Altec 1567A buzz.....ideas?
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David Kulka
Well-known member
Maybe try it at reduced voltage on a variac?
In my experience Altec gear is really bad news in the hum and buzz department. I often end up jumping through various hoops to get the noise down. I think they were inconstant in their grounding schemes. In some cases I've had good success with rewiring to achieve a star ground. Good luck with the beast.
In my experience Altec gear is really bad news in the hum and buzz department. I often end up jumping through various hoops to get the noise down. I think they were inconstant in their grounding schemes. In some cases I've had good success with rewiring to achieve a star ground. Good luck with the beast.
Bill's answer makes a lot of sense, given the lack of rhyme or reason as to who gets a usable one and who suffers with incurable hum/buzz. Line voltage levels vary from location to location and even building to building. And they are uniformly higher than they were when these things were designed/sold. I've been watching this thread angrily and that's the only answer that makes sense to me.
Actually, nominal AC line voltage in Japan is 100 VAC 60 Hz.
Brian Roth
Well-known member
Japan has two grids, one running at 60 Hz and the other at 50 Hz,
https://en.wikipedia.org/wiki/Energy_in_Japan#National_grid
Bri
https://en.wikipedia.org/wiki/Energy_in_Japan#National_grid
Bri
rock soderstrom
Tour de France
Interesting, I didn't know that. A good example of what consequences a lack of harmonization can have.
No difference at lower AC input voltage.
Winston OBoogie
Well-known member
Hey Doug,
dropping in to give moral support and see how it's going. I saw your last post 2 weeks ago but obvs. didn't have the fortitude or fibre to reply. Just wish you'd have found something that'd shut the damn things up.
Other than that, I've got nothing for ya
dropping in to give moral support and see how it's going. I saw your last post 2 weeks ago but obvs. didn't have the fortitude or fibre to reply. Just wish you'd have found something that'd shut the damn things up.
Other than that, I've got nothing for ya
Carlsoti
Member
Doug, did you ever find a solution to the noise issue you were experiencing?
No and I never want to see one of these turds again. I tried everything recommended anywhere, outside of a complete teardown. I suspect replacement power transformers might be a start, nothing else made any sort of appreciable dent at all. No one makes a replacement that I've found, and....well....don't get me started.......external PSU would do it......maybe.....
These things are the noisiest old garbage I've ever encountered, and I've worked on a LOT of ancient tube gear. They sold it as PA gear - it's PA gear - and there was better PA gear.....
These things are the noisiest old garbage I've ever encountered, and I've worked on a LOT of ancient tube gear. They sold it as PA gear - it's PA gear - and there was better PA gear.....
Carlsoti
Member
Fair enough. Thanks for the reply.
I never liked 12AX7 tubes as mic preamps. The 7025's weren't much better. I had decent luck with 1567's as long as quiet 12AX7's could be found. I wouldn't mind having a couple "throwaways" to play with. The Peerless input transformers were decent. Bypassed the "tone control" section. Transformer coupled the output for balanced. Now I am trying to remember if the B plus supply was derived from a voltage doubler like Ampex did with some of their gear.
Carlsoti
Member
The one on my bench still has the selenium rectum-fryer in a voltage-doubling circuit for the B+. I've read that 12AU7's make the unit much quieter, but I don't know if it actually betters the s/n ratio, or just lowers the overall gain. Given that mics are a bit hotter now than when these were designed and that there's more than enough gain on tap for a studio setting, that might be a worthwhile swap. I'd need to do the math to say with any confidence that it's the "right" thing to do, though. It's Friday and I have a layer of of dust, dirt, and rat-droppings to scrub off me, so I won't be working those equations today. The things we do for friends.
Remember, none of my noise problems have anything to do with the front end - it's totally disconnected - nor the back end - it's pickup around the mix resistor stage, which disappears when that's disconnected. I crushed tube and resistor noise (significant, 12dB?) right out of the gate, that's a walk in the park.
Carlsoti
Member
I'm aware that I'm fighting a losing battle and my best chances for success are reliant on luck-of-the-draw that the in, out, and power transformers aren't the source of the noise. Thankfully, I'm usually at my best when people say "It can't be done." They're usually right, though. 
swpaskett
Well-known member
What a fascinating trip down memory lane you have sent me on today. I came of age in the '60s and remember Altec as the quietest thing we could get in the ages of hum ('60s), hiss ('70s), and finally quiet ('80s) -- by then Altec had faded to oblivion. I thought the 1567 was an old box back in the early '70s; the 1592 is what I cut my teeth on.
An interesting thing about the not quite so old transistor gear is their transistor amps used the same topology as the old tube designs. Heavy, low power (100W was a lot back then) and indestructible.
Anyway, this old Altec stuff may seem terrible now, but I remember it as the best I could get back then. There wasn't a noise problem I couldn't solve with a tranny and proper termination, but I suspect I wasn't hearing what I had come to expect as "normal;" e.g., hiss and hum.
Sorry - couldn't resist commentiing. As usual, I have nothing helpful to add
An interesting thing about the not quite so old transistor gear is their transistor amps used the same topology as the old tube designs. Heavy, low power (100W was a lot back then) and indestructible.
Anyway, this old Altec stuff may seem terrible now, but I remember it as the best I could get back then. There wasn't a noise problem I couldn't solve with a tranny and proper termination, but I suspect I wasn't hearing what I had come to expect as "normal;" e.g., hiss and hum.
Sorry - couldn't resist commentiing. As usual, I have nothing helpful to add
sparechessroom
New member
What a fascinating trip down memory lane you have sent me on today. I came of age in the '60s and remember Altec as the quietest thing we could get in the ages of hum ('60s), hiss ('70s), and finally quiet ('80s) -- by then Altec had faded to oblivion. I thought the 1567 was an old box back in the early '70s; the 1592 is what I cut my teeth on.
An interesting thing about the not quite so old transistor gear is their transistor amps used the same topology as the old tube designs. Heavy, low power (100W was a lot back then) and indestructible.
Anyway, this old Altec stuff may seem terrible now, but I remember it as the best I could get back then. There wasn't a noise problem I couldn't solve with a tranny and proper termination, but I suspect I wasn't hearing what I had come to expect as "normal;" e.g., hiss and hum.
Sorry - couldn't resist commentiing. As usual, I have nothing helpful to add
I rebuilt one of these recently, and built a set of tube buffers for each channel as a direct out using the 12B4A into an output transformer, and actually replaced the output tube stage with the same tube stage and xformer- finding I was able to get a solid 24db into a 600R load with it being absolutely silent. But I also changed the heater supply to 12vdc and rewired the grounding scheme as well as changed all the plate resistors and increased filter cap values. it can be done... the biggest change was the output tube circuit though. I was initially worried that it would lose the mojo and the lo fi aspect that people love, but that really was not an issue, you can drive the output and eq, or run it clean with lots of headroom.
radardoug
Well-known member
Did you do it with the existing power transformer in the chassis?
