[Rob Tweed]

A couple of recent upgrades, one low cost, the other somewhat
expensive has got me thinking I've nearly reached audio nirvana.
Thought I'd share it:

Swapped out an Emu 404 USB for the Beresford TC-7520 DAC. An amazing
little box for a ridiculously small amount of money. I'll continue
using the Emu for recording. The Emu is a great DAC but to my ears
the Beresford is a definite improvement.

I use this to connect my Mac/iTunes/Apple Lossless seto-up to a
Behringer A500 power amp (again ridiculously cheap but a great amp).

As per recommendations here, where I've spent the big money is on new
speakers, and I splashed out on a pair of PMC TB2i's. As soon as I
heard them in the store I knew I had to have them, even though they
were considerably more expensive than I was planning on spending.
They just blew everything else I heard away - simply no contest. I
was shocked at the B&W floor-standers I heard: flabby overpowering
bass - what has become of B&W these days? The PMCs are as clean and
uncoloured a sound as I've ever heard, but bass aplenty too despite
their relatively small size.

The combination: as near faultless as I've every heard. A truly great
sound. I think I'll be happy with this set up for quite some time!

BTW no expensive cables or bi-wiring used :-)

---

Rob Tweed
Company: M/Gateway Developments Ltd
Registered in England: No 3220901
Registered Office: 58 Francis Road,Ashford, Kent TN23 7UR

Web-site: http://www.mgateway.com

[Sonnova]

On Fri, 7 Aug 2009 14:40:25 -0700, Rob Tweed wrote
(in article ):

A couple of recent upgrades, one low cost, the other somewhat
expensive has got me thinking I've nearly reached audio nirvana.
Thought I'd share it:

Swapped out an Emu 404 USB for the Beresford TC-7520 DAC. An amazing
little box for a ridiculously small amount of money. I'll continue
using the Emu for recording. The Emu is a great DAC but to my ears
the Beresford is a definite improvement.

I have one of those, only mine is called a "TEC" . Same model number and the
units are identical. I bought mine on E-bay for $90. It's pretty good but it
has a very pedestrian output stage. It uses an old 70's technology dual
op-amp (I forget the number) and that's its limiting factor. Otherwise, it
has a Crystal CS8414 input receiver and a Burr-Brown PCM 1716 24/96
converter. I bought it because my much more expensive (and admittedly better
sounding) Sonic Frontiers DAC 2.6/D2D upconverter lacks a headphone amp/jack.
I recently upgraded the DAC 2.6 with addition of a pair of the new National
Semiconductor LME49710NA output amps (in place of the original Burr-Brown
OPA134A (All the devices in the Sonic Frontiers converters are socketed
DIPS). Something I cannot do with the TEC because the dual op-amp is a tiny
surface mount part soldered directly to the circuit board.

I use the TEC it to listen to headphones late at night.

I use this to connect my Mac/iTunes/Apple Lossless seto-up to a
Behringer A500 power amp (again ridiculously cheap but a great amp).

I also have one of those! It IS a great sounding amp, as good as some I've
heard that cost TEN TO TWENTY TIMES it's $200 street price from places like
Zounds of Swee****er.

As per recommendations here, where I've spent the big money is on new
speakers, and I splashed out on a pair of PMC TB2i's. As soon as I
heard them in the store I knew I had to have them, even though they
were considerably more expensive than I was planning on spending.
They just blew everything else I heard away - simply no contest. I
was shocked at the B&W floor-standers I heard: flabby overpowering
bass - what has become of B&W these days? The PMCs are as clean and
uncoloured a sound as I've ever heard, but bass aplenty too despite
their relatively small size.

There we diverge. I haven't heard the PMCs. I use Martin-Logan Vantages
instead

The combination: as near faultless as I've every heard. A truly great
sound. I think I'll be happy with this set up for quite some time!

I'm sure you will. Any preamp?


BTW no expensive cables or bi-wiring used :-)

Good for you Bob!

