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Old 19th May 2009, 05:02 PM   #501
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I built my DAC in a chassis I used some years ago as EL84 amp:

Click the image to open in full size.

After finishing, it will look like this gainclone:

Click the image to open in full size.

Franz
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Old 19th May 2009, 10:41 PM   #502
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Quote:
Originally posted by Franz Gysi
I built my DAC in a chassis I used some years ago as EL84 amp:

After finishing, it will look like this gainclone:

Franz

That's nothing, check mine out !
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Old 19th May 2009, 10:51 PM   #503
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Okay, so it ain't much of a looker, but IT LIVES!!! Sorry, but I couldn't resist exposing this ugly duckling, I am so delighted with it!

Thank you everybody for this thread, especially those who answered my newbie questions (legarem, Franz Gysi, Kevin Wood).

It sounds good already, even with long, dodgy interconnects. Now then, where did I put that spool of Kynar wire..! (DIY interconnects!)
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Old 20th May 2009, 12:59 AM   #504
legarem is offline legarem  Canada
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Quote:
Originally posted by hoverdonkey



That's nothing, check mine out !
Try a EI standard transformer (big 9 volts 2A) to replace the toroidal and give me some news. You'll be surprized by the results.
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Old 20th May 2009, 01:27 AM   #505
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Here are my ugly dacs

There's one with lundahls and the other one has Studer uncapsulated transformers I bought from Franz. The first time I tried them, the sound was so bad so I decided to forget them.

Last night, I was thinking that Studer can't do something so bad so I decided to try them again but with a 600 ohms load like the Tams.

Humm ... It is now a real different story

Franz

If you still have a pair try them and give us your impression.
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Old 20th May 2009, 01:46 AM   #506
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Somday I'll make mine like the ones I do to other peoples who want clean jobs.

Prototyping is funny. Doing cosmetics is a nightmare. I hate that !

Here is one I made a year ago when Lukasz Fikus published my LM4562 op amp mod. There is two monstruous transformers.

Later, many peoiples asked me to replace their toroids with EI transformers when they heard the difference
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Old 20th May 2009, 07:19 AM   #507
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Quote:
Try a EI standard transformer (big 9 volts 2A) to replace the toroidal and give me some news. You'll be surprized by the results.
I am surprized about your findings. Could it be, you have dirty mains?

Do you filter the mains before the trannie?

Quote:
If you still have a pair try them and give us your impression.
Yes, I have some. As soon as possible (too many projects and now the LL1690 are built in the box) I will try them again.

Kind regards
Franz
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Old 20th May 2009, 08:36 AM   #508
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Nice thread!

There is som issues that makes me wonder a bit though.
First! Can anyone tell me precisely at which frequenzy the 4398s Switced capacitor filters noise appears and eventually the amplitude.

Next!
Why use a transformer?
Transformers for linelevel is normally used in pro gear, and only because it simply is necessary to avoid humming. Most microphones uses transformers as well, but for purists the very best microphones also comes in TransformerLess versions. Both DPA, Neumann amongst others do so, and they do so because the TL versions are the better ones.

The transformer provides isolation, but as a sideeffect it also provides hysteresis, which masks low level information a lot especially at higher frequenzies.
If the core in some way could be biased with some low level HF that could be filtered afterwards, it might work better at low levels. This principple is ie. used in analog tape recorders.
Btw. if it sounds nicer than op-amps I fully understand, op-amps are imho not the best solution for audio amplifiers.
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Old 20th May 2009, 10:54 AM   #509
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Quote:
Originally posted by Kurt von Kubik
Nice thread!


Why use a transformer?

Btw. if it sounds nicer than op-amps I fully understand, op-amps are imho not the best solution for audio amplifiers.
Your last sentence is the answer to your question.

Op amps are used to make desings cheaper. Today, some can be considered good but discrete parts sound simply better even if they don't have specs as good as op amps.

Op amps have their gain controlled with a ton of negative feedback. This often means good numbers but bad sound.
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Old 20th May 2009, 11:14 AM   #510
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Quote:
Originally posted by Franz Gysi


I am surprized about your findings. Could it be, you have dirty mains?

Do you filter the mains before the trannie?

Kind regards
Franz
Here we are reknowned to have good ac supplying electricity.

My system is feed by a 5 kva monster transformer in balanced mode. 4 - 10 gauge copper shield wire goes from the transformer to the system.

Each time I tried small line filters (corcom filters etc) I finish to take them out because they add some brightness to the sound I hate.

Even if your mains is good, Toroidal transformers by their high bandwith will transfer some garbage from the mains to the component.

Question of sound, EI transformers gives a more relax sound. Toroidal seems to give 'faster' 'zippy' forward sound I don't like.

Some peoples (mainly engineers) thought that i'm crazy with what i'm saying but when they try, they discover that they have ears to hear something.
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