[HiGHFLYiN9]

Sweet! Welcome to the Woo club Earl.

KZEE had told me that Wei had removed the input caps at his request based on what John had said here on this thread and he was pleased with the result, so I guess he'll be omiting them indefinently now, which is definently a good thing. Now I know there are a few more Wimas lurking in the Woo, two of which are closest to the center and two are attached to the preamp RCA outputs. What are the purposes of those caps and would they be better off being replaced or removed? Also were you able to determine the values of the ones in the center? One more question

... I'm trying to figure out which side is positive on the grey photoflash caps as it doesn't look like it's printed on them, might you be able to enlighten me on how to obtain that info? Thanks John.

 

[jamato8]

The side going to ground is the negative. The wima caps for the preamp are the decoupling caps for the output and need to be there. I think there are a couple of wimas for bypass of the B+ cap for the driver tube and there is a Wima as a bypass for the output cap (decoupling signal cap, the Wima is a .22uF), which allows for better high frequency response as the .22 tends to pass the higher frequencies better. With my Black Gates I do not use a bypass as they tend to be better if left alone. Bypass caps for the B+ tend to be better if kept down in the .01uF range as the high frequency riding on the B+ is best shunted to ground by a .01 (the purpose of the bypass cap in the B+). The higher you go, .1 or more, will start messing the frequency of the B+ and degrage the sound quality. Music is AC and rides on the DC voltage until it hits a capacitor in the signal path. A cap cannot pass DC but can pass AC (the musical signal). But if you have the DC corrupted with junk then that can in turn affect the AC musical signal. This is why I treat the B+ DC electric as good as I would the signal route, because it IS part of the signal.

The center caps you refer to are the decoupling caps for the preamp. They are 2.2uF. They need to be at least this large or the bass will suffer. I would go with 3 or 4uF since you are using one half of the 6DJ8 as preamp and this and you are going to have a pretty high output impredence. The higher uF cap will give you improved bass. Yes, a better cap would be good here but I would listen to it as a preamp and see how you like it first. If you like the premap section then I would go with something like a Mundorf Silver Supreme or a couple of other well thought of signal caps.

John

 

[HiGHFLYiN9]

Thanks for your thoughts John, they are most helpful. I actually don't plan on ever using the Woo as a preamp so I don't think I'll upgrade those center Wimas. Another question that I have is in regards to the four grey photoflash caps, are two of them for the pre-amp section of the amp or are all four of them used for the headphone section. I made a reference pic so people could see what we are talking about. I'm referring to A,B,F and G. I've already replaced the Elnas (C and D) with BGs and I know that it's pointless to replace that big brown one (E) as it's just for noise filtering. Those center Wimas I was asking about earlier are the ones closest to the Elnas.

 

[jamato8]

Quote:

Thanks for your thoughts John, they are most helpful. I actually don't plan on ever using the Woo as a preamp so I don't think I'll upgrade those center Wimas. Another question that I have is in regards to the four grey photoflash caps, are two of them for the pre-amp section of the amp or are all four of them used for the headphone section. I made a reference pic so people could see what we are talking about. I'm referring to A,B,F and G. I've already replaced the Elnas (C and D) with BGs and I know that it's pointless to replace that big brown one (E) as it's just for noise filtering. Those center Wimas I was asking about earlier are the ones closest to the Elnas.

The caps closest to the Elnas are the bypass caps for the signal going out to the headphones (they are paralleled with the Elnas). I would use better caps or try it without them. The other caps you refer to are for the headphone B+. The brown cap is used to smooth the AC after being rectified to get rid of the ripple. This ripple (AC left on the DC after rectification) is further reduced by the voltage dropping resistor. What you have is a CRC then CRC to the driver tube (C capacitor R resistor). This gets the ripple down very nice and gets you a nice clean B+. There is a bit more going on but that is the jist of it. The brown cap could be replaced with a Black Gate but at an expense. All caps are important. I would like to replace the photo flash with Black Gates but right now I don't want to spend the money and photo flash caps are normally pretty good in the application.

John

 

[HiGHFLYiN9]

Quote:

Originally Posted by jamato8 The caps closest to the Elnas are the bypass caps for the signal going out to the headphones (they are paralleled with the Elnas). I would use better caps or try it without them.

