Erik Mandaville Posted May 8, 2004 Share Posted May 8, 2004 The following show the GG finished and operational, but without control knobs and cover. Tubes are enclosed within a vented stainless steel chassis. Center control shaft on faceplate is the added balance control. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 8, 2004 Author Share Posted May 8, 2004 inputs and output connections Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 8, 2004 Author Share Posted May 8, 2004 Power supply board Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 8, 2004 Author Share Posted May 8, 2004 Preamp board (Yes, those are Solen coupling capacitors -- I also use them in my Foreplay, and they work very well) They can be changed as needed or desired, however. I actually thought of mounting the caps on terminal strips with lead that go to the PCB, and in that way making provision for capacitor changes in the future. These sound as good to me as Hovlands I have used in the past, and are much less expensive. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 8, 2004 Author Share Posted May 8, 2004 3/4 view of chassis without control knobs. We will have to do something about 3 matching knobs. I'm going to get 3 black Radio Shack knobs today when we're out for some errands, and will test the preamp over a week using they those (I actually think they look good, and have been reliable for me in the past -- they're those larger black knobs that have that slightly scientific instrumentation appearance). Quote Link to comment Share on other sites More sharing options...
3dzapper Posted May 8, 2004 Share Posted May 8, 2004 Eril, you do such handsome work. Rick Quote Link to comment Share on other sites More sharing options...
Dflip Posted May 8, 2004 Share Posted May 8, 2004 Erik, very nice work. It seems to be simply laid out with a good amount of space in which to do your work. Thank you for again sharing your work with us. Don Quote Link to comment Share on other sites More sharing options...
NOSValves Posted May 8, 2004 Share Posted May 8, 2004 Eric, What value are them Solens ? Let me know and I'll donate some descent caps for your little project ! Solens suck ! My Map-le tree came packed with them and replacing them was a ABSOLUTE must. I mean I could not listen to the preamp before but keep in mind were talking near a dozen throughout the preamp. Craig Quote Link to comment Share on other sites More sharing options...
leok Posted May 8, 2004 Share Posted May 8, 2004 Erik, Very nice work. Leo Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 8, 2004 Author Share Posted May 8, 2004 Thank you! ...but some frustration. The balance control I'm using came from my parts bin, and is from another preamp purchase. However, it came removed from that preamp, and was in a plastic bag (a sign of possible damage?!). If I had half a brain I would have tested it out thoroughly before making the connections. Now it's not working right -- again. There may be an intermittent or damaged internal contact on one of the wipers, or the centered, detent position isn't reliable...I just don't know. I can't send it off to Wolfram like this, and I feel bad (sorry Wolfram!!!) because I had everything going as it should last night. I'm going to get another volume control from Radio shack this morning, and install that in place of the balance pot. This way, each channel can be adjusted individually, but just a little less conveniently. Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted May 8, 2004 Share Posted May 8, 2004 What kind of volume and balance control are in there now? Quote Link to comment Share on other sites More sharing options...
jt1stcav Posted May 8, 2004 Share Posted May 8, 2004 Nice work, Erik! Love its simplicity. Wolfram should be proud to receive this piece. Just a side note...the RadioShack knobs are fine for the time being, but this unit deserves better knobs, and this audio parts firm in Taiwan has a great selection of high-end audio knobs to choose from. Either you or Wolfram should check them out...I ordered 3 champagne-colored brass knobs for my BEZ preamp (and amp, whenever it gets here), and it took less than a week for them to arrive! http://www.thlaudio.com/indexE.htm Quote Link to comment Share on other sites More sharing options...
dubai2000 Posted May 8, 2004 Share Posted May 8, 2004 Erik, and I was already happy about a functioning balance pot... . Anyway, you are doing a terrific job - many thanks! I am sure many people will now be keen to read how the unit performs....do I have to add: myself included ? Wolfram Quote Link to comment Share on other sites More sharing options...
bkrop Posted May 8, 2004 Share Posted May 8, 2004 Pretty and neat! A) why not get another balance instead of volume? Does Trancendant have a web site? Quote Link to comment Share on other sites More sharing options...