Rob Tweed
Company: M/Gateway Developments Ltd
Registered in England: No 3220901
Registered Office: 58 Francis Road,Ashford, Kent TN23 7UR

Web-site: http://www.mgateway.com

[Rob Tweed]

On 8 Aug 2009 01:57:18 GMT, Sonnova
wrote:


I have one of those, only mine is called a "TEC" . Same model number and the
units are identical. I bought mine on E-bay for $90. It's pretty good but it
has a very pedestrian output stage. It uses an old 70's technology dual
op-amp (I forget the number) and that's its limiting factor. Otherwise, it
has a Crystal CS8414 input receiver and a Burr-Brown PCM 1716 24/96
converter. I bought it because my much more expensive (and admittedly better
sounding) Sonic Frontiers DAC 2.6/D2D upconverter lacks a headphone amp/jack.
I recently upgraded the DAC 2.6 with addition of a pair of the new National
Semiconductor LME49710NA output amps (in place of the original Burr-Brown
OPA134A (All the devices in the Sonic Frontiers converters are socketed
DIPS). Something I cannot do with the TEC because the dual op-amp is a tiny
surface mount part soldered directly to the circuit board.

From what I've read, the Beresford is a modded variant of the one you
have. See thread by cjcoss at
http://www.avforums.com/forums/hi-fi...-7510-a-3.html

You'll see quite a few suggested further modifications along the lines
you suggest at Stanley Beresford's site:
http://www.homehifi.co.uk/main/main.html and you'll also see his new
"Caiman" model which came out just days after I bought the 7250. It
would be interesting to compare it with the 7250.

There we diverge. I haven't heard the PMCs. I use Martin-Logan Vantages
instead

Nice! But somewhat beyond my budget!

Any preamp?

No. The Beresford has a variable output so I have it directly
connected to the Behringer amp.

Connections to the DAC a

- Mac Mini via USB
- Humax Freeview PVR via optical SPDIF
- old Toshiba DVD player via coaxial SPDIF for occasionally playing
CDs.

Here in the UK, BBC Radio 3 is transmitted on one of the digital
terrestrial TV channels (known here as Freeview) as a 192k MP2 signal
(see http://www.digitalradiotech.co.uk/di...o_samples.htm).
The Humax makes it very convenient to record programs such as the live
Proms concerts and the results are excellent.

---

Rob Tweed
Company: M/Gateway Developments Ltd
Registered in England: No 3220901
Registered Office: 58 Francis Road,Ashford, Kent TN23 7UR

Web-site: http://www.mgateway.com

[Sonnova]

On Sun, 9 Aug 2009 15:02:21 -0700, Rob Tweed wrote
(in article ):

On 8 Aug 2009 01:57:18 GMT, Sonnova
wrote:


I have one of those, only mine is called a "TEC" . Same model number and
the
units are identical. I bought mine on E-bay for $90. It's pretty good but
it
has a very pedestrian output stage. It uses an old 70's technology dual
op-amp (I forget the number) and that's its limiting factor. Otherwise, it
has a Crystal CS8414 input receiver and a Burr-Brown PCM 1716 24/96
converter. I bought it because my much more expensive (and admittedly
better
sounding) Sonic Frontiers DAC 2.6/D2D upconverter lacks a headphone
amp/jack.
I recently upgraded the DAC 2.6 with addition of a pair of the new National
Semiconductor LME49710NA output amps (in place of the original Burr-Brown
OPA134A (All the devices in the Sonic Frontiers converters are socketed
DIPS). Something I cannot do with the TEC because the dual op-amp is a tiny
surface mount part soldered directly to the circuit board.

From what I've read, the Beresford is a modded variant of the one you
have. See thread by cjcoss at

http://www.avforums.com/forums/hi-fi...-dac-dacmagic-
muc
h-better-than-beresford-tc-7510-a-3.html

You'll see quite a few suggested further modifications along the lines
you suggest at Stanley Beresford's site:
http://www.homehifi.co.uk/main/main.html and you'll also see his new
"Caiman" model which came out just days after I bought the 7250. It
would be interesting to compare it with the 7250.

Someone on the forum that you referenced said that the output stage on the
Beresford was different than the one in the TEC unit. I wonder what OP-amp
Bereseford uses? I'd change it in a minute to a LM4562 (the dual OP-amp
equivalent to the LME49710) if the output stage that's in there wasn't a tiny
surface mount part!

There we diverge. I haven't heard the PMCs. I use Martin-Logan Vantages
instead

Nice! But somewhat beyond my budget!

Any preamp?

No. The Beresford has a variable output so I have it directly
connected to the Behringer amp.

And the Behringer amp, of course, has it's own level controls on the front.
8^)

Connections to the DAC a

- Mac Mini via USB

Do you use this as an audio server? I have an Apple TV that I use in that
capacity. It's great!

