy YouTube channel. Watch the full session here.
Table of Contents
- How Do the Pre-EQ and Post-EQ Toggles Work on the RSE TS508?
- Triode vs Pentode: Which Saturation Circuit Should You Use?
- The EQ and Saturation Combo That Makes This Unit Worth It
- Should You Put a Tube Saturator on the Drum Bus or the Master Bus?
- What Worked, and What to Watch For
- FAQ
- Quick Recap
- Final Thoughts
How Do the Pre-EQ and Post-EQ Toggles Work on the RSE TS508?
Of the TS508's four toggles, pre-EQ and post-EQ confuse people first, both off by default. Knowing what each routes matters.
Pre-EQ: EQing Before the Tubes
Engaging pre-EQ sends the built-in EQ, a low shelf at 200 Hz, a bell at 1 kHz, a high shelf at 2 kHz, into the tubes before saturation. Whatever you boost gets pushed harder into the tubes, not just shaped afterward.
So this sends our three-band EQ across the bottom here into the tube saturation. So this is pre the tube. So you can EQ the signal before you hit the tubes. [2:03]
Post-EQ: A Level-Matching Trick That Sounds Darker
Post-EQ trips people up, David included. Engaged, it turns the boosted frequency back down on the output, leveling that boost back out, which makes the whole thing sound noticeably darker.
This is the part that's a little confusing, but that's what these two toggle switches do. [4:55]
Try This In Your Own Mix
If your saturator or console strip has a pre/post EQ option, start with EQ before saturation, not after. Boosting into the tubes (or a plugin's saturation stage) pushes more signal into the nonlinearity, which is a very different result than EQing a signal that's already been saturated.
If you're brand new to gear like this, the free training courses at Home Recording Made Easy cover signal routing basics like this before you spend a dollar on hardware.
Triode vs Pentode: Which Saturation Circuit Should You Use?
Below the EQ, the TS508 has two saturation circuits you can blend between: triode and pentode, with a control that runs from all triode on one end to all pentode on the other, sweet spot at noon. These aren't just two flavors of the same distortion, they behave differently enough that picking the wrong one for the material changes the whole character of the effect.
Triode is more of a warm and a little bit more warm and fat on the low end, whereas the pentode is more aggressive and more bitey, I guess, for lack of a better word. [10:36]
On the drum bus, dialing all the way into triode thins out the low end as you back it off and thickens it back up as you push it, while pentode gets crunchy and audibly distorted almost immediately once it's dialed past the halfway point. Neither is right, they're just different tools: triode for glue and low-end weight, pentode for grit and bite on the transient.
Try This In Your Own Mix
If your saturation plugin has multiple circuit or drive modes, don't default to whichever one sounds loudest. A/B them at matched output level first, the way David does here, and pick based on whether you want low-end weight (triode-style) or upper-mid bite (pentode-style).
The EQ and Saturation Combo That Makes This Unit Worth It
This is the moment in the video where the unit goes from interesting to genuinely useful. With pre-EQ engaged, David boosts a touch of the 200 Hz low shelf and the 2 kHz high shelf before the signal hits the tubes, essentially using the EQ to decide what the saturation circuit has to work with.
That, to me, sounds killer. This EQ is really what makes the difference. [14:19]
David compares the result directly to his Gainlab Audio Empress, a tube EQ he already owns and uses regularly. The TS508 gives up some of the Empress's parametric flexibility, but makes up for it with a more flexible saturation section built into the same box, so the EQ and the tube coloration are reacting to each other instead of sitting in separate boxes in the chain.
Try This In Your Own Mix
On a drum bus, try a small boost around 200 Hz and 2 kHz before your saturator instead of after it, then compare. The saturator reacts to what you fed it, so a small pre-boost at those two points often does more than a bigger boost after the fact.
This exact kind of before/after EQ decision-making is a core part of what's taught hands-on inside The Mixing Academy.
Should You Put a Tube Saturator on the Drum Bus or the Master Bus?
With the drum bus demo done, David patches the TS508 into a full instrumentation mix, drums, bass, guitars, and keyboards, no vocals, still only lightly EQed and balanced with no other processing. The same 200 Hz shelf move from the drum bus section carries over cleanly into full-mix context.
