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-   -   DIY phono to replace roksan phono stage (https://www.diyaudio.com/forums/analog-line-level/134488-diy-phono-replace-roksan-phono-stage.html)

seroxatmad 8th December 2008 09:59 AM

DIY phono to replace roksan phono stage
 
Hi

I am disappointed with the phono stage in my roksan kandy when using my 24 year old Rega 2 (New Rega Bias 2 cartridge fitted.)

Before i upgrade my rega can anyone recommend a DIY phono stage.

I also use a Kumiza headphone amplifier and i guess it would be nice if it was a discrete design something like that if possible.

Cheers

John

P.S The phono stage in my now sold Cyrus one amplifier was much better. The roksan has NE5532 opamps )surface mount) and my 24 year old cyrus had NE5534AN. I always thought the 5534 was a higher spec and the AN suffix was a low noise version, so why so many years later i have bought a down grade :(

kevinkr 8th December 2008 01:58 PM

Perhaps you could start by replacing the op-amps in the Kandy with something better.

One to consider would be the National LM4562 which has about 5dB lower voltage noise (2.7nVrtHz) than the NE5532 here: http://www.national.com/pf/LM/LM4562.html

Other candidates should probably also be bi-polar types and selected particularly for low input voltage and current noise.

The TI OPA2134A is probably too noisy at 8nVrtHz.

This all presupposes that you are willing and able to remove the old soic (smd) op-amps and replace them.

Incidentally if you have the room, but don't have a hot air soldering tool at your disposal it is still not too hard to replace the op-amps (I have not seen the inside of a Roksan Kandy so if space is very limited you might want to find a tech who can do it for you.) Basically using an X-acto knife cut through the leads flush with the chip body, use a sharp blade. Once severed from its leads remove the body and use a small solder iron (Antex or small tipped Weller) to remove the leads. Clean up with soder-wick, place a tiny amount of solder on one pad, place the replacement IC and heat just that lead - make sure it is aligned properly before you individual solder the remaining leads. I use this technique fairly frequently and it works just fine, just don't do it too many times to a given device as you are likely to eventually lift pads and ruin the phono pre-amp.

One other concern is whether or not the unit in question is still under warranty, the above suggestion might be a non-starter if that is the case or if you are concerned about originality. (resale value, etc...)

seroxatmad 8th December 2008 02:59 PM

Hi

Thanks for the reply

The amp is still under warranty and the phono section is cramped to say the least.

A separate unit is what i am considering.

Cheers

John

djsb 13th December 2008 04:42 PM

Hi,
Try the hart phono kit (a John Linsley Hood design) from

http://www.williamshart.com/index_files/1450phono.htm

I have the fully discrete version and it sounds good to me.

Regards,


David.

seroxatmad 13th December 2008 05:22 PM

Hey

I was thinking of building either the discrete or opamp version from www.sjostromaudio.com

But i think i will buy the PCB of the JLH design and populate it.

Cheers mate I will order 1 after i build my millett max.

I bought all the manual for his kits before - hopefully they are still in the file off years ago.

John

P.S You any pictures of the finished unit? What turntable etc you using with the JLH?

I have emailed you via the forum.

djsb 14th December 2008 03:43 PM

Hi,
I'm using a Systemdek 11x 900 with a Roksan Tabriz arm and a Denon
DL110 cartridge.
I have a 4 amp active filter setup using Marchand active filters. The filters feed into a Rotel preamp and 2 Rotel power Amps. I use 2 IPL M3TL transmission line speakers that I built myself.
I will send pictures of the phono amp and its matching power supply (which also powers the active filters) with the build info if you still need it?

David.

JTT 14th December 2008 05:46 PM

This is an old stalwart which I still use now and then.

http://www.btinternet.com/~jaytt/html/mm_preamp.html

I have used it in more than one diy amp over the years, and have always found it to perform impeccably.


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