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SEN / CEN All JFET IV Converter Evaluation Pack

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#168
Latest early next week, we shall put our hobby website online.
Then you can download the assembly & test instructions there.
(Link to follow).

As I do not have the ES9018 handy, I have not tested the Vref version myself.
The instructions are thus only applicable for the standard version.
I suggest those subscribers to wait till qusp has finished his first build.
Then you can just follow suit.


Patrick
 
#169
sounds good Patrick!!

Yes i'll be trying a few different ways to produce vref bias. i would like to keep this independent from the dac itself by simply measuring it and reproducing it with a suitable reference + resistance divider + buffer so as to avoid extending AVCC ground and exposing the return to noise, but we will see how well this works in practice. happily the actual voltage for the bias is not so critical. the new common mode isolated and floating regulators from Johns TD1541 dac revision 8 look of interest to those wishing to avoid batteries too.

so on its way are the LT3092 and LTC6655 along with a few other bits and pieces, the LTC6655 require an adapter for the MSOP package, that you can make yourself, or i also found a suitable MSOP->DIL8 adapter at digikey that should actually provide a suitable platform to build the entire VREF assembly on

An externally hosted image should be here but it was not working when we last tested it.
 
#170
also we got some of the refs recommended by Patrick and these will be tested also, along with the method tapping the actual avcc reg + divider

i dont expect to see much difference between the linear part and the MAX6126, not with my ears anyway and the application will be the same, but we all have our favorites and ive come to favor LT due to the quality of not only the parts but the quality and thoroughness of the application notes

just a question regarding resistors in IV, has there been any empirical testing regarding the effects of voltage vs current noise in differing values?
 
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#173
Lazybutt said:
What would you say would make these better suited to the "Cen/Sen" design than another power supply (say compared to a Salas Shunt Reg for example) ?
Click to expand...

well; for starters they are isolated/floating from ground and each other, while salas shunts are not. this IV requires that all the supplies be floating as they are modulated by the load. i think not only would it be ungainly to use salas shunts here due to the shear number of regulators needed, but also very difficult and in order to do it you would have to lessen the effectiveness of the shunt. is it even possible? i havent given it much thought due to the practical obstacles

I suppose you could add a choke to the output and forget about the sense/feedback mechanism, but this seems a bit pointless. others with more intimate knowledge of shunt supplies might be better to answer the question, but it seems like a lot of work to me and may cause huge stability issues
 
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#176
its been more like 3 weeks here as well. i received an automatic email one week after ordering it, telling me my order had been updated to the following status..... 'processing' .....? i have heard nothing since. Jan was away on business at the time i last spoke to him and was unable to tell me whether it had shipped or not.

wrt the pdf i'm way ahead of you, i actually asked him if he had considered digital distribution at the time i made the purchase, imo its the perfect product for it and speaking for myself i would have ordered every volume had i been able to buy the pdf online, shipping adds delay and in my case almost 10eu to the cost; his readers are all tech savvy so thats not an issue and the cost of production would be lower once set up, electronic simulations and other rich content could be added etc. the only concern is intellectual property, but i feel that its not the sort of thing people are likely to make a habit of pirating.

he is however looking into it quite seriously and has been quite responsive any time ive emailed

since people will be following my process and progress it would be really good if i had it before the pcbs arrived, though that now seems unlikely and ive had to order parts a bit blind. i would like to read the article before i put myself out there further, as i'm sure the optimal operation is not as simple as it looks; i'm sure there are a couple of 'gotchas', the devil is in the detail.
 
#177
> though that now seems unlikely and ive had to order parts a bit blind.

The Bill of material can be found at the start of this thread.

> i'm sure the optimal operation is not as simple as it looks;

The article explains how it works and why the distortion is low.
But other than that there are no tricks, as the circuit is sooooo simple.

But talk to Jan at the Linear Audio. He now owns the copyright, not me.
And I know he is back at home now.


Patrick
 
#178
yes i know the parts values list is at the beginning of the thread, but i wanted to read the article before making my own specific parts, brands etc choices as there are only nameless broad part values and there are many different types of parts choices possible within those values. but its all good. for a working circuit i would not have to buy anything at all, i have it all in my parts bin except for a couple of bits for the psu, but I had to buy a few parts for the various vref experiments

i'll shoot him an email tomorrow, i'm dead tired. hopefully it shows up Monday.

nice to know theres no magic =) i left my Ouija board in Tasmania. i think the trickiest part is in the power supply
 
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#179
tricky if you arent using batteries and are into power supply exotica that is hehe. i need to buy more batteries for the full compliment, but ive got enough to get started on one channel at least. i'll be sticking to batteries personally

I should mention that i will only be doing stereo balanced and perhaps stereo SE using a combo of the SEN/CEN to form an instrumentation amp, i wont be doing any es9018 multichannel stuff. in fact i'll be basing most of my experiments using my ackodac, which is based on the ES9012, but its functionally identical to using 9018 in stereo balanced or mono mode. i may try with my buffalo II as well, but that will be secondary for me. anything i do with the ackodac is easily transposed to the buffalo without any changes bar physical layout
 
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#180
qusp said:
well; for starters they are isolated/floating from ground and each other, while salas shunts are not. this IV requires that all the supplies be floating as they are modulated by the load. i think not only would it be ungainly to use salas shunts here due to the shear number of regulators needed, but also very difficult and in order to do it you would have to lessen the effectiveness of the shunt. is it even possible? i havent given it much thought due to the practical obstacles
Click to expand...

OK I see what you mean: this supply can use the same DC-in to provide several floating DC-out.

But I was thinking using Salas regs, each having their own Tx secondary Input (Iron and copper are cheap where I live 😎, and price difference between a Tx with 1x40W secondary and 4x10W secondary is negligible). That way they are made floating and I don't see why I should change anything to the excellent SSLV design this way.
Unless anyone points out something that in my reasoning is wrong, I will try it and report about the subjective performance.

YES if you're using a stereo balanced DAC like I am (and presumably like you are), that's a lot of Salas Shunt regs for just an I/V, but I have many SSLV PCBs in hand, it's components are cheap, they're very high performance and they are quite compact! (besides, that's the paradox of this I/V converter anyway.. very simple in design, but whatever the supply choice: batteries+charger, floating supplies, etc.. it requires a relatively expensive and complicated power. But the beauty I guess lies not in its simplicity but in it's performance)

Sorry if that's slightly off-topic.
 
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