Archon 25 - Very Low Clean Volume, Noisy Lead

[Bergtown]

Hello forum! This is my first post so by way of brief introduction on my association with PRS, I currently have an S2 Vela semi-hollow, and an S2 Standard 22. Regarding the subject of this post, I recently purchased a PRS Archon 25. I had played it a couple of times in the shop and fell in love. Both channels worked as expected. After a couple of days at home I noticed that the lead channel had gotten very noisy and very loud with a constant hiss, while the clean channel had lost most of its volume. I can turn clean up to basically max and it's nowhere near as loud as it should be, while the lead is super loud and sensitive to changes

I pulled all the tubes out and inspected and re-socketed them with no change. Swapped the preamp and power tubes around with no change. I don't have a spare 12ax7 but do have a 5751, so swapped that in and out of the 4 preamp locations as well s phase inverter with no change. I visually inspected the sockets which don't have any obvious issues. I noticed that the impedance switch was set to 4 ohms, switched that to 16 with no change. I'm not sure if the switch comes into play when only one speaker is plugged in, the jacks aren't labelled internal and external, so I fear it does and maybe I've inadvertently massacred the output transformer. I don't know whether that switch was set properly in the shop, don't remember looking at it. The amp seemed fine in the shop, and I turned it up loud to make sure it worked correctly.

TLDR: symptoms are very loud noisy lead channel and dramatically low-volume clean channel. Speaker impedance switch was on 4 ohms instead of 16 with internal (factory) 16 ohm speaker. Any initial thoughts?

 

[DreamTheaterRules]

I think you have to buy at least new power tubes and a couple preamp tubes (if not all of them) so you can swap and make sure it's not just tubes. Have you looked for visual clues of a tube issue?

 

[Bergtown]

I think you have to buy at least new power tubes and a couple preamp tubes (if not all of them) so you can swap and make sure it's not just tubes. Have you looked for visual clues of a tube issue?

From visual inspection nothing stands out. All the preamp tubes glow orange as expected, and the power tubes have a blue glow, not crazy red. The 5881s are Tung Sol, unsure if they are original. The V1 tube is a psvane, almost certainly a replacement. The other three preamp are JJs as is the effects loop, while the phase inverter is a Tung Sol. I did swap what I believe is a known good 5751 around the 12ax7 sockets with no change. I should have thought to swap in the 6L6s from my Tremolux, I shall try that.

 

[Bergtown]

I pulled the 6L6s and 3 12ax7s from the Tremolux and first swapped the power tubes into the Archon. No change. Swapped the 5881s back in and put the Tremolux's 12ax7s into the three gain sockets in the Archon and started swapping the remaining tubes between the input, phase and loop sockets. No change. It doesn't seem like it's any of the tubes, but I guess without getting a full new set I don't absolutely know. None are microphonic so far as I can tell. Wiggling them in their sockets doesn't produce any noises.

With the volume and master knobs all at 9 o'clock and everything else at noon, the clean channel is very low volume, plus a quiet 60 cycle hum. The lead channel is many times louder at the same settings with a lot of distortion and noise. The noise is like what someone else described as a waterfall, not completely even all the time, little subtle changes. I can turn up the clean channel almost all the way without it being painfully loud sitting next to the speaker. The gain channel starts loud and gets crazy louder crazy fast. The half/full power switch seems to work normally.

So I guess I'm back to wondering about the impedance switch and if having it at 4 ohms on the 16 ohm speaker for an extended period of time could have hurt the transformer or something else. Or if something just coincidentally got shorted. Switching the impedance from 16 to 8 to 4 and back doesn't change the sound or volume appreciably, don't know if that's significant. The vast difference in channel volume seems significant but I can't find anything in searches.

 

[Bergtown]

Confusing update: I plugged the guitar into the loop return jack to see how that sounded, and it was clean and got very loud. I decided I should try the 5881s in the Tremolux to see how they worked there, but since I'd already powered the Archon on I switched the speaker plug to the other jack on a whim, and now the waterfall on the lead channel is gone. It's still hella louder than the clean channel at same settings, but now I'm wondering if that's just how this amp is. I swapped the speaker back to the original jack and it still sounds fine. I don't get it.

Before I touch anything else, can anyone with an Archon 25 confirm if the lead channel is significantly louder than the clean at similar settings?

 

[Bergtown]

I guess I will end what is essentially a blog at this point by saying based on web searches some people do seem to find a substantial difference in clean vs lead channel, others think it shouldn't be a dramatic difference. Given that I've bolted the amp back into its cabinet and it is still otherwise behaving normally I'm going to assume this is normal behavior for the moment and keep playing it. I'll order a new fleet of 12ax7s since some have been replaced but likely not all, and the power tubes seem fine. I have to assume I did something to cause this, maybe moving it temporarily exposed a weak point somewhere in the circuits, or maybe one of the sockets has a loose connection and eventually moving the tubes around tightened it up enough to work? Dunno. Will continue to bother me but I'm going to enjoy it as it is for now.

Thanks @DreamTheaterRules for gently pushing me to do the simple tests with the tubes. I was definitely leaping to a more complex issue before ruling out the simple things.

 

[DreamTheaterRules]

IMO, not fair to say they are mismatched or unbalanced or whatever, due to differences in volume level at the same master setting. First, the Archon is a high gain amp so it’s gain channel has a lot of gain very early on the gain control. Second, the clean channel is almost completely clean through the whole sweep of the master. This means, that with the gain control at say noon, and the master at 10:00 (where the gain channel is already LOUD) the clean channel won’t be nearly as loud… but it’s so low in it’s sweep that there is WAY more volume available. Hit it with a boost or OD and it will easily be as loud as the gain channel.

 

[Bergtown]

IMO, not fair to say they are mismatched or unbalanced or whatever, due to differences in volume level at the same master setting. First, the Archon is a high gain amp so it’s gain channel has a lot of gain very early on the gain control. Second, the clean channel is almost completely clean through the whole sweep of the master. This means, that with the gain control at say noon, and the master at 10:00 (where the gain channel is already LOUD) the clean channel won’t be nearly as loud… but it’s so low in it’s sweep that there is WAY more volume available. Hit it with a boost or OD and it will easily be as loud as the gain channel.

Thanks very much for the explanation, makes sense.

 

[Dennyz]

Suscribed.