It also serves to isolate the ground on one side of the reverb coil from the op amps. Reverb transformer as found in the fender 65 twin reverb reissue, 65 super reverb reissue, and 65 deluxe reverb reissue. Its both unlikely to help future visitors and confusing to current answerers. How do i begin troubleshooting a faulty builtin reverb. The relay consumes around 35ma which is a bit too much for a single stage. The reverb circuit runs in parallel to your main signal on the pre amp side. By taking advantage of highimpedance tanks usually intended for opamp drivers we can build much simpler valve drivers. Everything i know about spring reverb music thing modular. Oct 20, 2016 the hi and low cut knobs allow you to shape the fet drivers tone, but its the drive knob that adjusts your drive from a soft clip to an early stage distorted sound. The best course of action would now be for you to remove the followup question about the new circuit completely unrelated to driving led with 3. Its as cheap as doing it with discrete parts, and i dont think the relatively high distortion will matter. May 29, 2012 seems like it also might work for studio use to drive the reverb tank from a headphone amp. The reverb circuit is inserted just before a guitar amplifiers.
The esp pages suggest that a typical opamp does not give enough current to properly. Apr 29, 2012 the basic circuit is relatively straightforward, and consists of driver and recovery circuitry within the amp, the spring reverb tank figure 1 and a couple of wires connecting the remotely mounted tank with the amplifier electronics. I could try a tda 7052a i have around 1w btl power amp ic while im waiting for the parts. When replacing the reverb tank in an existing amplifier design, it is important to match. A transformerless constantcurrent reverb driver introduction. Mar 30, 2019 basic circuit operation the classab mosfet power amplifier with op amp driver stage circuit in fig. Common source power amplifier using an op amp driver stage. By taking advantage of highimpedance tanks usually intended for op amp drivers we can build much simpler valve drivers. Be sure that the opamp is inserted in the right direction. Although the reverb should be driven hard, driver overload or core saturation. A twostage overdrive pedal composed of an opamp flowing into a fet, the mxr fet driver does an amazing job of emulating creamy tube amp breakup. After thinking about it, im going to take the scums suggestion and use an lm386 to drive the springs.
Nov 12, 2017 everything i know about spring reverb. Help me diagnose a reverb driver circuit i built for belton. Basic circuit operation the classab mosfet power amplifier with op amp driver stage circuit in fig. Hammond organ company invented the spring tank reverb effect in 1960. In can fill in space between notes to thicken playing or just make you feel more comfortable in a dry room. The driver, at maximum expected input level, should drive the coil to near saturation. It would also be useful to know the characteristics of your spring line unit. The optimum impedance for opamp drive is 150 ohms b input coil, and even at. Current source op amp performance is greatly enhanced by a constant current source from the v rail to the differential inputs and class a driver. The opamp together with resistors r 4, r 5, and r 6 and capacitor c 2 constitutes a noninverting amplifier. Except for the messed up reverb, i think it sounds pretty good. The depth one adjusts the amount of drive into the spring and the mix one determines how much of the reverb signal is mixed into the clean signal. Apr 28, 2017 when the audio goes through the reverb tank, the signal needs to be amplified both before driver and after recovery the tank. But to be fair, almost any drive pedal sounds great through this amp.
Getting 17v rms at 6khz is easy, and only needs an input voltage of a little over 1. If the amp s connection to the reverb tanks phono jack shell is at ground potential, either insulated or grounded connector may be used at that connection point. Since the diodes dont allow current to flow until a certain voltage is reached, the sine waves fed into the op amp will be unaffected at low volume. This simple, inexpensive spring tank reverb circuit is taken from the fender hot rod deluxe. So clearly theres a problem with the driver circuit. The fet driver thickens up lead tones with musical, amp like distortion and sustain without the fragility and inconsistency associated with tubes. The transformer adapts the dual op amp output impedance to the reverb driver coil impedance.
Unraveling the mysteries of amp reverb uncategorized. The plates motion is then picked up by one or two contact mics and added to the dry signal at the mixer. The second amplifier u1b drivers the spring reverb. Level and drive controls let you dial in the amount of gain and responsive, organic saturation you want, with hi and lo controls to tweak your tone and a hi cut switch to roll of excess treble in. The signal coming out of the op amp is fed back into the op amp in such a way that the signal is opposite to whats being input. Mosfet spring reverb driver solid state guitar amp forum. The reverb driver circuit includes a 5vdc supply derived from the filament supply using a bridge rectifier and 7805 linear regulator, as well as an lm358 dual op amp dip used to buffer the send and return signals. Theres ic1 which is for the output you can test that also a small op amp for the input. There is no need to make r4 that particular value since this is a cmos op amp no matching of input bias currents. Build your own spring reverb tape op magazine longform. It is recommended that the driver be a current or voltage source with an.
