DX-1 XPL-200 Frequency Card Discrepancies

[pasadena]

Hi all,

After listening to my XPL-200A's for a little while, I was getting impatient looking at my DX-1's sitting there doing nothing because I did not have a second stereo amplifier to utilise them.

So, off I went to my wife's uncle's place and borrowed his Dr. Thomas Music Fidelity pre and stereo power amp. After fiddling with the power taps to convert my DX-1's to 220v, I went about horizontally bi-amping my 200's. I hooked up my exisiting NAD 208THX for low frequency and the Dr. Thomas power amp for high frequency.

Before I connected up the DX-1, I was using my NAD 208 to bi-wire the 200's. My impression of the 200's without the DX-1 was that the soundstage was moderately wide, replication of instruments was very detailed and revealing in the top end, vocals were forward and almost like you could touch them and the bottom end provided enough bass extension that was definite but not tight and not so much a fuller sound as compared to my B&W 801's.

With the DX-1 connected, my experience was somewhat surreal yet amazed with a dash of intrigue thrown in. So, the story goes like this.......

I hooked up my DX-1, turned everything on and waited with bated breath. My reference was Patrcia Barber's Cafe Blue, track 10 "A taste of Honey" and Nora Jones' Come away with me, track 10 "Painter Song."

To say that the DX-1 made a difference is an understatement. To me, the DX-1 was stunning, so much that I didn't think such a change was possible. The articulation of instruments was so defining. The sound stage was much wider and the definition of vocals was yet more revealing.

What I did notice was that the placement of the singer or vocals was more set back, it's as if the sound stage was stretched wider and the vocals pulled back into or further away from the listener. The other point I noticed was that even though the high end was so crisp.....I began to think that it was too crisp....like almost unreal and that the top end was somewhat too bright/tinny.

Something just didn't sound right. Funny, something so stunning yet I was so intrigued. I came to the conclusion the the top end was so accurate yet lacking some body. I started to think where or what might the problem be.

Than I started to think back when I purchased the DX-1 and cards and it came to me. The cards I purchased were a set of S5500 and a set of S9500 cards. When I found out that bbn04 sent his DX-1 back to Greg Timbers for modification, I contacted Greg personally and struck up a deal where I gave him my 2 sets of cards in return for 2 sets of XPL-200 cards. The S5500 cards were then sent back to bbn04. Everyone was a happy camper.

So, for arguements sake, I rigged up my second DX-1 and whacked it into the system and noticed a change where the soundstage was as wide but the vocals were more forward/close to the listener and the brightness was not so extraordinarily bright.

So, I decided to pull both DX-1's apart again and take photos of the both sets of cards and have posted them here to see if there were any differences. Looked at the photos/cards myself, I noticed the resisitors on the LF Set 1 R208 was inverted as compared to R207. LP Set 2 R208 and R208 are the same. The HF cards were the same and therefore should not have made any differences to the way the top end sounded. My question is, which cards are the proper 200's and what's the deal with the inverted resistor on LP Set 1 R208? Anyone care to explain if inverting the resistors was a mistake or made up to match another speaker? Maybe a remnant or a modified card that didn't get completely converted back to an XPL-200 card.

I've labelled the first set of cards, which I found to be really bright and crisp as DX-1 HP/LP Set 1. The set I am now running is DX-1 HP/LP Set 2 in a different DX-1. When I have a bit more time, I will inspect the internals of both my DX-1's and see if there are any differences.

I would also like to get some comments/suggestions on changing the op-amps inside the DX-1. Greg has suggested replacing with OP275's. I've heard and read that the AD826 is a much better choice and sounding op than the 275?

Any help here would be much appreciated.

Cheers
Pasadena.

[pasadena]

Values for LP and HP Set 1 (not in use).

LP:
C207: Y394
C208: Y394
C211: U273
C212: U273

HP:
C103: Y683
C104: Y683
C105: Y683
C106: Y683

[Robh3606]

Hello Pasadena

Two things, the resistors are not polarized so it should make no difference. If things sound a bit bright try increasing the low end level just a tad, It could be a slight in-balance in levels. If you look at the voltage drive the bass level is up a bit.

