Dan Kropp’s
AMP
LAB

This article was published in #Issue 19 in summer 2016.

Anything that shows up with the name “Genzler” on the box is going to come with a large number of expectations, memories, and stories attached for anyone in the bass community. The new Magellan™ 800 from Genzler™ Amplification is no exception. With a small, lightweight design, stuffed with a good selection of features, there can’t be a lot of room left for the high expectations of the Genzler name, but somehow it all seems to fit.

Walk Around

To kick things off with this amp, let’s take a walk around it to get an idea of the features and controls. Then we can get into some detail. As we approach this amp, we can see that the front panel in Fig. 2 is dominated by control knobs and a few switches. The only input on the front of the amp is the single ¼” instrument jack – which has an input impedance of .955 Mohms (measured with a 200Hz, 200 mVrms sine wave). Moving from left to right from the input jack, there is a Mute button (which mutes the speaker output and DI, but leaves the Tuner output active) and a Pad button, which imparts an 8.5 dB cut to the input, for use with “hot” instrument outputs.

Fig. 2 Front panel

Next up are controls for the different input channels this amp offers. The Clean Volume knob controls the input stage volume for the Clean channel. To the right of the Clean Volume is the Channel switch that selects the Clean vs Drive channel. Next, we find the controls for the Drive channel. The Drive Gain sets how much “drive” you want in the signal, and the Drive Volume sets the input stage volume for the Drive channel of the preamp. Moving along to the right of the channel controls are the Contour controls. The Curve switch selects between two very different frequency response curves (labeled A and B) as a base level to feed into the EQ. The A and B contours have very different frequency responses that can influence the signal to a varying amount, based on the setting of the Shape knob. Next, we have the controls for the 3-band EQ – namely, Bass, Mid, and Treble boost/cut, plus a Freq knob to control the effective frequency of the Mid band.

Last up is the Master Volume in the customary right-most position. Above all these controls is a line of LED lights to give status and indicate selections for all the controls. In addition to lights for the Mute and Pad function, and for showing which channel and which contour is active, the power LED above the Master Volume light will turn from blue to red in thermal overload conditions or shorts in the speaker outputs. A separate “Clip” LED above the Channel button indicates clipping of the preamp channels and EQ stages. Along both sides of the amp are vents indicating a side-to-side air flow for the internal cooling.

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A look at the back of the amp in Fig. 3 reveals all the rest of the connectors we normally find on a modern bass head, plus a few we don’t always see. There is a standard power cord connector and power switch, two Speakon® speaker connectors (with an associated Impedance Selector switch to select 2.67 Ohms or 4/8 Ohms), ¼” EFX Loop connectors, Aux In and Tuner Out ¼” connectors, and ¼” Phones and Foot Switch jacks. Wrapping things up is a balanced XLR DI, with switches for ground lift, pre and post EQ, and mic or line level.

Fig. 3 Back Panel

Construction

Of course, one of the first things to do to any amp on the test bench is to take it apart. But first, there are a few comments about the exterior. The knobs on the front have a pretty light feel, with a good knurled finish, but the EQ knobs do not have an indent to indicate the neutral position. Also, there is no external fuse. The only fuse on this amp is internal and is listed as not being user-serviceable. The case is all-aluminum, held in place with 12 Allen wrench screws. After opening the case, the top and bottom were measured to be 0.075 inch thick, while the back is 0.056 inches thick. The front is a solid machined piece of aluminum, measured to be 0.272 inches at its thickest point.

Fig. 1 (Fig.1 is the very top image)shows there are a total of six circuit boards in this amp: one input board, two output boards, two LED boards, and one power amp/power supply board (the ICEpower 700ASC/X module). The boards are very securely bolted to the chassis, and there is enough glue to hold components, without being messy. Solder joints and component placement are very good, as well. The details of tucking in and securing all cables are often times an afterthought, but in this case, everything is secure and solid.

All the potentiometers are micro-style, mounted directly to the circuit boards. The large aluminum heat sink is set to take good advantage of the airflow provided by the single variable-speed fan, and is helped along with internal aluminum baffling to keep air flowing the right way.