Do you happen to know that value of these John?

 

[jamato8]

Those are .56uF but that is not something set in stone. You could go anywhere from .1 to .56uF. It is up to your ear and what you may or may not hear. I often use a .1 or .22, which is where these will work for the frequency desired. Now capacitors have different esr (the series resistance of the cap) and so this can sometimes can mess with the sound. Some people like to bypass and some prefer not to mess with the frequency spectrum. Finding the right combination can take time but in general a good quality cap can work fine. I have a Syncore capacitor analyzer (an expensive toy) and I can measure esr. When Black Gate non polar are paralleled I get almost no esr. There is an inner and outer foil to caps. When you use two nonpolar caps and parallel them with the inner foil of one connected to the outer of the other and the other innner and outer connect, so the cap is paralleled, you have what is referred to as a "Super E" configuration with the least inductance and esr that you can obtain with said capacitor (this is what I do). With this you get the best AC music signal transfer.

John

 

[Rendell]

I hooked it up plugged in the headset and was working fine -- turned off and changed to an other headset and left channel was missing -- put other set back iand still no left channel -- Seems the connector for the headphone is dropping the left channel -- Can wiggle and get channel to come and off but will not stay on. This is sad since unit is only 4 hours old. Was wondering if this would be an easy fix or best to just send it back --

 

[HiGHFLYiN9]

Thanks John for sharing your knowledge with us, I feel like I'm learning a lot

I actually have a pair of Cardas Golden Ratio .47uf 600V coupling caps that I ordered for my Singlepower but Mikhail said he thought PIOs sound better in his amp, so I have these caps and nothing to do with them. I think I'll use them to replace those Wimas. IIRC with film caps the negative is on the right side and the positive on the left?

 

[HiGHFLYiN9]

Quote:

Originally Posted by Rendell I hooked it up plugged in the headset and was working fine -- turned off and changed to an other headset and left channel was missing -- put other set back iand still no left channel -- Seems the connector for the headphone is dropping the left channel -- Can wiggle and get channel to come and off but will not stay on. This is sad since unit is only 4 hours old. Was wondering if this would be an easy fix or best to just send it back --

Ahh! that sucks!

Shipping that amp back and forth could get expensive quickly. I'm not sure which type of 1/4" female Wei usually uses but if it's not encased I would think you would be able to bend it back into place, it should be the conductor farthest back if it's the left channel. Just be careful not to short it on one of the other channels. Also remember you are working with tube equipment and those caps retain their charge for a long time after you unplug the unit, if you are not comfortable with this I would not recommend you open it up as you could damage the unit or zap yourself

 

[Rendell]

How long to they hold charge normaly?

 

[jamato8]

There is a resistor to ground so the caps discharge after a minute or so. It very simple to fix but you have to open the bottom of the amp after disconnecting the power cord. It sounds like either a wire is loose or the contacts just need a bit of tweaking. It would be a shame to send it back and if you were near by I would be happy to fix it.

John

 

[KZEE]

Hey thanks for the reference photo Highflyer, and thanks for continuing to educate us and share your mods with us John.
My Woo continues to open up and sound better as I get more hours on it, and my only complaint about the sound is that there's some glare present. I've been informed that the 6922 input tubes are probably the cause of the glare, and I've ordered up some different tubes to roll into the amp to see if it will help the situation.
Just a quick note - if you order your WA3 without the preamp circuitry like I did, then Woo will wire the input tubes in parallel when building the amp.

 

[jamato8]

I emailed him about paralleling the tubes some time back. He never responded but it looks like he tried it out. I am glad he will do this.

Tube glare can be a problem easily solved with different tubes. The beauty of using tubes is that you have so many choices.

John

 

[rodentmacbeastie]

Your chatter is like a desert oasis and I am thirsty! John, I beg of you, please draw me a schematic. It can be ugly, I don't care, but us electronics idiots love beautiful sound too. Throw me a bone here man. I will even thank you everytime I fire it up. Over and out.

 

[Rendell]

Well I opened it up and played with the connector leads

- checked connections -- everthing looks good -

- repositioned the wires going to connector to releave so pressure to the connection. Put cover on and fired it up -- seems to be work ok -

- So looks like bad headphone jack -- it a closed type so will need to replace it if happens again --

Thanks for the suggestions...