Rob:)

[pasadena]

Another note I wish to add is a modification that has been done to both my DX-1's. They were already there when I bought them.

As you can see from the pic, the mod has been applied to the LF-R negative input. This section, if you refer to the DX-1 manual, states that you can use the LF-L neg and LF-R neg if using bridged amplifiers.

As I am not bridging my amps for the bottom end, this does not apply. However, this should not affect my current setup, is that correct?

Cheers
Pasadena.

[Robh3606]

Hello Pasadena

My DX-1 has a similar modification and if you look at the posted schematic it is on there as well.

Rob:)

[pasadena]

Hello Pasadena

Two things, the resistors are not polorized so it should make no difference. If things sound a bit bright try increasing the low end level just a tad, It could be a slight inbalance in levels. If you look at the voltage drive the bass level is up a bit.

Rob:)

G'Day Rob,

I noticed in your posts when you were making up your boards you quoted saying "There are a couple of issues that came up and both were mistakes in the DX-1 schematic. R104 and R106 are switched on the HF side and the right and left side LF blocks are also switched. The best way to verify the actual pin connections is to use photo's of the boards."

What did you find out in the end and does any of this apply here?

Cheers
Pasadena.

[grumpy]

Can you isolate whether it's the cards or the chassis? Perhaps you've done this already...

-grumpy

[pasadena]

Can you isolate whether it's the cards or the chassis? Perhaps you've done this already...

-grumpy

All I've done so far was to install the second set of cards into the second DX-1 and I have noticed a difference.

I have the sets of cards from the first DX-1 unplugged so when I get some time over the next few days, I'll plug these cards into second DX-1 I'm using and run some comparisons.

It could be that the chassis may be the problem, if so then it's something harder to isolate but I can go and run a multimeter over all the components to see if any of them have failed.

It could end up being a numbe of factors causing this anomaly, if you can call it one.

Cheers
Pasadena.

[Robh3606]

Hello Pasadena

The errors were just transpositions of the reference designations. The actual schematic was correct as far as part layout is concerned. The errors would not effect you at all, only if you tried to build from just the schematic with known resistor values. How did you set the gain for the lowpass section?? I had to use my RTA to balance the levels.

Rob:)

[Ian Mackenzie]

Mark,

I would be surprised if some level adjustments were not necessary.

Ian

[pasadena]

I can't help notice that sound levels seem to be higher from the right channel as opposed to the left. It's noticable enough to be of concern. I've noticed this with both DX-1's.

My next step will be to swap the cards out in my DX-1 currently in-use and see what the results are. If the outcome is still the same, then what changes internally on the DX-1 can be made to even things up?

I could increase the DB levels for the left channel on the receiver or what about the toggle switch on the back of the XPL-200's, which is to set the high frequency contour, currently set to flat but can be changed to -2db?

I've been reading some forums around the place and since I want to get into hi-fi consulting I might as well invest in some alayzing equipment, which would be useful in my case.

I'm thinking of getting the Behringer ECM8000 measurement microphone, TrueRTA Level 4 software analayzer and a Behringer UB 802 8 channel mixer. I've heard that the BFD's Parametric Equalizer, the Feedback Destroyer Pro DSP1124P is useful product to get as well. All the above are pretty cheap and a worthwhile investment.

If anyone has any other recommendations or opinions are most welcome.

Cheers
Pasadena.

[Robh3606]

I can't help notice that sound levels seem to be higher from the right channel as opposed to the left. It's noticable enough to be of concern. I've noticed this with both DX-1's.

Hello Mark

Something doesn't sound right?? You have a level balance issue between channels??? That's something I didn't have an issue with at all. The DX-1 was a drop in except for setting the level on the Low Pass section. You have this problem with both of them??? Are you sure it's the DX-1. How are you doing the biamping?? You using the same amp on the woofers and a different amp on the upper 3 drivers??? It just seems odd as the Low pass levels are slaved to the same knob and that's the only adjustment you have. You can't adjust the high pass gain at all.

