We all wish to leave more that footsteps in the sand to prove we were here. I am lucky enough to have been awarded several utility patents for inventions I came up with in the course of my design work. What follows is an abstract and brief discussion.


US04166245  Roberts

08/28/1979   Simultaneous display of multiple characteristics of complex waveforms. This was a clever way to display the “peak” and “average” value of a given waveform on a single LED array. The average or RMS value was displayed as a connected bar while the peak was a single LED floating above the bar. This patent was assigned to Loft Modular Devices a console and rack effects products company no longer in business.

This was my first patent and I still like it.

click on picture for video  or here for another or here for yet another


 US04818951  Roberts

04/04/1989   Gain control or multiplier circuits. This was a circuit design that utilized separate DC and audio frequency feedback paths to automatically bias transistors in a VCA design so unmatched transistors could be used in production. This VCA was used in the old AMR CDS-2 compressor/limiter/de-esser. The Patent was assigned to Peavey Electronics.  

This was a useful to avoid factory trims and selected parts but class A VCA was not very high performance and eventually abandoned.


 US04953222  Roberts

08/28/1990 Multiple channel gated amplifier system. This is a specialized logic arrangement for a multi channel noise gate. One channel in addition to responding to it’s normal threshold control would automatically open if all other channels were gated off. This allowed conversational speech between songs with normal (higher) thresholds during performance. This technology was incorporated into Peavey’s “SmartGate”. Patent was assigned to Peavey Electronics.  


This was a nice idea but for a pretty narrow specialized application so didn't find a broad market.



US05119426  Roberts

06/02/1992 Linear array level meter displaying multiple audio characteristics . This is a variation on my earlier ’79 meter invention. In this version the Peak value is represented as the top of a floating bar graph, the average or RMS as the bottom of the same floating bar graph. When the display is calibrated in equally spaced dB increments, the number of LEDs lit shows crest factor. Still being used in Peavey’s SRC 6 bus series. Patent assigned to Peavey Electronics.

This was an improvement patent on my original meter and worked OK but I kind of prefer my first meter approach.



US05509080 Roberts

04/16/1996 Bass clipping circuit. This circuit combines a simple clamp diode with a Baxandall tone control circuit to provide frequency selective (bass only) clipping. The benefit is allowing relatively large amounts of bass boost at low level but simultaneous clamping of the bass at high amplitude. Further the clamping of bass frequencies only, allows the high frequencies to mask the clamping. Limiting high amplitude bass frequencies prevents saturation of transformers commonly used in constant voltage distribution systems. This invention was used in several Architectural Acoustics mixer/amp products. Patent assigned to Peavey Electronics.

This was an pretty elegant inexpensive solution to the common problem of saturating magnetics in 70V audio systems due to too much loudness and bass boost. Still in use AFAIK







 US05652800  Roberts

07/29/1997 Automatic mixer priority circuit. This is an improvement to the classic “Dugan” automatic mixer patent that shares total gain based on relative amplitude. This invention tricks the computing circuits into thinking a channel is louder than it really is, providing a variable priority without giving up the unity gain before feedback relationship. This is used in the AA “Automix” products. Patent assigned to Peavey Electronics.   US05652800

A useful variation on the classic Dugan automatic mixer invention.


US05737428  Roberts

04/07/1998 Circuit for providing visual indication of feedback. This circuit uses a compound differential absolute value detector, with a bank of band pass filters commonly used in graphic equalizers to provide a single LED indication above the frequency band with the loudest signal. During feedback this the illuminated LED shows which fader to pull down. This invention is used on all Peavey FLS products. Patent assigned to Peavey Electronics.

 This was easily my most commercial patent at Peavey. FLS LEDs were built into every Graphic EQ Peavey made including those in powered mixers.


6,515,859 Roberts ,   et al. February 4, 2003

Heat sink alignment

A heat sink alignment apparatus having an internal chamber with a plurality of heat sinks placed at an angled relationship to one another creating a tunnel through which air streams flows. At least one heat source is attached to a heat sink. A plurality of air streams enter the heat sink alignment apparatus through an ambient air intake and over a fan into the tunnel. The tunnel gradually narrows thereby increasing the velocity of the air streams which increases the cooling of the heat source. The narrowing shape of the tunnel creates turbulence within the plurality of air streams increasing the transfer of heat to various airstreams from the heat sink thereby lowering the temperature of the heat sources also.

I was a co-inventor on this with two other power amp guys. Simple but it works and is still in use in several amp lines.



6,925,880  Roberts  August 9, 2005

Apparatus and method for measuring the acoustic properties of a membranophone


Apparatus and method of measuring acoustic properties of a drumhead of a drum are disclosed. The acoustic properties are measured by exciting the drumhead with a source of energy and detecting the acoustic energy emitted by the drumhead. The acoustic energy emitted by the drumhead may be measured using a microphone or other acoustic sensor. The use of multiple energy sources provides isolation of acoustic energy and allows measurement of local resonance of the drumhead.

This invention isolates and precisely measures the lug tension of individual lugs compared to a reference allowing precise matching for clearest drumhead sound.



link to AMR console manual