Channel Selection

The Channel switch on the front selects between the Clean and Drive channels of the input stage of the Genzler Magellan 800 (the foot switch input on the back performs the same function). The Clean channel is a FET-powered, straight pass-through of the input signal, with the Clean Volume knob controlling the input stage volume. The Drive channel shapes just about every aspect of the signal. The Drive Gain knob controls the amount of modification to the signal, while the Drive Volume knob controls the pre amp stage volume.

Figs. 4 and 5 show the scope traces for the Clean and Drive channels. The Clean channel can be seen to be a straight-up sine wave. A close comparison shows that the Drive channel is “fatter” around the middle, and not quite identical on both sides of the wave. This effect is intensified as the Drive Gain knob is turned up. Figs. 6 through 9 show the harmonic characteristics of the amp through the Clean channel and three settings of the Drive Gain for the Drive channel. The Drive channel bumps harmonics H2 and H3, while cutting the higher-order harmonics when the Drive Gain is set at 9 o’clock. With Drive Gain on the noon setting, the Drive channel increases all harmonics, but proportionally affects the higher-order harmonics more. Going to 3 o’clock on the Drive Gain has almost all its effects on the higher-order harmonics.

Fig. 4 Clean channel

Fig. 5 Drive channel

Fig 6. Harmonic characteristics: Clean channel

Fig 7. Harmonic characteristics: Drive channel, 9 o’clock

Fig. 8 Harmonic characteristics: Drive channel, noon

Fig. 9 Harmonic characteristics: Drive channel, 3 o’clock

The Tone Stack

Another effect of the channel selection is the base level of the tone stack. Fig. 10 shows the frequency response of both the Clean and Drive channels. The blue trace shows the Clean channel, which is a flat response with a sharp drop below 35Hz, and only a small curve above 9kHz. The green, red and brown traces show the frequency response for the Drive channel with Drive Gain at the 9 o’clock, noon, and 3 o’clock positions. These traces show that the curve gets slightly more pronounced as the Drive Gain is increased, as well as affecting overall gain of the preamp. The green 9 o’clock trace shows about a 5 dB drop from 800Hz to 20kHz, while the brown 3 o’clock trace shows about a 13 dB drop in the same range. Overall, the Drive channel softens both the high and low frequencies, as well as affecting overall gain of the preamp.

Fig. 10 Frequency response, Clean & Drive channels

Before the signal gets to the EQ, it passes through the Contour circuitry. This gives the choice of selecting two frequency response curves as your baseline feeding the EQ. Both settings are affected by the Shape knob, which adjusts the intensity of the frequency response curve applied to the signal. Fig. 11 shows the frequency response for different Contour settings. The blue and black traces are the Contour A and B setting with the Shape knob turned all the way down. These traces are hard to distinguish on the graph, because they are mostly the same, and are very flat, as advertised. The red and green traces show the Contour A selection with the Shape knob at the noon and max positions, respectively. These settings create a mid-frequency cut centered at about 600Hz, while boosting frequencies above 2.5kHz and below 150Hz. The pink and orange traces show the frequency response for the Contour B selection with the Shape knob at the noon and max positions. Contour B has a boost centered at 200Hz and cuts all frequencies above about 700Hz.

Fig. 11 Frequency response for Contour settings

After passing through the Contour circuitry the signal runs through the active 3-band EQ. Fig. 12 show the sweep of all the bands of the EQ. The blue trace shows the very low +/-0.546 dB variation in the 80Hz to 8kHz range with all EQ controls at noon and the Shape knob of the contour control turned all the way down. By tweaking the EQ settings, as shown in Fig. 13, the variation can be reduced to +/-0.138 dB in the 80Hz to 8kHz range, as shown on the brown trace. It is almost impossible to distinguish between the blue and brown traces on this graph because of the already very flat response of the all noon setting. The only reason an optimally flat trace is included is to show the very fine level of control available with this EQ. The pink and green traces of this graph show the all EQ settings at minimum and all EQ settings at maximum, respectively. This shows the entire range of the EQ to be around +/-15 dB and all of the bands stay distinct without a lot of overlap.

Fig. 12 Frequency response, max boost/cut settings

Fig. 13 Optimally flat settings

Fig. 14 is the frequency response for the Bass band. The blue trace is the Bass knob at noon, while the red trace is Bass set at minimum and the green trace is Bass set at maximum. The green trace shows a 13 dB raise at 40Hz, while the red trace shows a 15 dB cut at 40Hz.