Rob:)

[Ian Mackenzie]

Mark,

Should'nt you be doing some Work??

If you want to discuss it I am at home...on new mobil.

Ian

[Don C]

I think that you just need to get a function generator and an AC voltmeter and test the cards.

[Ian Mackenzie]

I agree.

The needs to be some analysis and measurement done.

If Mark would like to mail one over I could check it out.

I must says its odd.

Ian

[Robh3606]

Hello Ian

Somethings odd. I built my cards based on Marks information and the measured voltage drives using CLIO were dead on from the posted curves he got from GT. Damn this is frustrating. It sucks being 12,000 miles away.

Rob:)

[Ian Mackenzie]

Mark.

I would look at your wiring to the loudspeakers and check phase continuity of both amps outputs and the connections at the loudspeakers.

If for example you have one woofer out of phase and but the mid/hi end in phase, it will sound strange in one channel. much like you are describing.

I crossover boards look okay but without actual testing we can't be sure.

Ian

[pasadena]

After having a chat with Ian, my plan of attack will be as follows:

1. The most obvious and easiest will be to check that all wiring has been installed correctly.
2. Doubly check that the power taps are set correctly to 220v.....Maybe I'll wear my glasses.....just kidding :blink:
3. Swap out the LF/HF cards with my spare set. This will give me an indication straight away if one of the cards are problematic.
a. Swap out the LF card, leave HF card as is.
b. Re-insert original LF card and swap out HF card.
c. Swap out both cards.
4. Move the Dr. Thomas power amp from HF to LF and the NAD 208THX to HF. Note: The Dr. Thomas power amp is a loan from my wife's uncle so it's an newly deviced introduced into the system....could be a possible problem.
5. Disconnect the DX-1 entirely and drive the 200's using only the NAD or the Dr. Thomas at any one time. The Dr. Thomas is not able to drive the 200's bi-wired, whereas the NAD can.
6. Check the parts on the DX-1 cards and on the DX-1 itself are working correctly.
7. Compare the internals of both DX-1's to see if there are any visual differences.
8. Check the voltage drives.

I'm sure I'll think of other tests, once I've started.

It's like almost 4pm and I still haven't head off to work yet.....I've been trying so hard to take off for work all day but all these things keep popping that side tracks me. Terrible. :p I'll be heading in for a couple of hours and then if I have time when I get back tonight I'll start some of the test. :bouncy:

Cheers
Pasadena.

[Robh3606]

How's it going???

Rob:bouncy:

[pasadena]

How's it going???

Rob:bouncy:

G'Day Rob,

Haven't done a thing as I haven't had the chance to yet...AARRGGH!!:banghead:

BUT...I will be starting on it tonight. I told my wife that there's no TV and that I'll be working on the hi-fi, so hopefully I'll have some answers tomorrow!! :)

Cheers
Pasadena!

[pasadena]

Hi Guys,

Sorry for disappearing for a while but I've been tied up with a court claim that's currently in progress for my accident I had a couple of years ago.

Just received notice today that the other side have delayed appearance so I don't know when we're going in next. Oh what fun......can't wait for this damn thing to blow over.

Anyway, back to the fun stuff.

I managed to record some voltage levels on the outputs of the DX-1 and the attached image shows the results. I used TrueRTA Level 4 and adjusted the oscillator output volatge to 1 volt and recorded values between 25hz up to 10khz.

The only issue tha I can see is that the left channel on the low pass is down by .001 volt from 75hz and up.

I checked all the cabling and everything seemed ok. What I'll do next is insert the other low pass card I have into the current DX-1 and record the voltages again. I'll then swap out the high pass with the spare card and record those values and see what I come up with.

After this, I'll set the XPL's to run on only the NAD 208THX power amp and then using the Dr. Thomas power amp and see if I can hear any differences.

Can you do voltage drive tests on the outputs of the power amps and the receiver as I did with the DX-1?

Will keep ya'll posted!

Cheers
Pasadena.

