The Hammond Organ

The Hammond organ is one of the most underestimated instruments for pop and rock. There is a reason why it has been around for almost a century now, as it has an unmistakable sound that can be heard in countless pieces of iconic music. From the classic Hammond B3 or C3 to the A100 series tonewheel organ, the Hammond organ covers a wide range of sounds that can be used in many genres. It’s a unique electro-mechanic instrument that produces a warm and organic tone, making it well-suited for pop and rock. The Hammond organ was popularized by artists such as Jimmy Smith, Stevie Wonder, Jackie Wilson, and The Doors. This instrument also opened up new possibilities for jazz musicians, as it enabled them to perform in clubs without needing to hire an entire band. Even today, many modern bands still use the Hammond organ in their songs, helping to create a unique sound. The Hammond organ is an incredibly versatile instrument that can be used to create various sounds and tones. Whether you’re looking for a classic vintage sound or something more modern, the Hammond organ is capable of providing both. Its ability to blend tones makes it ideal for recording and layering complex sounds, allowing producers to create something truly unique.

Schematic and parts list of the Hammond Preamp AO-28 (B3, C3)

Schematic of Hammond Preamp AO-28 Schematic of Hammond Preamp AO-28

AO-28 Capacitors

AmountCapacityTypeVoltageSchematic Nr.Mouser Part Nr.
125/25VElectrolytic25VC3075-TVA1205
230/25VElectrolytic25VC9, C2675-TVA1412
110/350VElectrolytic350VC5975-TVA1705
130/350VElectrolytic350VC5875-TVA1907
140/400VElectrolytic400VC5775-TVA1712
140/450VElectrolytic450VC5675-TVA1712
150/300VElectrolytic300VC6075-TVA1713
3100PFceramic500VC3,C8,C295982-15-500V100
1150PFceramic500VC355982-10-500V150
2220PFceramic500VC18, C205982-10-500V220
124PFceramic500VC75982-10-500V24
130PFceramic500VC65982-15-500V30
1390PFceramic500VC32**, C35*5982-15-500V390
139PFceramic500VC25982-15-500V39
151PFceramic500VC155982-15-500V50
1680PFceramic500VC175982-19-500V680
182PFceramic500VC245982-15-500V82
10.0015uFceramic500VC3475-715P600V0.0015
30.001uFceramic500VC25,C21,C3475-715P600V0.001
20.0022uFceramic500VC19,C33*75-715P600V0.0022
10.0033uFceramic500VC33**75-715P600V0.0033
20.0047uFFILM100VC11, C1275-715P600V0.0047
10.0082uFFILM1000VC3275-5GAD82
10.01uFFILM200VC575-715P200V0.01
20.033uFFILM400VC23,C1675-715P400V0.033
10.047uFFILM400VC2875-715P400V0.047
30.33uFFILM200VC4,C10,C3175-715P200V0.33
11.0uFFILM200VC1375-710P105X9400

AO-28 Resistors

AmountResistanceWattageTypeSubtypeSchematic Nr.Mouser part Nr.
647K0.5WMetalFilmR6,R16,R47,R52*,R53*,R54*273-47K-RC
21.2K0.5WCarbonComp.R42,R1730BJ500-1.2K
11.5M0.5WCarbonComp.R5730BJ500-1.5M
41.8M0.5WCarbonFilmR30,R32,R27,R4293-1.8M-RC
2100K0.5WMetalFilmR41,R62**273-100K-RC
1100 Ohms0.5WCarbonComp.R2530BJ500-100
310M0.25WCarbonFilmR5,R14,R18291-10M-RC
115M0.25WCarbonFilmR34291-15M-RC
11M0.5WMetalFilmR21273-1.0M-RC
12.2K0.5WCarbonComp.R4930BJ500-2.2K
22.2M0.5WCarbonComp.R7,R2030BJ500-2.2M
12.7M0.5WCarbonFilmR15293-2.7M-RC
1220K0.5WMetalFilmR62273-220K
122K0.5WCarbonComp.R5630BJ500-22K
122 Ohms0.5WCarbonComp.R5030BJ500-22
3270K0.5WMetalFilmR37,R3,R12273-270K-RC
13.3M0.5WCarbonFilmR35293-3.3M-RC
13.9M was 6.8M0.5WCarbonFilmR10293-6.8M-RC
2330K0.5WCarbonComp.R36,R2930BJ500-330K
1330K0.5WMetalFilmR39273-330K-RC
2390K0.5WMetalFilmR38,R63273-390K-RC
139K0.5WMetalFilmR61273-39K-RC
14.7K0.5WCarbonComp.R5130BJ500-4.7K
14.7M0.5WCarbonFilmR13293-4.7M-RC
14.7M0.5WCarbonComp.R5830BJ500-4.7M
2470K0.5WCarbonComp.R8,R1930BJ500-470K
1470K0.5WMetalFilmR48273-470K-RC
647K0.5WMetalFilmR6,R16,R47,R52*,R53*,R54*273-47K-RC
268K0.5WMetalFilmR31, R33273-68K-RC
1820K0.5WMetalFilmR9273-820K-RC
1820 Ohms0.5WCarbonComp.R2230BJ500-820
182K0.5WCarbonComp.R5530BJ500-82K
222K1WCeramicComp.R23, R24588-OX-22K
1180 Ohms5WCementR99280-CR5-180
22.7K5WCementR100, R101280-CR5-2.7K
34700 Ohms5WCementR94, R95, R96280-CR5-4.7K
1900 Ohms10WCementR91280-CR10-910
17500 Ohms10WCementR98280-CR10-5.0K

* These components are for AO-28-1 amplifiers with no code letter only
** These components are for H-AO-28-5 amplifiers

Leslie 122RV Pictures

Here’s some pictures I took of my Leslie 122 RV. From what I could find on  this model I understand that they usually come with a Leslie-designed reverb amp which is not deemed all that desirable, but this one actually has a Hammond AO-44-1 reverb amp in it, the very same as is found in the A-100 series. I think it sounds great, even through the small speaker that is mounted on the side of the cabinet.

Leslie 122 Amp
Leslie 122 Amp

Potentiometer for Leslie 122RV Hammond Reverb Amp