I just thought you all should know. Through my, 50+ year career. Having cut my teeth on, UREI 1176 limiters. Since the early 1970s. Restoring them. Fixing them. Calibrating them. When adjusting your very important, extremely important, Q transistor bias adjjustment. While transistors are not vacuum tubes. Where vacuum tubes take, 20-30 minutes to come up to full temperature. Transistors run very cool. And as a result. They take much longer. To come up to temperature. Like, 4 hours. To come up to full operating temperature. Within their closed chassis. Lid on. Once your, 1176 (original or clone) has been on all day. And up to temperature. Only now. Should you flip the top off. And only now should you, adjust your, Q bias adjustment. Because… If you don't give it that much time. Before you aadjust the Q bias adjustment. It's going to drift. Over about, 4 hours time. And that will change. The way your 1176, works and responds. And I have not knowwn anybody to date. To give their 1176, enough time to, properly warm up. Before that Q bias adjustment is made! A good example of this likely possibility. A very famous remixer in LA. Has a rack full of original, UREI 1176's. And of his numerous blue stripe and blackface and silver version, 1176's. He has one blue stripe version. He uses, virtually, strictly. On his lead vocal tracks. Because as he says. All of the others. Don't sound or work like this one. Geez…? I wonder why? Let me guess? So it is likely. Not that, thatt unit was brought up to temperature. Before tweaking that Q bias adjustment. We don't know? But it could be indicative. As to how mmuch variation might exist. Within the FFET limiting circuit. That is dependent upon that Q bias adjustment. Right or wrong. He prefers the way that one responds and performs. Over the other identical units. From what I've discovered, through the years. With these devices. So it really doesn't matter whether you get that, transistor Q bias adjustment, correct or not. It only matters. How you like the way that 1176 works for your purposes. Consider that Q bias adjustment to be the, overall, character control. Where, if you get it right. It'll work as intended, by design. If you get it wrong? Where there really is no wrong. If, it gets you a sound, you want. Out of the artist. But I cannot stress enough. That in order to have some, factory intended consistency? One would want to let the unit warm up for at least 4 hours. With the lid on. Before one makes the Q bias adjustment. To the factory specifications. Which is what I did with my 5 originals. Numerous ones of which. I could then get away. With direct stereo strapping. Without the need of the stereo coupler. Provided the, FET transistors were a close match. Not all are.. But mine were remarkably close. To indicate less then a 1/4 DB difference. When stereo strapped. After I had spoken with the original UREI 1176 team. Back in the late 1970s. When they still existed. In their heyday. There was also a very cool, high frequency limiter modification one could make. From a factory recommended, modification. Now lost to history. As the new kids on the block. The Putnam boys. Know nothing of this modification. I discovered. I was taken aback by. As it's a very useful, very important, modification to make. As it takes your 1176 to the next level. The modification was a simple one. Though, I lost my, hand written schematic I obtained from UREI.. Back in the day. And I believe it was a, point 5 µF, non-polarized, capacitor. Connected to a, SPDT, switch. In line with the, peak detector input. With switch on. The .5 µF capaccitor is insserted, in line. And rolls off most frequencies below, 5000 Hz. Creating a 75 µs, high-frequency preemphasis boost. To the,, peak detector. Meaning that. High frequencies. Will be more highly controlled. Lower frequencies will be more normally controlled. Providing for a high frequency limiter. If, say, you wanted it as the last stop. Going into your FM transmitter. To help compensate for the FM high-frequency preemphasis curve. Creating a high-frequency dynamic limiter. Which then allows you to add more, upper midrange and high-frequency boost. To your lead singer. To get more that breathy, airy, edgy, sound. Without excessive, sibilance. It's essentially a high-frequency De-Esser. And it does wonders! On all sorts of vocals and instrumentation. Such as adding more sparkle to, cymbal crashes. Without them blowing up your tweeters. More to your high hat, high-frequency boost. Without cutting through you like a