[pasadena]

The DX-1 has been removed from my setup and shipped to Ian Mackenzie along with the second DX-1 for testing and upgrade.

As per my previous testing, with just the NAD connected to the XPL's the difference in detail is notably less but the bright/harshness is not so evident as when the Dr. Thomas amp hooked up only to the mids/high's.

Whether or not it's the combination of the DX-1 and the Dr Thomas amp that made it so bright I don't know but tonight I'll put the Dr Thomas in place of the NAD. I'm thinking the Dr Thomas was causing the harshness (would be nice if it was so simple) but will find out tonight.

As per Greg T's options to upgrade the DX-1's, I have asked Ian to remove the current LM833's and reaplced with socket IC's for op-amp rolling to try a combination of op-amps to see what gives the best results. Secondly, would be to replace the input and output capacitors from electrolytics to Polypropylene capacitors. Greg said that the Polypropylene caps would be too larg to fit inside the DX-1 case but will get around this by cutting the top plate out, about 10-15mm from the edge and raise it to look like a hood. I'm also thinking about drilling smallish type holes throughout the top plate for better heat dissipation.

Should make for an interesting upgrade. :bouncy:

Cheers
Pasadena

[Ian Mackenzie]

Oh No,

Not another crossover project...muhhhahahaahahahaha

Ian

[pasadena]

Oh No,

Not another crossover project...muhhhahahaahahahaha

Ian

Hahaha, I can picture you as the mad scientist. ;)

[pasadena]

Greg. T replaced all his LM833 op-amps with OP275's (his favourite).

I've read that the LM833's are the cheap variety and old technology. The OP275 though a much better replacememnt for the LM833's, still seems to be lacking in some departments.

Of the op-amps I have researched, so far the AD826 seems to be the one I'm leaning towards.

I'd like everyone elses opinions on op-amps, which one's you've heard and prefer.
come on up... you're opinions All welcome.....:D

Cheers
Pasadena.

[Ian Mackenzie]

DX-1 XPL-200 Frequency Card Discrepancies

Mark and I discussed the DX1's he sent over to me earlier in the week today on the phone.

The plan is to verify the crossover card parts values, verify the voltage drives and consider upgrading the units where it is felt appropriate and desirable.

I have checked the cards this afternoon against the values advised on a memo from G.T 9-24-90. Everything appears correct.

Mark, FYI the J1XXX parts on the boards that look like diodes or resisters are shorting links. These boards are un-biased.

My measurements indicate there are no discrepancies.

All appears to be in order. Both channel track quite accurately. It should
be noted the crossover is asymmetrical. The crossover point is 270 hz according to my measurements. (I have limited knowledge of the XP 200).

The unit(s) appear to be made and designed to a high standard.

Ian

[Earl K]

Hi Ian ( Mark )

FWIW ; Marks' impressions of all the differences he heard between the two cards remind me of at least two or three things. I'll talk about capacitors and not opamps ( which I've never studied ) .

(1) Burning in of capacitors ; In the last year I've paid much more attention to this phenomena. MPP ( or KP ) caps that haven't yet been burnedin will move the soundstage forward ( I figure mostly due to the resonances that the ear easily fixates on )

(2) Dielectrics ;
- Polypropylene as a dielectric (as a for instance ) always seems to offer up its resonances from the presence range to lower sibilance range . Resonances in the lower region of this FR area will make things seem a bit louder ( Hovland comes to mind , from past descriptors) . Slightly above the "loudness effect" voices and cymbals will seem unnaturally strident or thin. Above that unnatural sibilant sounds will dominate the sound.
- Polystyrenes resonances seem to be located a full octave above those of polypropylenes. Their resonances offer a real high end haze ( or air ) .
They do work nicely together ( in my setups ) as a result of these complimentary characteristics.

(3)Mix Ratios of Dielectrics ;
- IME, Mixing these two dielectrics together in different ratios ( while still not burned in ) will have a bunch of predictable results to the soundstage ( in speaker level crossovers / which is beside the point of this discussion ). "Predictable" only to those who have studied the phenomena . GTs' ratios ( in speaker level crossovers ) do in fact make a lot of sense to my ears / for those people after a certain sort of HF & UHF voicing . I actually prefer a larger 1 to one 1, but I could see that it's not for everyone .

