Guest David H Posted January 19, 2009 Share Posted January 19, 2009 Are those unplated boards with no solder mask? Good eye. No this is not masked, however because of the adequately spaced layout, I dont think it is of any concern. I have had no issues of solder bridging, and as stated earlier, when using board like this simply space the components so they do not touch the traces or each other. This board does offer large traces and through hole circuits. Very nice to work with. Sorry Mark, I didn't realize that was you. I am sure you didn't need a lesson in assembly. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 19, 2009 Share Posted January 19, 2009 Thanks Mark, I appreciate that. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 20, 2009 Share Posted January 20, 2009 Tonite, I am thrilled to see that my chassis arrived, and is much nicer than I thought. These chassis are built in the U.S.A. and are avalable from Tubes4HiFi. This chassis is 16wx12dx4t perfect for projects. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 20, 2009 Share Posted January 20, 2009 Anxious to get started I marked and drilled the removable rear plate, mounted my rca jacks and IEC connector. I was entertainig the notion of having the back pannel silk screened, but decided the $$$$ would be better spent on the front pannel. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 20, 2009 Share Posted January 20, 2009 I learned a valuable lesson today, when drilling this aluminum even on a wood surface is very easy to scratch. A good way to avoid these minor scratches is to put a layer of the blue removable no residue masking tape over the suface to protect it while you are working with it. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 20, 2009 Share Posted January 20, 2009 No luck on these questions? Here is where I need your help, The output coupling caps are .33uf Solens Roy informed me that I could replace them with a larger value, which would pass lower frequencies, but they may not fit on the board. My thought was to use multiple sets of output coupling caps on a rotary swithch and be able to select the ones I like best. I have plenty of room in the chassis I have coming to add a cap board. What cap values do you think would work well, for a 2 tube gain stage? What reasonably priced caps would you suggest? Russian PIO, Sonicaps, Kimber, dayton, etc. No need to mention expensive V-Caps etc, not going to spend more on caps than the rest of the kit. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted January 20, 2009 Share Posted January 20, 2009 GotHover You can add russian teflons to your list. As far as chaning the coupling cap values...Roy should provide more info...what hi-pass do you get with .33uf. If it's 10hz, that's probally good for an SS amp, but suspect for a tube amp...most tube amps can't do 10hz...also...there might be a coupling cap on the amp input (if tube) as well...whats the low end of the amp you want to use...if it's 20hz....maybe the current value is fine. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 20, 2009 Share Posted January 20, 2009 Thanks for the input Fritz, The input caps are .10uf, I have a pair Audiocap Theta's for them. I am only asking about to output coupling because my other tube preamps use 2.2uf and 3.0uf for output. I am going to use the original Solen .33uf on one selector position and was looking for options on the other positions. I agree there is no need to produce lower than the amp can reproduce. Russian teflon on the list. Currently I have Kimber Caps, Dayton Film and Foil, Solen and Clarity. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted January 20, 2009 Share Posted January 20, 2009 I would get the pre-amp going, and listen to it with the stock output coupling caps for awhile before you start rolling coupling caps. Get a idea of the pre-amp's sonic signature first, then you may have a better idea of how different coupling caps affect the sound. I would guess the output coupling caps are the ones that would affect the sound the most....a guess.... Mundorf might be a thought......but there is about eight billion flavors of caps out there. If you know the resistor value of the following stage, I think you can use this formula to determine the low frequency cut-off point. 1 divided by 2XPIXRXC. Brain-dead example: 2 times 3.14 is 6.28. 6.28 times 470000(R value), times 0.1 uF. Equals 295160. 1 divided by 295160, equals 0.000003388. Slide the decimal over six places to the right, and it is 3.3-3.4Hz. The decimal needs to be moved six places to the right, because the cap value is in microfarads, something like that......I'm not the best at math. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 21, 2009 Share Posted January 21, 2009 I would get the pre-amp going, and listen to it with the stock output coupling caps for awhile before you start rolling coupling caps. Get a idea of the pre-amp's sonic signature first, then you may have a better idea of how different coupling caps affect the sound. I absolutely agree, I am considering using this or something similar to switch the in different coupling caps. Product Description Need a rotary switch for switching between the two coupling capacitors? Four-pole, three-position, non-shorting switch and some hookup wire is all that is needed. All four coupling capacitors attach to the PCB and each channel's output connects to either coupling capacitor C1 or C2 or both capacitors in parallel. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted January 21, 2009 Share Posted January 21, 2009 That's a interesting idea and kinda cool. If you are to use that switch, and if I were you, I would listen to one type of coupling capacitor for like a week. And then switch to the next type and listen to them for a week. Switching on the fly back and forth trying to discern differences in the types of coupling capacitors may be a futile exercise, to me anyway. They will always sound the same, I would think. Maybe not..... That's how it works for me trying to discern differences between amplifiers on the fly. I have better luck listening to a amplifier for a week or two, and then switch to another amplifier. Right when I switch is I when I notice the differences, then it is quickly forgotten...... Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 22, 2009 Share Posted January 22, 2009 I have got most of the wirng done today. Just a day or two more and I should have the faceplat back from the local laser graphics guy and the power supply. Here are some pics of the wiring. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 22, 2009 Share Posted January 22, 2009 Anther pic Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 22, 2009 Share Posted January 22, 2009 One more for now. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 25, 2009 Share Posted January 25, 2009 Latest update. I received the transformer and capacitors yesterday. I got the preamp up and running with only 2 minor kinks, none of which were the fault of the manufacturer. First issue I had was no audio from the right side phono section. The cause of the problem was a bad capacitor in the phono section. The faulty cap was one of the upgrade caps I installed not the originals. The other issue was a ground loop problem. This issue was caused by "yours truly" What I did was couple the chassis gound to the phono ground. After I decouple this additional ground the noise was almost undetectable. Then I pulled my original Dynaco Telefunken Tubes out and installed a set of low noise NOS JAN Phillips 12AX7's in the phono stage. Now all works perfectly. I am still tweaking with capacitors etc. I have a ton to talk about where this preamp is concerned, but it's to early to make any real judgements. So I leave you with this. "BASS...man thats good BASS" More to come. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 27, 2009 Share Posted January 27, 2009 Ok the preamp is done, I have more info and pics, I will start with the transformer. This transformer is a PA-522 manufactured in the USA for Triode Electronics, This is a universal voltage 110/220v and is a direct upgraded replacement for the Dynaco PA-211. The transformer voltage is 330-0-330 at 15ma and has a secondary 12v for the heaters. This transformer is available from www.triodestore.com and www.Tubes4Hifi.com . Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 27, 2009 Share Posted January 27, 2009 Here are the hookup instruction for the PA-522, I am adding them because of the dual voltage hookup differs from the VTA's wiring diagram. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 27, 2009 Share Posted January 27, 2009 As I stated easlier in this post, I had a hummmm in the the phono stage, in this picture you can see where I made the error. The black coax going to the rear pannel jacks are the phono in wires, if you look close you can also see I carried the common ground across the rear pannel to the phono jacks. That was my first mistake. The proper way to wire the phono is to Isolate it from the common ground. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 27, 2009 Share Posted January 27, 2009 Mistake #2 let me tell you from a hard lesson learned, if you want to change coupling caps in the line stage, more power to you, but leave the Phono section alone. You can see here I reinstalled all of the original phono stage caps supplied in my kit. My suggestion for upgraded caps is pay the extra $40 for the Auricap upgrade, and follow the instructions exactly. As you can see in this pic I have a solid state rectifier installed. This is one of my DIY Coppercap clones that uses a pair of 1000v-piv diodes and a 5watt 300ohn resistor, to emulate the 12X4. The SS rectifiers one particularly good aspect is that is doesn't draw current from the transformers heater circuit. The down side is they can cause a power on thump and cathode stripping. I have never experianced any negative effects of using the SS rectifiers. I have tried both in this preamp, no issues with either, but the builder (Roy Mottram) reccomends the 12X4 therefore that is what I am going to stick with. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted January 27, 2009 Share Posted January 27, 2009 Here is a photo of control pannel. Because I wanted a clean front pannel I used rotary switches in all positions except for the alps volume pot. Left to right from the rear: output coupling, balance-not used, volume, Input-selector, power. I was leary of using the Alps Blue, because I prefer stepped attenuators, but he Alps is truly a quality piece I would absolutely reccomend again. For the selector I used a Greyhill sealed 6 position mini rotary switch, I have used these in the past for projects and feel the quality is top notch. Quote Link to comment Share on other sites More sharing options...
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