- Humax Freeview PVR via optical SPDIF
- old Toshiba DVD player via coaxial SPDIF for occasionally playing
CDs.

Here in the UK, BBC Radio 3 is transmitted on one of the digital
terrestrial TV channels (known here as Freeview) as a 192k MP2 signal
(see http://www.digitalradiotech.co.uk/di...o_samples.htm).
The Humax makes it very convenient to record programs such as the live
Proms concerts and the results are excellent.

Sounds like you have a nice system. Of course any system with the Behringer
A500 amp is going to sound mighty good because those amps are so excellent!

[Rob Tweed]

For anyone interested in more info on the Behringer A500, here's an
intesting review I found:

http://theaudiocritic.com/wordpress/?p=23

[ excessive quoting deleted -- dsr ]

---

Rob Tweed
Company: M/Gateway Developments Ltd
Registered in England: No 3220901
Registered Office: 58 Francis Road,Ashford, Kent TN23 7UR

Web-site: http://www.mgateway.com

[Rob Tweed]

On 10 Aug 2009 04:40:16 GMT, Sonnova
wrote:

Someone on the forum that you referenced said that the output stage on the
Beresford was different than the one in the TEC unit. I wonder what OP-amp
Bereseford uses? I'd change it in a minute to a LM4562 (the dual OP-amp
equivalent to the LME49710) if the output stage that's in there wasn't a tiny
surface mount part!

Found lots of modding info for the Beresford he

http://theartofsound.net/forum/showthread.php?t=2352

Looks like the 7520 (the DAC I have) is easier to upgrade than the
7510 model you have as the opamps are socketed in the 7520, so it
looks like it's a simple drop-in upgrade to the LM4562s. Quite a few
other opamps have been tried out and recommended in this thread too.

I've read that the stock opamps in the 7520 are 5532's

So it looks like I'll be ordering a pair of LM4562's and popping them
in to hear the difference.

Connections to the DAC a

- Mac Mini via USB

Do you use this as an audio server? I have an Apple TV that I use in that
capacity. It's great!

Yes. I use iTunes on the Mac. I have a 400Gb USB hard drive attached
to the Mac Mini and have all my CDs (and many LPs transferred to
digital too) on the drive. Although I started with straight WAV
ripping, I now use Apple Lossless. As the disc is now full, every now
and again I'll convert a few WAV tracks to lossless to gain some more
room. 10,000 tracks and counting now :-)


Sounds like you have a nice system. Of course any system with the Behringer
A500 amp is going to sound mighty good because those amps are so excellent!

Interesting video he

http://www.youtube.com/watch?v=RWj5CUl7rio

Looks like it's perhaps not such a good idea to use the Behringer's
gain controls!

Can't say I noticed any real audible difference to be honest - indeed
with zero input on the DAC and full gain on the Behringer, I get a
quiet hum through the speakers...a bit of an earthing issue perhaps?

I do have to say about the Behringer amp, I had to send two back
before I got one I was happy with. The first developed an audible
mechanical hum after a few days and the second developed a dangerously
crackly gain control after a few days. My conclusion was that the
price you pay for such a ludicrously low price was poor quality
control. However the retailer I used here in the UK (Digital Village)
was excellent and swapped the units without question - they even paid
for the couriers each time which impressed me greatly.

Anyway the A500 I have now has run faultlessly for a year and a half.

Yes, so all in all, a great sound now and I'd recommend this
combination of components to anyone interested in experiencing serious
high end sound on a relatively small budget (about 1600 UK pounds in
total for the DAC, power amp and speakers). I exclude the cost of the
Mac as I had it anyway and was surplus to work requirements.

---

Rob Tweed
Company: M/Gateway Developments Ltd
Registered in England: No 3220901
Registered Office: 58 Francis Road,Ashford, Kent TN23 7UR

Web-site: http://www.mgateway.com

[Sonnova]

On Mon, 10 Aug 2009 06:01:35 -0700, Rob Tweed wrote
(in article ):

On 10 Aug 2009 04:40:16 GMT, Sonnova
wrote:

Someone on the forum that you referenced said that the output stage on the
Beresford was different than the one in the TEC unit. I wonder what OP-amp
Bereseford uses? I'd change it in a minute to a LM4562 (the dual OP-amp
equivalent to the LME49710) if the output stage that's in there wasn't a
tiny
surface mount part!

