Comparison of Denon DVD-2900 Mods

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Anyone out there using a modified Denon DVD2900?

If so, which mods do you have?

I'm interested in making comparisons of three popular modifications for the DVD-2900:

1) Underwood HiFi (style) mod
2) SACD Mods Budget mod (not their full mod which substitutes a discrete Zapfilter in place of Denon's three stage opamp design)
3) The DIY "Dutch" Mod, as described in this forum.

I'm interested in anyone else who is interested in participating in listening comparisons (I can share source material).

Getting Started

I've got the boards ready to go, and have taken pictures to show the primary differences between the three mods.

Power Supply:

Left is our version for the "Dutch Mod", with film/foil bypasses on the PS input filter, beefed-up LCR filter and large B.G. capacitors at the outputs of the regulator for the D/A board.

Center is similar to the Underwood Mod, with film/foil bypass on PS input filter, large BG cap after the diodes, and a mixture of B.G.'s, Rubycon ZL's and Oscons throughout the PS.

Right is the power supply of the SACD Mods unit, with beefed up LCR filter and large B.G. capacitors at the outputs of the regulator for the D/A board.

Next up are the D/A Boards...



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(One other difference in the Power supplies is the substitution of FRED-type diodes in the Underwood-style mod).

Digital/Audio Boards:

Left is our version for the "Dutch Mod", with Polypropylene output caps, beefed-up PS bypasses, BG's and OPA627's (on adapter boards) for output buffers .

Center is similar to Underwood Mod, with Polypropylene output caps, upgraded opamps in I/V and output buffers (Burr-Brown OPA627AU's). Key resistors and capacitors in signal path have been upgraded (with Rikens and audio-grade polycaps). Opamps have polystyrene bypasses on power pins, and B.G.'s are used as local reservoirs.

Right is the D/A board of the SACD Mods unit, with Polypropylene output caps, AD826's under the board (we substituted OPA627's on Browndogs in place of their AD826 for the output buffers, for these comparisons). The L/R opamps are class-A biased in their budget mod.

The SACD Mods uses 4.7uf Auricaps for the output caps, but we substituted other similarly-rated Polypropylenes with film bypasses for the others, using what was on-hand (Audiocap/Theta and MIT/TRT/"Wondercaps"). In our opinion some past capacitor comparisons have shown these premium polypropylenes sound pretty similar, within a few percent on a scale of 100 (as were reviewed by M. Colloms, HiFi News, et al). These small differences should be swamped by the large differences in these circuit mods.

Once reassembled, and after a period of run-in, repeated listening comparisons will be made on familiar source material.

Lacking any facility for blind-testing, these listening comparisons will be made reviewer-fashion(subjectively, comparing with a known reference -a stock DVD-2900) and notes will be made on hearing noticeable differences in P.R.A.T., timbre, imaging and soundstage.

Stay tuned...



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Help me Mr. Wizard!

First off, I’ll admit that maybe I bit off more than I could chew at one time!

This listening comparison has turned out to be one of the most challenging I have done in a long time, due to the sheer number of variables:

1. Different DVD-2900 players used for each mod;
2. Different power supplies used with each board;
3. Different output coupling caps(maybe there is more audible difference between caps than I expected- !?);
4. The SACD mods unit includes a DEXA D-Clock, while the other two use the stock crystal clock at their respective price points.*
5. Slightly different output levels, despite the care taken to use the same model output buffer opamps (OPA627) on each audio board.
6. I'm having to switch the analog bypass cables from player to player after each listening selection, matching output levels at the speaker (checking with both a voltmeter and a sound level meter).

Rather than trying to compare the different mods’ D/A boards with all three types of power supply board, and then each combination with & without the D-clock(18 possible combinations), I’ll just stick to comparing each mod as a complete entity- much as one would if purchasing a modded player or having an existing player modified.

First up is the “Dutch Mod” with its slightly modified power supply...

* although for substantially more money, the Underwood mod can have an upgraded clock added.
Stock vs "Dutch" Mod

First, the easiest part- comparison with the stock player.

