HA17741

Single BJT-Input Op-Amp DIP-8 / SOIC-8.1 circuit uses this part.

Substitutes same socket

Parts that fit the same socket: the same function, pin count and pinout. The figures are read off each part's datasheet (this one's from page 5), typical where the sheet gives a typical value, otherwise the maximum. Closest first; the last column says what differs. A different part can change the sound, and a circuit may lean on one particular figure, so read the build document's notes before you swap.

This part

Part	Input	Supply	GBW	Slew	Noise	Iq	Boards
741		10–30 V		0.5 V/µs		0.13 mA	256

This 2026 revision lists pins 1 and 5 as no-connect on the DIP, so an offset-trim pot there does nothing.

Fits the same socket

Part	Input	Supply	GBW	Slew	Noise	Iq	Boards	Differs
OP07CP	bipolar	6–36 V	0.6 MHz	0.3 V/µs	9.8 nV		1	Precision but slow (0.3 V/µs); its offset trim uses pins 1 and 8, not the 741's 1 and 5.
TS321	bipolar	3–30 V	0.8 MHz	0.4 V/µs	50 nV	0.6 mA	1	input range reaches the negative rail; draws 0.6 mA per amplifier. Single-supply LM321-style op-amp sold only in SOIC-8 and SOT-23, so a DIP socket needs an adapter.
LM308	bipolar	10–36 V				0.3 mA	96	needs a compensation capacitor across pins 1 and 8. Needs a compensation capacitor (30 pF typical) between pins 1 and 8; the cap sets slew rate and tone.
TL061	JFET	10–30 V	1 MHz	3.5 V/µs	30 nV	0.2 mA	34	Low-power JFET op-amp at 200 µA; the pin table gives offset null on 1 and 5 though the drawing marks them NC.
LM301A	bipolar	10–36 V		1 V/µs		1.8 mA	23	needs a compensation capacitor across pins 1 and 8; draws 1.8 mA per amplifier. Externally compensated: needs a capacitor (30 pF for unity gain) between pins 1 and 8, and the value sets its slew and treble response in fuzz and distortion circuits.
LF355	JFET	?–36 V	2.5 MHz	5 V/µs	20 nV	2 mA	1	draws 2 mA per amplifier. Lower-power, slower sibling of the LF356.
LF356	JFET	?–36 V	5 MHz	12 V/µs	12 nV	5 mA	14	draws 5 mA per amplifier. JFET single drawing about 5 mA; specified at ±15 V.
TL071	JFET	4.5–40 V	5.25 MHz	20 V/µs	37 nV	1.4 mA	178	draws 1.4 mA per amplifier. JFET input; this revision shows pins 1, 5 and 8 as no-connect on the DIP, so no offset trim.
TL081	JFET	4.5–40 V	5.25 MHz	20 V/µs	37 nV	1.4 mA	20	draws 1.4 mA per amplifier. JFET input; this revision shows no offset-null pins on the DIP.
TL051	JFET	10–30 V	4.5 MHz	17.8 V/µs	10.8 nV	2.1 mA	8	draws 2.1 mA per amplifier. Trimmed-offset upgrade for the TL071/TL081; pins 1, 5 and 8 are no-connect in this revision.

Faceplate	Circuit	Based on	Category	Vendor	Box	Knobs	Price	BOM
	Electro Harmonix Frequency Analyzer 4 4558 · 4558D · AD633JN · HA17741 Electro-Harmonix Frequency Analyzer 4	Electro-Harmonix Frequency Analyzer 4	Ring Mod / Synth	Experimentalists Anonymous	—	3	—	39