Modding/tweaking my system

Hi all

I thought I would start this thread almost like a diary.

After living with my system for 12 years, purchased 2nd hand, i find myself wanting to see if i can improve on the sound.

I tried modding a Marantz cd67 player years ago with some success then went too far and wrecked it.

The system is 

Rotel RCD02 cd

Cambridge Audio Dacmagic

RC03pre amp

2 RB03 power amps running as mono blocks


The first thing I wanted to do was tame the overly bright high end by modding the PMCs to + after years of searching I finally found the crossover layout bought the parts and set about the mods.

1st impressions are the highs are tamed however I have 1 speaker that "sounds" louder than the other, more on that later.

I bought the Dacmagic el-cheapo without the box or instructions. I recently downloaded the instructions and realised the Spdif requires the use of a 75ohm digital cable, I've been using a standard RCA all these years.

The room, HiFi and speaker placement are far from optimal but it is was it is and cannot be changed.

I noted I can feel the CD chassis vibrating with music at reasonable levels so that needs a change.

The overall voicing of the system I would describe as slightly forward with a muddy mid range.

It's the highs and mids I'm looking to resolve.



So moving on.

Today a digital cable has arrived along with some Dynamt extreme.

The system has been played?powered up all day I'm about to play a reference track which I love and is what has caused me to start this journey 

Pink Floyd Comfortably Numb

One thing in very sharp focus is the idea the better the system the more it exposes poor recordings.

I've noticed some tracks on The Wall sound amazing, others incl. Comfortably Numb less so

I will move the rack to have access to the cabling play the track, replace the cable and go again. I'm hoping the new cable will resolve the midrange better and an added bonus would be better soundstage but as already mentioned the placement causes pretty big issues on that front.

The chosen cable is  QED performance 

Other cables in the system are QED XT350 and Monitor Audio 3

Ok so the previous RCA has been yanked after a reference listen the new "digital" cable plugged in and played again.

Whilst the change is not Night and Day its a genuine step forward.

The "out of balance" highs seem to be resolved? I didn't expect that!

I fact I had to re position to hit the sweet spot. I would also say the new cable seems overall slightly quieter?

With plenty of power on tap thats no issue whatsoever

The mids have opened up a little the overall soundstage aligned and sibilance reduced.

Lesson learned here? Use the right cable for the job.

Still we have work to do to unleash what I feel can be achieved by this mid range set up


So opened up the hood and knock, knock 

Plenty of resonant surface to pay with.

Installed approx 2/3 of the cover with dynamat extreme

Next up a couple of pieces on the crystal itself, cleaned the lens and back together.

Listening test

I didn't expect much change here after all its just damping.

I'm shocked actually.

Whilst the sound is cleaner more mid focussed its lost a lot of bass! I know right how is that possible?

Bass extension is still there just lacks weight and overall sounds bright, slightly thin and "cold" but  the level of detail is amazing

I even tried a goto bass work out, Goldfrapp Supernature yup its gone!

Pop goes the hood again targeting the crystal as I suspect that can be the only suspect. I admit the detail currently displayed may go but thats a trade off I'll have to live with.

Life is about compromise 


So the damping material on the crystal removed.

The detail is now lost but the bass (to some extent) is now back.

The player looks nicely set up inside albeit pretty basic.

Nice large rubtcons on the power supply think i'll leave them alone.

The effect of damping the crystal leads me to believe a clock may possibly yield greatest results followed by op-amps and decoupling caps.

The aim is to keep the bass performance whilst opening up the detail especially through the mid-range. Tonight has shown me what the player can yield!

From this point on parting with £ may be in order.

As Floyd says

Tear down the wall

@notdeadyet Are you familiar with the member systems section of audiogon? 



Hi Spenser Just about, I'm pretty new but did use it to post some pics requested by other members


@notdeadyet Here's the link to create your system: just click CREATE SYSTEM on top right. 

I’m saying that you have many interesting comments about your journey and a system page with photos is a great way to show what you have, let others comment & ask questions about it, and over time as you make changes, we can easily follow your path and learn from it.

One of my favorite ways to learn here is to gain insight into how member’s choices and decision process evolve over time. Occasionally, prospective purchasers might ask for your insights to their situations.

Just a thought for you to get more enjoyment from the forum. Cheers,


Just a quick update 

The right hand speaker still seems brighter than the left, but not on all recordings.

I may Have to pop the x-over check the resistor and reflow the solders?

The Sorbothane isolators have arrived today so warming the old girl up and will pop em in later, not expecting any change but a £10 tweak is worth a go.


Looking at your setup...I would be inclined to address the placement of your speaker system in your room... along with a readjustment of the room layout to be conducive to a proper setup.

You're on the right track with what you're doing but the things you're using are getting all the poor results I would expect. That mat material you're using is more for quieting cars than audio gear. A much better material is TA-102 fO.q tape. This damps micro vibrations revealing inner detail without losing bass or dynamics. Looks expensive but a little goes a long way.

