tube fanatic Posted November 20, 2016 Share Posted November 20, 2016 The Grundig xfmr is the best of the bunch for the build, and the shields attached to the frame will be very helpful in blocking the magnetic field (assuming they are ferrous) from the opts. I need to know if tubes other than V8 are using the V/W filament winding and, if so, how many. Maynard Quote Link to comment Share on other sites More sharing options...
davesans Posted November 20, 2016 Author Share Posted November 20, 2016 Looks like just only one the other tubes are using the X/Y taps. The leeds on the transformer are very brittle also I guess do to age and heat. Dave Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted November 21, 2016 Share Posted November 21, 2016 If the power xfmr leads are so brittle I would not use it. It's not worth taking a chance that you could wind up with the insulation cracking off at some point resulting in a short. Unfortunately, your other xfmrs are not suitable for this application. Do you want to build a stereo amp with a split p/s rail for each channel, or just go with a pair of mono amps? Personally, for the relatively small difference in cost, I'd go with the latter. Based on what you want to do, I can come up with a plan. Maynard Quote Link to comment Share on other sites More sharing options...
davesans Posted November 21, 2016 Author Share Posted November 21, 2016 1 hour ago, tube fanatic said: If the power xfmr leads are so brittle I would not use it. It's not worth taking a chance that you could wind up with the insulation cracking off at some point resulting in a short. Unfortunately, your other xfmrs are not suitable for this application. Do you want to build a stereo amp with a split p/s rail for each channel, or just go with a pair of mono amps? Personally, for the relatively small difference in cost, I'd go with the latter. Based on what you want to do, I can come up with a plan. Maynard I am good with building mono amps thanks Maynard for your help. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted November 22, 2016 Share Posted November 22, 2016 No problem. Hang in for a couple of weeks and I should be able to draw out the schematic for you. I saw your comment in another thread about the bottom end issue with the ST70. This will include some compensation which should make things very nice with your speakers. Also, do you want to be able to adjust the high freq. response? I can include that as well. Maynard Quote Link to comment Share on other sites More sharing options...
davesans Posted November 22, 2016 Author Share Posted November 22, 2016 4 hours ago, tube fanatic said: No problem. Hang in for a couple of weeks and I should be able to draw out the schematic for you. I saw your comment in another thread about the bottom end issue with the ST70. This will include some compensation which should make things very nice with your speakers. Also, do you want to be able to adjust the high freq. response? I can include that as well. Maynard I really don't like the Curcio mod for the ST70 the MKlll's I did years ago sounded better. I know a lot people use those other two driver boards that are out there and like them a lot. I thought of doing a complete overhaul of the amp but just don't want to spend the money on it and fine out I still don't like it. Two question one do you know what driver tube your going to use and why would I adjust the high frequency response just in case it to much is it like a tone control or are we taking something different? Thanks Dave Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted November 23, 2016 Share Posted November 23, 2016 We can use almost any high-mu triode for the driver. So, if you happen to have some 12AX7s laying around, using one section would be fine. Let me know what tubes you have on hand. In response to many requests I began including a variable low pass filter in all of the amps quite a while ago. Given how many recordings employ lots of high frequency boost, it's nice to be able to roll off the response of the amp a bit to make the recordings less grating. It can be set up as a front panel control for use as needed, or it can be installed under the chassis and set to your personal taste and forgotten. By chance, do you have a 'scope? Maynard Quote Link to comment Share on other sites More sharing options...
davesans Posted November 23, 2016 Author Share Posted November 23, 2016 I have all sorts of tubes 12AX7,12AU7, 12AT7.6922,6DJ8,12BH7,6SN7 Also I do have a scope a Tektronix 475 Regards Dave Quote Link to comment Share on other sites More sharing options...
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