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Old 11th October 2012, 06:21 PM   #7541
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Nice, then Lars must be one of the first that used transimpedance open loop structures.
There is another guy in Norway that did that back in the 90th.
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Old 11th October 2012, 06:29 PM   #7542
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Here we go.....Audio
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Old 11th October 2012, 06:44 PM   #7543
pdul is offline pdul  Denmark
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I just hope it will go well with Paradise
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Old 11th October 2012, 06:53 PM   #7544
pdul is offline pdul  Denmark
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Those pcbs you have there could very well get a second lease of life, based on peoples endless superlatives about the sound of paradise, the next natural question will probably contain the word "Linestage"
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Old 11th October 2012, 07:12 PM   #7545
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Sure, we can pick up on this. I just did not want to spoil the proceedings with just another project. The preamp and buffer work well and sound good.
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Old 11th October 2012, 08:49 PM   #7546
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I got the Hammond transformers so i have now all parts to make a prototype of the pre regulator.
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File Type: jpg Hammond trans.jpg (253.5 KB, 234 views)
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Old 11th October 2012, 09:30 PM   #7547
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Quote:
Originally Posted by Joachim Gerhard View Post
Some new information :
In an open loop phono like the Paradise it can happen that the channels have a slight mismatch in gain, say 1dB. That can be corrected by using slightly lower value emitter resistors on the softer channel.
To quote Joachim and as I promised him, I was going to post it to help other people with their build.
What happens is that gain varies big time with the minimum variation due to the OL nature of the design.
A little disclaimer is that I didn't have matched devices in the first place and ended up with 1dB difference within CH R and L.
So I took the channel with slighly less gain and I lowered the resistors from 31.6 down to 30.9 and the gain was matched down to 0.08dB.

This makes you think that it is not important to go crazy matching devices since offset is taken in care by the Servo, and matching can much easier being adjusted by emitter resistance.
By doing that the distortion difference between the two channel was under 0.001%.
Listening confirmed that both channel seem to sound pretty equal, so it's up to you guys if you want to take the extra time to match device.
Sure, having matched device might offer a tiny improvement on the sound, unfortunately I don't have time to try this out on this design, I will leave it up to you guys and if anybody tried this, please let us know if there was any significant improvement from matching.

Another thing that people have been concerned about is tolerance on the RIAA: should it be 0.1% or can it be more?
Well long story short, I have put 1% tolerance parts and the RIAA curve between the two channel is perfectly in track and among the entire audio band there is not even 0.1dB difference between the two channels

Let's now talk about RIAA's value.

I made precise/high-resolution RIAA measurements.
With 73.2K 9.91K 11nF and 32nF the RIAA curve is below 0.1dB on all the audio band.
If 73.2K could be made 73.18K or something like that precision would be even higher than 0.1dB.

Last subject I want to go through, but just as important as the points above, is: in order to make Paradise sound really nice and match RIAA to such a high level of precision you need to use no more than 4700uF on the boosting capacitor.
Forget about 6.8m or even wors 14mF which sound dull and velied.


That's it for now.

If you guys will follow the tips above and the other useful tips that the guys here have made available you will have a very fast, simple, smooth build with a very nice result.


Cheers!
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Old 11th October 2012, 09:32 PM   #7548
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Quote:
Originally Posted by Joachim Gerhard View Post
Sure, we can pick up on this. I just did not want to spoil the proceedings with just another project. The preamp and buffer work well and sound good.
I think we should hold on with the preamp and wait for the balance masterpiece to come alive and then build a balance linestage on the technology eventually learn from it that can also work SE of course with Paradise.

Just my two cents, then you guys can do it the other wat too
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Old 11th October 2012, 09:42 PM   #7549
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I first suggested 6800uF elcaps and MiiB raised them to double. When you lower the elcaps in value you get less deep extension in the very low bass, much under 20Hz. To lower the value of that caps can bring a welcome subsonic filter effect if you have a stability problem in your system.
As far as i know Stefano has rather big B&W speakers that have very high mass woofers.
Actually Stafano hears his complete system so i am not prepared yet to except the lower value as default.
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Old 12th October 2012, 03:50 AM   #7550
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Joachin,

thanks for your reply.
Both simulation and measurements on the bench show a +0.08dB at 20Hz.
A typical subsonic filter has -3dB at 20Hz,

Either way listening tests carried out today show a very nice bass extention.
Cello and double bass are reproduced with power and deeper notes have the right articulation.
In this configuration, final bass response will strongly depend on the rest of the equipment.
For instance, using a highly modified denon 103R brings a very nice soundstage and very clear highs and mids.
Unfortunately it's missing the high energy on the bass and body on the mids compared to the upper range ZYX 4D.
If I didn't know this difference on these 2 carts, I could wonder if the value were a tad low (although I could almost say the sound is blameless even with this conficuration and Denon on).
So, depending on what you put on the paradise, it will respond accordingly.

I can say based on measurements and listening test to try these values with confidence and then try also the one that Joachim suggested and then decide for your own.
People who will try different values, please post/share your opinion/experience here.

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