Pull your speakers out into the room. Close to the wall muddles imaging and muddies bass. Worst is the rack by the right speaker, reflections off that are bad. Use a tape measure to align the speakers absolutely equidistant and symmetrical. Then experiment with toe. You will probably want them toed in a lot more for better imaging. But this is a tradeoff, you get better imaging and less room effects being toed in a lot, but also more direct might exacerbate your bright top end. Only you can decide the right balance. 

Get some Nobsound springs and put them under everything. These will clean up a tremendous amount of grunge and smear and get you a more natural sound. Springs are sensitive to loading. By adjusting and listening you will be able to tune your system to a lot better sound. It will take some time to figure out the best combination but it will be well worth it as you will be able to tame that top end without losing anything in the process.

Bear in mind a certain amount of top end glare will always be there simply due to what you are using. But there's an awful lot you can do to ameliorate it without trying to mask it creating problems in other areas like with the mat stuff you tried.

Thanks for the replies guys

The room/life simply won't allow any other positioning.

What you can't see is most of the right side opens into the kitchen over a breakfast bar!

Yes I have to deal with the fridge dishwasher etc.

I've shifted the speakers wider in an attempt to get a wider ss, they've gone backwards and forwards many times over the years. Presently I'm trying the tight right tight back layout seen.

I simply cannot decide the best fit, close as they are seems to allow less toe in helping to open the sound.

Think i may remove the spikes and have a long positioning session, long overdue.

i sit far end of the room behind are patio doors. I have heavy curtains to cut rear reflected sound.

I'm considering an DIY rack with closed off sides and back for transport, dac and pre open back for amps.

The next stage I've been considering is a re-clock, op-amps and some recapping.I want to see how far I can get before open heart surgery.

@millercarbon I'll have a peek at the products mentioned ty

Once everyone has gone to bed I'll play with the sorb balls lol


@millercarbon ty ty ty

Your comment on toe in reminded me of an article where a guy auditioned the FB1s removing a much larger set of PMCs.

The PMC engineer when positioning them had them closer together but with much more toe in than the reference set up.

I've just shifted a bit away from the wall then toed in more than usual and just wow.

Playing my reference back end of the wall I couldn't stop grinning

Things have snapped into position, details never heard before (unless I'm imagining it) bass tighter but remains the same weight. The crashy symbols have shifted backwards allowing more delicate percussion to come to the fore.

Yes its still bright but as you referred to its what I've got.

Rotel kit Fb1s both known as a bright presentation

Now its time to play with those balls

Nobsound springs will allow you to play with loading to tweak the top end down a bit. This will warm up the bass at the same time. Mass loading, adding mass to some of the lighter components like a DAC, is another way of improving bottom end while smoothing out the top. This is all trial and error so can take a fair bit of time and usually no one thing is a silver bullet, but it does add up and you can wind up with a lot better sound in the end.

Thanks millercarbon

The tape you suggested is a bit eye watering! 

Trial and error is the last thing I need, £££s

The Nobsound alone for all components would be £150!

I can re-clock, swap out op-amps and recap for about that price

Do you believe you can over-damp and end up dulling the sound?

Installed the sorbothane hemispheres but had to wind down the volume as even when low the bass can be heard in every room. Can't say if there was a difference other than the a more forward presentation and the bass dropped but that's likely down to the volume at a whisper.

I'll play around with adding toe-in and the bally-bits tomorrow if I find the time.




All good advice thus far. You're going to learn a lot about different damping properties with some of these experiments. Far too many materials over damp, using damping is not the way to tame brightness, Brightness is symptom of something wrong upstream, usually inherent to components and/or parts within components. Need to fix this prior to damping experiments.


You're ideas about modding cd player are more on right track. Re-clocking may be problematic, likely present clock circuit won't support clock upgrade. Op amp upgrade may be beneficial, research your op amps, make sure its compatible op amp. Coupling caps good place to start. Discrete voltage regulators can be another nice upgrade. Keep in mind if you're novice, may damage cd player beyond repair if you make mistakes.


Not sure you're in position for upgrades in equipment, but that would be of greater benefit than mods. However, if you're intent on mods and learning what they can offer, you're on right track.

The trick with Nobsound, most components will only need 2 to 4 springs per footer, and some only 3 not 4. This leaves you with enough springs to do 2 components per set of 4. Springs fit perfectly into. 1/4" hole. So with a 1/4" drill bit and some wood, MDF, acrylic or whatever you can make your own.

Easily the bargain tweak of the century.

Yes it is very easy to over damp and dull the sound. All these things go a little at a time. Evaluate each step. When something sounds better, listen for what it made worse. Because usually there is a tradeoff with a lot of this stuff. Somewhere. The trick is to avoid using so much that the negatives don't start to outweigh the positives.

After a bit of an extended listen I can't say sorborthane hemispheres have changed anything at all.

I don't know a great deal about internal workings of cd players but it struck me the idea of swapping op-amps and caps is a non starter.

As I'm using an external dac surely the signal for sprig is being taken prior to those components within the player itself?

If correct that makes me think the op-amp and cap mod would need to be the DacMagic and the clock on the player? I'm also guessing the dac also utilises a clock? Would they both need to be done to have a significant gain?

Maybe I should focus on power supplies with the aim of cleaning everything up prior to the clock signal?

