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Old 6th January 2012, 04:54 AM   #591
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by DF96 View Post
Could you expand on this comment? Even bad crossover distortion will not necessarily cause non-monotonicity. I explicitly excluded clipping behaviour, as there it could be common.
Class B/AB crossover distortion is not monotonic. This was the angle I commented on. And this kind of distortion (which D. Self comming from Class B calls GM Doubling distortion and I, coming from a Class A angle would call GM halving distortion) is endemic in almost all modern amplifiers.

Ciao T
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Old 6th January 2012, 04:58 AM   #592
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Location: berkeley ca
A. Wayne, I and my associates, some of whom I have known and worked with for about 40 years, got first place in Amplifier, preamplifier, and phonostage, in the latest edition of the TAS. Maybe, just maybe, we know what we are doing?
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Old 6th January 2012, 05:15 AM   #593
jcx is offline jcx  United States
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or maybe they listened with their eyes open?
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Old 6th January 2012, 05:31 AM   #594
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by a.wayne View Post
Thanks for the response, are you affiliated with Allnic?
No, with AMR and Diyhifisupply (and I used to modify Shanling Gear for the UK Importer).

Quote:
Originally Posted by a.wayne View Post
could you be more specific about the stereophile article you want me to look at...
Coming out in March 2012. I doubt JA would be happy for me to say much more.

Ciao T
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Old 6th January 2012, 06:02 AM   #595
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I'll be looking forward to seeing it, T.
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Old 6th January 2012, 06:12 AM   #596
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by tvrgeek View Post
Much thanks on specifics of the Rotel topology. The 5532 is the phono stage, so it's not involved at all.
The Schematic I have shows them also in the linestage...

Quote:
Originally Posted by tvrgeek View Post
I wonder what my little Creek does?
Do try it on her.

Quote:
Originally Posted by tvrgeek View Post
I have this Aimor integrated that sounds like ****, so it would be real low risk to play with it. No schematic of course. I don't know if they painted over part numbers like some do, so drawing it out may not be too hard. Done worse. Good solid chassis, transformer and heat sinks, so that is most of the cost to do a DIY.
I had an amp like that (Audio Innovation Alto), except it had already expired. I ended up putting a "gainclone" inside, with caerfully chosen passive parts (Elna Silmic PSU Cap's, Allen Bradly Carbon Comp resistors and an Alps Blue Pot). It does quite well...

The only things I can see to recommend the topology of the Gainclone chip (which is really a generic Self blameless - see attached) is that thermal sensing of the output junctions is almost instant (much better than the "thermaltrack" transistors for example), that all BJT Bases are buffered by followers and that the output stage forms part of the miller loop and is fitted with high value emitter resistors, which means the handover between the halves will be better managed, IF the biasing is right, which is assured by chip design.

Otherwise there is really not much unusual there. I can also see easily why this chip reacts so strongly to power supply design (hint - it's the miller compensation loop), my one is CRC filtered, but well designed regulated PSU's do better...

Ciao T
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Old 6th January 2012, 07:48 AM   #597
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by tvrgeek View Post
Fishy schematic.
Not really.

Quote:
Originally Posted by tvrgeek View Post
It has a few things I had not seen. The fuse on the output is bypassed with a 33K resistor. I guess that is for safety, but have never seen it before. Global feedback is from post fuse through 43K.
The 33K is there so the global feedback does not "open up" when the fuse blows. 33K seems excessive, a 1K value should be better, but let's not blow that fuse in the first place, shall we?

Quote:
Originally Posted by tvrgeek View Post
Here is the odd part, I wonder if put in the drawing just to mess someone up. A 2.2K resistor in series with the output. Then followed by a .22 and the Zobel. I''ll have to pull it apart tosee what is really there.
The schematic I have lacks these, but it has a 120 ohm resistor (mislabeled 120K) to the headphone sockets. I guess proofing service manual schematics was no Rotel's strong suit in these days.

Ciao T
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Old 6th January 2012, 07:50 AM   #598
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by gaetan8888 View Post
Would you name this sound involving or engaging ?

The TDA1541 do have this sound and that's why it made it so special.
I guess you could call it that. It is hard to describe, but if this quality is present I am willing to overhear many other flaws, if this quality is not present I immediately become hyper critical of certain technical aspects of the sound quality, the Bass's, the Trebles, this little bit of grain and so on...

And yes, the TDA1541 has it, some Delta-Sigma DAC's have it, much tube gear has it, some transistor gear has it, even some VERY HIGH feedback transistor gear has it, but loop feedback less tube gear seems to have it most reliably, as do Multibit DAC's.

Ciao T

PS, for disclosure, my current personal system is:

PC Source (1)
TDA1541 Non-Oversampling DAC (2)
Passive Pre (3)
EL34 Push Pull Amp without looped feedback (4)
Average 3-Way speakers (5)
Silver and Silver/Copper Signal Cables (6)
AMR Prototype Mains Cables (7)
Ikea Lack-Rack (8)
appx. 100m^3 Room (9)

1) PC-Source -

dedicated build, fanless, Atom 330 with touchscreen,

SPDIF from motherboard audio chipset (VIA Vinyl Codec, Bitperfect up to 96KHz),

Fidelized Windows 7 with Mediaportal and Pureaudio ASIO Music Player, all music as FLAC, also acts as AV Source

2) TDA1541 DAC -

active transformer coupled CS8414 frontend, Wildmonkeysects PLL Filter, SMD decoupling using 0603 Cap's directly on pins, 1206 on the SMD to DIP Adaptor
Pins