Sr1 spring reverb build guide the instructions for the spring reverb kit are divided into the 3 main sections of the circuit. The reverb circuit is inserted just before a guitar amplifiers phase inverter in a pushpull amp or just before the driver last gain stage before the power tube in a single ended amp. Drive and recovery circuits these schematics are examples of drive and recovery circuits from popular guitar amplifiers. The constant current source insures that the current through the differential inputs and the class a driver remains absolutely constant regardless of any changes in the supply rails. Capacitor values are determined by the desired lower corner frequency. Vacuum tube reverb circuits traditionally have used a lowimpedance reverb tank coupled to the driver tube by a small output transformer. As seen from figure 4, the actual reverb drive coil impedance varies over a wide range, but that will not cause stress to the driver circuit shown in figure 7. It can also be used to simulate a large space and make your guitar huge sounding for ambient effects. It uses a single, less than one dollar tl072cp op amp as the reverb driver and reverb recovery amps. In figure 3, the op amp is wired as an inverting amplifier with a 10k r1 input impedance. There are normally two controls, one for depth and one for mix.
Spring reverb tanks explained and compared antique. Common source amplifier using an op amp driver stage. I know the lm386 is supposed to be for audio output. The way i know how to do this is to use an op amp and a npnpnp push pull the op amp alone cant provide enough current. And theres also a small 3 leg raised transistor tr1 which controls the switching for the foot pedal sometimes this can fail so the reverb is stuck in the off position. But that is not the only way to drive a reverb tank using a vacuum tube, and in fact it is not the best way. Another design that is probably worth a look is the opamp reverb driverrecovery section that can be found in laney amps, simple, effective and easy to tweak imho. Jul 26, 2014 when guitar amps fail, then test panel mounted pots first. Fender, magnatone, and ampeg all quickly licensed the technology and adapted it to their amps. This fantastic effect was lightweight and inexpensive, making it very adaptable to both organs and guitar amplifiers. Hi, im looking to make a mosfet power amp, to drive a spring reverb unit. Ive been using a 1k pot for r10 but this seems to make no difference on the verb.
Op amps in drive pedals tech article the gear page. This is of utmost importance in applications where a speaker is mounted in the same enclosure as the reverb, such as a guitar amp or organ. The reverb driver amp consists of a phase inverting pushpull circuit made from dual sections of a 5532 high quality audio opamp. Information on driving spring reverb using valves tubes seems to be rather. The reverb circuit is inserted just before a guitar amplifiers phase inverter in a pushpull amp or just before the driver last gain stage before the power tube in a single. Bassman 5, twin reverb, showman reverb, quad reverb, vibrosonic reverb. Spring reverb tanks explained and compared amplified parts. Single supply opamp audio amplifier electrical engineering. In 2011 i published a schematic for a little spring reverb driver based on roy mallorys tech note for using a very simple op amp circuit to drive a. Everything i know about spring reverb music thing modular notes. Mar 26, 20 we are using a op amp based relay driver in a electronic starter where 2 stages of lm324 quad op amps are paralleled without any current sharing resistances. Many such amplifiers use tubes for their sonic and overdrive characteristics, but for interfacing to a spring reverb, the monolithic op amp offers superior capabilities. When the input signal is negative, the op amp output swings positive, forward biasing d1 and developing an output across r2.
In 2011 i published a schematic for a little spring reverb driver based on roy mallorys tech note for using a very simple op amp circuit to drive. Works best through my hitone dg amp, which is basically a handwired, pointtopoint dr103 circuit. The circuits on the input and output of the reverb tank are op amp amplifiers, specifically a noninverting amp. I checked the spring reverb by using a headphone amp to power an aux send from my mixer, so it does work, it just needs a lot of gain. Fet driver featuring a unique circuit design, the mxr fet driver captures the rich, creamy sound of an overdriven tube amplifier by cascading an op amp gain stage into a fet stage. This provides a voltage swing of approximate twice the supply voltage to the reverb impedance matching transformer, allowing higher power transfer. Without the transformer, one of the op amp outputs may be shorted to ground at the reverb case. Jun 06, 2018 a thorough comparison of four remakes of the electroharmonix version 4 op amp big muff, which ehx released in the late 1970s with the previous versions transistors replaced with op amps or.
Try running the effect completely wet with a long reverb time to. A driver attached to the plate excites it, and as the sound waves travel through it, the plate flexes. Low impedance reverb tanks seem to be persisting in valve amp design, which makes little sense since valves are not well suited to driving low impedance loads. Transients do not twang or boing like in a spring reverb, but behave much as they would in a reverberant room, sounding smooth and natural.