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prelude with opa627 opamp - Page 2

post #16 of 39
Originally Posted by ROBSCIX View Post
The Prelude doesn't use a 8788 Chipest. It uses a 20KX series (X-fi) processor. The X-Meridian from Auzen used the Oxygen chipset. Which is also a very nice sounding card. Those (8788) chipsets power some very decent cards. I know a few guys that dumped Razors for Prelude and they were very happy with the new Preludes. I am thinking of ordering some new high end amps for this card such as the OPA627's or 637's should kick the sound up a notch..
Ahh, thank you for the clarification, I think I just got the older card mixed up I may actually have to give this card a try now!
post #17 of 39
"Is Incredible - Only In Bit Perfect -
In Resampling Mode - Is Not

Please explain this part. "

Sample rate conversion (SRC) is a process by which audio's sampling rate gets changed without affecting the pitch of the audio. Generally, SRC is best done at even multiples, such as 22.05 KHz to 44.1 KHz, or 96 KHz to 48 KHz. However a common SRC task is moving audio between sampling rates of 48 KHz and 44.1 KHz, and this is a task Creative's 10Kx audio processors had trouble with. The crux of the problem is that much audio content is sampled at 44.1 KHz (an Audio CD's standard sampling rate), and the 10K's core had a locked sample rate of 48 KHz. That meant that two SRC operations were needed to get the audio in and out of the processor, not one, which would have been the ideal case.

In other words, incoming 44.1 KHz audio got converted to 48 KHz, some processing was executed, and the audio was then converted back down to 44.1 KHz as it left the 10K audio processor. The adverse result was higher intermodulation distortion (IMD) due to band-pass ripple, and Creative has taken some deserved knocks for the 10K's shortcoming in this area. But to its credit, Creative also took the problem to heart, and dedicated about 70% of the X-Fi's MIPS budget to SRC operations. The result? Creative has stated that it's measuring THD+N on a 44.1 KHz to 48 KHz SRC operation out of the X-Fi at around –136 dB, with +/-0.00025dB pass-band ripple (using a 997Hz test tone). "

The SRC block in the X-Fi is expressly designed to make SRC an essentially lossless operation. It's a hybrid design between fixed-function and programmable hardware, where you get the execution efficiency of highly optimized hardware, plus some flexibility to those operations via programmability.
The X-Fi's core can run at two internal sampling rates, 44.1 KHz and 48 KHz, although it will only run at 44.1KHz in Creation mode, and if you specifically tell it to do so -bit perfect -

Between the beefy SRC processing horsepower and the ability to run at 44.1 KHz or 48 KHz sample rates, Creative stated that the X-Fi's audio signal quality performance will essentially be ADC/DAC (Analog-to-Digital Converter/Digital-to-Analog Converter-limited). So, high-end products will likely be outfitted with better DACs, whereas entry level offerings will have more modest DACs

Here's where it gets interesting: The X-Fi has a Creation Mode that, when activated, will let the X-Fi process dry (no effects) 96KHz/24-bit content at its native resolution. So for example, if playing a DVD-Audio disc, you could switch to this Creation Mode and have a pure 96 KHz/24-bit signal path for your playback, provided you don't apply effects. However, the X-Fi still runs its effects engines at either 44.1 KHz or 48 KHz. It cannot run them at a sampling rate of 96 KHz, but Creative has implemented what's called band-splitting to be able to apply effects to 96 KHz/24-bit content.
post #18 of 39
I think the Prelude would sound great with newer high end opamps installed. Auzentech must think this also as they will be offering them for their customers very soon.
post #19 of 39
Originally Posted by ROBSCIX View Post
I think the Prelude would sound great with newer high end opamps installed. Auzentech must think this also as they will be offering them for their customers very soon.
How much of a difference does it make with the new opamp (if you can post some details as to the sonic difference)?

