To: archosjukebox6000@yahoogroups.com From: "mons00n1" Date: Mon, 24 Jun 2002 20:08:40 -0000 Subject: [archosjukebox6000] Re: I modified my JB6000 for more volume and bass I just wanted to add a little more information to your mod. a. The existing capacitors in the JB6K are 10uF (prob. 1210 10V) So around 200Hz minimum output. Dependent on your phones. b. If you use 8ohm resistors (which are just barely safe) make sure they are 1/2 watt. c. Personally I like a 1206 10 ohm, fits *almost* perfect and at DC output levels from the DAC it would still just barely be safe. Also I found that after you have the HD out, it is much easier to break/cut the tabs holding the SH1 processor board in place. This means that you no longer need to desolder/solder the battery PCBs. But I am slightly uncomfortable with this route due to the fact that the processor board then might not get pressed 100% into the MAS's board. But as long as you're careful it's ok. Thanx for the great mod! Nice web page. I really enjoy the additional power and frequency response. Anyone who sez it is loud enough should know that it's not about adding volume, but more about the available power. You don't want to unnecessarily starve your system. Same for the frequency. Finally, just to save people time: you will not fit a decent sized (value wise) capacitor between the MAS and processor boards. Locate the capacitors near the USB connector, just make sure to insulate them somehow (heatshrink here). My Caps were 150uF surface mount and still didn't fit! Height of approx. 200mils/5mm. Remember Kids to ROCK THAT BOX! (plug for Rockbox!) ========================================= Thank you for your comments on my Archos modification. Congratulations on successfully completing the modification yourself. I guess I did have 1/4-watt resistors added to it instead of 1/8-watt ones I stated. I've changed my webpage accordingly. These should be good for a 12.5 ohm total load (which is a shorted output in my case) getting a continuous undistorted sine wave at full power, which is not exactly the characteristics of the music I listen to. 1/4th of that would be the typical power dissipation for the density of most music. I did plug the JB into a set of 8 ohm speakers, just to see how it sounded, it drove them to a "background music level" and had reasonable bass response. Yours should perform slightly better. I did post your email on my website so that others would benefit from your tips on this modification. If you have a problem with that, please let me know. I've received some replies about where the best source for the capacitors is. Your thoughts would be appreciated. James Stewart ============================== An update: I've since purchased a pair of Koss KTX/Pros on suggestion from someone at: http://groups.yahoo.com/group/archosjukebox6000/. They were on sale at www.buy.com for $12.95 + free shipping. I've been told Radio Shack sells the equivalent model under their brand name. In any case these things were probably the best $12.95 I ever spent! They were very loud, and had bass response that finally gave Enya's music justice. Upon examining the specifications for these headphones, the sensitivity is rated at 103db/1mw and the impedance is 60 ohms. At this impedance, these headphones should still sound very good with an unmodified jukebox. This makes these (or others with similar specifications) a more practical solution to the weak output of the Archos Jukebox. =============================== Date: Fri, 20 Sep 2002 09:42:23 +0200 From: "Johan Nilsson" To: wartstew@yahoo.com Subject: archos modification Hello! I have always felt that my Archos 6000 (1 1/2 years old) sounded very thin and without any proper bass response. It has been a disappointment. After searching the Internet I found your page about modifying the Archos and yesterday I decided to give it a try. I must say that I'm very impressed and I wish to thank you a lot for publishing this modification. It gave my Archos a new life and it now sounds almost 100% perfect!! I used the same components as you did but I used another type of capacitor. These capacitors were a little bit bigger and I couldn't fit them inside the Archos. I then came up with the idea to remove the line-in connector because I don't use (and probably never will). That gave me plenty of room to store the capacitors and now I'm thinking of changing the 100uf for 150uf or better. They should most likely fit. It should be quite easy to solder back the line-in connector again if I want to use it (but then I have to get rid of the capacitors). Thanks again for a superb page! Regards, Johan Nilsson ================================= To: archosjukebox6000@yahoogroups.com From: "Goldshteyn, Michael" Date: Thu, 31 Oct 2002 15:59:25 -0600 Subject: [archosjukebox6000] Archos Recorder hardware mods for better sound This is a followup to the mods at: I have some ideas that improve upon your hardware mod for the Archos. Although I haven't done this yet, I am planning on starting this project soon: - Buy a Burr Brown PGA2311 stereo volume control ( http://www-s.ti.com/sc/ds/pga2311.pdf ), this offers 0.5 dB steps of volume from +31.5dB to -95.5dB, with 0.05dB step accuracy, 120dB dynamic