DIY thoughts of the day

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montechristo358
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Re: DIY thoughts of the day

Unread post by montechristo358 » Thu Sep 06, 2018 2:18 pm

liking your chains and sprocket idea Stu, I've been toying with a similar solution to adding a volume remote to a purely passive preamp

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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Thu Sep 06, 2018 2:53 pm

montechristo358 wrote:
Thu Sep 06, 2018 2:18 pm
liking your chains and sprocket idea Stu, I've been toying with a similar solution to adding a volume remote to a purely passive preamp
I mess about with machinery a lot so get lots of ideas from my work. Chain must be tight and be in contact with as many sprocket teeth as possible. Easy with two sprockets as the chain goes almost all the way round each one. Idler pulleys would be useful to take up slack or get more of the chain on the sprocket.
Naim, Linn & Harbeth fanboy

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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Fri Oct 05, 2018 8:05 pm

Latest diy ideas have come from reading the pfm diy archives. Started at the last page (page 666 - is that a sign ?) And got to about p630 so far. These posts are from 2004, 3 years before i joined and learned solder juggling.

Anyways, read a few threads on modding the CD3.5 (i have already modded the bollox off mine) and a few things cropped up that i had not thought of.

1)I2S can be taken from the connection between the decoder and dac and taken to a new dac if wanted. Has to use the same clock frequency as the dac already in the 3.5 but changing the clock frequency should not be too problematic

2) Another guy bypassed the anologue output stage altogether and reported good results. That gets rid of 6 opamps and loads of resistors and caps. The best opamp is no opamp after all. There is an opamp in the dac which has enough balls to drive what ever comes after the cdp.

Might give the bypassing of the output stage a go. Easily put back if no likey. Lots of components removed from the signal path and a psu with 500va twin ct secondary transformer removed from the equation as well.

What would be really cool would be plumbing the £3.40 Chinese dac in there.

I love it when a plan comes together :happy-wavemulticolor: :happy-wavemulticolor:
Naim, Linn & Harbeth fanboy

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Latteman
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Re: DIY thoughts of the day

Unread post by Latteman » Fri Oct 05, 2018 8:24 pm

You are 🤪
What is this Chinese DAC - seems popular 👌
Analogue Source-ARB Turntable & 10” dual pivot arm, Grado Gold MI, Nva Phono 1.
Digital Sources- Meridian 206 cdp, Pro-Ject Bluetooth E for iPhone 4s & Genus DAB all to Beresford TC7510
Amplification-NVA P50 & 2x A20
Speakers-Diy Cubes; Mid/bass; 4” Royd drivers with LS5; Tweeters; Richard Allan Cb4 with Ls1
Interconnects-SSC throughout
Mini BMU

eagwok33
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Re: DIY thoughts of the day

Unread post by eagwok33 » Fri Oct 05, 2018 9:29 pm

Hi Stu,

Your plan to bypass the analogue output stage of your CD3.5 sounds interesting. Does the CD3.5 also have a Philips 1541 DAC CHIP in it?

Here is a link to the Lampizator site, who did something similar with a CD3 (of course a tube had to be used in the output stage, too 8-) ).
http://lampizator.eu/lampizator/REFEREN ... imcd3.html

just food for thought...
Norbert

Tubes and Vinyl rule, Music rocks! :icon-wink:

eagwok33
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Re: DIY thoughts of the day

Unread post by eagwok33 » Fri Oct 05, 2018 9:45 pm

Latteman wrote:
Fri Oct 05, 2018 8:24 pm
You are 🤪
What is this Chinese DAC - seems popular 👌
Hi Latteman,

There's info to be found on this forum about this Chinese DAC (from earlier this year). Just do a search. It is a recommendation of the Doc :clap: and everyone who tried it with an external - I believe 5V - linear power supply has been very impressed :-)
Norbert

Tubes and Vinyl rule, Music rocks! :icon-wink:

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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Sat Oct 06, 2018 7:23 am

Hi Norbert,

Thanks for your interest. No, my cdp does not have the lovely 1541 in it unfortunately. They are hard to find now and apparently difficult to apply. Thanks for linking the lampizator stuff, i have read that before many years ago but forgotten much of it now. Tubes scare me to death.

The output stage is a 7 pole bessel filter with the last two opamps being a buffer to the outside world. The weird thing about the dac (TDA1305) is it has an internal opamp IV stage so the rest of the antialias filter can be removed. There may be a decrease in sq however, dont know til you try. Seems to fit in with the less is more, keep it simple philosophy.

I have not heard the Chinese dac yet but have one out of its case and have started to try and trace the voltage supply tracks. Not easy though with the tiny pcb tracks and components.

:dance:
Naim, Linn & Harbeth fanboy

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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Wed Oct 10, 2018 4:46 pm

Well, Naim CD3.5 output stage is now bypassed along with the output relay and associated circuits plus two psu's removed from the equation.

The TDA1305 dac is a voltage out affair as it has an internal opamp for current to voltage conversion (IV stage). That can be seen as a good or bad thing. Good is I don't have to have another opamp (although it can be done passively) and psu to do it. Bad - I cant change the internal opamp for something better. :cry:

So I lifted a leg of the first coupling cap after the dac added 100k resistor to signal 0V and a wire to the output phono sockets. Hey presto - 6 opamps, and 10's of resistors and caps removed from the equation. I was worried there may be pops, clicks and other nasties with the removal of the output relay but I have used all the commands on the remote and there has not been any :guiness;

Listening has been an interesting experience. More detail for sure, less fatigue and harshness. I was worried about aliasing and hearing nasty dac artefacts as the TDA is a bistream and they are said to need a lot of filtering afterwards. I have one 1st order filter consisting of a 680pf cap to ground as soon after the dac as is possible but that is what Naim had put on the pcb anyway (and is suggested in the data sheet as all that is needed ?). 10uf film coupling cap and 100k to ground take of any DC (which was 2.5V without it). My amps have no coupling caps (obviously) so amplifying 2.5V would have resulted in many melted voice coils :naughty:

Listening to Stevie Wonder at the moment I am amazed at what this simplicity has brought. Earlier in Led Zep 1 I heard very low level detail that I had not been able to distinguish before.
Naim, Linn & Harbeth fanboy

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karatestu
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Re: DIY thoughts of the day

Unread post by karatestu » Fri Oct 12, 2018 4:32 pm

Still listening without the cdp anologue output stage. Liking it very much so more evidence to me that KISS really pays .

Not being one to sit still though I decided to play around with my potential divider volume circuit. It has been sat on its own with only phono and din sockets near by and a star ground. 1 metre of new style TIS between cdp and potential divider. No input selector.

I have moved this to the cdp now that the psu for the anologue stage is no longer needed and has been removed. The TIS has been moved to duties between cdp/pre and Avondale monoblocs. NVA based amps already had a TIS.

Currently enjoying a bit of Bob Marley and the musical improvements brought by my recent adventures :dance: . Crowd are a bit louder than usual in the background on no woman no cry :lol:
Naim, Linn & Harbeth fanboy

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Dr Bunsen Honeydew
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Re: DIY thoughts of the day

Unread post by Dr Bunsen Honeydew » Fri Oct 12, 2018 4:38 pm

I thought Audio Addicts and that arse Westie was your forum now. Do you like the insults I and we get there. same goes for DSJR.

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