glass cutter. To add more snap to your snare drum. Without it cracking your tweeters. Apparently. I was one of the very few people. Who was making this mod. For my 1176's. And I have 4 used UREI 1176 limiters out there I sold. Years ago. With that mod. Wherre, lo and behold! On a Vintage King demonstration of, both new and old blue stripe and blackface rev D 1176's. There was one of my blackface units! With that mod I made. Decades ago! I always wondered what happened to that unit? It was supposed to come back to me with the matching one. When there door wwas padlocked by the bank. And it was auctionned off. And there it is! Vintage King got at least one of those! I felt like a proud mother. And remember. Mother… Is only one half a word. So remember what I told you kids. And you'll love Your 1176's, all the more. Peace. Love. Hey. I'm from the 1970s scene. I'm old. Real old. As in, actual original. One-of-a-kind from that era. And all of my 1176's were expertly aligned. All matching extremely closely. Closer than the factory indicated they should be. Because even they never quite realized this, thermal situation. With transistors. In fact. I discovered. This even held true for my, numerous, as in, three separate, Ampex, MM-1200-24, multitrack analog audio recorders. Those machines. Also took. About one half a day. To come up to, proper temperature. Before you align those machines! Because if you don't wait after switching on the machine to align them. Your bias will drift by over 1 DB! And that's a huge differencee. In the way the machine will sound and respond.The same was true for, earlier MCI machines. As they were Ampex clones. And one could swap, audio cards. Between their Ampex and earlier MCI recorders. As my used Ampex 1200's. Had a couple of, MCI audio cards in them! And my MCI machine. Had a couple of Ampex cards in it. As they were cross compatible. They were identical clones in every way. So while transistors run cool. They still have to come up to temperature. Which takes them way longer. To heat up the chassis. With its low heat load. And the reason it takes hours. Tubes glow orange hot. They are little ovens. And they heat up there chassis, right quick. In mere minutes time. And transistors take as long as molasses in February. To heat the chassis. And you do not want to tweak. Until your chassis are hot. From the low heat load of transistors. Granted. Power transistors can get really hot, really fast. But that's not these low-power low current, low heat dissipation, circuits. These circuits take forever. So, no rushing through this procedure. Do not get impatient! Better working limiters come to those, who wait. You'll see. It's real. And everyone has to learn this. Because no one waits to tweak those. After they've, switched them on. To tweak them. From the trenches RemyRAD
I had a weird problem: it passed audio and the LEDs changed when I turned the Q bias. But, no matter what settings I changed nothing changed the output at all... As I took it out to check every component again and resolder, I noticed a switch in my chassis I'd forgotten about labeled "slot bypass". Which was engaged 🙄 works much better now! Then once I started to calibrate, my ears must not have been calibrated because even though you said 0.775 VAC many times I heard 7.75 VAC. Got there in the end thought 👍 thanks for the great video.
So when you adjusted the Q bias, you originally said you needed to rotate the pot Clock-wise until the voltage no longer changed. Later, you said you rated the Q bias pot counter-clock-wise until the voltage didn't change. So, which direction for initial adjustment is correct. I ask because I'm currently trying to calibrate a FC256 XFMR, which has a slightly different procedure, but the Q bias is thoroughly confusing me. Thanks.
I'm trying to adjust the Q bias on a FET 500 (Rev. D) and I'm stuck on the very first step. I adjusted the Q Bias pot until it stopped rising (roughly 5.5v AC), but it continues to fluctuate up and down by more than 1v even when I'm not touching it. Seems like it will be very hard to do the next steps with the voltage jumping around like that. Any thoughts?
Hi Mike, can you recommend a multimeter that won't break the bank that will work for this application? I've tried two and i don't get a reading at all. Both are under 50 bucks so maybe that's why. thx!
I just thought you all should know. Through my, 50+ year career. Having cut my teeth on, UREI 1176 limiters. Since the early 1970s. Restoring them. Fixing them. Calibrating them.
