It can be pushed and handle itself very well gadget thanks. Any tips on caps of any particular brand that you may have noticed a dif in ? Just a passing question beings you have one of the amps yourself. Hefty is one way to also describe them. And gold of course.I believe the reciever Pilot was a 602 too beat today to dig at stuff right now. Wish I knew someone in Maryland who has done lots of work on Fisher Amps they are also very hefty and well built amps. Good thread.
Pilot SA-232...Can it rock?
- Thread starter MadcapLaughs
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MadcapLaughs
Active Member
Well it’s been a little while but just thought I’d add a photo of the pilot, it’s honestly really amazing overall, the “curtain of sound” really is accurate, it’s just a wall of beautiful midrange thrown at you. Not scientific, but you get the idea. Haven’t played much metal yet, just enjoying some Merle haggard and stones right now. It’s got the Mullard el84 quad and some Raytheon 12ax7s for the phase splitters. I might sub in my teles in those spots soon.
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For what it’s worth, I have a recapped Pilot 240 which is an EL84 amp with ~15 WPC. I’m running them into a pair of Klipsch Heresys which are 96db efficient. I have no problem getting super loud rock music out of the amp with no clipping that I can hear. Very clear and tight. Love this amp.
I actually don't have a 232, I have an SA-260. Mine has the blue Arco film caps it came to me with. They aren't original, best guess is they were installed in the 70s or 80s, but thats all I know about them. The only caps I changed in it were the ones between the input jacks and the first tube. It had some orange caps I didn't like the sound of, swapped for old Soviet PIO caps and it got a lot better. My usual go-to are Illinois MPW caps. They're cheap, reliable, and sound fine to me.
talk to @larryderouin if you want to know a guy in Maryland who knows Fisher gear.
MadcapLaughs
Active Member
Ive been digging through old pilot threads for the 232, it sounds like the normal terminals for hooking up the speakers are counter intuitive for this amp, they should be reversed in their polarity because apparently the 232 and its matching preamp have a weird phase inversion that only corrects when matched together. So if you are using a different preamp you need to hook up the leads to the opposite polarity. (black goes to positive and red to negative on the back of the 232).
Does that make any sense to you all? Am i needlessly complicating things? Is this BS? right now i have them hooked up to their conventional terminals but am now thinking the stereo image may be more correct if i swap them as i stated above. Not really noticing any issues as is though.
MadcapLaughs
Active Member
Cool ill give it a shot and let you all know if theres an audible difference. Heres the underside of my 232, it appears the previous owner used orange drop capacitors. I'm sure i can make some more upgrades to really hot rod this amp, ill have to look into it more, but as it stands the sound is perfect.
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I'd get rid of that wax capacitor top center. Not sure what its doing, but its probably not doing it very well anymore. The two silver caps that look to be floating in space with a long wire attached to them also might be questionable. Don't know what they are, but at a minimum I'd prefer to see them attached to something so they can't move around.
I rebuilt this SA-232 ground up, a couple years ago. It was pretty well baked when I found it in a console. Using a matched quad of Sovtek EL84M,s.
Does it rock, absolutely. I recently rolled some speakers on it and it performed well on all of them. JBL L36, Dynaco A-10, Altec 601C, and B&O R60.2s.
This was a very helpful thread I want to thank all who contributited to it and I mean it. I will follow the instructions and may ask you guys some more questions. Not blowing smoke this really helped me out. The follow up to suggestions got me hyped about the projects. Just so everyone knows. Reminds me of the 60'a if you were into it we stuck together and helped each other out. Music is the blookdline of my life pure. Jezz think I went too far but I dont care music means that much to me.
Blues
Blues
MadcapLaughs
Active Member
Well I noticed an issue with the amp! Didn’t take long, I have a red plating tube, swapped its position and it followed with that particular tube. I am not noticing any noise or functional issues, just that slight plate glow. I ordered a single Mullard el84 today as this amp came with real vintage Mullards, hopefully it’s 9/15 rating will serve me for a while until I can test all of them as a quad and see what the lifespan is.