Floating, common mode suppressed supplies with extra choke filtering and CCS / local shunt regulator arrangements with "crazy" regulator bypassing including Sanyo ultra Low Z 2,200uF/6.3V caps, Sanyo Os-Con and 10uF 1206 SMD Caps

Tube Analog Stage without feedback (GEC five star 6072A), silver capacitors including output coupling cap bypass plus AMR Tinfoil output coupling cap, SINC Rolloff correction with silver cap and copper choke, CLC filtered PSU with added RCRCRC filtering and Film PSU Caps in the final RC filter stage

silver wired with air-dielectric, CMC RCA's

3) Passive Pre -

Grayhill selector switch, 10K Noble Potentiometer,

silver wired with air-dielectric,

uses a collection of RCA's including Cardas, AN-Silver CMC Gold & Silver (what was lying around basically, after testing all these I setteled on the goldplated pure copper CMC as "good enough" and affordable).

4) Push Pull Amp -

output stage with local feedback uses cathode & screengrid feedback only, Antique Sound Labs output Transformers, Shugang EL34B (basically 6CA7 clones, hence not pentodes but beam tetrodes), automatic fixed bias

concertina phase-splitter running a russian black plate octal 5687 analog with 10K loads,

E83CC (Mullard Box Plate CV4004) parallel voltage gain stage with 80uF/35V Film Cap Cathode Bypass (so no local feedback),

silver coupling caps and silver wired with air-dielectric, goldplated CMC RCA's & binding posts,

around 30W output and a dumping factor of a little over 2

5) Speaker -

10" ceramic coated Alu Cone Woofer, 5" ceramic coated Alu Cone Wideband as Midrange, HiVi circular magnetostat as Tweeter

20mm stone fillet lined MDF Cabinet, Avalon Style "stealth" front panel, polyfilling applied internally

first order series crossover at 300Hz/3KHz, no baffle step correction (as it would lead to non-flat power response), Copper Foil inductors, AMR Film Cap's, single resistor (HF attenuator/EQ) is multiple parallel carbon composite ones, silver wired with air-dielectric, CMC Binding posts

mostly flat 6 Ohm impedance above 120Hz, +/- < 0.5 Ohm 250Hz - 10KHz, dropping above 10KHz to 4 Ohm (this is how it came out, it was not actually a design goal, but flat response also required flat impedance, funny that), modest LF impedance peaks from a damped MLTL bass system - so friendly to work with low dumping factor amps,

around 87dB/2.83V/1m and LF cutoff in the upper 20Hz region in room

6) Cables -

SPDIF - Belden Plenum Video with WBT Nextgen Plugs

LINE - Silver Special cables - that is 5 * 0.6mm bare silver in air cells for ground, 1 * 0.2mm enameled Audio Note Silver for Signal, Metalised mylar weave for screen (one side connected only), Neutrick Pro RCA Plugs

SPEAKER - 80 Conductor SCSI 3 Ribbon, single core silverplated copper conductor in FEP Teflon, interleaved connection so approximately 2.5 Ohm CI, single piece pure copper gold plated spade connectors

7) Mains Cables -

use a variety of different cables and plugs by Oyade, Yarbo and others, power distribution strip is re-wired with solid core wire and has a number of RC circuits and capacitors fitted across life & neutral

8) Ikea-LackRack -

Three Layer Rack build from Ikea Lack Tables, 2-component epoxy used during assembly to create a rigid structure, on adjustable spikes with brass cups on the floor

9) Room - we just moved here a few weeks back

28m^2 open plan living space, varying hight ceiling between 3.2m and 4.5m high,

several well stuffed Sofas, a carpet in the seating area, no other room treatment, but the various paintings (the whole place has a faint art galery feeling to it the way we designed it) will soon get Basotect backing

The single plane widows in the somewhat loose doors forming one wall are a great plate bass absorber, around 6m^2 worth

Speakers are placed around halve-way along the long axis of the room, generally not my preferred way of doing things and hence strong toe-in. Sofa's on the sidewalls within 1m of the speakers front help absorb early reflections somewhat.

Doing a handclap test reveals no slap echo or reverb tail, bass is tight and controlled, still did not get around to do an RT60 measurement, but from hearing the room it should be okay
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Old 6th January 2012, 08:07 AM   #599
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Join Date: Apr 2007
Quote:
Originally Posted by ThorstenL View Post
Hi,

I guess you could call it that. It is hard to describe, but if this quality is present I am willing to overhear many other flaws, if this quality is not present I immediately become hyper critical of certain technical aspects of the sound quality, the Bass's, the Trebles, this little bit of grain and so on...

And yes, the TDA1541 has it, some Delta-Sigma DAC's have it, much tube gear has it, some transistor gear has it, even some VERY HIGH feedback transistor gear has it, but loop feedback less tube gear seems to have it most reliably, as do Multibit DAC's.

Ciao T
Hello Thorsten

"some Delta-Sigma DAC's have it"

Which one ?

Thank

Bye

Gaetan
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Old 6th January 2012, 10:01 AM   #600
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by gaetan8888 View Post
"some Delta-Sigma DAC's have it"

Which one ?
Pioneer PD2026, PD2028, PD2029
Cirrus CS4328
Nippon Precision SM5872

These I know for sure. Standard implementations of these (except Cirrus) tend to be grotty.

Give a Pioneer PD202X DAC a low jitter data source, a decent 5V regulator and a decent analogue stage and it can perform quite outstanding, same for the SM5872, it is very difficult to apply well.

The CS4328 is perhaps the easiest, it is direct line out, also needs a very low jitter source.

Ciao T
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