When adjusting your very important, extremely important, Q transistor bias adjjustment. While transistors are not vacuum tubes. Where vacuum tubes take, 20-30 minutes to come up to full temperature. Transistors run very cool. And as a result. They take much longer. To come up to temperature. Like, 4 hours. To come up to full operating temperature. Within their closed chassis. Lid on.
Once your, 1176 (original or clone) has been on all day. And up to temperature. Only now. Should you flip the top off. And only now should you, adjust your, Q bias adjustment. Because… If you don't give it that much time. Before you aadjust the Q bias adjustment. It's going to drift. Over about, 4 hours time. And that will change. The way your 1176, works and responds. And I have not knowwn anybody to date. To give their 1176, enough time to, properly warm up. Before that Q bias adjustment is made!
A good example of this likely possibility. A very famous remixer in LA. Has a rack full of original, UREI 1176's. And of his numerous blue stripe and blackface and silver version, 1176's. He has one blue stripe version. He uses, virtually, strictly. On his lead vocal tracks. Because as he says. All of the others. Don't sound or work like this one. Geez…? I wonder why? Let me guess?
So it is likely. Not that, thatt unit was brought up to temperature. Before tweaking that Q bias adjustment. We don't know? But it could be indicative. As to how mmuch variation might exist. Within the FFET limiting circuit. That is dependent upon that Q bias adjustment. Right or wrong. He prefers the way that one responds and performs. Over the other identical units. From what I've discovered, through the years. With these devices.
So it really doesn't matter whether you get that, transistor Q bias adjustment, correct or not. It only matters. How you like the way that 1176 works for your purposes. Consider that Q bias adjustment to be the, overall, character control. Where, if you get it right. It'll work as intended, by design. If you get it wrong? Where there really is no wrong. If, it gets you a sound, you want. Out of the artist.
But I cannot stress enough. That in order to have some, factory intended consistency? One would want to let the unit warm up for at least 4 hours. With the lid on. Before one makes the Q bias adjustment. To the factory specifications. Which is what I did with my 5 originals. Numerous ones of which. I could then get away. With direct stereo strapping. Without the need of the stereo coupler. Provided the, FET transistors were a close match. Not all are.. But mine were remarkably close. To indicate less then a 1/4 DB difference. When stereo strapped. After I had spoken with the original UREI 1176 team. Back in the late 1970s. When they still existed. In their heyday.
There was also a very cool, high frequency limiter modification one could make. From a factory recommended, modification. Now lost to history. As the new kids on the block. The Putnam boys. Know nothing of this modification. I discovered. I was taken aback by. As it's a very useful, very important, modification to make. As it takes your 1176 to the next level.
The modification was a simple one. Though, I lost my, hand written schematic I obtained from UREI.. Back in the day. And I believe it was a, point 5 µF, non-polarized, capacitor. Connected to a, SPDT, switch. In line with the, peak detector input. With switch on. The .5 µF capaccitor is insserted, in line. And rolls off most frequencies below, 5000 Hz. Creating a 75 µs, high-frequency preemphasis boost. To the,, peak detector. Meaning that. High frequencies. Will be more highly controlled. Lower frequencies will be more normally controlled. Providing for a high frequency limiter. If, say, you wanted it as the last stop. Going into your FM transmitter. To help compensate for the FM high-frequency preemphasis curve. Creating a high-frequency dynamic limiter. Which then allows you to add more, upper midrange and high-frequency boost. To your lead singer. To get more that breathy, airy, edgy, sound. Without excessive, sibilance. It's essentially a high-frequency De-Esser. And it does wonders! On all sorts of vocals and instrumentation. Such as adding more sparkle to, cymbal crashes. Without them blowing up your tweeters. More to your high hat, high-frequency boost. Without cutting through you like a glass cutter. To add more snap to your snare drum. Without it cracking your tweeters.
Apparently. I was one of the very few people. Who was making this mod. For my 1176's. And I have 4 used UREI 1176 limiters out there I sold. Years ago. With that mod. Wherre, lo and behold! On a Vintage King demonstration of, both new and old blue stripe and blackface rev D 1176's. There was one of my blackface units! With that mod I made. Decades ago! I always wondered what happened to that unit? It was supposed to come back to me with the matching one. When there door wwas padlocked by the bank. And it was auctionned off. And there it is! Vintage King got at least one of those! I felt like a proud mother. And remember. Mother… Is only one half a word.
