fini Posted October 3, 2005 Author Share Posted October 3, 2005 Good morning, Gents (afternoon to you, Max!)! Well, I scratched out a little time Sunday (after appeasing my wife by cleaning some--not all--of my crap off the kitchen counters) to take out the Mac 1900 and insert the Fisher SA-16. After carefully bringing this all-original vintage EL84 amp to life on a Variac (and swapping out a few of the power tubes that were obvious duds), I played a few CDs. VOILA! The veil has been lifted! I will have my first chance in 3 weeks today to have the house to myself, and I will confirm last nights results, but I think the Blueberry and the Mac amp were just a bad combo. The best way to describe the change with the Fisher in there, I wanted to stay in the sweet spot, soaking it in. I wasn't finding faults, or missing things, but was being drawn in, hearing things I hadn't heard before. Some tunes with which I've become VERY familiar seemed to be LONGER! I think it's because I was now paying closer attention, not because I had to (for testing purposes), but because I WANTED to. Very cool! This listening was all done with CDs. I will begin to tackle the turntable/arm/cartridge adjustments today. I've been getting more inspired about finally tackling the MK-IV restoration myself. As Shawn pointed out to me, thousands of folks before me have built these on their kitchen tables, many with much less than my Fluke DMM (my only test equipment), so why not me? I may have to find a different work area, away from the kitchen, though... Quote Link to comment Share on other sites More sharing options...
fini Posted October 3, 2005 Author Share Posted October 3, 2005 Hi Eric! Yes, I was using only the amp section of the Mac. I had no idea I could use one of the line level inputs. Whaddaya expect? I only have a DMM! ;^) Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted October 3, 2005 Share Posted October 3, 2005 Glad you got the veil lifted. Is good sound bliss or what? Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted October 3, 2005 Share Posted October 3, 2005 Hey, Fini: Sound like you've got this figured out, and I also agree with Shawn! You could easily do that Dynaco restoration yourself. The only test equipment I have is a multi-meter, but one can do a significant amount of work even with that! I think it would be rewarding and tons of fun for you! I think it might be worth-while to try the BBextreme with an AUX. input of the Mac. receiver. The sort of ironic thing about preamps, is that they are really more used to attenuate a signal than amplify it. In order to get an idea of this, all one would need to do is use one's CD player straight into an integrated amp or receiver -- and then turn the volume all the way up. The output voltage of almost all CD players is easily enough to swing many power amplifiers into and beyond the clipping range. That's why so many people prefer 'passive' to active line stages -- though there are of course those who do not care for the sound, perhaps, again, because of possible impedance matching problems with some tube equipment. In any event, you might just give the BB another try with the Mac, but maybe start with the volume control on the BB up about half way, and then adjust as needed with the main volume control on the McIntosh. It would be interesting to see if this would make a difference (but it would of course involve extra work on your part since you already have the Fisher up and running.) IOWs, the BB would just be used as a source, and the input and output sections of the McIntosh, which were designed to work with one another, will have the chance to do so. Sounds like you're having fun, Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted October 3, 2005 Share Posted October 3, 2005 I just remembered something! I can't remember the exact year, but it must have been the early 90s, or there abouts. I had built a little 12AU7 linestage preamp, and did the exact thing I mentioned above, Fini -- bypassing the preamp section in an integrated amplifier, thinking it was the right way to do this. Sure, I got sound, but it was very, very poor quality -- dull, weak, veiled, thin -- all of that bad stuff. So, instead of bypassing, I just used the preamp as a regular source going into one of the standard inputs to the amplifier. It worked perfectly then, and the sound was what I was hoping for. What I was essentially doing, although I probably wasn't aware of it then, was using the preamp as a vacuum tube 'buffer' between our CDP and amplifier. It surely didn't 'fix' the signal or anything, but it may have improved the impedance matching between the two components. So, I found out that bypassing the front end of the amp resulted in very poor performance, even though the components themselves were of decent quality. Maybe this is what happened with the Blueberry and Mac!? Erik Quote Link to comment Share on other sites More sharing options...
fini Posted October 3, 2005 Author Share Posted October 3, 2005 Eric, Thanks for the vote of confidence with regard to tackling the restoration. I go back and forth now with regard to how extensively I want to "upgrade" the MK-IVs (i.e. new sockets, RCAs, binding posts, what type of caps and resistors, etc.). For a person like me, all those choices can be crippling! A personality glitch, I guess...I guess that's why many vendors have just put together restoration packages. Shawn pointed me towards Digi-key, but their website was not very newbie-friendly. I was a bit overwhelmed... Quote Link to comment Share on other sites More sharing options...
fini Posted October 3, 2005 Author Share Posted October 3, 2005 Eric, If it worked well, one advantage of using the Mac would be that my kids could listen to music in that room without firing up tubes. I'll need a spider web of interconnects and splitters, though! Quote Link to comment Share on other sites More sharing options...