I am not in a position to fork out for separate linear supplies as they appear to be quite pricy.

Has anyone hear of gains being made by replacing a wall wart for say a larger amperage laptop type supply or diy shielded  power cables? Both of those can be achieved with relatively low outlay.

I can live with (for the moment) the slightly bright presentation, its the the midrange clarity I'm after which is still a bit muddy on some recordings?

After a bit of messing around with toe in I feel the system is getting there.

I'm now leaning towards the room/placement is likely the main cause for the issues I experience, that combined with the greater detail afforded by the new crossover, tweeter and using the correct cable for S/Pdif.

It seems moving around and messing with placement the sweet spot is just out of reach, something always has to give, overly bright, muddy mids or lack of bass extension. 

I also pulled the networks and checked resistance values which are pretty much even across both.

I did however swap the networks which with a short listen seems to have brought about a bit more balance, I've been finding the right channel much more forward than left despite a rough check with phone db meter app telling me the opposite.

I'll have an extended listen later to see if its just an immediate feeling rather than an actual change

Just a caution that mics in phones can't pick up low frequencies, so those sound meter apps are just measuring mids/highs with some very high notes also cutoff. Still handy, but just take it with a grain of salt. Cheers,


Hi Spencer it was just to see if an app would agree with what I'm hearing, right hand HF more prominent than left. I used music as I have no access to test tone.

I played the same 2 mins of the same track with centre balance, left and right.I expected right to be louder however left channel was actually 1db louder on peak.

I'm not reading anything into it.

I'm beginning to feel the system as a whole is now more revealing in upper mids and HF exposing some recordings for what they really are. The room layout, system set up and acoustics are far from ideal. I would really like to get the system away from the drivers, speakers further apart and sit further back with more space behind but its just not possible

You keep mentioning channel imbalance. Unless there is something wrong electrically somewhere there should be none. It is very easy however to get imbalance, all it takes is one speaker one inch closer than the other, either to you or a wall or something that might reinforce, or some furniture or something that might absorb. Or even if everything else is right but one is toed slightly more or less than the other. You get the idea. Everything has to be perfectly symmetrical down to the nth degree. Which is why I always say start with the tape measure. 

If you are gonna measure anything, measure distance. Measure angles. Those you can get a handle on. Try and measure sound, you are gonna find you got your work cut out for you just trying to figure out what it is you are really measuring. Then why. Finally how. Guarantee in the end wind up learning, nobody agrees on even the tiniest aspect of any of it. Where hopefully everyone agrees if the speakers are cockeyed so is the sound.

Thank Millercarbon

I think I've got it as sorted as I can get considering the constraints of a kitchen/diner bloody great ceramic top weighs a ton table, plants and chairs!

Playing around with damping and swapping out the RCA to dedicated digital cable brought about some benefits.

Using a greater degree of toe-in really changed the dynamics and I think made me even more conscious of what this system could deliver.

Hunting around the net for hot iron mods I found a simply non invasive tweak thats been implemented today.

The result is truly astonishing, the closed in sweet spot is now wide open, the crashing trays are symbols with timbre and decay.

The congested mids now allow for delicate percussion instruments to be recognised and placed in the ss.

The tweak is so simple anyone with a DacMagic should definitely give it a go.

The tweak is using the XLR outputs for RCA using standard adaptors.

The pair cost me £4.85 delivered!

Apparently the trick is to ensure the pins are connected Pin 1 GND pin 2 V+ and pin 3 unused. The reason it works is the feeds for the RCA are taken from the balanced feed routed through OP27 op-amps which combine and buffer for the unbalanced output. You effectively bypass the op-amp and associated circuits.

Thanks to everyone who contributed to the thread passing on your knowledge and experience its been gratefully received 

Happy New Year to all


Well I just couldn't help searching for other ways to improve what is already a decent system.

My attention turned to removing components from the signal path.

After a suggestion to try a passive pre I researched something I previously didn't know existed.

For anyone that doesn't know of said items they are in basic form a volume pot and possibly a source switch with no active components.

They do vary greatly in quality, complexity and price

I only use one source so just a pot was required. Simple right? Wrong.

The use of a passive requires the source and power amps are suited to each other with output voltage and more importantly impedance 

As it was going to be trail and error I did't want to pay good money for something that just wont play well with my gear. I opted for a cheap £27 pot in a box from amazon listed as an alps 16 pot I took the plunge.

I plugged in the mini beast and well pretty disappointing. it was ok (ish) my system leans on the bright side, this hit the brakes on that effect.

High frequency rolled off pretty heavily so back went the active.

Turns out the pot is a 50k, some clever guys on another forum quickly ran the numbers and informed me I need a 10k. They came up with other work arounds but a pot swap seemed the least invasive.

A 10k alps blue ordered and now installed 

Swapped out the pots and after a first listening session...

HF no longer rolled off in fact it offers more detail with the passive even at low volume listening.

The midrange is less congested and depth of sound field seems to be slightly improved.

No real affect on bass, maybe a little tighter?

I'll give it some more time with various cd's but i'm thinking this is here to stay.

I would say it sounds maybe a little clinical so my attention is now moving toward a bit of recapping.