[Promee]

Alright! Mod complete! Just a couple pics:

Prepping the patient:

Operation complete:

It is sounding awesome! To be fair it sounded awesome before, but I think it made the 2 exact subtle improvements I wanted. Of course it is entirely possible that it is placebo effect, but I think there is a significant improvement of bass control and the authority with which it is delivered to my low impedance Focal Clear OG’s. The second, and more subtle improvement I have noticed is a very slight reduction in top end hash. Finally, the power tubes I’m using (NOS Svetlana “Winged C” 6H13C) have a very low hum when music is paused, but unexpectedly the hum itself feels like it somehow moved farther out to the sides and forward in the soundstage - I haven’t noticed a difference in staging of the music. Overall, I’m very happy with the upgrade, and I don’t foresee going back to do the resistors, as it sounds pretty much exactly as I had hoped at this point. From here on, I’m going to focus on enjoying the music and rolling some tubes for a while

 

[skhan007]

Alright! Mod complete! Just a couple pics:

Prepping the patient:



Operation complete:



I don’t foresee going back to do the resistors, as it sounds pretty much exactly as I had hoped at this point.

You only changed the two capacitors on each of the power tubes and not resistors, correct? You mentioned resistors, so just clarifying. Changing resistors and effecting current/voltage would be (possibly) unsafe for the tubes and amp circuit. Is there a mod for resistors for this amp?

 

[Promee]

You only changed the two capacitors on each of the power tubes and not resistors, correct? You mentioned resistors, so just clarifying. Changing resistors and effecting current/voltage would be (possibly) unsafe for the tubes and amp circuit. Is there a mod for resistors for this amp?

That’s correct, I ended up just changing the coupling capacitors between the driver and power tubes. I was asking about the resistors because I had seen another set of pics in this thread from several years ago where it looks like several of the resistors were replaced with Mills resistors, so I was curious if anyone had advice on whether to do replace those. From the pics that had been posted, it looked like he had replaced them with resistors of equivalent spec, so I would guess that it is safe, but it looked like it would be a bit tricky to fit them in, and I’m just not sure what if any benefits there would be to replacing those specific resistors. It appears to me that there aren’t really any resistors in the signal path, though I’m no electrical engineer, and I wouldn’t be surprised if someone told me those could have an effect on sound or technically are in the signal path. It just didn’t seem like it would be worth the work, potential for damage, and the wonky fit for what I’m guessing would be an extremely marginal improvement. I think the capacitor replacement already almost falls into that category, but I’m very glad I did it. This really sounds like my dream headphone amp now

The mod with the resistors was on page 29 of this thread. Looks like it is a second gen WA22 with the phase splitters, but an earlier revision of the board. Other mods I have seen online (I’ve only been able to find a couple) only replaced capacitors, though one, I believe on the first gen, was truly wild - the person had replaced all of the capacitors on the board including all of the electrolytics with foil caps - it was a bit of a wiring mess, and I can‘t imagine that improved things much (maybe even the opposite), but I respect the obsession and the hustle! I will attempt to paste a link to the one with the Mills resistors: https://www.head-fi.org/threads/woo-audio-wa22-amp-owner-unite.826386/page-29

 

[Blackrao]

Got to check out the WA22 and was quite impressed with its tube sound!

 

[u2u2]

Got to check out the WA22 and was quite impressed with its tube sound!

Generally a nice video and Woo makes solid well performing kit. I may be alone in this view but I think a brand is cheapened by going the route of providing gear to you tube influencers for reviews... To be honest, had he discussed the fact it was Woo provided on loan for his review at the beginning of the video, rather than the end, I may not have watched it. Well, I may have continued to watch for comments on the tubes themselves, or tube rolling, but the video was a little thin on these topics. Back to music interspersed with you tubes on my WA22. Enjoying Buddy Guy and The Blue Don't Lie thanks to another thread on Head-Fi! Stellia on SE cause my 22 don't hiss.
Got some 1943 USN National Union 6SN7GT to roll in with a 1958 Valvo GZ34 and several variations of GEC 6080 to pick from for power... Big winter storm descending on this area today so the Woo will help keep things warm and pleasant.