Enough has been written already about the stock DVD-2900, which is very good as far as stock players go. HiFi News selected it as their reference universal disc player for many moons, calling it
...night and day superior (to the newer DVD3910) with its beautifully open, transparent and tautly positive sound...

Well, the Dutch mod improves upon the stock unit in several important areas, including
Cleaner, more detailed bass, mids and highs and noticeably improved dynamics along with more specific imaging across a slightly bigger soundstage .

For a parts investment less than $200 (plus a couple hours labor), you get a remarkably improved player, comparable to CDP’s costing a lot more than the total investment (even if you bought your Denon new) here… PLUS, you get DVD-A and SACD playback that can even exceed that fine standard (with the right source material), not to mention excellent video playback. :cool:

Next up will be the “Dutch” mod vs the “Underwood-style” mod.

How long to "break-in" Black Gate Caps?

Well, I've been putting-off the serious listening comparisons while "running-in" the players, due to the large number of Black Gate capacitors used, to be sure the sound is representative of the finished mods and results are not skewed by "Green" caps!(?)

Do the B.G. caps REALLY require 200+ hrs to sound their best?? :eek:
I sure hope I can hear any further difference, as they sound great right now !

(I've got to acknowledge that prior mods with B.G.'s have made both my Pre-Pro and Power amps sound better).

As Carly Simon once sang:
"Anticipation is making me wait- keeping me way-ay-ay-ay-aiting" (cue: pouring ketchup bottle)

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Joined 2007
I've used Black Gates personally and I, too have found the sound quality to improve after a length of time.

Both a Google search and a search of this forum produced several opinions, with most commonly:
The break-in time for the Black Gate capacitor is at least 200 hours and it does depend on how it is being broken-in, continuously or on/off (which takes much longer). The sound of the Black Gate caps before break-in is tight, dry, less dynamic and not as musical.The sound will be excellent after broken-in with good dynamics, well controlled bass, neutral and musical sound with dead quiet background.

Take heart! The Black Gates are so good sounding after the first few days that you'll forget all about "breaking-in or burning-in" and will just enjoy the music - until one day when you might hear things you'd never before noticed in familiar source material.

Interim results

Extended listening comparisons between the "Dutch" modded player and either of the other two mods reveals that upgrading the I/V opamps yields another significant step up in audio quality from the more basic mod. The difference was almost as large as going from the stock player to the Dutch mod!

The differences between the "Underwood-style" mod and the SACD's budget mod, however, were much smaller and more subtle in nature (think "seasoned to taste").

It has required more time to quantify those differences, and there was a surprise (at least to our listening team) ending, which will be detailed in the next post (once we agree upon the various descriptors and adjectives that best convey them).

So Close! - upgrade time?

Well, at least in our sound systems, we're having a hard time consistently hearing differences between the audio boards of players #1 & 2 in our informal A-B/X comparisons; Consequently, I feel we've identified another limitation to the resolution of my system, at least: the crossover caps...

I've upgraded key components before- now it's time to address the loudspeakers' 3rd order crossovers (high-pass uses large Solen & Axon caps in series). I've obtained large Clarity Cap PX's to be paralleled with smaller Hovland Musicaps (making up around 15% of the total value), to achieve the final values needed. This is an affordable way to get closer to the potential of the system, without spending a fortune on really exotic capacitors, or completely redesigning the loudspeakers (not likely).

I hope replacing the Solen/Axon caps will remove the remaining veils that prevent hearing the small differences between these two well-tweaked sources.

:att'n: Since the price of used Denon DVD2900's has come down recently(no doubt due to some owners upgrading to Blue-Ray, etc.), now is a good time to snap one up and mod it! I still havent found another universal player with its combination of fine audio/video qualities, instant layer changes and roomy chassis in which to work.


Source: Modded Denon DVD2900
Amp: Modded Forte Model 4
Preamp: Modded Fosgate FAP-T1+
Speakers: Ariel/ME-2 modded with Vifa XT25
IC's: Silversonic Air-Matrix
Cables:Biwired with AQCV4 & SS.T-14
Still awaiting the replacement caps from Hovland, so we bought some from Empirical Audio to get finished right away...