range, <-130dBfs interchannel crosstalk. All of this, for under $10, and the thing can directly drive headphones up to 600 ohms. Now you're asking, why do I need a volume control, if my Archos already has one. The simple answer is because it is garbage, has way too few steps and because the Burr Brown can add gain to the signal and drive ANY set of headphones, upto 600 ohms. Just set your Archos to max volume and use this circuit to do volume control/add gain. - Connect the outputs of the MP3 chip directly to the Burr Brown, removing the resistor and capacitor in the way. Issues: Problem 1: How to control the volume. The Burr Brown has a serial data in for setting the volume. This presents an immediate problem, since you can't use a simple N position dip switch. However, I have a cheap solution. Use a parallel to serial shift register, such as the 74HC165 CMOS IC. You will also need an LM555 timer, an 8 or more position switch (256 binary steps), a switch with a debounce circuit to send your volume setting to the Burr Brown after you have set it with the 8 position switch. All of this should be had for a few dollars. Problem 2: The Burr Brown needs a +5 v/Gnd digital power supply and a +5 v/Gnd/-5 v analog power supply. This is the more difficult problem. If you resort to using 1.2v rechargeable cells, you will need at least fifteen of them. Five each for the digital, +5v/Gnd analog and -5v/Gnd analog. This is insane, both in terms of cost and weight. The alternative is to use three rechargeable nine volt batteries to drive this. I think this is the minimum weight/price option. Problem 3: All of the added weight. Well it would be best to put the circuit board, which you will have to build (I recommend wire wrap), into some sort of aluminum case, with easy access to the volume control switch and the debounced "confirm" switch. This will also have to hold the three nine volt batteries. I am not sure what that would add up to in weight and volume, so it's left at your discretion. Problem 4: Mods to the archos. The only mods are really to short the output resistor and capacitor on each channel. This introduces a potential short situation, which can ruin the MP3 chip, if you slide a connector in the headphone jack while the unit is on, so you may want to leave the resistors in place, since the input impedance of the Burr Brown is 10k ohms with a 3pF capacitance. You can also reduce the resistors to some other value that is much smaller like maybe 15 or 18 ohms. I would also recommend replacing them with metal film 1% tolerance resistors if your soldering skills are up to it, since this would considerably cut down on the noise, although the original surface mount resistors are probably pretty good at for noise rejection, if not necessarily tolerance. Of course changing the resistors is optional, and the simplest course is to just leave them be, and short the capacitors. This way, you can connect the headphone output directly into the Burr Brown with minimum signal degradation, and get one hell of a volume control/pre-amplifier circuit, which would be able to not only provide for accurate analog stereo volume control, but also upto a 31.5 dB boost to the signal, all while retaining excellent sonic parameters (i.e. interchannel crosstalk, SNR and dynamic range). Problem 4b: After doing more research, it seems that if you have the soldering skills, it may be better to bypass as much of the output circuit on the DAC chip as possible. It may be possible to connect the outputs of the de-emphasis circuit (is this used for modern MP3s?) directly to the Burr Brown. This way the volume control on the DAC chip, with its max 18dB of gain gets totally bypassed. This would most certainly lead to a sonic improvement by reducing the number of active gain stages in the output circuit. I am concerned, though, about which output pins on the DAC can actually drive the Burr Brown inputs. Note that the crappy output of the DAC is rated at a measly 12mW at 1% THD (with 5 v power), assuming a headphone load. The gain error is as much as 2 dB if you reduce the volume significantly vs. 0.05dB on the Burr Brown. Five dB of SNR is lost at the headphone input, you can go from 90dB SNR, the standard archos rating, to 98dB, by simply bypassing the headphone amplification circuit. Also, notice how the SNR on the DAC at the headphone outputs drops to a measely 62dB typical with a -40.5dB signal. This garbage deserves to be bypassed ;) . Unfortunatelly, there is not much that can be done about the crosstalk, because it is the same 80dB at both FINL/FINR and the headphone output. Conclusion: I will do more research on the DAC to try to figure out how to best get the outputs out of it into the Burr Brown, while bypassing as much post de-emphasis circuitry as possible. Let me know what you think and feel free to post this e-mail on your site at http://mywebpages.comcast.net/jstewart228368/comments.txt . ==================================== Another update (Dec/2002): (after neglecting this site for awhile) Sorry about losing a lot of other peoples' good comments. Some things that were missed was that many people are putting in much larger value capacitors. Doing so should give the bass response that