Fig. 14 Bass sweep

Fig. 15 shows the frequency response for the Mid band of the EQ. There are a lot more traces on this graph, since there is a Freq knob to control the effective frequency of the mid band of this amp. The light red and green traces show the Mid minimum and Mid maximum with the Freq knob turned to its lowest setting. This shows a nice clean +/-15 dB variance, centered at 160Hz. The black and pink traces show the minimum and maximum of the Mid knob with Freq set at noon, and the orange and brown traces show the minimum and maximum of Mid with the Freq set all the way up. All these traces show a very consistent +/-15 dB change, varying from centering on 160Hz to 3kHz.

Fig. 15 Mid sweep

Fig. 16 shows the frequency response for the Treble knob, with the green trace showing the maximum and the red trace showing the minimum. The Treble band of this EQ gives a very nice +/-14 dB shelf for frequencies higher than 10kHz.

Fig. 16 Treble sweep

Thermal Properties

How an amp handles and recovers from thermal overload conditions is a difficult situation to test in normal operation. In general, amps are designed to avoid thermal overload, but on the rare occasion where it could happen in real life, it would be catastrophic if the amp does not behave well. Because of this, every amp on the test bench is driven to thermal overload in order to allow us to observe the amp’s behavior. The test bench has the ability to drive an amp much harder that anything that would be seen in real life, so it is the best place to check these thermal issues. If it behave well under these grueling bench tests, it definitely should behave well on the gig.

Driving this amp at very high volumes with a continuous sine wave did eventually lead to thermal overload. As the amp heated up, the variable-speed fan increased speed to cope with the added demand. When the amp finally hit thermal limits, the output was cut off completely, until the heat dissipated. After the amp cooled to below its thermal limits, it re-enabled the output and operation resumed with no issues. No user action was necessary, as the amp handled the condition in a safe manner on its own. Overall, this amp handled overload very well. The amp was protected from damage and required no user interference to recover.

Gain

Yet another area of performance that is affected by the Channel selection is the gain map of the amp. Fig. 17 shows the gain of the amp as a function of input level. The blue trace is the gain map for the Clean channel. It shows a very typical response that is very flat up to a rather sharp drop-off that starts between 500 mVrms and 600 mVrms. The rest of the traces on this graph are with the Drive channel selected. The pink trace is with the Drive Gain set at 9 o’clock, the brown trace is with Drive Gain set at noon, and the green trace is with the Drive Gain set at the 3 o’clock position. In all these positions, the Drive channel produces a much earlier knee in the curve, with a much gentler cut off. As the Drive Gain in increased, the effect on the gain map is also increased.

Fig. 17 Gain as a function of input level

Output Power

One of the most important factors regarding output power testing is selecting an appropriate THD+N percentage to use during our measurements. The baseline that is used is the THD+N that is measured right at the point where visible clipping of the signal starts to take place. A bass amp will sound the same up until this point, but the signal will start to degrade at levels beyond this clipping point. The point at which this degradation becomes audible is variable for different amp designs, personal hearing thresholds and style. This creates a reproducible conservative power rating that will work for all amp designs. For this amp, we determined the appropriate THD+N value to be 5%, and all of the following power tests were done with a 5% THD+N value as the maximum allowed. For all of these tests, our Audio Precision unit utilizes a 1kHz sine wave signal, and the amp is connected to a purely resistive dummy load. The amp is powered by a standard, unregulated wall socket with at least 120V available.

Genzler rates the Magellan 800 as supplying 400 watts into an 8-ohm load. The measured output for continuous power was 383.93 watts into an 8-ohm load (at 5%THD+N). Into a 4-ohm or 2.67-ohm load, Genzler rates the MG-800 as supplying 800 watts. On the test bench, set up for continuous power, the Magellan produced 728.44 watts into a 4-ohm load and 752.67 watts into 2.67-ohms. Burst mode testing of output power yielded very similar numbers: 374.54 watts into 8-ohm load, 741.2 watts into a 4-ohm load, and 738.71 watts into 2.67-ohm load. These are all very solid numbers for an amp rated at 800 watts.

Power Supply

The ICEpower output module utilized in the Magellan 800 is equipped with a switch-mode power supply. This power supply will automatically sense the input voltage and set itself up, accordingly. This power supply design also eliminates the need for a heavy transformer, which makes the whole amp quite lightweight. As previously noted, there is no external fuse, although there is a fuse on the power input line of the amp (but it is internal, and not user serviceable).

