INTRODUCTION

After the good result obtain with the DAC End I have design with Nguyen Quang Hao a set of boards to create a cheaper project with a sonic performances very near.

The No Oversampling DAC give a more natural sound but if you ear the TDA1541 and TDA1543 seem to lose details.

The AD1865N-K with passive I/V give a perfect combination, natural sound and all the details.

The AD1865N-K give the better performances with a 200ohm MK132 Caddock as passive I/V.

In this configuration the output signal is too low to drive any amplifier so I have design for the AD1865N-K the better output stage.

This DAC use a single ended vacuum tube amplifier without the expensive output transformers used in my original DAC End.

The DAC board follows the original design but has been inserted a jump to switch the phase of output signal.

In any vacuum tube stage the signal on the anode is in out phase...

The Takman resistors have thick copper wires. This makes for wonderfully strong little spiders.

I've also used ceramic terminals strips for the first time and it makes for a nice strong construction.

And I did the ccs for the phase splitter a while ago.

[edit] I used silver solder. But found out that it is NOT necessary with these fakes. Fake or not it make for a great construction.

"TEKTRONIX CERAMIC STRIPS, HISTORY and GENERAL INFORMATION
Tektronix first developed and used ceramic strips in their oscilloscopes in 1952. During the manufacturing process, silver in liquid form is painted in and on the notches of the strips prior to the application of the final glaze and final firing. The silver is then firmly bonded to the ceramic and wires can be soldered directly to the ceramic.

Special silver-bearing solder should be used when soldering to ceramic strips so the silver bonded to the strip does not...

Tonight I found out it is a really good idea to ground the shaft/body of the rotary switch in order to eliminate pick up of 60Hz and its harmonics. I noticed moving my hand closer to the metal knob on this switch resulted in a >20dB increase in 60Hz spectra and the addition of somewhat lower level harmonics at 120Hz, 180Hz, and 240Hz.. I grounded the switch with a piece of 28ga wire between the lock washer and the body of the switch and grounded it to the board ground. This totally eliminated any pick up with no noticeable line frequency or related spectra. (My case is totally shielded on the top and bottom, but not sides, front or rear - and does not appear necessary to do so.)

https://www.diyaudio.com/forums/tubes...-question.html

I have been side tracked lately. not enough time to do the F5 like I wanted.

I ended up digging up the BOM for mini aleph and ordered the parts for that.. started to solder the parts and found that I needed to soldier mount the resistors because they are way too big for the PCB

I need to double check all the blank spots, clean up the flux on the board and start on the power supply..

10 Feb 2011. AndrewT pointed out something really dumb I had done (in a most polite way) in the original circuit. The caps in the filter section are in series and effectively halved in value. The circuit will behave much better simply by deleting half the caps. I've uploaded the latest version of the file. Sorry to the 125 people who have already downloaded, and I hope I didn't cause too much head scratching as to why I had done that, I'm not even sure myself, and I'm surprised I never realised. I'm going to revamp this blog entry as there are some things I have realised since I first posted, but that will be over the next couple of weeks. Hopefully I will finally build it soon.

I have been spending an inordinate amount of time using LTSpice lately. The more I use it the more I like it! For someone like me who is somewhat challenged mathematically, and who's electronics theory knowledge level is well below where it should be (to be doing this sort of design anyway),...

from AndrewT

Apply 16Vdc through 100k resistor and measure how the resistor voltage varies with time. The resistor voltage is a rough indication of the cap leakage+charging current.
Once charging is substantially over the remaioining current is predominantly leakage +-a little bit of chage/discharge current depending on the stability of the supply.

The apparent leakage is very much affected by the DC supply voltage. A good regulated DC supply that is held at constant temperature will help a lot.

You may find that 6hours at 100k gets to within 105% of the ultimate leakage current. But tell us what you find.

You can reform a bank of caps using one resistor to feed each capacitor.
Measure across each resistor to see how similar or different the caps are.

this one seems to seperate THD from noise

www.Virtins.com

Use RG58 on all your shunts for sense wiring. Use as thick main ''force'' wiring as you like. Remember that the sense nodes are voltage nodes, don't worry about gauge. Their mission is to skip the voltage drop on the current carrying force wires and ''see'' the remote nodes directly. I believe that you will see less stuff on your scope in difficult termination situations if you shield your sense wiring. If you need extra thin and flexible enough, see about Belden (RG style) 179DT also, which I like for signal too BTW.

I have been tinkering with speaker ever sense I was a kid back in the seventies and have always been trapped in the box. My newest efforts are an improvement but remain in the box Durring the last 6 years I have visitd this site for ideas and must say thanks for all I have picked up. My system is now compiled of all dyi speakers and is a vast improvement over the commercial systems I have purchased over the years “due to lack of funds to buy the good stuff of course.” I have over the last few years tried a few open baffle approaches with little success. The back loaded horn with the fostex sounds great but it’s a little to honky for my taste. The small box using silver flutes and vifa tweets crossed at 2.5k and dampened using automotive damping pad made of polyester and kanaf “I have access to many exotic damping materials” sound good but appears to fade in and out (I need help with this one) I used decent crossover components Bennic caps and jantzen 18 ga air core ind. all connections...