 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
71.254.154.253
Hi all,
I am new to this. Had being reading many and many previous post on this subject. However, after spend days reading the old post, can not seem to find a definite answer. Please help if you can.
I want to begin tweaking my cd player by going the opamp swapping method. Already bought the sockets and opa2604.
However, it seems other than directly swap, I might need to solder some cap to some of the pins. and the value might be different for different opamp.
Is this correct?
Can anyone please verify for me? What are available direct swap opamp for this player?
I got opa2604 and will get ad826. Are they direct swapable?
If this is successful, I will jump into nonos mod next.
Thank you for your help.
Follow Ups:
I've had this player for many years and tweaked almost anything imaginable within. Though its basic tone was among the most natural even to date (CDM4, TDA1541A, BG's, Philips film rectifiers, very good carbon resistors-better sounding than Vishay IMO) its resolution sucked, I had two machines and in both almost all P.S caps ran dry, replace those with other Nichicon audio grade this time. As for op-amps replacement, I've tried the lot, DON'T even consider those fast-video ones, even when bypassed they make the sound thin dull or shrill-the AD826 were horrible f.i. If you want to waste your time please go ahead though, Put in a couple of good sockets and try several audio op-amps, IME, the opa2604 would be your final choice. For other mods search authors: Ryan and gads. There's not much to tweak in this player for Rotel really put in the best stuff considering its retail price, Put good female jacks and solder them directly to the PCB using the original wire, put fresh on/off switch and of course replace original diodes with FREDs or IR's 11DQ10 Schottkys.
Thank you for your input. I got the OPA2604 already. Can not wait to put them in.
What does 11DQ10 do to the sound. Are they also straight replacement for the old? Which old ones I should replace, I am guessing , from what I read, 11DQ10 are diode and should replace old diode, it that right.
Thank you
Hmm, that wasn't my experience with the faster opamps. I never tried 2604s, but the AD826s and LM6172s both sounded good in mine. I have tried OPA2134/2132 in it and they sounded pretty good as well. The stock Signetics NE5532s in mine sound slow and dull comparatively.
Mine does have 11DQ10 rectifiers for the +/-5 and +/-15 V supplies. And a Tent XO on a custom Flea board with onboard /2 for direct DAC clocking (sep. PSUs for clock and divide logic). Didn't bother with the jacks. What is the problem with the power supply switch? I should probably replace the PSU caps on mine with Pana FMs or FCs.
Thanks. I will try the AD826 too. Seems like I will be using this player for quite sometime and I could have all the time to play around with different Op.
At lease, I kind of get a idea that each op will do differently to each person who tried. Matter of taste I guess, and without trying, I will not know what suite me best.
So, I will try opa2604 and ad826 along with 11DQ10. How many 11DQ10 do I need to buy?
Thank you
You should really get the service manual/schematics if you don't have them (email Rotel US and they will send you a .pdf for free). And you also should make certain you understand what you are doing before you start playing around with power supplies or anything near the AC.
I replaced 8 diodes on mine (the bridges for the +/-5V and +/-15V supplies). There are some other 1N4003 (IIRC) diodes in the player, but I haven't gone thru the supply enough to determine what they are there for, so I left them alone.
Adding a clock must have really advanced the player to today's resolution minor league, good move.
After trying so many op-amps, all sounded better than the stock ones, all made an improvement in different areas-the OPA2604 is the most "wholistic" IMO.
Replacing the switch is a good idea with any 20Y old component, I took apart the one in my 855 and it was totally charred, I had a similar laying around, easy to replace and cleaned up the sound a little.
if the opa 2604 is the correct op amp then most any dual will fit ....not all of course will sound any good ....
the 2604 is a good starting point you could try the opa2227 I've had good results from this.
you can connect a tantulum bead say 10uf 30v across each supply rail ie +ve rail connect + to the positve supply and the -ve leg to ground. remember that the ground will be more positive than the negative rail so it needs to go the other way round. positioning should be as close to the opamp as possible ....
get id of any bipolar caps or electrolitic dc blocking caps in the signal path and replace with 10uf of film caps or my fave paper in oil ...
Hi,
Thank you for the replay. I am going to replace the old with opa2604. I believe what's in there now is NE5532.
Just want to make sure I understand you correct, the recommendation is to connect a cap + to + and - to ground. I am thinking that I will connect it to the bottom of the ic socket, direct soldered. It is correct + is 4 pin and - is 8 pin? Or the other way around?
Do you have a brand of film caps you recommend. So replace all the caps in the signal path with 10uf, does not matter if the original value is not 10uf?
I am green to this, would appreciate as much help, as much clarification as possible.
Many thanks
I have a modified 855. You can use the OPA2604s. I haven't tried those, but have used: AD826, LM6172, LM4562s. The LM6172s probably need at least a cap from V+ (pin 8) to V- (pin 4). I have 0.1uf ceramics from both V+ and V- to ground (on the bottom of the board). For the LM6172, I also used a 0.33uf stacked film between the V+ and V- pins (right on top of the chip).
The stock bypass and coupling caps in these are BG stds., 100uf. I put in BG NX 47uf (IIRC), some improvement there for the coupling caps. Film would probably be preferable, as long as 10uf doesn't roll the bass off too much. No caps at all would be even better, but the configuration of the output stage has about 3.3Vdc on it, so that isn't possible without completely redoing it.
A better mod would be to replace the opamp output stage entirely with a discrete (working on that now), as opamps aren't particularly suitable for I/V conversion.
So how do the sound compare among different op you tried?
From my reading, I noted general comment on ad826 is that is is more audiophile, more high, tigher bass, greater details and wider soundstage. And on opa2604, it is "sweet"!! Is that your finding as well?
How about LM6172 and LM4562?
Just think about how many options I can have rolling the op brings excitment. Is it true that each op will require run in period to function its fullest? How long would that be? I am assuming that run in is for the op, so is it correct that if an op is fully run in, say 100 hours, then if I take it out and later insert it again, it would be considered as already run in or do I need to go through the process again?
What is a discrete? Seems complicated from the name suggested.
Thank you so much for great info and help.
As I said, I never tried the 2604s. The three that I mentioned sound more alike than different. The LM6172s are probably the most neutral or analytical of the bunch (and the crankiest, being bipolar input). Check any opamp you put in for excessive heat (since with the DC offset already present in the stage, you can't judge by that). If an opamp gets hot, chances are it is oscillating, which is a bad thing.
I'm not much of a believer in break in, so no comment there.
A discrete I/V stage is just that... discrete components. Search diyaudio.com or diyhifi.org for jocko's simple I/V stage, the Pass D1, etc. Commercially, there is the LC Audio zapfilter.
Most neutral sounds good to me. I will give it a try as well.
If an op gets hot, and too much oscillating, any way to reduce the oscillating? Or just forget about that particular op?
I also remember someone mentioned putting some kind of sorbothane on top of the chip, is that for solving oscillating?
Many thanks
The bypass capacitors are one primary means of attepting to control or prevent oscillation. If the opamp is oscillating, you do not want to use it. Barring access to a scope, you can also measure the current draw and compare it to the datasheet to determine whether it is oscillating or not. Or heat... as they will heat up.
The sorbethane, etc. is not to combat oscillation but vibration. Unrelated.
Thank you very much for all these info
read this .....
http://www.zero-distortion.com/start.htm
choosing op amps
Many thanks. Great site and a must read for newbie like me.
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
