http://www.diyaudio.com/forums/blogs/kevinkr/ A community dedicated to helping everyone learn the art of audio. Projects by fanatics, for fanatics! en Mon, 13 Feb 2012 00:26:56 GMT vBulletin 60 http://cdn1.dastatic.com/forums/images/diy/misc/rss.jpg http://www.diyaudio.com/forums/blogs/kevinkr/ http://www.diyaudio.com/forums/blogs/kevinkr/500-playing-vinyl-td-124.html Thu, 06 Jan 2011 21:50:42 GMT I acquired a TD-124MKII back in late September and after some months feel like I have come to some understanding of its strengths and weaknesses. ... I acquired a TD-124MKII back in late September and after some months feel like I have come to some understanding of its strengths and weaknesses.

I finally understand that the drive train will never be silent, and needs some periodic maintenance to perform quietly.

Belts are problematic on the MKII, and later versions of the MKI with the dual in chassis intermediate pulley. For some reason very early units seem quieter in this respect.

Motor rebuilding is pretty worthwhile, mine of course was not running so it was mandatory. My experience with motor bearings is limited, but based on replacing a number of bearing sets I would recommend the bearings available from The Analog Depot over others I've tried. They are very precisely made and run well from the get go.

I've added a Bren1 record weight which I feel clamps the record more effectively to the table's moving mass, and I thought improved some areas of performance significantly. Bass in particular.

I've also added a recent audiogon acquisition - a Merrill-Scillia mat which is a composite of lead, cork and rubber. This reduces coupling of mechanical noise (not much) from the table, as well as damping the vinyl effectively. It significantly improved overall resolution whilst removing the "air" I had come to like along with several objectionable and obvious colorations I didn't. I've managed through careful tweaking to get some of that sound back when it is actually present on the vinyl itself and not an artifact.

Recently I discovered that removing the bedplate grommets on my SME 3009 Series II was also beneficial in taming a bit of mid bass bloat, tightening things up on the bottom end considerably. Also seems to have improved resolution, soundstage and imaging. In general sounding a bit less confused than before.

The DL-103 is not the last word in trackability but through careful adjustment of tracking error, VTA, tracking force, and a significant reduction in anti-skating force I seem to have improved that issue as well.

I recently had the opportunity to listen to an SME 3012 Series II arm as part of the restoration process I am doing for a friend. I liked what I heard, clearly some improvements in tracking as well as the bass. Everything just seemed to sound a bit more cohesive. I was a bit surprised.. So I thought I would buy my own SME 3012, but studying eBay and Audiogon prices convinced me to look at acquiring a Schick instead - a modern and far better arm than the 3012 according to many. I have had the opportunity to use and listen to several, but had not considered it affordable.. A 12" Schick will be ordered soon.

Finally a slate plinth should complete the package. Not sure when this will happen.

The effort has been worth it so far, the sound is very good and often better than the comparable CD ignoring the obvious advantage CD has in inherent noise levels (no clicks and pops) and convenience. ]]> kevinkr http://www.diyaudio.com/forums/blogs/kevinkr/500-playing-vinyl-td-124.html http://www.diyaudio.com/forums/blogs/kevinkr/254-projects-projects-projects.html Fri, 16 Apr 2010 17:07:17 GMT Like most of us here I seem to have more projects than I can handle. Just added another one - I'm going to do a simple little 6BQ5/6V6/7C5 based SE amplifier for nostalgia. (My first tube amp as a teenager was a 6BQ5 SE)

I've just added to the stack by ordering a pair of 6V6/6BQ5 SE OPTs from Tony over at Twin Audio. The price with shipping was pretty hard to beat, and I figure that the effort they put into building their amplifiers probably is also reflected in the quality of the parts they use. This amplifier will be pretty simple, most likely using pentode mode with some cathode feedback, a single stage high mu triode driver, and some limited global feedback to get the output impedance down. Hopefully I can make enough power to drive the HCC with it. I could conceivably incorporate the baffle step correction into the input of this amplifier if it is dedicated to driving the HCCs. As a firm believer in the benefits of fixed bias the output stage will incorporate that.

I'm working on a small but lucrative commission assembling/tweaking/testing an LCR based phono stage designed by Thorsten Loesch. Should be interesting - I've not heard one before and a comparison between that and my D3A/5842 gyrator loaded and passively EQ'd design could be a revelation. I may have to do a design of my own at some point. We'll see.

I made the decision some weeks ago to go with IT coupling on the GM70 amps and the Lundahl LL1635 ITs just shipped from K&K Audio. Should have them soon, and will be able to decide based on measurements whether to go with the ITs or chokes or something else altogether..

The HCC are sounding a bit better, but I still can't get over how directional they are, and how little bass they produce. The reference are my diy Onkens which are just better. The HCC though should do nicely in competition with other similar full range designs. They would be fine in a secondary music system which of course I don't have..