Found lots of modding info for the Beresford he

http://theartofsound.net/forum/showthread.php?t=2352

Looks like the 7520 (the DAC I have) is easier to upgrade than the
7510 model you have as the opamps are socketed in the 7520, so it
looks like it's a simple drop-in upgrade to the LM4562s. Quite a few
other opamps have been tried out and recommended in this thread too.

I've read that the stock opamps in the 7520 are 5532's

So it looks like I'll be ordering a pair of LM4562's and popping them
in to hear the difference.

The LME49710NAs certainly made an audible difference in my Sonic Frontiers
DAC 2.6!

Connections to the DAC a

- Mac Mini via USB

Do you use this as an audio server? I have an Apple TV that I use in that
capacity. It's great!

Yes. I use iTunes on the Mac. I have a 400Gb USB hard drive attached
to the Mac Mini and have all my CDs (and many LPs transferred to
digital too) on the drive. Although I started with straight WAV
ripping, I now use Apple Lossless. As the disc is now full, every now
and again I'll convert a few WAV tracks to lossless to gain some more
room. 10,000 tracks and counting now :-)

Wow, that's a lot! I have nowhere near that many tracks on my Apple
TV/iTunes.


Sounds like you have a nice system. Of course any system with the Behringer
A500 amp is going to sound mighty good because those amps are so excellent!

Interesting video he

http://www.youtube.com/watch?v=RWj5CUl7rio

Looks like it's perhaps not such a good idea to use the Behringer's
gain controls!

Can't say I noticed any real audible difference to be honest - indeed
with zero input on the DAC and full gain on the Behringer, I get a
quiet hum through the speakers...a bit of an earthing issue perhaps?

The guy in the video said that at it's worst, the distortion went up to about
0.4-0.5 %. I do mot consider this "unacceptable listening distortion" as it
seems as if the ear is not real sensitive to this kind of distortion which is
probably why neither of us have noticed it. There used to be a very expensive
French tube amplifier (I forget it's name) that TAS was nuts about. It
measured almost 2.0% THD and that didn't keep it from sounding excellent. I
heard one once, I never noticed any distortion!

I do have to say about the Behringer amp, I had to send two back
before I got one I was happy with. The first developed an audible
mechanical hum after a few days and the second developed a dangerously
crackly gain control after a few days. My conclusion was that the
price you pay for such a ludicrously low price was poor quality
control. However the retailer I used here in the UK (Digital Village)
was excellent and swapped the units without question - they even paid
for the couriers each time which impressed me greatly.

The first one that Behringer sent me was likewise defective and hummed, but
the second one was perfect.

[quoted text deleted -- deb]

[Rob Tweed]

On 10 Aug 2009 13:01:35 GMT, Rob Tweed wrote:

Yes, so all in all, a great sound now and I'd recommend this
combination of components to anyone interested in experiencing serious
high end sound on a relatively small budget (about 1600 UK pounds in
total for the DAC, power amp and speakers). I exclude the cost of the
Mac as I had it anyway and was surplus to work requirements.

Actually I got that wrong - should be 1400 UK pounds. OK throw in the
cost of some decent speaker stands (I picked up some Atacama ones
second hand a few years ago on EBay - filled the tubes with sand to
deaden them)....and cables and call it 1500 :-)

Regarding the Behringer amp, further research makes me wonder whether
the EP2500 isn't a better and more reliable (and apparently a very
highly regarded) option
(http://forums.audioholics.com/forums...d.php?t=35767). Only
potential problem is an apparently noisy fan, though mods are
possible, eg see
http://forums.audioholics.com/forums...ad.php?t=45137

The EP2500 is about twice the price of the A500: about 280 UK pounds
here - still a ludicrously low price for what appears to be quite a
monster.



---

Rob Tweed
Company: M/Gateway Developments Ltd
Registered in England: No 3220901
Registered Office: 58 Francis Road,Ashford, Kent TN23 7UR

Web-site: http://www.mgateway.com

[Codifus]

On Aug 7, 5:40*pm, Rob Tweed wrote:
A couple of recent upgrades, one low cost, the other somewhat
expensive has got me thinking I've nearly reached audio nirvana.
Thought I'd share it:

Swapped out an Emu 404 USB for the Beresford TC-7520 DAC. *An amazing
little box for a ridiculously small amount of money. *I'll continue
using the Emu for recording. *The Emu is a great DAC but to my ears
the Beresford is a definite improvement.

