for me the 627 is a reference. However, 1641 is definitely on the same level but with more '"warmth" and a refund of the acoustic scene that defines the performers with great precision.Your very welcome. A member of my audio club found them and it is our opinion that it is a great substitute to the rather expensive OPA627 (SOIC). Love the option of singles, duals and quads.He is using his in an active high pass crossover to a line array mid tweeter DIY loudspeaker. I hope to hear it this season at the Audio Society of Minnesota. OPA627... I don't remember where I heard it however the 627's are so expensive because it uses an older fabrication technique and I was told there was only one factory still able to produce them. Wish I could remember where I heard that. Anyway I will use the ones I have on hand however have no plans to purchase any additional 627's in the future.
The OPA1641 is more democratic
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...... Love the option of singles, duals and quads.
Is there any possible benefit in using the quad OPA1644 with multiple stacked AD844? It seems like its its an obvious fit to feed each AD844 output directly to one of the OPA1644's four channels.
I believe that will drop the current output demands on each AD844 by one quarter. It should also lower the OPA164x output impedance which is a bit high at 300-ohms at 20Hz (dropping to just 1-ohm at 20kHz). I dont know if that will be audible? Any suggestions?
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I would say that probably has the rest of the setup which obviously is an independent variable but its weight determinant.
I have already said that the OPA627 is and remains a reference.
Yes you can, but just make sure that the total input impedance of the 1644's that the TZ ouput of the 844 sees, is >100kohm.
Cheers George
And like I said a real 627 is a touch warm/dark sounding, and to me I wouldn't want any darker sound.
Cheers George
George
Perhaps you are thinking that I did not use a real 627?
I provide the electronic equipment only from Farnell or Mouser.
I do not think they have supplied me with a "fake" 627
You have to consider that we have the different listening systems.
OPA1641 VS OPA627
Hi George, The dip version of the 627 is very dark sounding. The soic version is not when comparing dip and soic versions. The OPA1641 has the same timbre as the 627 (soic). Where I hear the difference is in detail and a smooth quality that is hard to define. The bonus is the holographic details are better with the 1641. It isn't subtle. A touch more bass as an added bonus. YMMV...
Hi George, The dip version of the 627 is very dark sounding. The soic version is not when comparing dip and soic versions. The OPA1641 has the same timbre as the 627 (soic). Where I hear the difference is in detail and a smooth quality that is hard to define. The bonus is the holographic details are better with the 1641. It isn't subtle. A touch more bass as an added bonus. YMMV...
Of course that comes into it as well.
I've gear'd my system (below) to be as neutral as possible, and these are my findings of the 627, as it is also well documented that a real 627's sound a little on side of dark/warm not neutral or bright, and I wouldn't want for it to be any warmer.
2 x MP-02 Plasma tweeter 10khz up
ML esl Monolith's (latest aluminium deposited panels) 10khz-130hz
Bass unit heavily moded with ACI SV12's 130hz down -3db at 25hz
18db Passive xover to esl panels at 130hz to 10khz
my own 24db active xovers to the bass
2 x massive BJT massive (attached) one very highly biased (50w) into Class A for the esl's and plasma's.
Cheers George
Attachments
I would have said the same things.Hi George, The dip version of the 627 is very dark sounding. The soic version is not when comparing dip and soic versions. The OPA1641 has the same timbre as the 627 (soic). Where I hear the difference is in detail and a smooth quality that is hard to define. The bonus is the holographic details are better with the 1641. It isn't subtle. A touch more bass as an added bonus. YMMV...
We must add that you are comparing two operational very similar and both very high level.
Hi George, The dip version of the 627 is very dark sounding. The soic version is not when comparing dip and soic versions. The OPA1641 has the same timbre as the 627 (soic). Where I hear the difference is in detail and a smooth quality that is hard to define. The bonus is the holographic details are better with the 1641. It isn't subtle. A touch more bass as an added bonus. YMMV...
"The OPA1641 has the same timbre as the 627 (soic)."
Sontero said he heard the 1641 to be warmer/darker compared to the 627???
Cheers George
OPA1641 VS OPA627
In my system the timbre is the same. No warmer or darker comparing the soic version... Just more detailed and more holographic. The smooth quality I am as of yet unable to describe better. I find my Ribbon planar speakers to be pretty truthful.
In my system the timbre is the same. No warmer or darker comparing the soic version... Just more detailed and more holographic. The smooth quality I am as of yet unable to describe better. I find my Ribbon planar speakers to be pretty truthful.
Sounds great. Just ordered 2 for listening. Currently, I am quite satisfied with LT1468, but still looking for some good JFET alternatives.
OPA1611/12
I had a listen to a OPA1612 yesterday on a headphone amp. It wasn't ideal in that circuit. Although it sounded good. I had to adapt my buffer on the PCM1704 DAC for the discrete op amp, so the OPA1611 should be drop in now. Will get some ordered up.
I had a listen to a OPA1612 yesterday on a headphone amp. It wasn't ideal in that circuit. Although it sounded good. I had to adapt my buffer on the PCM1704 DAC for the discrete op amp, so the OPA1611 should be drop in now. Will get some ordered up.
opamp sound colouration
I've been following this thread for some time and had decided upon two pairs of AD844 for my dual differential 1541a dac (using Iancanada's I2s to pcm pcb).
I was pondering which opamp to buffer the TZ output of the 844s - Op627, OPA1632, OPA 1611, 1641 etc.
However from comments on this thread, it worries me that there appear to be audible differences between them and I do not want to get bogged down swapping opamps for ever.
I am now thinking of going back to my I/V transformers driven from the dac outputs across 47r resistors, with no active devices between DACs and power amp input.
The transformers will colour the sound of course, but I was happy with the sound using a single or pair of parallel dacs. In differential mode, the transformer will connect between the + & - dac outputs and with a 5:1 step up, provides just about enough gain. (a Quad 405 is quite sensitive)
My dac pcb should arrive from the pcb manufacturer next week so won't be long now.
I've been following this thread for some time and had decided upon two pairs of AD844 for my dual differential 1541a dac (using Iancanada's I2s to pcm pcb).
I was pondering which opamp to buffer the TZ output of the 844s - Op627, OPA1632, OPA 1611, 1641 etc.
However from comments on this thread, it worries me that there appear to be audible differences between them and I do not want to get bogged down swapping opamps for ever.
I am now thinking of going back to my I/V transformers driven from the dac outputs across 47r resistors, with no active devices between DACs and power amp input.
The transformers will colour the sound of course, but I was happy with the sound using a single or pair of parallel dacs. In differential mode, the transformer will connect between the + & - dac outputs and with a 5:1 step up, provides just about enough gain. (a Quad 405 is quite sensitive)
My dac pcb should arrive from the pcb manufacturer next week so won't be long now.
Op amps
Just an opinion... If you have OPA627's in your parts bin then go with that. The OPA1641 has another level of detail and transparency. So if you have to buy something then that would be my op amp of choice. AD844's are good in a stack. I have actually moved on to Pedja's DDNF circuit. It has far more current in the mirrors and to my ears is capable of better performance if buffered. Again just an opinion. I have nothing against the AD844's. It is by most accounts current starved. YMMV...
Just an opinion... If you have OPA627's in your parts bin then go with that. The OPA1641 has another level of detail and transparency. So if you have to buy something then that would be my op amp of choice. AD844's are good in a stack. I have actually moved on to Pedja's DDNF circuit. It has far more current in the mirrors and to my ears is capable of better performance if buffered. Again just an opinion. I have nothing against the AD844's. It is by most accounts current starved. YMMV...