The TT project is set to start moving ahead again, although I have to admit I should have my head examined - for what I have spent I could have had a ready to play Project or a good used VPI or similar in the > $1000 range. I really hope this thing is half way decent. (Premotec motor in pod, 2" clear acrylic plinth, Thorens TD125 platter and main bearing, Rega RB301 arm..)

Undoubtedly I will cook up some other project for which I have no time in the near future.. :D

FIFO system is not working, but currently I operate closer to LIFO afterall the HCC were the last project added to the list and the first to get completed. The TT will probably get some attention some, Freud metal cutting blade has been ordered and I can finally start machining the last bits and pieces soon.. (I'm a bit of a hack unfortunately - won't be nearly as nice as some I have seen in the forum.)

Wore my 10yr burn in T shirt to the rink the other night, only two people asked about it, and of those only 1 actually knew what it was.. I wore it with pride.. :D ]]> kevinkr http://www.diyaudio.com/forums/blogs/kevinkr/254-projects-projects-projects.html http://www.diyaudio.com/forums/blogs/kevinkr/205-project-dilemas.html Fri, 19 Feb 2010 17:41:21 GMT Isn't it odd how sometimes the things you intend to do first end up being the last things you actually get done? Or am I the only one with this problem?? :D

I always have a few projects on the back burner, and few that are supposed to high priority and sometimes one or two that just appear because of an unforseen opportunity or a seemingly good idea.

In order of supposed priority I have been working on a new GM70 based SE amp design, an acrylic plinth TT, a pair of Half Chili Changs, and quite unexpectedly an FFT based audio measurement set up.

The turntable and the GM70 are more or less stalled. I need to purchase a mini-lathe, and a good metal cutting blade.

On the GM70 despite designing a choke coupled driver stage that really performs well I am still waffling over whether I want to use IT coupling instead. And the kicker is I need the above tools to fabricate the chassis for these amplifiers which ultimately will be 4 chassis for a stereo pair..

The TT is a boondoggle - not quite completed I now realize I could have bought a mid level high end TT for what this thing is costing me - I hope it turns out to be worth it.

Oddly enough the two lowest priority items on my current project list are basically finished with the exception of a few niceties..

The FFT measurement set up happened abruptly because Pete Millet came out with a soundcard interface board that I could not resist. (My old diy set up long in the tooth was no longer functioning reliably.)

The HCC have gotten the lionshare of attention and will shortly get a set of Planet10's phase plugs as icing on the cake. It is very interesting how important having BSC turned out to be - acoustical measurements reveal this very clearly. They sounded dreadful without BSC, and tolerable with it, as the drivers break in they have noticeably improved. They aren't Onken killers nor were they intended to be, however they will be well suited for use when we have audio club meetings and small parties. ]]> kevinkr http://www.diyaudio.com/forums/blogs/kevinkr/205-project-dilemas.html http://www.diyaudio.com/forums/blogs/kevinkr/155-more-ipods-n-things.html Thu, 03 Dec 2009 01:22:58 GMT Well those PX100 headphones came a couple of weeks ago, have to say acoustic sounds was quick on the shipping.. To say they are an upgrade over... Well those PX100 headphones came a couple of weeks ago, have to say acoustic sounds was quick on the shipping..

To say they are an upgrade over my old JVC folding phones would be just a bit of an understatement. They're just clearly better in every not so subtle way. Much more extension at both extremes, and much improved clarity - a surprising amount of resolution IMHO for $69..
They're not circum-aural, and have open backs, but surprisingly ambient noise does not seem to be much of an issue. And they're reasonably comfortable.

On a slightly different note I have a fairly large number of songs on my iPod that I downloaded from iTunes. Recently I swapped a not so well liked Pixies album for BT Emotional Technology on Swaptree. I have listened to it a few times and realized that the songs I actually like best are none of the ones I purchased on iTunes! I ripped it to the iPod last night using Apple Lossless and removed the original AAC encoded copies. The difference in sound quality even on this electronica was evident. More disturbing to me is the fact that I missed a whole slew of good songs because I bought piecemeal on iTunes based on their samples. I think there is an argument for buying music by the album rather than by the song based on this experience.

Also although I prefer higher resolution media like the SACD or 24/96 pcm I am once again swapping or purchasing CDs in preference to iTunes downloads for the above reason and sound quality. The risk of missing some good music is just too high.

The economics are pretty attractive if you swap or purchased new or used on Amazon - a lot of very good deals, and in many instances not significantly more than the iTunes album cost with a much higher quality medium. ]]> kevinkr http://www.diyaudio.com/forums/blogs/kevinkr/155-more-ipods-n-things.html http://www.diyaudio.com/forums/blogs/kevinkr/124-ipods-n-things.html Sun, 15 Nov 2009 00:23:28 GMT Went to the gym this afternoon with my iPod (Classic 160GB) as usual - about 15 minutes into a torturous session on the elliptical the left channel... Went to the gym this afternoon with my iPod (Classic 160GB) as usual - about 15 minutes into a torturous session on the elliptical the left channel just died. PANIC.. I had a further 45 minutes of time to reflect on the meaning of music in my life - in this case it really helps me to get through what I find to be an exceedingly tedious activity. Sonic wall paper to my life outside of my house??