I use this to connect my Mac/iTunes/Apple Lossless seto-up to a
Behringer A500 power amp (again ridiculously cheap but a great amp).

As per recommendations here, where I've spent the big money is on new
speakers, and I splashed out on a pair of PMC TB2i's. *As soon as I
heard them in the store I knew I had to have them, even though they
were considerably more expensive than I was planning on spending.
They just blew everything else I heard away - simply no contest. *I
was shocked at the B&W floor-standers I heard: flabby overpowering
bass - what has become of B&W these days? *The PMCs are as clean and
uncoloured a sound as I've ever heard, but bass aplenty too despite
their relatively small size.

The combination: as near faultless as I've every heard. *A truly great
sound. *I think I'll be happy with this set up for quite some time!

BTW no expensive cables or bi-wiring used :-)

---

Rob Tweed
Company: M/Gateway Developments Ltd
Registered in England: No 3220901
Registered Office: 58 Francis Road,Ashford, Kent TN23 7UR

Web-site:http://www.mgateway.com

What a co-incidence. You were the one whose opinion made me get the
EMU-0404 and now I also have the TC-7520. I have even done the
LM4562NA upgrade with the MLC5/6 caps removal. The sonic improvements
with the LM4562 upgrade are perfect......almost!

For some reason, and I think if you'll read between the lines at the
AOS forums, the LM4562 with caps removed makes the bass a wee bit
lighter than normal. This is when using the line-out to a stereo, not
headphone use. From about 40 Hz and below there is definite
attenuation in my system. If not for that one minor issue my yearn to
upgrade would be satisfied.

Stan has mentioned yet another possible PSU upgrade for the 7520/
Caiman and hopefully that will bring the bass back. Interestingly,
people who have the Caiman with the LM4562 upgrade have observed that
the bass has returned, with heft.

Comparing the EMU-0404 to the 7520, what I noticed as the biggest
improvement was the detail/resolution. Listening to the 7520 I close
my eyes and not only hear the instruments but can practically point
them out individually in space. The EMU gave you everything, but it
was somewhat blended together. It all sounds very very good, but
resolution was a bit lacking. On another forum, someone described the
sound of delta-sigma DACs as substituting frequency resolution for
amplitude resolution, and that they always sound too polite. After
reading that observation I realized that he was in fact describing the
EMU-0404 to a tee.

Anyhow, I continue in search of the ideal opamp for my 7520.

CD

[Sonnova]

On Mon, 10 Aug 2009 15:57:54 -0700, codifus wrote
(in article ):

On Aug 7, 5:40*pm, Rob Tweed wrote:
A couple of recent upgrades, one low cost, the other somewhat
expensive has got me thinking I've nearly reached audio nirvana.
Thought I'd share it:

Swapped out an Emu 404 USB for the Beresford TC-7520 DAC. *An amazing
little box for a ridiculously small amount of money. *I'll continue
using the Emu for recording. *The Emu is a great DAC but to my ears
the Beresford is a definite improvement.

I use this to connect my Mac/iTunes/Apple Lossless seto-up to a
Behringer A500 power amp (again ridiculously cheap but a great amp).

As per recommendations here, where I've spent the big money is on new
speakers, and I splashed out on a pair of PMC TB2i's. *As soon as I
heard them in the store I knew I had to have them, even though they
were considerably more expensive than I was planning on spending.
They just blew everything else I heard away - simply no contest. *I
was shocked at the B&W floor-standers I heard: flabby overpowering
bass - what has become of B&W these days? *The PMCs are as clean and
uncoloured a sound as I've ever heard, but bass aplenty too despite
their relatively small size.

The combination: as near faultless as I've every heard. *A truly great
sound. *I think I'll be happy with this set up for quite some time!

BTW no expensive cables or bi-wiring used :-)

---

Rob Tweed
Company: M/Gateway Developments Ltd
Registered in England: No 3220901
Registered Office: 58 Francis Road,Ashford, Kent TN23 7UR

Web-site:http://www.mgateway.com

What a co-incidence. You were the one whose opinion made me get the
EMU-0404 and now I also have the TC-7520. I have even done the
LM4562NA upgrade with the MLC5/6 caps removal. The sonic improvements
with the LM4562 upgrade are perfect......almost!