Can anyone confirm if this amp has a fixed non adjustable bias? I was thinking it was as an el84 amp, you basically just plug in your el84s and are set to go? Or does it require a manual bias recalibration any time you insert a new power tube?
also, should I avoid playing the amp with the tube in that kind of shape until the new one arrives? It sounds so nice as is but I don’t want to risk taking out a transformer or something
Can anyone confirm if this amp has a fixed non adjustable bias? I was thinking it was as an el84 amp, you basically just plug in your el84s and are set to go? Or does it require a manual bias recalibration any time you insert a new power tube?
also, should I avoid playing the amp with the tube in that kind of shape until the new one arrives? It sounds so nice as is but I don’t want to risk taking out a transformer or something
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It is really important to have a closely matched quad. I use Mcshane,s EL84M,s. (No affliation) No problems afterwards. You can chase your tail trying to match up 4. It is a great tube and very reasonable priced.
Years ago I used my Pilot SA-232 to drive a pair of Altec 604-8G speakers. That setup could rock loud and proud. 
FlaCharlie
Super Member
The term "fixed bias" often confuses people because it actually refers to a bias system that is adjustable. Think of it as saying that you can "fix" or set the bias where you want to.
This amp uses cathode bias, which consists of a resistor and a cathode bypass cap. In this case, each channel has its own cathode resistor and cap combo. Because each channel is biased separately, you only need two matched pairs of output tubes not a matched quad. There is no adjustment with cathode bias.
Although most EL84 amps use cathode bias, not all do. So the use of a particular tube type doesn't have anything to do with the bias method.
Ideally, you should use a matched pair of tubes in each channel. The use of unmatched tubes typically won't damage anything but a matched pair (or quad, depending on the bias scheme) will function better.
Don't use the amp with a red plating tube.
except when it isn't
I've had several non-adjustable fixed bias amps. I've also seen cathode bias amps that are adjustable This particular one happens to be non-adjustable cathode bias though, which is the most common cathode bias setup.
FlaCharlie
Super Member
Yes, there are always exceptions. I guess I should have added "typically".
I've used battery grid bias on tubes, which is non-adjustable fixed bias. Did this in the 1626 "Boogie Factor" Preamp I recently posted about. And, although I've never done it, putting a pot or a variable resistor in a cathode bias circuit will make it adjustable.
I was trying not to confuse him so I over-simplified a bit.
I've used battery grid bias on tubes, which is non-adjustable fixed bias. Did this in the 1626 "Boogie Factor" Preamp I recently posted about. And, although I've never done it, putting a pot or a variable resistor in a cathode bias circuit will make it adjustable.
I was trying not to confuse him so I over-simplified a bit.
MadcapLaughs
Active Member
So checking back in here. I had some red-platting issues that I thought were related to the old el84s in this amp, but my tech checked everything over and re-tensioned the sockets, checked the bias and all good since then. I now have a new quad of tube amp doctor brand el84s. I’ll be hunting for vintage EL84s now. (I should know better than to throw around words carelessly on audiokarma, I knew these were cathode bias amps)...anyways I love the little pilot, it’s running full time duty on the Altec boleros. This is about the best combination I have heard with all the gear that’s made it’s way in an out of my home over the years (including accuphase, Sansui AU series, fisher, scott etc). Seriously awesome midrange, but it also was surprisingly able to push my inefficient Polk monitor 10s to loud, undistorted levels in my descent sized living room. Ride the lighting never sounded better, but maybe Polks aren’t the perfect match. Now I find I’m playing Donovan, Jefferson Airplane and, mingus on the altecs. It really works best. Cheers!
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problem with cathode bias amps is that if the tubes aren't reasonably matched, it is possible to have one red plate without anything actually being wrong. One tube that biases considerably hotter than the others can just run away with itself. This one does want 2 pairs (or a quad is fine) for best performance. 4 randoms may not work out so well.
Need some Frankie Yankovic or even some of Wierd Al's polkas for those Polk speakers to perform at peak.
Need some Frankie Yankovic or even some of Wierd Al's polkas for those Polk speakers to perform at peak.