 

[Contrails]

That’s correct, I ended up just changing the coupling capacitors between the driver and power tubes. I was asking about the resistors because I had seen another set of pics in this thread from several years ago where it looks like several of the resistors were replaced with Mills resistors, so I was curious if anyone had advice on whether to do replace those. From the pics that had been posted, it looked like he had replaced them with resistors of equivalent spec, so I would guess that it is safe, but it looked like it would be a bit tricky to fit them in, and I’m just not sure what if any benefits there would be to replacing those specific resistors. It appears to me that there aren’t really any resistors in the signal path, though I’m no electrical engineer, and I wouldn’t be surprised if someone told me those could have an effect on sound or technically are in the signal path. It just didn’t seem like it would be worth the work, potential for damage, and the wonky fit for what I’m guessing would be an extremely marginal improvement. I think the capacitor replacement already almost falls into that category, but I’m very glad I did it. This really sounds like my dream headphone amp now

The mod with the resistors was on page 29 of this thread. Looks like it is a second gen WA22 with the phase splitters, but an earlier revision of the board. Other mods I have seen online (I’ve only been able to find a couple) only replaced capacitors, though one, I believe on the first gen, was truly wild - the person had replaced all of the capacitors on the board including all of the electrolytics with foil caps - it was a bit of a wiring mess, and I can‘t imagine that improved things much (maybe even the opposite), but I respect the obsession and the hustle! I will attempt to paste a link to the one with the Mills resistors: https://www.head-fi.org/threads/woo-audio-wa22-amp-owner-unite.826386/page-29

If you referring to my post, they are Caddock resistors. Not that I could tell the difference between Mills and Caddock. But they were recommended by Glenn. A renowned HF member who built some amazing amps. I almost sent my WA22 to him to change to Lundahl transformers but the cost associated made the whole idea seem like a waste. I was living in New Zealand at that time.

 

[skhan007]

Need help please!!

My WA22 won't turn on. There was a spark from somewhere towards the back and now it won't power up. Does anyone know where the fuse is located? I took off the under panel and don't see one. I'm totally stressed.

 

[VanHai]

Need help please!!

My WA22 won't turn on. There was a spark from somewhere towards the back and now it won't power up. Does anyone know where the fuse is located? I took off the under panel and don't see one. I'm totally stressed.

It is right under the power plugin, you will see a small rectangle. Use a flat screwdriver pops it open and replace the fuse .

 

[skhan007]

Thank you!! do you know where I can locally find a 3.1 5A fuse? I really hope there was no other damage to tubes or anything else.

It is right under the power plugin, you will see a small rectangle. Use a flat screwdriver pops it open and replace the fuse .

 

[skhan007]

Wow, I just noticed that Woo includes a spare fuse directly below the fuse that is in use. I put the new fuse in and it's working.

I have no idea what caused the fuse to go in the first place, so still somewhat nervous. I put the stock tubes in to test drive and it's working for now.

 

[Promee]

If you referring to my post, they are Caddock resistors. Not that I could tell the difference between Mills and Caddock. But they were recommended by Glenn. A renowned HF member who built some amazing amps. I almost sent my WA22 to him to change to Lundahl transformers but the cost associated made the whole idea seem like a waste. I was living in New Zealand at that time.

Thanks for weighing in! It sounds like Glenn knows quite a bit about amps, so I would definitely defer to his opinion on whether it can impact sound. I think it would be tricky to get those resistors into the spots where you have them, so I would be curious to know how significant the change to sound is there because the benefit would need to be pretty high to take the risk and hassle of dropping them in. If you have thoughts on that or if Glenn would want to weigh in, I’d love to hear them!

 

[Promee]

Wow, I just noticed that Woo includes a spare fuse directly below the fuse that is in use. I put the new fuse in and it's working.

I have no idea what caused the fuse to go in the first place, so still somewhat nervous. I put the stock tubes in to test drive and it's working for now.

Just to have some around, here is a pack I ordered and can confirm work.

10Pcs T3.15AL250V 5x20mm 3.15A... https://www.amazon.com/dp/B078QB3538?ref=ppx_pop_mob_ap_share

Thoughts on what happened - if this turns out to be a 1 off, then I wouldn’t worry much about it. If you put the other set of tubes back in and it happens again, I would start by going back to the stock tubes and replacing each stage separately with your aftermarket tubes and letting them run for a few hours of listening at each point to see if you can narrow down which tube is causing it. Unfortunately with slow blow fuses, if one of the tubes is causing a very small but repetitive surge it makes it harder to find the source, but IMO running fast blow fuses is even more frustrating because they can just randomly go even if everything is fine. The good news is that with the slow blow if it takes a long time for it to go out (several hours of listening) I think that means that none of your tubes / other parts are in really bad shape. If you have a tube that is totally wrecked, it will blow even a slow blow fuse almost immediately on startup. I had that happen with a LinLai KT-88 in my main stereo amp that was ultimately confirmed faulty by Grant Fidelity and replaced.