Really brings out the low end really, really nice with this 200 hertz shelf. [20:19]
David's own conclusion is that while it works well on a drum bus, this unit is really built for a master bus role, gluing a full mix together rather than coloring one element. That's a placement decision worth making on purpose rather than by default: a drum-bus saturator and a master-bus saturator are being asked to do different jobs, even when it's physically the same box.
Try This In Your Own Mix
If you're only using a saturator on individual buses, try moving it (or a similar unit) to your master bus for one mix pass at a very light setting. You're listening for glue across the whole mix, not character on any one element.
What Worked, and What to Watch For
What Worked
- The pre-EQ into tube saturation combo (200 Hz + 2 kHz) gave a genuinely useful, musical result David compared favorably to a dedicated tube EQ he already owns.
- Triode and pentode are distinct enough to use as real tonal choices, not just two versions of the same effect.
- The 200 Hz shelf move translated cleanly from an isolated drum bus into a full instrumentation mix.
What to Watch For
- Post-EQ's level-matching behavior is genuinely confusing at first, even David says he's still working out its logic on camera.
- This session has no other compression or processing in the chain, so the TS508's effect will read differently once it's fighting a compressor and other EQ moves in a real session.
- Pentode gets crunchy fast. What sounds exciting soloed on a drum bus can get fatiguing quickly once it's up against a full mix.
FAQ
1) Should I EQ before or after a saturator?
Boosting EQ before saturation pushes more of that frequency into the nonlinear circuit, so the saturator reacts to it, which is what David demonstrates with the 200 Hz and 2 kHz pre-EQ boost on the TS508. EQing after saturation shapes a tone that's already been colored, which is a valid but different move. Try both and compare, since the right order depends on whether you want the saturator reacting to your boost or not.
2) What is the difference between triode and pentode saturation?
On the TS508, triode saturation is described as warmer and fatter in the low end, while pentode is more aggressive and bitey, getting audibly crunchy as it's pushed. They're not better or worse than each other, they're suited to different jobs: triode for low-end glue, pentode for upper-mid grit and excitement.
3) Is a tube saturator better on the drum bus or the master bus?
In this session, the TS508 sounds great on the drum bus, but David concludes it's really better suited to a master bus role, gluing an entire mix together rather than coloring one element. Which placement is right depends on whether you're trying to add character to one bus or cohesion across the whole mix.
4) Do I need the exact RSE TS508 to use these techniques?
No. The specific moves shown here, pre-EQ into saturation, blending two saturation circuits, and choosing bus placement on purpose, apply to any saturator plugin or hardware unit with similar controls. The TS508 is the example, not a requirement.
5) What does the RSE TS508 cost?
David notes it runs a little under $1,000 USD, which is in line with other boutique 500 series saturation modules. RSE Audio is a small, hand-built shop based in Ukraine.
6) Does this session use any compression along with the saturation?
No. David is intentionally isolating the TS508's effect: the drums and full mix in this session are only lightly EQed and balanced, with no compression or other processing running. That's why the saturation and EQ moves are so easy to hear clearly in the video.
Quick Recap
- Pre-EQ pushes your boosted frequencies into the tube circuit; post-EQ levels that boost back out afterward, which reads as darker.
- Triode saturation leans warm and low-end heavy; pentode leans aggressive and bitey.
- A small 200 Hz and 2 kHz pre-EQ boost into the tubes was the single most useful move in the whole session.
- The same EQ move that worked on an isolated drum bus carried over cleanly into a full instrumentation mix.
- David's own conclusion: great on drums, but really built for master bus duty.
Final Thoughts
The RSE TS508 is a genuinely flexible little box, but what makes this session worth watching isn't the unit itself, it's watching someone work out on camera which controls actually matter and which ones just add options. If you're chasing that same kind of pre-EQ-into-saturation move and don't own a TS508, start with whatever saturator you already have and try boosting before it instead of after.
Ready to Mix Like This Yourself?
Learn how to make deliberate signal-chain decisions like pre-EQ into saturation, circuit blending, and bus placement inside The Mixing Academy. Use code ME25OFF for 25% off any single-title course (bundles excluded).
Useful Links
- Full RSE TS508 session on YouTube
- The Mixing Academy
- TK Audio Transformer HB Review: Flexible Analog Saturation
- Exploring the Solid State Logic Bus Plus: Part 1
The techniques shown here reflect one engineer's real-time decisions and reactions in a live gear demo, not a universal rule for every mix. Use this as a starting point for your own ears, not a substitute for them.