DRBILL Posted May 8, 2004 Share Posted May 8, 2004 Beautiful job. I am wondering if additional center support might be needed on the power supply board? That's a lot of iron! DR BILL Quote Link to comment Share on other sites More sharing options...
scrambler400 Posted May 8, 2004 Share Posted May 8, 2004 www.transcendentsound.com Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 8, 2004 Author Share Posted May 8, 2004 Wolfram: If the volume and other controls in the Eico amp are stock, they are very likely carbon composition potentiometers. Same is probably true for many of the vintage Scott amplifiers mentioned and discussed here and elswhere. They do the job well for a very low price compared to other options. I've used a number of different types of volume controls, and think the inexpinsive Alpha pot that came with the kit is totally up to the job. As I told you, there will be some who really prefer stepped attenuators with fixed resistors, and those may add some improvement. I've done this long enough to hear both sides of lots of different stories, and the only 'right' answer in this equation is simply what sounds best to you in relation to how much you would like to spend. I have two mono Alpha controls in the preamp right now, and it's working just fine. Sounds very, very good, actually. One thing that has become evident, is that both the 50K ohm stereo pot and now the 100K ohm mono pots are too 'hot' or sensitive with my system. Higher input impedance tube amps, especially vintage amps, might require a preamp with a less sensitive control; and in this case what I think would work best is 25K ohms -- maybe even as low as 10K. Since some of these question have been brought up on the forum, maybe some others might benefit from the discussion, too. Capacitors are another issue. I liked what Jensen PIOs did for my Moondogs, and you will probably get some suggestions to use those. I've also used Hovlands, Kimbercaps, and others. I first used the Solen capacitors in my Foreplay preamp and got totally satisfactory results. Hey Craig -- thanks for your input here, too. Again, I think personal taste comes into play, and you and I are fortunate in that we can switch things in and out to find what's preferred. My preference would be to go with two mono controls, but this isn't my preamp. Think about what you would like to do, and we can go about getting it done. I order from Mouser Electronics all the time, and can get a couple of controls in a few days. I've forgotten that the SE OTL is less powerful than my own system, and may in fact benefit from the stock volume control value of 50K ohms. With regard to some other questions that have come up: The balance control is a Noble control -- well made but behaving strangely. The 3 transformers are actually quite small, and present no problem at all for the PCB in terms of being too heavy. The preamp is light, and sounds very open and clear. On top of that it's truly DEAD QUIET! I mean nothing! No hiss, no buzz, no hum. I think with the SE OTL it will be very, very nice. All of my preamps seem to add something to the mix, but this thing is just so easy to forget about. That's nice for a change. Wolfram: There are many opinions about the capacitor issue, and you must decide for yourself. I want to stay out of that, but I am open to whatever you think you might like. I wish you could solder, because what would be the best to do IMO, is to try it stock first, and then experiment later. I will say that if the preamp were my own, I would be happy with what is in there right now. I wouldn't change a single thing. Also: All hookup wire is 18AWG silver plated copper insulated with Teflon. I thought this might be good over what the kit comes with, but it's designer would not think so. I'm sure he's right, too, but I just like to work with the Teflon insulated stuff. I got a very good wire stripper that does a great job with cleanly stripping that slippery Teflon spaghetti! I'm standing by, ok? Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 8, 2004 Author Share Posted May 8, 2004 Thanks for that link, Jt! Thanks for the compliment, Leo. Honestly, the Grounded Grid is like a passive preamp with gain! It's just so quiet, and really an ideal preamp for high impedance/sensitive amps and very efficient speakers. Erik Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 8, 2004 Author Share Posted May 8, 2004 I can knock off a few dBs of gain by installing a 50K ohm resistor between the selector switch an volume controls. I've got an assortment of brand new metal film resistors that would work fine for this. A new terminal strip can be installed on the PCB mounting screw closest to the selector switch. It would have the same effect as adding lower value potentiometers, making the volume controls less sensitive. And it would be free. No shipping costs, either, which in this case would be more than the controls, themselves -- unless you get a couple of Noble pots. Le me know! Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted May 8, 2004 Author Share Posted May 8, 2004 The complete picture of GG. The next one is of my own amps with the AVVT meshplates! Just let me show them off, ok?! Quote Link to comment Share on other sites More sharing options...
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