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RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → ADI2 op amp 1602
Hello there,
I would be interested to know which op amps in the ADI2 are responsible for the headphone output and the line output. In the ADI 2, I believe, eight op amps of the type 1602 are installed.
Headphones amp in ADI-2/4 Pro SE is 4x OPA1688 per channel.
These are Dual-OP-Amps, so you have 8 amps in parallel per channel.
Thermal design in ADI-2/4 Pro SE seems to be improved too.
I can run the hardest to drive ‘phones ever, the Ergo A.M.T. 3.5 Ohm, with heavy 20 dB bass boost, an indefinite time.
This is not the case with ADI-2 Pro.
Hello,
are they also for the other outputs or only for the headphones?Aare they also for the other outputs or only for the headphones? Are they all the same then? As far as I remember there are three different versions, i.e. different DAC chips.
First please clarify your opening post. What ADI-2 are you exactly talking about? Or you mean the ADI-2/4 Pro?
First please clarify your opening post. What ADI-2 are you exactly talking about? Or you mean the ADI-2/4 Pro?
Sorry for that, i talk about ADI-2 DAC FS with 4493 Chip.
MC wrote:First please clarify your opening post. What ADI-2 are you exactly talking about? Or you mean the ADI-2/4 Pro?
Sorry for that, i talk about ADI-2 DAC FS with 4493 Chip.
The ADI-2 DAC has:
• 6x OPA1688 Dual OPAs (12 OP-amps total) as main headphones amp.
• One 1622 for the extra low noise IEM out.
• Line out is OPA1602.
The power characteristics and the reasons for these configurations are thoroughly documented in the manual.
If you are further interested in those OPAs you should read their data sheets.
It’s been a long way from TL071 and NE5534 to those dedicated high end audio chips.
Not that I feel the sound is worlds apart if used within their capabilities - isn’t that funny?!
Budda4130 wrote:MC wrote:First please clarify your opening post. What ADI-2 are you exactly talking about? Or you mean the ADI-2/4 Pro?
Sorry for that, i talk about ADI-2 DAC FS with 4493 Chip.
The ADI-2 DAC has:
• 6x OPA1688 Dual OPAs (12 OP-amps total) as main headphones amp.
• One 1622 for the extra low noise IEM out.
• Line out is OPA1602.The power characteristics and the reasons for these configurations are thoroughly documented in the manual.
If you are further interested in those OPAs you should read their data sheets.
It’s been a long way from TL071 and NE5534 to those dedicated high end audio chips.
Not that I feel the sound is worlds apart if used within their capabilities - isn’t that funny?!
Hello,
I've now even made the effort and made a picture of the ADi where everything is drawn.
I'll summarize what I've understood so far:
The "blue" 1622 is for the IEM only.
The "green" 1688, 6 pieces in number, are then all for the 6.35mm jack output.
The current question: Which of the "red" 1602 are responsible for the line output? Only the one sitting in front of the line output (6)? Or are (1;2;3;4;7) also included? To put it another way, does the signal, whether line or XLR, go through 1;2;3;4;7 anyway?
Right, according OPA1622 (IEM), and 1688 (6.3mm TRS).
Here’s some educated guess from my side, based on location of parts, typical circuitry and know ADI-2 DAC functionality:
• 1+2 are the analog filters and current/voltage converters for the (AKM) DAC chip.
This means all audio signals starts here.
• 3+4 are the Reference Level Gain stages and buffers for the line outs.
• 7 does the same for the main headphones out (OPA1688 group).
• 5+8 are balanced line drivers for the XLR Outs.
• 6 are the line drivers for RCA Outs.
Kai,
the AKM DACs 4490 and 4493 are voltage out DACs. So they should not need I/V conversion.
Kind regards, Ernst
... the AKM DACs 4490 and 4493 are voltage out DACs. So they should not need I/V conversion. ...
Thanx, then it’s a voltage buffer, maybe a little low pass filter, I see caps for that.
A brave one could trace all signals, analyze and reverse engineer the circuit and built his own ADI 
Headphones amp in ADI-2/4 Pro SE is 4x OPA1688 per channel.
These are Dual-OP-Amps, so you have 8 amps in parallel per channel.
inside 2/4 the hp buffers are opa1622. there's no 1688 used.
2/4 has mixed use of 1602 and 1612. 1612 are used for the first/last stage of analog in/out stage that directly interfacing user's device.
1602 is for iv, gains, etc.
emeissl wrote:... the AKM DACs 4490 and 4493 are voltage out DACs. So they should not need I/V conversion. ...
Thanx, then it’s a voltage buffer, maybe a little low pass filter, I see caps for that.
A brave one could trace all signals, analyze and reverse engineer the circuit and built his own ADI
the op amps close to the 4493 are differential amplifiers with LPF, and remove the bias from the output.
the circuit is designed in a way that the hot and cold signal in the differential output is always with the same amplitude.
the chip output does not guarantee that and instead each phase has distortion/noise that can be canceled out in a differential circuit.
as a result, you can use hot and ground in the xlr output as single ended output, and still get noise and distortion free signal.
In fact you find that (not the first sentence) in the manual.
RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → ADI2 op amp 1602
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