Will Auzentech offer upgrade by installing the opamp for you or will they just release a completely new card altogether?
post #20 of 39
They said, you can order the opamps
1. Installed on the cards front channel
2. Ship with the card but not installed
3. Sold separately.
The amps come in DIP8 adapters, they snap right into the front channels on the Prelude or ANY channels on the X-Meridian or other cards that have sockets.
post #21 of 39
How is he using the opa627 if it's a single output chip? The prelude needs 1 (single) dual output chip. I tried to use a opa637 myself and it only output in the left channel and I was told that the voltage requirements could kill the opamp if used on the prelude.
post #22 of 39
You need an appropriate adapter 2x-single-to-dual. 2xSOIC to DIP8 should take less place than 2xDIP8 to DIP8.
post #23 of 39
Oh, so you'd need some pin-point soldering skills for that I assume?

I've got a bunch of dif opamps to try out coming to me soon.

lt1361, LT1469, AD8599, AD8620 (actually AD8610 before I figured out there was a difference. hopefully they can change it for me)

Might have to go that route if I don't like any of these.
post #24 of 39
Has anyone tried LT1364 with Prelude?
I'd like to try LT1364 and OPA627 with prelude, but I have no idea where/what to buy. Any other recommendations?

Could someone please help me out a bit?
post #25 of 39
I'm using the LT1361. IMO it's a huge improvement over the lm4562.

I tried the opa2107, which is meant to sound similar to the opa627, and it wasn't a good match for the sennheisers. Too dark and reserved. I'm fairly new with all of this but I have tested out a few different opamps and here are some of my thoughts.

OPA2107 - Dark & muddy. Sounds very poor with sennheiser 650s. Mids are reserved and in the distance. Not a good match for my equipment.

LM4562 - Stock Opamp. Mids are very compressed and sterile
sounding. Bass is very fake sounding. Highs are harsh. Someone mentioned that this opamp was like a robot on steroids. I would agree with that. Might be ok if you have an insanely warm amp or something but I just didn't like the way it sounded on my setup at all.

LT1361 - Mids are more pronounced. Warmer than the LM4562 but more detailed with more impact at the same time. More airy as well, doesn't sound as compressed. Better separation I would say. Bass sounds more natural, also deeper. Highs are warm and not harsh. I think this is a very good match for sennheisers. Very natural and pleasing sounding.

LT1469 - This opamp is clinically precise, very fast and extremely detailed at higher frequencies. I would say it borders on being ridiculously detailed at higher frequencies. You're able to hear things you wouldn't otherwise hear, and perhaps wouldn't want to hear because it's so bright. Everything else kind of sucks with it though. Sounds very sterile and digital. Bass isn't as deep and doesn't have the same impact as the lt1361's. It's also missing the nice warm and detailed mids of the lt1361.

I'm very happy and have to say very surprised, as well, that the LT1361 sounds as good as it does. This is one of the best improvements to my system to far I would say.
post #26 of 39
I ended up taking the lt1361 out. My initial impressions were correct, atleast for the music I'd listened to at the time, but I found that it doesn't suit other forms of music very well. Mids are too forward. Theres also lack of clarity in the high frequencies. For some music it sounds very natural, for other stuff it just doesn't sound right. What were once balanced vocals and guitar are now quite vocals and guitar or loud guitar quite vocals. Almost like an EQ graph has pushed the mids forward. I guess I should spend some time with these before I write out long impressions.

Right now I'd got a lt1469 opamp in and a yaqin tube buffer connected to my DV332. Sounds interesting so far. Will have to spend more time with it though.
post #27 of 39
Currently I am running OPA627's in my Prelude. I soldered in a set to a adapter. They have a nice signature and are very,very clear. I liked the LM4562 but there are others out that I would like to test out. I find with new opamps you need to audition them for while to get the idea of how they actually sound. It is hard to find one that is compatible with all music genres.
I have to put together a new shopping list of opamps to order.
post #28 of 39
can someone tell me if the prelude has quality DACs on the rear output as well?

Reason I ask, is I get buzzing audio if I use my headphones dual RCA to mini stereo to a dual mini stereo to male in the Front output on the prelude, the other dual mini stereo being for my pc speakers. (I probably should get some a good dual RCA to mini stereo interconnect)

The front panel headphones is craaaaaap. I've also tried a simple audio switch from Radioshack, still buzzes.

ps. Is it true that putting your card close to the psu in the chassis can cause noise?
post #29 of 39
Does the prelude have enough gain for two 637's in an adapter or would that cause them to oscillate?
post #30 of 39
Can I just replace original LM4562 with LT1364 DIP-8?
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