Dual Op-amps

I have an RCD955, in which a previous tweaker has installed OPA 2604's.

The op-amp sockets are surrounded by a Black Gate forest, so using Brown Dogs to run a pair of Op27's (thus far my preferred opamp) not an option.

Any suggestions on substitutes which might improve on the 2604's?

 

Yep ....the black gates are probabley killing the sound !

I've heard the rcd 955 ....seemed it was quite 'up and at them' sharp bright ? Have you thought about the ad 826/827 or the ad 8022 or ad 8066.

What other mods .....have you done the diodes ?

 

The output caps are currently Stargets. I removed some (unknown to me) film caps installed by the previous bodger, as the player did not sound happy, and at the time had no BG's (I've got some now ). While I was at it I replaced the main PSU cap with a Panasonic FC, and tightened up a couple of loose screws attaching the mech to the board. Haven't done diodes yet.

Sounds much better, not as you describe; could that tendency have been courtesy of the original op-amps, presumably 5532's?

I'll check local availability on the op-amps you mentioned.

 

Do you have the schematics for the player?

I'm not a great fan of black gates, I find they take forever to run in and therefore never really give there best, whilst stargets may not be so good but actually sound better over the life of the cdp. I've noticed that if you switch a player off for an extended time you need to reburnin the black gates again. They are also rather expensive and now hard to get. I've used wima's oscon silmics and stargets with excellent results instead of bg's ...but thats just my preference.


If you reduce the capacitance after the opamp this often improves thev sound. caps after the opamp are normally dc blockers for the pre. If the pre is any good it should have its own dc blockers on its inputs, therefore you can try with out....this of course has its pit falls when you try the cdp out with kit that might not have them!

Its three years at least since I heard the rotel so I may have been mistaken but I was not greatly impressed !

the 5532 are the industry stock opamp...they can sound good especially the AN version,which is specially selected.

Do the diodes, its the best bang for buck mod ! [imo]

if you have 1n400x do a straight swap for 11DQ10's my personal fav's even if you have ultrafasts the schottky's will have a lower noise floor. RS do 11DQ10's for about 80p each so your not going to break the bank!

Have you damped the case ?

Are the original sockets in place ?

which mains lead are you using ?

Does the cdp sit on a suitable plinth?

Have you bypassed any of the bigger caps ?

 

Got to agree about Black Gates. The only place for them is the PSU.

 

Im not actually a fan of swapping out op-amp usually as it more often than not merely changes the sound without improving it. I did have some success with the lt1364 in a Rotel 855 though Very clean sounding to my ears.

I prefer nichicon muse around op-amps and decent black gates around digital stuff (as an easier solution than fiddling with smt caps).

 

By "output caps" do you mean AC-coupling for the signal? If so, one of the worst possible things you could do would be to put an electrolytic cap (be it polarised or non-polarised) in there...

 

Isaac is right of course. Marantz use back to back silmics in some of their players like the CD63 KI which effectively creates a bipolar lytic but a film cap is best if you can get one to fit. Failing that a non polar (N or NX type) blackgate works well.

 

I do hope that the DIY board doesnt descend into the level of total tweak-o-bollocks.

If you have some repeatable results and conclusions from substitution of the manufacturers components then please elaborate in correct electronic details. Some results including HF spectra [to demonstrate stability] would be nice.

Otherwise you is just one jive-talking homey..

 

Graham - I have done some tests using the Audio Precision SYS-2722 test suite regarding decoupling caps, and they can have a surprising effect on measurable (repeatably) characteristics. This applies not only between caps of different manufacturer/series, but also between "identical" caps before and after running in.

Manufacturers are aware of this, but when it comes to building amplifiers by the 10000s then every cent counts on the BOM.

 

Have you damped the case ?>>Yep

Are the original sockets in place ?>>Yep, so far.

which mains lead are you using ?>>Stock

Does the cdp sit on a suitable plinth?>>Nordost Pulsar Pts

Have you bypassed any of the bigger caps? Nope.

Graham C: unless you've got something useful to contribute, stick your head back in your 'scope.

 

I quite accept that caps of all flavours can have an audio sound.

I can't see the point of discussing 'chinese whispers' bodges to an already bodged piece of kit.

We have quite a few 'suck it and see' posters on ZG already. I dont object to people saying 'I changed X for Y and I think its improved - see what you think..?'

I really cant see any benefit in the thread above though.

Still, best wishes everyone!

Graham

 

"I do hope that the DIY board doesnt descend into the level of total tweak-o-bollocks...."

"I can't see the point of discussing 'chinese whispers' bodges to an already bodged piece of kit." WTF does that mean?

I really think you should take a look at yourself, and ask do I make a useful contribution to the forum. If the answer is no, then clear off and go and insult someone else.

I do not need to provide evidence....all you need to do is listen. If your unaware of the difference between the electrical characteristics of one cap, and multiple caps of the same total value...please do some research and listining tests before you bring your tweak -o- bollocks philosophy to this discussion. If your too anally retentive try reading Audioconversions issue 6 "Choosing capacitors" by Grahm Nalty to get the feel of what your obviously missing you can then move on to the more prosaic texts. If and when you have done that please feel free to come back and discuss the issue without further profanity.

If you don't like what people freely discus on this forum find another.

 

To improve the performance of the cdp with out resort to whole scale redesigning of the player ...

The use of a good diy or after market power cable can make a difference.
replace the rca sockets with teflon insulated ones Maplins do some there a bit pricey but sound ok.
These should be wired to the pcb using the very best cable you have...I'd use silver in ptfe.
Have you fitted a good copper pinned socket for the opamps ? though this will only keep the quality you have ...it makes swapping opamps so much easier.
To offend GrahamC further .....!!! The psu caps can be replaced with say 10 smaller ones who's total value is the same as the one removed this is like super bypassing and will improve the ability of the psu with transient signals. If this is too big a job or space is limited add bypass caps of 10% values ie if the cap is1000uf add 100uf 10uf 1uf etc.

 

Does this Rotel RCD955 use the TDA1541?
A circuit diagram would be helpful
Are you planning on just doing a simple op-amp swap?

 

Yes the RCD-955 uses the TDA1541A

 

Have you tried NOS yet? it costs nothing and is reversable if theres a SAA7220 filter chip inside, theres a fair amount of things you can try out that would bring more of an improvement than a straight op-amp swap.
I've modded and built various dacs with various output stages (Including Thorstens,Pedja Rogics and Lesha's) using the TDA1541's, with some time and effort spent these chips are hard to beat IMHO
It just depends how far your willing to go and how capable you are.

 

I'd agree with that to but you need to do one thing at a time !

I could have listed 50 plus mods but what would the point have been ? keep things simple, work through the output stage first then mod the dac. Once your happy with the output stage you 'll then have a clearer understanding of all the other changes in sound created by the mods.

 

Well NOS costs nothing to try, he may like it and not feel the need to change the op-amps, OPA2604's are not too bad, they could be a lot worse
We could do with knowing what sort of nulling circuit on the dacs output is used before any op-amps are changed

 

I'd agree but I don't have the schematics for that player so its a bit difficult. The opamp mods though are fairly generic...as a standard opamp the 2604 is a good one at its price point. I've pushed them into class A for a small improvment. The alternative would be a photo of the curcuit [back and front]. As I say I'm not disagreeing with you !