For some reason, and I think if you'll read between the lines at the
AOS forums, the LM4562 with caps removed makes the bass a wee bit
lighter than normal. This is when using the line-out to a stereo, not
headphone use. From about 40 Hz and below there is definite
attenuation in my system. If not for that one minor issue my yearn to
upgrade would be satisfied.

Stan has mentioned yet another possible PSU upgrade for the 7520/
Caiman and hopefully that will bring the bass back. Interestingly,
people who have the Caiman with the LM4562 upgrade have observed that
the bass has returned, with heft.

Comparing the EMU-0404 to the 7520, what I noticed as the biggest
improvement was the detail/resolution. Listening to the 7520 I close
my eyes and not only hear the instruments but can practically point
them out individually in space. The EMU gave you everything, but it
was somewhat blended together. It all sounds very very good, but
resolution was a bit lacking. On another forum, someone described the
sound of delta-sigma DACs as substituting frequency resolution for
amplitude resolution, and that they always sound too polite. After
reading that observation I realized that he was in fact describing the
EMU-0404 to a tee.

Anyhow, I continue in search of the ideal opamp for my 7520.

When you installed the LM4562s did you notice any improvement in the noise
floor? When I replaced the Burr-Brown OP-amps in my DAC 2.6, i certainly
notice that the music appears from a much "blacker" background than before. I
wonder if you noticed a similar phenomenon?

CD

[Codifus]

On Aug 10, 11:08*pm, Sonnova wrote:
Anyhow, I continue in search of the ideal opamp for my 7520.

When you installed the LM4562s did you notice any improvement in the noise
floor? When I replaced the Burr-Brown OP-amps in my DAC 2.6, i certainly
notice that the music appears from a much "blacker" background than before. I
wonder if you noticed a similar phenomenon?



CD

That was the other thing I noticed. Definitely a blacker background on
the 7520 when compared to the 0404. This improved noise floor was
apparent even before I started upgrading. The LM4562NA upgrade
improved the musicality of the 7520.

CD

[Sonnova]

On Tue, 11 Aug 2009 06:02:38 -0700, codifus wrote
(in article ):

On Aug 10, 11:08*pm, Sonnova wrote:
Anyhow, I continue in search of the ideal opamp for my 7520.

When you installed the LM4562s did you notice any improvement in the noise
floor? When I replaced the Burr-Brown OP-amps in my DAC 2.6, i certainly
notice that the music appears from a much "blacker" background than before.
I
wonder if you noticed a similar phenomenon?



CD

That was the other thing I noticed. Definitely a blacker background on
the 7520 when compared to the 0404. This improved noise floor was
apparent even before I started upgrading. The LM4562NA upgrade
improved the musicality of the 7520.

CD

Yes, I noticed that as well.

[Rob Tweed]

On 10 Aug 2009 22:57:54 GMT, codifus wrote:

Anyhow, I continue in search of the ideal opamp for my 7520.

I think it's great that Stan has seen fit to socket the opamps in the
7520 to allow this kind of experimentation (a bit like the old
turntable tweaking of old, only now in the digital domain!):

Interesting observation and comparison with Benchmark here
(http://community.whathifi.com/forums...howThread.aspx) :


"You have to wonder why, if this op-amp swap is such a revelation,
[Beresford] doesn't use them in the first place. Don't you?"

to which a response was....:

"Yes I think the same ought to be asked of Benchmark too.

They did not start using the LM4562 until the £1300 DAC1 Pre. (The
£900 Benchmark DAC1 USB had the same standard NE5532 opamps that the
Beresford gets shipped with.)

The difference is that Beresford made it convenient and easy to
upgrade. "



---

Rob Tweed
Company: M/Gateway Developments Ltd
Registered in England: No 3220901
Registered Office: 58 Francis Road,Ashford, Kent TN23 7UR

Web-site: http://www.mgateway.com

[Sonnova]

On Tue, 11 Aug 2009 06:15:58 -0700, Rob Tweed wrote
(in article ):

On 10 Aug 2009 22:57:54 GMT, codifus wrote:

Anyhow, I continue in search of the ideal opamp for my 7520.

I think it's great that Stan has seen fit to socket the opamps in the
7520 to allow this kind of experimentation (a bit like the old
turntable tweaking of old, only now in the digital domain!):

Interesting observation and comparison with Benchmark here
(http://community.whathifi.com/forums...howThread.aspx) :


"You have to wonder why, if this op-amp swap is such a revelation,
[Beresford] doesn't use them in the first place. Don't you?"

to which a response was....:

"Yes I think the same ought to be asked of Benchmark too.