(4)Charge Coupling ™ ;
- DC Biasing removes ( at least to my ears ) just about all of these resonances / which is why I'm such a fan of the topology. It offers such a nice stable foundation for the control and thus creation of these sounds .
- DC Biasing only marginally effects that other contributor to the sound of cap makes & models. That's the difference in "spectral dynamics" that I hear with all caps. They all seem to have unigue signatures derived from how "quickly" they'll pass certain frequency areas. Different makes will have different signatures. Passing one FR area quicker than another will alter the spectral balance of what one hears by altering the emphasis of one set of harmonics to the others.

(An) Ad Hoc Conclusion ;

- I'd certainly do a proper burnin of Marks' (suspect ) set of cards before moving on to any of my other points of reference . Some of the worst resonances can disappear after the caps are burned in and that will alter the soundstage .

:)

PS ;
- FWIW; my Passive Line Level HiPass uses only large value DC-Biased Polystyrenes . I haven't mixed dielectrics at this low a signal level. I haven't studied or looked for any sonic effects that may be a consequence of this sort of dielectric mixing ( maybe I should ) .;)

[Ian Mackenzie]

Hi Earl,

I will audition then try the off station FM treatment.

Thanks for your thoughts.

Ian

[Ian Mackenzie]

Given Earl's pearls of wisdom I have elected to burn in DX1's with FM white noise for a few days while I prepare some cables.

Later in the week I will hook them up.

Ian

[Ian Mackenzie]

Sunday EST

After organising interconnects and setting up for biamp mode I got it
working.

Both DX-1's work and sound identical.

The short report is this unit does not need modifying.

Mark, your only getting one back!!

My view is it performs to a very high standard and as they say if it ain't
broke don't fix it.

I would still like to consider the charge-coupling of the crossover boards
and do the opamp updates but I think to interfere with it in other areas
would be unwise.


Ian

Attached image of the DX'1( note the glowing red Leds) and the humble HiFi.

[Ian Mackenzie]

I played a very familiar recording and could not detect what I felt to be any brightness.

It is important to note that bi amping at this frequency has the effect of removing the bloom, grit and other rubbish from the mid cone driver that can otherwise mask the upper frequencies unless great care has been taken with the full passive crossover network.

For this reason an inexperienced user may interpret the subjective result as bright. The apparent bright presentation in Mark's system could be due to a number of environmental factors.

Careful adjustment of the level controls can be used to fine tune the overall balance.

Ian

[Ian Mackenzie]

A modification with potential for improvement of the DX1 is to completely bypass C25, 26, 27, 28, 21, 22, 23 and 24.

These are input/output coupling capacitors (highpass output buffer only) and serve to stop dc entering or leaving the DX1. I was unable to measure any offset that might be consider an issue.

The result is improved transient performance and transparency.

The DX1 is really hitting its stride now.

I have not charge - coupled the crossover boards at this point. Will do do soon.

Ian

[pasadena]

Ian,

With both DX-1's shipped over to Ian, I pulled aprt the NAD 208THX (finally) to check out a suspect connection on my left channel. I am currently using the NAD to bi-wre the XPL's.

Indeed it was as the solder had come apart from the pin due to what looks like plugging and unplugging of the RCA socket over time, which cracked the solder a from the pin. The pin was sliding up and down through the solder.

So, I reheated/resoldered all the joints for all pins for each RCA plug so now they’re workin’ like a gem.

I've noticed an immediate difference as getting more detail through the bottom/top end than I was before and now the over sound is more even to both sides. This may have contributed to why the left channel wasn’t as audible/detailed as the right channel.

I still haven’t plugged the Dr. Thomas power amp on its own to the XPL’s….I know, lazy me but I will get there.

I don’t think that the XPL’s firing with just the NAD is harsh or bright at all but I will keep testing. J

Cheers
Pasadena

[pasadena]

Hi Guys,

Reviving an old thread.