last 10% or so, especially with lower impedance headphones. One trick for squeezing these in was to use more compact and better shaped surface mount capacitors. Another trick was to remove the mostly useless "Line In" jack completely thus freeing up all kinds of space to put things. Another thing to add is that I'm told that the later products, starting with the recorder models, do not have this design problem in the output stage. Therefore there is nothing to gain from this modification. If this is true, this feature alone would probably make the recorder worth the extra money. If anyone would like to verify this, I'm sure we would all like to know. I'm also told that even if you use 60 ohm or higher impedance headphones, much better sound can be gained from this modification. I bought my 60 ohm headphones after I did this modification, so I personally did not observe this. James Stewart ==================================== Date: Thu, 19 Dec 2002 --- Oliver Daudey wrote: > ok, a lot of ignorant questions comin' down the hatch. > I am still considered a noob. I have soldered only > stuff included in kits, etc.. > Heres my few questions. > 1.) I've seen a few different types of resistors/capacitors. > If i were to head on down to radio shack, what exactly should I ask for? A) The capacitor must be rated for at least 5 volts. B) The capacitor must fit physically inside the Archos (this is the hard one) C) The capacitor needs to be of the highest value you can squeeze inside the thing. There is a 10mf in there now. Ideally it should be about 500mf, but you won't find one small enough. I used 100mf and it works great with my headphones, but you might hear a difference with some of those 16-ohm earbuds if you can go larger. Several people solder two 100mf in parallel to make 200mf. This seems like a good solution. The best capacitors to satisfy the above requirements are surface-mount (SMD) tantalum capacitors. Radio Shack won't have them. You can order some from places like www.digitkey.com. I only used the epoxy dipped tantalums in mine because I happened to have a couple laying around. Their round shape are less efficient to squeeze inside the JB than the SMD types. For pictures of the SMD solution look at http://www.mctubster.com/sound.html or some in the pictures section of Yahoo group: archosjukebox6000. As far as the resistors, the best thing is to use SMD type resistors as well and solder them right on top of the existing 47 ohm resistors. Again I used 1/8th watt standard axial lead ones only because I had them laying around. I recommend a value of 10 ohms, which in parallel with the 47 ohm resistors, works out to be about 8.2 ohms. Remember 8 ohms is the minimum the amplifier can deal with and this resistor will guarantee that you won't blow it out even you completely short out all the wires connected to earphone jack (as might happen in a headphone cable failure). I used 15 ohm ones because I had them but again, you might hear a slight difference if you try to use a 16 ohm earbud. Since I currently use 60 ohm Koss KTX/Pros, I would never hear a difference between the ideal components and the ones I used. > 2.) how much more unsafe is it once its done? If your craftsmanship is good, it is very safe. Obviously the amplifier will need to work harder to put out the extra power you'll get, but it is rated for it. Mine has been working great in its modified form for almost a year. If your craftsmanship is not so good, you can mostly destroy your JB. I think so far two people have written me to report that their unit did not work after they performed this modification. I think one of them got it working, but the other one did not. > 3.) does it reduce the lifespan of it. The modification, done well, will not reduce life span. However, I feel that every time you disassemble the unit, you probably reduce the life span a little from the wear and tear you put on the physical parts you have to pull apart. 3a.) Also, what does it do to battery life? At the same volume output (which you'll get at a less volume level and bass setting), you'll get slightly improved battery life because you are no longer burning up half your audio in those 47-ohm resistors. If you take advantage of the extra bass and rattle your brain with it, you'll get slightly decreased battery life because the amplifier was not previously allowed to produce this much bass. This is only in theory, I have not measured any of this. In fact most of the power is consumed running the processors and hard drive. A few extra percent change in the amplifier power consumption will likely go unnoticed. > 4.) I own an Archos Jukebox studio 10. Is there any > difference between this and the 6k? Not that I know of (other than the larger hard drive). Your unit will benefit from the modification, the circuit boards and components should look the same. > I know it sounds ignorant. No it doesn't. They are good questions! > I think that you should > put an FAQ up with certain questions like this. Okay, I'll put this email on the end of my "comments" page whose like is at the bottom of the my page. > I'm fine with soldering, but I've never had to buy > solo pieces, i've only worked with kits. > > Thanks, > DeadCast