Got home and quickly checked with another set of headphones and determined that my iPod was just fine.The aftermarket JVC folding headphones I purchased a couple of years ago just before this iPod apparently have an open connection somewhere. They never entirely pleased me so I am not too sad to see them go.

Have ordered a set of the folding PX100 made by Sennheiser to replace them - should be a lot better sounding than the failed JVC headphones.

It does rather make me realize just how important a role music plays in my daily life.

As an aside I rip mostly CDs to the iPod using Apple Lossless these days and they do sound noticeably better than the standard 128K AAC I purchased through iTunes which has forced me to buy the actual CD instead in most cases rather than or in addition to an iTunes download.

IMO the iPod is no winner in terms of sound quality - it is quite "acceptable" through modest headphones, but I think sounds absolutely terrible connected through its dock to my stereo system. Some people actually believe this thing is the pinnacle of audio technology?!

Not knowing whether or not it was the headphones or the iPod that had failed I was not too happily thinking about the $400 this thing cost me 2 yrs ago, and realized that I am at a computing turning point. I no longer use windows on a regular basis, and iTunes does not play nice with WINE - so I will probably replace this with something that is not so platform dependent when the time comes.

I maintain an extensive library of both standard res and some high res flac files on my media server and was thinking how nice it would be to be able to put that on a media player without having to convert it to mp3 or mp4 for my iPod. ]]> kevinkr http://www.diyaudio.com/forums/blogs/kevinkr/124-ipods-n-things.html http://www.diyaudio.com/forums/blogs/kevinkr/122-phono-stage-shoot-out-conclusions.html Sat, 14 Nov 2009 18:26:53 GMT For some time I've had the feeling that there was something not quite right about the sound I was getting out of my most recent phono stage. The phono stage in question had never been compared to anything else, so it was difficult to understand what was going on. To add to the complications I use a Grado Reference Platinum cartridge that has a reputation for being rather laid back - so I was not really sure if the often boring sound was due to the cartridge or a problem with my phono stage design.

The design is a two stage with Lipshitz based passive eq., high transconductance type tubes, and gyrator loads. The tube complement is triode connected D3A in the front end, fixed biased 5842 output stage and gyrator loads based on the 5687.

The problem seemed to center around my choice of cathode bias in the first stage with the D3A. This resulted in a 60 ohm resistor and a 1000uF electrolytic cap shunted by a variety of other caps, after a long succession of problems I thought I had the ideal combination.

Something about the laid back, uninvolving sound quality told me otherwise. Last week I hosted the fourth annual Quincy Audio Fest and had the opportunity to compare this phono stage to one designed and owned by Arthur Loesch - this provided the required reference point..

I'm going to quote from an email I sent one of my friends (an attendee) about the whole experience:

"The phono stage A/B just adds ammunition to my contention that electrolytics have no place at all in the signal path of tube electronics. I have used diode and LED biasing in the past and honestly thought that having some dc current feedback because of the very high slope of the transconductance curve of the D3A would be a good thing. (I.e. tiny changes in effective grid bias voltage result in large changes in the operating point) Turned out that despite multiple iterations with ever more expensive electrolytics that I was wrong.. The diodes were clearly much better, and I should have chosen operating points that allowed the use of a single led instead. I don't generally use current sources as a load and using fixed bias whether by diode/LED or actual grid bias is a mixed bag because of the very high transconductance and the tolerance on it - no two tubes bias up the same and if the load resistance is not high enough gain mismatches will then ensue. Turns out that the supposed benefit of a small amount of dc cathode degeneration came at a very high price from an AC performance perspective.

It was an interesting lesson in why I should take my own advice.. LOL Obviously now I should really be making sure that I match the tubes over some range about the intended operating point or go to bonafide current sources as loads.

The Grado while not the ultimate cartridge was clearly not entirely to blame for the lack luster sound I was hearing. I had that nagging suspicion, but before ripping the phono stage to pieces blind I needed a reference point. Now I've got one."

The cathode bias resistor and bypass cap were replaced by a pair of 1N4148 which provide the proper bias level and a low dynamic impedance. A LED would be better, however I would have needed to set up the input stage slightly differently to have the proper operating current, note that because I do not use CCS I do have to select tubes that match and reach the target plate current of ~15mA. Fortunately these tubes are rather long lived so I should not have to do this again soon, gain matching between the two channels is better than a couple of tenths of a dB. ]]> kevinkr http://www.diyaudio.com/forums/blogs/kevinkr/122-phono-stage-shoot-out-conclusions.html