I have a couple of questions I wanted to ask about both DX-1's I have. Long story short, I've moved into our new nouse not long ago and finally I have a dedicated room for my home theatre. I've pulled my XPL-200A's and DX-1's out of storage and started putting everything together.

When I packed everything away into storage, I didn't take not as to which DX-1 was sent to me by Greg Timbers. I have attached a set of pictures of one DX-1 and will post again with pics of the second DX-1. Let me know what you guys think. One set of the DX-1 cards have been modified and I wanted your take on it.

Before hooking my DX-1, I've been using a Marantz AV8801 Pre-Processor running a pair of Electrocompaniet AW400 monoblocks. Am extremely pleased with the sound and still love to this day how good my XPL's are ;)

However, always a but somewhere. After hooking my DX-1, I connected the AW400's to the high pass section through the DX-1 and my DIY Passlabs XA100 Monoblocks feeding the low pass section. Both the AW400 and XA100's have XLR connectors only. A bit of a pain as my AV8801 have both balanced and unbalanced but seeing the DX-1 is unbalanced, I decided to run RCA out of the marantz into the DX-1 and then using XLR-RCA cables to the monoblocks.

Last time I had the DX-1 running, I was truly amazed at what it could do. This time was different. After getting everything connected and working and putting on Nora Jones, the High Frequency was absolutely amazing but the bass was completely lacking. The DX-1 is meant to provide a bitter bass extension as well as tighter bass, as logged in my previous posts about the DX-1 but that was all missing. I swapped out my DX-1 to my spare only to find the same issue. I even changed out my XA100's for a NAD208THX and it didn't fair much better.

I remember last time have the DX-1 working away with my Meridian 568.2MM processor was spectacular. I'm happy with the high pass section, in fact it's even way better than before but the bass is missing.

I'm going to have to go through everything again and see if I've missed anything. I though it might have been the XLR-RCA cables not being grounded correctly but tried a different with similar results.

I must be missing something somewhere. Will post back when I've tinkered a bit more.

60811

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[pasadena]

More Pics from the first DX-1

60816

60817

60818

[pasadena]

Pics of the second DX-1. This seems to be stock. The only difference is the rubicon caps next to the transformer.

60819

60820

60821

60822

[Robh3606]

Hello Pasadena

Not sure what you are looking for but one set is obviously set up with CC capacitors. If you have the cards out can you put up a good sharp picture of the LF stock card so you can really see the backside foil pattern?

Rob:)

[Don C]

My XPL200s just failed with foam rot a few months ago. Check them out. Also I had a midrange fail on me recently. Listen to each driver with your ear close and make sure they all still work. Seems ovvious, but it still took me a few days to discover all of the problems.

[pasadena]

It seems to be bass deficient on both sides. The speakers play perfectly fine without the DX-1, it's only when the DX-1 is introduced that the lack of bass is apparent. There is a dial at the front of the DX-1 to increase bass output but I have to set it at around 90%, which to me is not right but the bass is fine at this dial point. When I had my DX-1 running a few years back, I remember never having the dial cranked up so high.

There is more bass saturation through the driver range without the DX-1. I know that introducing the DX-1 the bass was more tight. I'll have to keep figuring it out. I do paired spares for all the drivers except for the 2214's. Too costly to ship.

[Robh3606]

Did you remember to flip the biamp switch to the correct position??

Rob:)

[pasadena]

Did you remember to flip the biamp switch to the correct position??

Rob:)

Yes I checked all that. I'm always mindful when bi-amping that I don't do anything stupid or blow anything up, I'm good at doing that . ;) I did have the switch on one speaker flicked to -2db and sat there ages for thinking why one speaker sounded different. Something simple as checking cords or switches can be easily overlooked.

I know Ti Dome has a DX-1 and would be interested to see what position the front dial on the DX-1 is set to? If its set do high like mine them its probably the characteristic of the DX-1, if not, <scratches head>.

I'll have to dig up my posts from GT about installing an op-amp on the low pass card for bass boost, anyone remember what and how to do that?