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500 Series Tube and Solid State Preamp
MSRP: $649

The LaChapell Audio 500DT is a 500 series microphone preamp that features two separate topologies or amplification paths. When the blend knob is fully to the TUBE side, the signal will pass through a transformer before being amplified by a TrueTube™ powered 12AX7 vacuum tube. TrueTube is LaChapell Audio’s proprietary method of supplying a full 250V to the vacuum tube so you get loads of clean tube gain.

When the blend knob is turned fully to the OPAMP side, the signal passes directly to a solid state preamplifier. This input is transformer-less and will provide clean gain with exceptionally low noise Placing the blend control anywhere between the two extremes will “blend” the two topologies for a wide variety of tonal options.

500DT DualTopology Front


Lachapell audio 500 series modules icon
500 Series Tube Mic Preamp

An extremely versatile tube mic preamp in the 500 series format.

lachapell audio truetube power 250V icon
TrueTube™ Powered Tubes

TrueTube™ technology supplies both the plate and filament of the tube with the proper voltages they need to access the full characteristics of the tube. Other tube preamp designs cannot supply the needed 250V and don’t have the headroom or harmonics that characterize that classic tube sound.

lachapell audio hi-z input icon
Autoswitching front panel Hi-Z input

The front panel Hi-Z input allows the 500DT to be used as an instrument preamplifier. When a 1/4″ jack is inserted into the Hi-Z input, the 500DT switches into instrument mode, bypassing the input transformer so the instrument accesses the preamp directly.

Lachapell Audio dual drive icon
Dual drive knobs

The Dual Drive knobs on the 500DT provide an incredible array of tonal options. The input knob drives the input preamp and the second knob drives the output for sounds ranging from pristine to gritty.

Dual Topology Web Circle - Mic Preamp
Dual Topology Mic Preamp

With both a Truetube™ powered full sized 12AX7 vacuum tube preamp AND a solid state preamp, the 500DT Dual Topology preamp is exceptionally versatile. Blend between the tube and solid state sides to mix the two sounds.

Tube Path



    Frequency Response

20 Hz to 20 kHz

    Maximum Output

12 dBu

    Typical EIN


Solid State Path



    Frequency Response

20 Hz to 46 kHz

    Maximum Output

28 dBu

    Typical EIN


Internal Gain

67 dBu

Input Impedance

1.5 KΩ Mic / 10 KΩ Hi-Z

Tube Complement/Type

1x 12AX7 (ECC83)

500DT Dual Topology tube preamp hybrid - kick example


On Kick, try leaning on the OPAMP path so that the attack of the beater comes through. Blend in some of the TUBE path to get more weight and body with the INPUT GAIN lower than the OUTPUT GAIN.

500DT Dual Topology tube preamp hybrid - snare example


On snare drums, the OPAMP path will provide fast transients where the TUBE path will provide natural compression and a bit slower transients. To let some transients through, with some natural compression, try setting the BLEND at about 30%.



Drum overheads need clarity so try the BLEND at around 70-80%, the INPUT GAIN around 20-30 and the OUTPUT GAIN making up the rest of the needed amplification.

500DT Dual Topology tube preamp hybrid - vocal 1 example


On vocals, try using the TUBE path for an intimate vocal, balance the INPUT GAIN and OUTPUT GAIN to accentuate a proximity effect on a condenser mic.

500DT Dual Topology tube preamp hybrid - vocal 3 example


For an aggressive vocal, try moving the INPUT GAIN to the 50-60 range, set the OUTPUT GAIN so that it doesn’t clip the converters and then play with the BLEND in the 30%-60% range.

500DT Dual Topology tube preamp hybrid - vocal 2 example


For a gorgeous and soaring vocal, lean on the OUTPUT GAIN more, with the BLEND closer to the OPAMP path.

500DT Dual Topology tube preamp hybrid - bass example


On bass guitar, run the INPUT GAIN at around 50-55, setting the level to your DAW with the OUTPUT GAIN. With the blend at 60% the bass will growl courtesy of the tube path yet have clarity and articulation from the OPAMP path.

500DT Dual Topology tube preamp hybrid - guitar modeler example


Try using the 500DT as the front end to a guitar modeler. With the INPUT GAIN up, you can add some true tube distortion to your tracks.

500DT Dual Topology tube preamp hybrid - guitar example


With the INPUT GAIN lower and the OUTPUT GAIN up, the TUBE path adds some life to software modelers, while the OPAMP path adds some bite. Blend between them for your perfect tone.



The 500DT features a full 12AX7 tube powered by TRUETUBE™ so you get a fully powered vacuum tube and all the harmonic richness and clean gain that only a properly powered tube can deliver.

This is a question that we are asked often and the answer is no. Yes there is a glowing vacuum tube in your 500 series module but it is a 9A type preamp tube. This is the same type used in the AKG C-12, Telefunken 251, etc. While these mics only have one section of the tube active, they also have less internal volume for the tube to cool and yet the surface temp of these mics never exceed room temperature. As long as you don’t block the venting that is already part of the 500 series power supply you will be just fine.

The 583S mk2, 583E, 500TDI and 500DT will get warm but nothing more than any other 500 series module drawing 110-120ma. It’s never a good idea to block or cover ventilation holes that are on top covers of the 500 series power supply.

All LaChapell Audio products feature a 2 year warranty on parts and labor for issues relating to manufacturing. The tubes have a 6 month warranty. Please see the Digital Audio Labs Warranty page for more information.

Yes. The manual will provide guidelines in this regard. The 2-bay 583’s (583E and the original 583S) have square openings that are intentionally designed to allow users access to the 12AX7 and replace with other like tubes for additional flexibility. Generally speaking, it’s the input tubes (the 12AX7s or 12DW7s) that would be replaced if you are looking to alter the sound of the amplifier. The 992’s output tubes require a critical balancing step so, for that reason we don’t recommend messing with these. In any case, if there’s ever a question related to swapping out tubes PLEASE give us a call.

LaChapell Audio has been incredibly fortunate in having a great user base. We’ve had folks like Brad Paisley, Hans Zimmer, Phil Keggy, Depeche Mode, M83 and other personally choose our preamps over others for critical productions. Many studios in Nashville, LA and the rest of the world rely on LaChapell Audio to track the sound they want.

Not at all. From the beginning we set out to not only make the first tube preamp for the 500 series, but the world’s first HIGH-VOLTAGE tube preamp for the 500 series. Think of the 583, 500DT and 500TDI as having a secondary high-voltage supply within the unit. All LaChapell Audio 500-series modules with tubes feature both a full 250 volts to the plates and a full 12 volts to the filament. This is the proper way of powering a vacuum tube and, more importantly, allows the tube to behave the way it was design sonically without stress from a lack of power.

First, it provides for the basic need to attenuate the input signal for “hot” or loud sources. For example, there are some microphones out there that generate such a large signal that a pad is required in order to prevent unwanted distortion.

The second reason is for sonic shaping. All LaChapell Audio preamps place the -20dB pad function in such a way that, when engaged, the gain contribution from the input transformer is effectively eliminated. When that loss of gain is made up by dialing in INPUT gain, the user has essentially traded transformer gain with vacuum tube gain. As a result, the distortion is different, the frequency response is different, etc. User who use this this technique express hearing more “air” and “depth” to the sound. It’s not always preferred but it demonstrates the preamps sonic flexibility. A couple areas where this technique is routinely used are drum overheads and stereo piano overheads.

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