Op-Amps for TDA1540 - TDA1541A

Since these digital-to-analog converters do not provide a ready-to-use audio signal, the subsequent operational amplifiers must handle two fundamentally different tasks: first, the current-to-voltage conversion (I/V conversion) and then the reconstruction filtering and buffering (buffer). Previously, these differing requirements were mostly solved by a standard dual op-amp with two identical halves � a technical compromise. This optimized module concept instead relies on two specialized single op-amps that are precisely tailored to their respective fields of application:

Thermal decoupling: Separate chips prevent waste heat from the I/V conversion from negatively affecting the parameters of the filter stage.
Avoiding internal crosstalk: Spatial separation eliminates electrical interference (crosstalk) that would occur within a shared housing.
Specific slew rate: This enables extreme speed in the first stage and high stability against high-frequency interference in the second.
Optimized noise management: Through the targeted combination of chips with minimal voltage noise (stage 1) and low current noise (stage 2), the signal-to-noise ratio is maximized.
Higher voltage resistance: Single op-amps offer significantly better load behavior than compact dual systems.
Maximum signal fidelity: Minimal changes in mass through new micro-pins (optionally available in pure silver) ensure an unhindered signal flow.
Decoupled power supply: Each of the two operational amplifiers is decoupled at the supply voltage pins using two Murata C0G 150nF capacitors. An optional, separate ground connection at the top of the adapter board effectively shunts both differential noise (between + and -) and common-mode noise to ground. This prevents the ultra-fast operational amplifier in the I/V stage from oscillating�an effect caused by the inductance of supply lines or cables.

1. I/V conversion stage: AD825 or OPA828 (successor to the OPA627)
2. filter and buffering: OPA604 or OPA1655

Dual Op-Amps

* Image similar, color white

• 1x OP-amp double AD825-OPA604
• 1x OP-amp double OPA604-AD825

• 1x OP-amp double OPA828-OPA1655
• 1x OP-amp double OPA1655-OPA828

• 1x OP-amp double OPA627-OPA1655
• 1x OP-amp double OPA1655-OPA627

• 1x OP-amp double AD825-AD825
• 1x OP-amp double OPA828-OPA828
• 1x OP-amp double OPA627-OPA627

• 1x OP-amp double OPA604-OPA604
• 1x OP-amp double OPA1655-OPA1655

One double op-amp is added to the shopping cart; you can adjust the required quantity in the cart afterwards.

Single Op-Amps

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• 1x OP-amp single AD825
• 1x OP-amp single OPA828
• 1x OP-amp single OPA627

• 1x OP-amp single OPA604
• 1x OP-amp single OPA1655

One single op-amp is added to the shopping cart; you can adjust the required quantity in the cart afterwards.

Transparent pricing for ready-to-play modules

• Basis: The basis is the current purchase price for guaranteed genuine components incl. micro-pins, C0G capacitors & PCB
• Surcharge: Single +�12 | Dual +�18 (incl. soldering service & shipping costs, excl. VAT)
• Result: A fairly calculated final price that honestly cannot be beaten

Found it cheaper? The market is flooded with counterfeit 'audiophile' op-amps�cheap components where the original markings have been laser-etched away and replaced with high-end model numbers. The performance of these fakes in no way reflects the quality of the genuine parts. We source our operational amplifiers directly from the original manufacturers, Analog Devices and Texas Instruments / Burr-Brown.

Sound assessment of the combinations

AD825-OPA604

Sound character: Very lively with a powerful, warm foundation.
Character: Creates a dense, emotional soundscape reminiscent of classic analog playback.
Focus: Joy of playing and an organic overall experience.

OPA828-OPA1655

Sound character: Highly precise, silky highs, and impressive spatial depth.
Character: Sounds very calm and sovereign with excellent instrument layering.
Focus: Transparency and fine, detailed imaging.

The essential difference: While the combination of AD825 and OPA604 interprets rather punchy and direct, the duo of OPA828 and OPA1655 brings elegance and spatial width to the fore. Both setups harmonize perfectly with the converter and each set their own aesthetic accents.

Examples of different configurations

Different circuit designs in CD players can use either the first or second half of a dual op-amp first. In some devices, both variants are used.

2x 825-604 or 828-1655
The most commonly found variant with the same circuit for each stereo channel. For e.g. all Philips from CD100 to CD304 and also subsequent models like CD460, CD650, CD880 ...
Grundig CD903, CD8400MKii, CD9000 ...

2x 604-825 or 1655-828
Some Marantz models use the second op-amp half first, such as the CD40 and CD50 models ...

825-604 or 828-1655 and 604-825 or 1655-828
Models with different circuits for each stereo channel include Revox B225, Marantz CD84 and Sony CDP 337ESD ...

single op-amp
A Philips CD960, Marantz CD94 and several similar models use 4x single op-amps. This requires two 825 or 828 and two 604 or 1655.

Questions about other models are welcome via email.

metronom module 2.0
no oversampling bridge