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Old 23rd January 2008, 12:39 AM   #11
Filburt is offline Filburt  United States
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Default Re: Opamp Comparisons

Quote:
Originally posted by LNeilB2
[B]I'd be happier with warm, or even bloated sounding opamps (as opposed to the current sound I'm getting).
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Old 23rd January 2008, 07:16 AM   #12
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Quote:
Originally posted by munosmario
Thanks, Georgehifi. Question, does the TentsLink mode described in the Tent's site accomplishes the same as the slave/master mod you suggest?

http://www.tentlabs.com/InfoSupport/page25/page25.html

Cheers....Munosmario
Go back to the XO2 and XO Supply as this is the answer I got from Guido when I asked him about the XO-DAC for the A3.24

"Hi george
The 3.24 has a sample rate converter, no use for XO DAC
best"

Cheers George
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Old 23rd January 2008, 04:20 PM   #13
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Default Re: Re: Re: Re: Opamp Comparisons

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Originally posted by georgehifi


Not at all, but you will need the circuit diagram to do it, and here it is.
And if you want something more dynamic and detailed and more etched than the OP275 use the AD825 on brown dog boards.

I did this (below) over 3 years ago .

Note: one half of the opamp is the dc servo, just cut it out and set up what's left, +input (pin 3) to deck (earth)
I think for memory that's all I had to do to get rid of the dc servo, but just to be safe for now, just change out the opamp you have for the OP275 or the AD825's on brown dogs and listen with the dc servo.


Cheers George
You might also want to consider the LM4562 as a potential candidate for this mod. You can defeat the dc servo using this op-amp as well. All you need to do is short C48/58 (right pn hopefully, schematic is a bit hard to read) to ground and jumper C47/57 to keep the servo from going open loop and slamming to the rail. (Op-amp behavior can be unpredictable depending on type when this is allowed to happen.)

I would also reconfigure the relay if the inputs are not used such that the signal does not go through those contacts on the way out.
To retain the mute function you can connect it such that when the dac mutes the closed contacts short the output.
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Old 23rd January 2008, 07:24 PM   #14
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I'll second Kevin's recommendation of the LM4562/LME49720. IMO, its a lovely (if such adjectives apply to opamps) chip, lacking grain, with extended, resolving, controlled treble and bass. Its also one of the few bipolar input chips that might function well sans servo, given its unusually low input bias current demands.

That being said, tonally, its not that different from the LT1364, albeit with far less propensity for that solid state 'grit' and hardness. You might well find those tonal characteristics far more to your liking with the removal of those nasties you described.

As George mentioned, the OP275 is also a very nice, 'warmer' chip. If you are looking for a bit of 'tube warmth', without the stereotypical (but when well implemented oftimes undeserved) charaterisation of mushiness, you might also consider the OPA2107. A di-fet input dual, IMO, it does everything 'mo betta' than the typical BB fet input duals. These are pretty much unobtainium from the distributors, but are available on FleaBay -
http://cgi.ebay.com/OPA2107-dual-Low...QQcmdZViewItem
I really like this chip, as much as those Nationals, but a different flavor.

The LT1364 is substatially faster and wider bandwidth than the other opamps suggested by everyone on this thread, so their choice sholdn't be problematic as a replacement.

FWIW
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Old 23rd January 2008, 11:11 PM   #15
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Quote:
Go back to the XO2 and XO Supply as this is the answer I got from Guido when I asked him about the XO-DAC for the A3.24
Thanks, Georgehifi. Since you have planted the seeds of temptation, could you tell me if the HK HD970 can work with US voltages 110-120V. Looking at pictures of the rear panel, it does not seem to have any external user adjustable settings but it could well be that there is an internal switch or a transformer circuit with an easy alternative wiring arrangement for the transformer to work within a 110-250V (50/60Hz) range.

cheers...................munosmario
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Old 23rd January 2008, 11:19 PM   #16
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Quote:
Originally posted by munosmario


Thanks, Georgehifi. Since you have planted the seeds of temptation, could you tell me if the HK HD970 can work with US voltages 110-120V. Looking at pictures of the rear panel, it does not seem to have any external user adjustable settings but it could well be that there is an internal switch or a transformer circuit with an easy alternative wiring arrangement for the transformer to work within a 110-250V (50/60Hz) range.

cheers...................munosmario
They were never made for the US market, pitty then it really would have taken off, and HK never made them in 110v only 220v-240V, it has what looks like a Sony R-Core mains transformer in it, no switch mode rubbish in this unit.
But all is not lost I have from a good source who is doing it in the US, they can be used by using a 240v to 110v (1amp) step down transformer in "reverse", it also then doubles as an isolation transformer and sound even better as well as uping the 110v mains to 240v.

Cheers George
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Old 25th January 2008, 06:08 PM   #17
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Georgehifi, brilliant. Thanks
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Old 25th January 2008, 07:21 PM   #18
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Georgehifi, do you happen to remember if the signal at the coaxial digital output of the MFA3 24 is the upsampled digital signal corresponding to that entering the analog conversion stage, or is it the same as the original digital signal fed into whatever of the two digital inputs that has been selected?

Cheers.......................munosmario
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Old 25th January 2008, 08:48 PM   #19
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I think it maybe just a pass through, maybe someone else can answer better than me. Here's that part of the circuit.

Question: Will the spidf digital OUTPUT be upsampled to 192khz as well when the 192khz upsample switch SW1 is turned on.

Cheeres George

BTW
munosmario, did you know the HK HD970 upsamples to 384khz!!
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Old 30th January 2008, 01:19 PM   #20
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Georgehifi., I talked to Musical Fidelty and the answer is no. The digital output of the A324 is just a buffered passthrough and presents the original signal fed to the unit, not the upsampled digital signal that is converted to analog by the A324's internal DAC. This means that the A324 cannot double as an external upsampler. Regarding the HK HD970, it is interesting that the manual refer to 384Khz "oversampling," not "upsampling." 384Khz oversampling is the same as 8X Oversampling which has been around for quite a while. It appears that mathematically the two processes are the same, the diference beeing in the implementation of the algorithms in the filters used. If you Google the two words --upsampling oversampling--you will get several entries on the subject, one of the the best (ironically?) from Stereophile's John Atkinson.

Cheers....................Munosmario
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