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Old 31st May 2006, 01:24 PM   #251
MGH is offline MGH  United States
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vatofale...As the title of this thread indicates,

"Building the ultimate NOS DAC using TDA1541A"
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Old 31st May 2006, 02:00 PM   #252
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I just called a company in England that showed the tda1541a available at a cost of 3 pounds each.
http://www.nikko-electronics.net/cat...b3f24e9f6d5edb

Actually it costs 14 pounds..each. So, for the ones (like me) that thought having found a cheap source...

Erik
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Old 31st May 2006, 02:26 PM   #253
tubee is offline tubee  Netherlands
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I bought the 1541A's here in a group buy for 6,15 Eu each. Maybe he has still some left. Bought them from Bruno.

Ecdesigns: thanks for reply, i look forward to the schematics. I have seen somebody made a ringcore for Spdif elsewhere.
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Old 31st May 2006, 04:33 PM   #254
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Quote:
I bought the 1541A's here in a group buy for 6,15 Eu each. Maybe he has still some left. Bought them from Bruno.
Hi Tubee

I also bought 4 TDA's in a group buy. They were ordered from Reichelt, but they don't have them anymore.

I placed a WTB on the market place for 16 pieces, for 2 DAC's - one for myself, the other for a friend who lives at the same student house. Let's see if can get them for not to much money (they seem available from various sources, but prices are about 13 euros/piece now)

Erik
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Old 31st May 2006, 07:55 PM   #255
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Ecdesigns:
Quote:
As already mentioned, the OP-amp diff amp has a very accurate bass (DC coupled) and an accurate almost analytical output signal, it only lacks the beautiful rich and open sound of the differential tube output.
At the risk of receiving unplesant replies from technically oriented mates , one way to get some of the effect you are looking for would be trying Riken-Ohm resistors on any R on the signal analog path. This had allways helped me, in my limited experience...

Good luck
M
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Old 1st June 2006, 01:41 AM   #256
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ECdesigns:

Perhaps the best thread I've seen on DIY digital. I would love to build this kit if available. My question is, have you tried running the op amp output stage unregulated on very low-impedance SLA batteries? I suspect that if you tried this you might abandon a tube ouput stage. My reference is the Enersys Odyssey PC2150 (12V/100 AH/2.2 milliohm internal resistance), filtered at the application with parallel array of low-ESR caps such as 10 or more Rubycon ZA 470uf/16V.

Dave
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Old 1st June 2006, 01:51 AM   #257
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Quote:
Originally posted by MGH
vatofale...As the title of this thread indicates,

"Building the ultimate NOS DAC using TDA1541A"
My bad, too much reading in circles

Quote:
Originally posted by ErikdeBest
I just called a company in England that showed the tda1541a available at a cost of 3 pounds each.
http://www.nikko-electronics.net/cat...b3f24e9f6d5edb

Actually it costs 14 pounds..each. So, for the ones (like me) that thought having found a cheap source...

Erik
Grandata do appear to have TDA1541A chips for 6 pounds each (www.grandata.co.uk catalogue search will bring them up).
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Old 1st June 2006, 07:29 AM   #258
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Default The sound of resistors

Hi, maxlorenz

Thanks for the tip [post#255],


> After reading some articles on the internet about the "carbon resistor" sound, an important factor is noise. Wirewound (foil) resistors have the lowest noise, followed by metal film, metal oxide, carbon film, and carbon composition. Noise is also proportional to the current that flows trough a resistor, higher current, more noise. Also higher Ohmic values will increase noise, higher resistance, more noise. Noise can be reduced by using higher wattage types.

Carbon (composition) resistors seem to produce noise similar to "pink" noise, when a alternating current runs trough these resistors (audio signal) the "noise is modulated (increased current produces more noise) by the audio signal, but not all frequencies produce the same noise level this way. So the sound get's "colored" and determines the resistor's "sound". Technically, if you want to create a signal that is as clean as possible, NON-inductive wirewound or metal foil resistors are a good choise, followed by high wattage metal film.

But then, you might like this effect and the (carbon composite) Riken-Ohm resistors are an enrichment of the sound quality. Others might prefer a clean signal with nothing added to it. I try to keep the signal as clean as possible because a lot of "things" are already added to the sound along the audio chain.

Tubes produce a more open "warm" sound. This "sound" persists even with very low distortion levels. A tube is a very "basic" one component amplifier that needs little feedback (depends on tube gain). An OP-amp is a complex circuit composed of many individual semiconductors, resistors and capacitors. In order to produce low distortion it needs a fair amount of feedback. I think, feedback can compromise the audio signal. With feedback, you need a specific amount of time to get the output signal "locked" to the input signal. It's basically a "servo" loop. The audio signal disrupts this "servo" loop causing distortion being added to the audio signal, during the time this "servo" tries to lock-in again. This "servo" noise is one of the factors that determine the "sound" of an amplifier stage. The amplifier that responds very quickly, without overshoot or "ringing", and does the "locking" in the same way over the entire audio spectrum will have the most neutral "best" sound.

Question is, what sound comes closest to natural sound, tube sound, semiconductor sound or both mixed together. I think this question can only be answered by listening sessions and direct comparison. Fact is, the octal D-I DAC will have all 3 options, and they can be "toggled" directly during listening.
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Old 1st June 2006, 08:32 AM   #259
tubee is offline tubee  Netherlands
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Quote:
I think, feedback can compromise the audio signal.


I can confirm this for sure.
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Old 1st June 2006, 01:04 PM   #260
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I too generally prefer zero-feedback tube designs over SS. My observation about trying op amps on batteries comes from another direction that may or may not be relevant to your goals, depending on whether you're aiming to market. First, regarding choice of preferred output tubes for a CDP/DAC, in the States at least we see that custom designers like ModWright & APL (who modify commercial players), as well as hi-end manufacturers like BAT and Audio Research, increasingly prefer the 6H30 tube. Have you considered this tube? Even at that, within the community of hard core tube audio buffs, many still prefer SS to tubes when choosing a very hi-end CDP/DAC. So, yes, it's a great idea to include both SS and tubes in your design; the question becomes how to get both tubes and SS to the highest level for a fair comparison. Personally, I've found that there is no comparison between running monolithics such as BUF634 and op amps on AC/DC discrete regulation vs. unregulated low-impedance SLA batteries. The unregulated big batteries take these devices to different level in terms of grainless transparency and resolution. Also battery supplies will improve the down-regulated circuits in the DAC, such as the TDA chip. But the batteries need to be selected for low internal resistance in the 2-3 milliohm range and NiMH will not do it and many SLA will not do it. Also, you might just find that if you took this step you would no longer sense the need to complicate design & add cost with a separate tube stage. For the committed DIYer, of course, all bets are off.

Dave
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