JT, since you've asked:
The surprise is that, while differences between the SACDmods and Underwood-style audio boards are pretty subtle* , the lower cost SACDMods Budget Mod is the clear winner with its included Dexa D-Clock for less than half the price. Plus, for about 15% more, you get the multi-channel upgrade as well!
(now, I'm afraid, I've spoiled the ending! ) :eek:

Still hoping to finish detailing the sonic qualities of the mods after extended listening comparisons with the new crossovers.

FYI, the other system used in the listening comparisons is an older one comprised of Magnepan IIIa speakers driven by AudioResearch D130 and Conrad Johnson PV5 electronics- very transparent, yet musical (but mine rules with multi-channel).

*about as good as it gets with the DVD2900. Perhaps the newer (more expensive)DVD3930, with its linear PS & dual-differential DAC's would show more difference...?
Guess we're done

We've spent the better part of a month comparing the SACD Mods DVD2900 to the Underwood-style mod (when we say style, it's because we performed the mod ourselves, and omitted the upgrade of the output jacks using silver wire).

Our notes were pretty similar for both units, and the only variations in the notes were no doubt due to use of the Dexa D-Clock:subtle improvement in image focus and soundstage dimensions as well as incremental improvements in noise and dynamics-
BUT, we could not identify either one consistently in AB-X comparisons.

For all pratical purposes, they sounded VERY similar- which is quite a compliment to the SACD Mod's player, since it offers a lot more for the money (clock and multi-channel mods).

So whichever mod you choose, they're both quite impressive, and give substantial improvements over the stock Denon multi-player.

Disabled Account
Joined 2007
DVD2900 for under $100?

Chas wrote:
Since the price of used Denon DVD2900's has come down recently(no doubt due to some owners upgrading to Blue-Ray, etc.), now is a good time to snap one up and mod it!

Just saw a couple Denon DVD2900's on eBay for about $100-

I agree, it's a great deal and when modded these sound great!!
Bypass capacitor

Can anyone supply specification of replacement film foil bypass at L909

Do you mean a bypass capacitor across C950, at the output of L909?

For all three of the mods above, we made the following changes:

C950 was originally a Nippon Chemcon 220uf/16v, but was changed to a Blackgate Std(a bit cramped for an FK).
Bypass can be a 0.1uf/50v NX bypass (although one could bypass with a film cap, such as a Wima FKP or even a nice ERO MKP1837)mounted on the bottom of the board.

More importantly,
C917 was changed to B.G. 1,000/16v Std*.
L909 increased to 330uH*, with much better filtering of noise from the SMPS.
C958,C959 at the outputs of the regulators were replaced with 1,000uf* Black Gate Std (or one could substitute 470uf B.G. FK's).

Good luck on your mods, and don't forget to post, comparing the sound with mods in place.



* credit for these mods must go to Matt at S.A.C.D. Mods.


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Disabled Account
Joined 2008

Thanks for advice. Now going for mix of FK & standards, and will fit 4A 600v TO220 FRED's at D901-4.

Will high current ferrite bobbin Delevan series 4590-334K fit for L909?

Progressing with fitting LCaudio clock & Zapfilter so will post back with comment on completion

I believe we used PN# 4590R-334K, mounted vertically(see photo in post#2).

Progressing with fitting LCaudio clock & Zapfilter...

Great choices! Your player should easily out-perform the Underwood mod (Zapfilter vs opamps) on 2-channel material.

Please keep us posted.


p.s. One other popular mod is to replace, or bypass the X2 caps in the PS input CLC filter, using 100-470nf/600v+ film/foil(or even Auricaps, as some have done). We just bypassed with FKP's.
Denon DVD player mods


Did your company do any comparisons of player mods to a Denon DVD-2910 player.
Believe this was the successor to the 2900; and while it may have limitations vs. the 2900 and the 3910, it's all I got for the moment.

Would be interested in any mods you compared that were done to the audio and PS boards; the other guys mentioned has mods for this player, so would like your opinion.

Since I'm a newbie, the webmaster will not allow me to send PM's or email directly to you.
Apologize if this post is somewhat off topic.

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