Woo3 Modified - Page 3

I have a Ken Rad 6AS7 with copper shields internally. It is very different and interesting just to look at. My other ST types have the more typical black shields. I like the ST but the Bendix has better bass control and slam.

John

As I quite messing with the changes to the Woo 3 I notice, as with all of the modifications I do, it is settling in and in this case sounding very open. I have noticed that I need to leave something alone for a while to really gage whether the changes I have made enhanced the sound or degraded it ( after years of modifying and tinkering I am very well aware of break-in and so forth but sometimes I just like to pick up the soldering iron). Now you could say, well how do you know if you know longer have the base line you were working with, as in the original shipped model? I have two other amps that I compare with and in noticing the difference decay, transparency etc, I can gauge the changes and just the overall enjoyment or lack thereof in listening to the unit.

I have done one more change, of course, to the cathode bias resistor, which I went back to as the battery bias is too low and shifts the operating point of the tube down for the plate voltage. I am using a Riken Ohm for the cathode resistor in place of the metal oxide and I have bypassed this resistor with 200uF's ( I normally use about 400 to 500uF’s so I will experiment more here) of nonpolar Black Gate caps. This adds to the bass impact and enhances overall impact. How much you use in the bypass can affect the sound in either a good or negative way. Too much can color the mids, too little the same and can decrease the ability to add to the bass impact. Some designers prefer to use no bypass some use it. I prefer to tastefully add high quality capacitance. In this case it has also added to the fine detail and hall ambiance.

I also replaced the coaxial cable in with my solid, flat high purity silver, which I do not use sheilding on as I find that sheilding, unless really needed, slightly dulls the sound. The original wire is multi stranded and I do not care for multi stranded wire in the musical path, or much of any where. I use flat silver with teflon tubing so I get about 95% air dieletric.

Oh, and try some 5998 tubes (just drop in). These are a little beefer and enhance the sound.

John

Ok, now for an update.

The decoupling/output caps are like the output transformers in any other amp, very important since the signal has to get from one side of the cap to the other with the least amount of coloration and impact to the signal.

First I got some Black Gate 470uF polar. Not cheap and somewhat better than the original. Then I realized I am passing an audio AC signal through polarized caps; poor judgment on my part. So I up and spent more money on 4 220uF 160 volt nonpolar Black Gates (two per channel soldered pin to pin in a “super E” configuration). Well these really get the music out of your head and into the stage before you! Transient speed, bass impact and overall WOW factor is great. For an OPT amp these or some type of very good nonpolar would be either an upgrade or just part of the original package. Oh, and I am not bypassing the Black Gates. I have found that bypassing, as often done with lesser caps, does not work well with Black Gates.

Good listening.

John

Great mod! :^) I would like to have a silver or champagne.

Further update on sound:

I thought when I added the dual 220uF nonpolar Black Gates for the output that the sound had settled in. It was detailed and refined and very enjoyable. I normally figure about 500 hours for everything to really break-in or longer but the sound after about 100 was already great, but nothing is constant.

1. The new output caps have about 400 hours on them now. They did go through a change sounding a little muddy for a while and have now opened up with vibrant detail and clarity (transparency). My speaker system is very fine and for me with well recorded music rivals live but the Woo 3 is often more tempting as it is open, airy and also very real.

2. I installed Vampire oxygen free copper RCA's, which I believe for RCA's are some of the finest available.

3. I installed a Neutrik locking (silver plated contacts) jack for the headphones. This required enlarging the existing hole to 15/16's. I am glad this is aluminum and not steel.

4. The rest of the changes have been noted earlier.

The Woo 3 continues to entertain a present a very realistic musical picture. I notice that voices that were cupped in my head now have a natural air surrounding them and background clapping is distinct and at a distance. Instruments, when recorded correctly, have a natural distance between them and from my listening perspective. This is all with the stock tubes. Using my NOS 6922's and 5998 output tubes steps everything up a notch but I could be very happy with the stock tubes.

John

I have been listening all day with great pleasure as I work at home. I have a IBM 5998 (I think Tungsol made it but I am not sure) and the sound is really fine. The 5998 has more gain than the 6080 but is just a little more magical.

John

Well I have made a bit of a circuit change and the enhancement to the sound quality is worthwhile.

In my dac I use a 6DJ8 type (6BZ7) per channel that is paralleled. I do not plan on using the Woo 3 as a preamp and I don't really care for the 6DJ8 as the only tube for a preamp as the output impedance will be high without some means of lowering it. So I paralleled each 6DJ8, which doubles the current, reduces the Miller effect and possibly increase the high frequency response.

Well with the 5998, which I definitely prefer to others, the sound is more open and what I have been looking for. With headphones and the slightest amount of heaviness or "in your head" sound the fun for me is gone. Somehow this clears most all of that up. There is a transparency and drive that changes the character of the amp, for me, way to the positive.

This change only requires that you drop the cathode resistor on pin three and tie pin 3 to pin 8. You then drop the B+ going to pin 1 and tie pin 1 to pin 6. The grids pin 2 and 7 are already tied together. On pin 2 there is a .22uF cap to the output for the preamp section. As long as the preamp section (rca’s) is not used you could leave it in place.

Photos are nice but if you draw out the pin schematic from Duncan’s Tube page you will have a better guide and understanding.

I sometimes listen to my speaker system and the headphones, to compare sound. A while ago, as the speakers add a bit more of dimension, I thought they were influencing the staging quite a bit so I turned the speakers down and it was the headphones that had the dimension. I have not heard staging to this extent before on the headphones.

The level of detail and musicality are mesmerizing

John

The 421A is on its way. I do have a 5998 that is perfectly matched so I am not sure how much difference there will be. I am not sure if WE made all of their 421A;s but they are supposed to have made all of their tubes but the 421A looks just like a Tungsol, down to the same mica shape and placement. I hope they did make it as the testing and materials are normally the very best.

John