Of course if you are looking into why this happened now, the most recently changed tubes are the most likely culprits. Alternatively, this could happen from a major static electricity discharge, particularly in winter. Finally, it could also happen with changing headphones or input connections while the amp is on. Woo Audio says volume has to be a 0 if changing headphones while powered on. I have blown fuses in other devices by doing each of the above things, so on some level, I think it comes with the territory, and no need to stress too much, because that’s what the fuse is there for, it’s the weak link that should go out before you are able to fry anything else.

These days, any time I get a new audio toy with a fuse, I just get a pack of replacements right away, because eventually you’ll probably have to replace one and nothing is more annoying and somewhat stressful than to see it sitting there while you wait for one to come in… Also, depending on the type and size, you can sometimes get them at Lowe’s or Home Depot, but definitely check on their website / app before heading over to make sure they have what you want in stock. Of course, my experience is limited, so take with a grain of salt, and if anyone feels like I’ve got any of this wrong, please let me know so I don’t lead myself or anyone else to destroy expensive gear!

 

[skhan007]

Just to have some around, here is a pack I ordered and can confirm work.

10Pcs T3.15AL250V 5x20mm 3.15A... https://www.amazon.com/dp/B078QB3538?ref=ppx_pop_mob_ap_share

Thoughts on what happened - if this turns out to be a 1 off, then I wouldn’t worry much about it. If you put the other set of tubes back in and it happens again, I would start by going back to the stock tubes and replacing each stage separately with your aftermarket tubes and letting them run for a few hours of listening at each point to see if you can narrow down which tube is causing it. Unfortunately with slow blow fuses, if one of the tubes is causing a very small but repetitive surge it makes it harder to find the source, but IMO running fast blow fuses is even more frustrating because they can just randomly go even if everything is fine. The good news is that with the slow blow if it takes a long time for it to go out (several hours of listening) I think that means that none of your tubes / other parts are in really bad shape. If you have a tube that is totally wrecked, it will blow even a slow blow fuse almost immediately on startup. I had that happen with a LinLai KT-88 in my main stereo amp that was ultimately confirmed faulty by Grant Fidelity and replaced.

Of course if you are looking into why this happened now, the most recently changed tubes are the most likely culprits. Alternatively, this could happen from a major static electricity discharge, particularly in winter. Finally, it could also happen with changing headphones or input connections while the amp is on. Woo Audio says volume has to be a 0 if changing headphones while powered on. I have blown fuses in other devices by doing each of the above things, so on some level, I think it comes with the territory, and no need to stress too much, because that’s what the fuse is there for, it’s the weak link that should go out before you are able to fry anything else.

These days, any time I get a new audio toy with a fuse, I just get a pack of replacements right away, because eventually you’ll probably have to replace one and nothing is more annoying and somewhat stressful than to see it sitting there while you wait for one to come in… Also, depending on the type and size, you can sometimes get them at Lowe’s or Home Depot, but definitely check on their website / app before heading over to make sure they have what you want in stock. Of course, my experience is limited, so take with a grain of salt, and if anyone feels like I’ve got any of this wrong, please let me know so I don’t lead myself or anyone else to destroy expensive gear!

Thank you!! Fuses ordered from Amazon. I’m really glad Woo provided a spare. Your response was very reassuring, so I really appreciate it.

I ran the amp with the stock tubes for a while (about an hour) and powered off and put back the NOS power and driver tubes. I left the stock tube rectifier and listened for another 30 minutes or so and it worked fine. I’ll try swapping in the NOS rectifier at some point.

 

[CAJames]

Need help please!!

My WA22 won't turn on. There was a spark from somewhere towards the back and now it won't power up...

My first thought is the rectifier arcing. I'd be inclined to give it a decent burial and move on if your amp is OK with the stock rectifier but if you insist on trying the old one I wouldn't put it back in until you have your spare fuses. It's possible if you put it back in it will work fine... for a while. But IMO once a rectifier arcs it is done.

 

[Contrails]

Thanks for weighing in! It sounds like Glenn knows quite a bit about amps, so I would definitely defer to his opinion on whether it can impact sound. I think it would be tricky to get those resistors into the spots where you have them, so I would be curious to know how significant the change to sound is there because the benefit would need to be pretty high to take the risk and hassle of dropping them in. If you have thoughts on that or if Glenn would want to weigh in, I’d love to hear them!

We would all love to hear from Glenn. But sadly, he has been away from the website for more than a year due to his health. I follow the Glenn amp thread from time to time and I may fear the worse.

I took the amp to a local valve amp repairman and he managed to fit it all in there. The guy had also worked on Pink Floyd’s equipment when they were touring NZ (back in the good old days). He charged me $50 NZD for the whole job.