They did not start using the LM4562 until the £1300 DAC1 Pre. (The
£900 Benchmark DAC1 USB had the same standard NE5532 opamps that the
Beresford gets shipped with.)

The difference is that Beresford made it convenient and easy to
upgrade. "

[quoted sig deleted -- deb]

Yes, the LM4562/LME49710 is a significant improvement over earlier designs in
such areas as noise (only 2.5 nanovolts/root Hz typical) and symmetrical slew
(meaning that the slew rate is identical for both the positive and the
negative-going halves of the waveform) and extremely low total distortion. In
most op-amp designs, the slew is asymmetrical because the path through the
op-amp itself, for the negative going half of the waveform, is usually longer
than the path for the positive-going half. This is probably not important for
other than audio applications, but it is quite important for audio for the
slew to be symmetrical for bot halves of the waveform. IOW, no audio designer
worth his salt would ever design a discrete-component amp with the
characteristic of an asymmetrical slew rate. The actual slew rate of the
LM4562/LME49710 isn't all that out of the ordinary at 20 volts/microsecond
(the Burr-Brown OPA134As that I replaced with the LME49710s were also 20
volts/microsecond slew and 8 nanovolts/root Herz of noise typically).

[Codifus]

I've tried the LME49720s, the dual opamp versions, that is equivalent
to the LM4562NAs. From my basic understanding, the LME49720s are
basically a metal can version of the LM4562NAs. Sonically, though,
they are very different.

Keep in mind that my observations are with my TC-7520 with the MLC5/6
caps removed, as shown in the 2nd diagram from mod page here;

http://www.beresford.me/others/7520mods.html


For me, the LM4562NAs really really shine. They are almost perfect,
but their bass is just a bit light.

The LME49720s, which are basically a metal can version of the
LM4562NAs, are quite a different story. They have deep bass, but they
don't have the musicality of the LM4562NAs. Not even close. It's funny
how the plastic "inferior" quality chip out shines the "better" metal
can version. I think it all comes down to the synergy of all the
components. The TC-7520 may be better suited to plastic opamps.

I plan to try the Burr brown OPA2134s next. I hope they take well to
the MLC5/6 removal. Putting those caps back is not really an option
for me.


CD

[Sonnova]

On Tue, 11 Aug 2009 20:10:08 -0700, codifus wrote
(in article ):

I've tried the LME49720s, the dual opamp versions, that is equivalent
to the LM4562NAs. From my basic understanding, the LME49720s are
basically a metal can version of the LM4562NAs. Sonically, though,
they are very different.

Keep in mind that my observations are with my TC-7520 with the MLC5/6
caps removed, as shown in the 2nd diagram from mod page here;

http://www.beresford.me/others/7520mods.html


For me, the LM4562NAs really really shine. They are almost perfect,
but their bass is just a bit light.

The LME49720s, which are basically a metal can version of the
LM4562NAs, are quite a different story. They have deep bass, but they
don't have the musicality of the LM4562NAs. Not even close. It's funny
how the plastic "inferior" quality chip out shines the "better" metal
can version. I think it all comes down to the synergy of all the
components. The TC-7520 may be better suited to plastic opamps.

I plan to try the Burr brown OPA2134s next. I hope they take well to
the MLC5/6 removal. Putting those caps back is not really an option
for me.

HMM. The OPA2134 is essentially the same as the OPA134 in specs:
20V/microsecond slew rate, 8 MHz gain bandwidth, 8 nanovolts/root Hertz
noise. These are old op-amps (10 years old) and have much more noise (8
nanovolts/root Hertz vs 2.5) than do the LME49710 family. I also believe that
the Burr-Brown op-amps do not have symmetrical slew (I deduced this from the
large signal step response oscilloscope photo in the data sheet. The falling
edge of the square wave exhibits an offset of almost 4 microseconds at the
'0' crossing point. An offset that is not there on the rising edge. This is
indicative that the falling edge (negative going) portion of the signal takes
a longer path through the IC than does the positive going rising edge) and
the Burr-Brown OPAs have orders of magnitude more THD than do the newer
National chips. I replaced OPA134s in my DAC with the Natty chips and noticed
a big improvement. It costs little to experiment this way, but in my humble
opinion, replacing members of the LME49710 family with members of the OPA134
family is taking a big step backwards. Your milage may vary 8^)