sfogg Posted October 3, 2005 Share Posted October 3, 2005 " For a person like me, all those choices can be crippling!" I'd keep it simple for your first rebuild. Maybe do it in small steps to increase your confidence. Start off small with even something as basic as replacing the selenium recitifiers and then verify the amp is working. Then rebuild the bias circuits and check it out again. Then go for the restoration of the other parts. " Shawn pointed me towards Digi-key, but their website was not very newbie-friendly. I was a bit overwhelmed... " Request a paper catalog, less likely to freak you out. Remember they have the same part made by different companies so you see a lot of duplication in available parts. As far as most parts just replace them with the same value/voltage/wattage components. You can increase the wattage/voltage ratings if you want but don't decrease them. Metal film resistors fine. For the bias caps use 'axial' package capacitors, ditto with the few other PS upgrade caps recommended by AVA. Those are all electrolytic capacitors. For the upgraded coupling capacitors I used a film/foil caps in there. Nothing fancy... just something Digikey stocked. If you still have the selenium rectifiers in the MKIVs use a 1N4007 diode to replace it in each amp. If you go by the parts lists in that AVA article keep in mind that is for a Stereo 70. For some of the parts you will need to order 2x the amount because of your amps being mono-blocks. For example the bias supply rebuild and the additional capacitance in the PS. Shawn Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted October 3, 2005 Share Posted October 3, 2005 Fini: I'm going to go out on a limb and suggest that they way you had the Blueberry connected to the Mac was probably what caused the problem you experienced. Input and output stages are designed to work together, and my thought is that bypassing the front end may have compromised the performance. I've done the same thing, as I mentioned above.... In addition to Digi-Key, may I also suggest Mouser Electronics -- www.mouser.com Their online catalog is good, but yeah, the amount of choices available is pretty huge. I order from them all the time, and they have been very reliable. For small and inexpensive parts like low-power metal film resistors, I always order several 'just in case.' JJ electonics makes very good quality filter capacitors ( with mounting hardware), and they are available at another source I often use: Antique Electronic Supply @ www.tubesandmore.com They also have a huge inventory of tubes. Tons of neat stuff to check out. Erik Quote Link to comment Share on other sites More sharing options...
3dzapper Posted October 3, 2005 Share Posted October 3, 2005 fini, If you are going to do your Dynacos yourself, may I reccommend that you use the loaded boards from "Uncle Ned" at Triode Electronics. http://store.triodestore.com/mk4boards.html for only $45 per amp, all the parts needed are included. Or for more money, the Full Monty with driver board and cap boards from Joe Curcio http://www.curcioaudio.com/mk4upg_3.htm. Download a copy of the Mark IV assembly manual and do just one amp at a time so you can see where the leads go. Once the first is assembled and tested, copying it for the second. IMHO, the cap boards or at minimum a new multisection cap are a need given the blown power tranny you had on that one amp. http://store.triodestore.com/40ufat52twis.html Rick Quote Link to comment Share on other sites More sharing options...
fini Posted October 3, 2005 Author Share Posted October 3, 2005 Boy, those drop-in boards certainly have a can't-go-wrong appeal! I also understand Shawn's suggestion, knowing I'd learn more along that path. Hmm... Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted October 3, 2005 Share Posted October 3, 2005 Take the more difficult path![] Quote Link to comment Share on other sites More sharing options...
fini Posted October 3, 2005 Author Share Posted October 3, 2005 That IS the only way to learn that stuff, right? Can I be assured to know the secret handshake when it's all said and done? I mean, that's why I'm REALLY here... ;^) Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted October 3, 2005 Share Posted October 3, 2005 Fini: What I said about taking the more difficult road might not be right for you, or anyone else, for that matter. Rick indicated a great way to fix up those amps, and it might be just the right thing for you at this point. I've seen those boards, and they are really pretty neat. You could get them already stuffed and just hook them up, or buy the boards plus the parts and put them together yourself. Either way you get some practice. I guess it just depends on how much time and effort you want to put into them. It's nice to have some different options. Do get those selenium rectifiers out pretty soon, though. Although I've never had one go bad, I've heard that they can be pretty nasty when they fail. The IN4007s Shawn mentioned are really cheap, and can be found at Radio Shack (at least they used to carry them). I might even have some here I can send you. Erik Quote Link to comment Share on other sites More sharing options...
fini Posted October 3, 2005 Author Share Posted October 3, 2005 OK, I've doodled around with the VTA, and cleaned the stylus, and I think I'm on the right track (knock on the beautiful walnut Xtreme case!). I brought the SME arm up as high as it would go (which is really not terribly high), and the souns was too strident. Brought it down a bit, and it's sounding pretty good. In addition, following Eric's suggestion, I put the Mac back into service, this time using the Tape Monitor input. Much improved, although not as good as the Fisher in terms of soundstage depth, width, and clarity (individual instrument definition). Definitely something I can live with while doin' the Dyna's. Hmm, do you think my wife will be singing, "fini's in the kitchen with Dyna..."? Quote Link to comment Share on other sites More sharing options...
Marvel Posted October 3, 2005 Share Posted October 3, 2005 For those doing an ST-70, I would recommend Shannon Parks board. It is constructed a lot better than Joe's. There are pics here: http://diytube.com/phpBB2/viewtopic.php?t=773 I wish he made boards for the Mark III and IV. Bruce Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted October 3, 2005 Share Posted October 3, 2005 Fini: You might try one of the other inputs in the Mac, as well. It may be that there are different input impedances associated with them, and one or another might better suit the output impedance of the BB. Also, doesn't the Blueberry have a couple of different output options? I'm pretty sure the Peach does. You could try one or the other to see what work best using the chosen input on the McIntosh. I'm glad the combination is working better for you! Erik Quote Link to comment Share on other sites More sharing options...
fini Posted October 3, 2005 Author Share Posted October 3, 2005 Bruce, I poked around a bit over at that site. Looks like at least one guy has modified the ST-70 board for use in the MK-IVs: http://diytube.com/phpBB2/viewtopic.php?p=3158&highlight=#3158 Quote Link to comment Share on other sites More sharing options...
fini Posted October 3, 2005 Author Share Posted October 3, 2005 Mark, Read through the post, I think I've fixed the problem. I'm running the BB into the "Tape Monitor" input, rather than directly into the amp section (you know, it has those "horseshoe nails"). This was suggested by Eric. Tried the Fisher amp last night. It sounded very nice (better than the Mac), but I hesitate to run it too much before a thorough check-up. I will check the BB as you suggest as soon as I find where Cathy hid, er, "put away" my DMM... Quote Link to comment Share on other sites More sharing options...
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