Conclusion

Genzler has certainly come through on the build quality of this amp. Not very many pieces of electronics, let alone bass amps, have the quality and attention to detail that is in this amp. From a physical point of view, this amp will likely have a long life, with few issues.

The Contour and Channel features are nicely adjustable to get a wide range of sounds, even before you hit the tone stack. Anything from clean and flat to distorted and peaky can be dialed in to create the sound you want. The Drive Channel effects on all aspects of the signal are well thought-out and implemented. The power output is right where one would expect, and with the exceptional attention to detail and quality of the build, it will likely be putting out that power for you for a long time to come.

bass test
DNA Guitar

Genzler
Magellan 800

ENCLOSURE

Material:Aluminum
Dimensions:11 1/4” W x 10 1/2” H x 3” D
Weight:9 lbs
Rackable:No

PREAMP

Inputs:1 x mono jack 1/4”
Mode:Solid state
Tubes:N/A
Input Impedance:.955 Mohms 200Hz, 200 mV Sin
EQ Type/Features:3-band (variable mids)
Compressor/Limiter:No
DI Output:Balanced XLR, pre/post, line/mic, ground lift
Effects Loop:Yes
Construction:PCB
Additional Features:Clean drive channels, contour A/B, pad, aux in, headphones & mono out

POWERAMP

Mode:Class-D
Tubes:N/A
Outputs:2 Speakon®
Impedance Options:4/8 or 2.67 ohm
Construction:PCB
Power Supply:Switched-mode
Cooling System:Single Fan, variable speed
Line Voltage Options:100 - 240 V, auto select

MEASUREMENTS

Full Bandwidth All Controls at Noon:20Hz - 20kHz +/- 5.665dB; 250 mV
swept sin input
Limited Bandwidth All Controls at Noon:80Hz - 8kHz +/- 0.456dB; 250 mV swept
sin input
Limited Bandwidth Optimally Flat:80Hz - 8kHz +/- 0.138dB; 250 mV swept
sin input

POWER

8 Ohm4 Ohm2.67 Ohm
Continuous Power:384 W728 W753 W
Measured Voltage:55.42 Vrms54.65 Vrms49.08 Vrms
Burst Power:375 W741W739 W
Measured Voltage:55.08 Vrms54.45 Vrms44.66 Vrms
Wall Voltage DUT:125.3 Vrms124.1 Vrms121.6 Vrms
THD+N:5%5%5%

GENERAL

Company:Genzler Amplification
[email protected]
www.genzleramplification.com
County of origin:Taiwan
Year of origin:2015
Warranty:3 years
List Price:$759.00
Street Price:$759.00
Test Unit Options:None
Accessories:Padded carry bag (optional)
Available colors:Silver
Available Options:None (will work with most “generic” footswitches)
Acquired from:Genzler Amplification
Dates:December 2015 to April 2016
Locales:Ohio
Test gear:Genzler BA12-3, Pedulla Nuance 4, Vigier Excess 5, Sterling by
MusicMan Ray34CA, Mesa/Boogie D-800, Bergantino B|Amp,
Peavey MiniMega

TEST RESULTS

1-5 (unacceptable to impeccable)

In-hand

Features:4.5
Tonal Flexibility:4.5
Ease of Use:4.5
Aesthetics:4.5
Tone:4.5
Value:4.5

In-hand Score 4.50average

On-bench Score 3.97average

On-bench

Internals parts4.5
External parts4
Overall assembly4.75
Output power rating3.5
Ease of repair3
Instructions/manual4
Quality per price4.5
Layout/cooling3.5

EDM-1 SONIC PROFILE:

Low: Dynamic and controlled, especially on the Drive channel
Mids: Capable of a wide range of midrange tones/personalities, but articulate and full
Highs: Harmonically rich, lots of cut and bite, but nothing brittle about it


TONE-O-METER

The MG-800 is aggressively articulate, but full and balanced, with lots of dynamic headroom and “punch” on hand. The Drive channel allows for dialing in more harmonics/distortion. Both Contour A and B allow for meaningful tonal shifts, and the tone stack takes you anywhere you want to go.