So remember what I told you kids. And you'll love Your 1176's, all the more. Peace. Love. Hey. I'm from the 1970s scene. I'm old. Real old. As in, actual original. One-of-a-kind from that era. And all of my 1176's were expertly aligned. All matching extremely closely. Closer than the factory indicated they should be. Because even they never quite realized this, thermal situation. With transistors.
In fact. I discovered. This even held true for my, numerous, as in, three separate, Ampex, MM-1200-24, multitrack analog audio recorders. Those machines. Also took. About one half a day. To come up to, proper temperature. Before you align those machines! Because if you don't wait after switching on the machine to align them. Your bias will drift by over 1 DB! And that's a huge differencee. In the way the machine will sound and respond.The same was true for, earlier MCI machines. As they were Ampex clones. And one could swap, audio cards. Between their Ampex and earlier MCI recorders. As my used Ampex 1200's. Had a couple of, MCI audio cards in them! And my MCI machine. Had a couple of Ampex cards in it. As they were cross compatible. They were identical clones in every way.
So while transistors run cool. They still have to come up to temperature. Which takes them way longer. To heat up the chassis. With its low heat load. And the reason it takes hours. Tubes glow orange hot. They are little ovens. And they heat up there chassis, right quick. In mere minutes time. And transistors take as long as molasses in February. To heat the chassis. And you do not want to tweak. Until your chassis are hot. From the low heat load of transistors.
Granted. Power transistors can get really hot, really fast. But that's not these low-power low current, low heat dissipation, circuits. These circuits take forever. So, no rushing through this procedure. Do not get impatient! Better working limiters come to those, who wait. You'll see. It's real. And everyone has to learn this. Because no one waits to tweak those. After they've, switched them on. To tweak them.
From the trenches
RemyRAD
"probaby won't have one lying around" jokes on you, that's exactly the multimeter I have lol
I had a weird problem: it passed audio and the LEDs changed when I turned the Q bias. But, no matter what settings I changed nothing changed the output at all... As I took it out to check every component again and resolder, I noticed a switch in my chassis I'd forgotten about labeled "slot bypass". Which was engaged 🙄 works much better now!
Then once I started to calibrate, my ears must not have been calibrated because even though you said 0.775 VAC many times I heard 7.75 VAC. Got there in the end thought 👍 thanks for the great video.
Great video Mike. Thanks for posting
So when you adjusted the Q bias, you originally said you needed to rotate the pot Clock-wise until the voltage no longer changed. Later, you said you rated the Q bias pot counter-clock-wise until the voltage didn't change. So, which direction for initial adjustment is correct. I ask because I'm currently trying to calibrate a FC256 XFMR, which has a slightly different procedure, but the Q bias is thoroughly confusing me. Thanks.
Initial adjustment is always to the side that gives maximum output.
Great, thanks! CW for me. BTW, I'm loving the two Lola pres I've built. They are rad!
weird. mine doesnt have a q bias adjustment on the front?
I'm trying to adjust the Q bias on a FET 500 (Rev. D) and I'm stuck on the very first step. I adjusted the Q Bias pot until it stopped rising (roughly 5.5v AC), but it continues to fluctuate up and down by more than 1v even when I'm not touching it. Seems like it will be very hard to do the next steps with the voltage jumping around like that. Any thoughts?
Hi Mike, can you recommend a multimeter that won't break the bank that will work for this application? I've tried two and i don't get a reading at all. Both are under 50 bucks so maybe that's why. thx!
Is the multi meter connected to the input measuring VAC when you put the q-bias into pinch mode?
+Dennis Ward you start at the input to establish a good line level input signal (0dB), then you move to the output to measure the q-bias adjustment.
Is this procedure the same for the Rev A 500 series?
Yes, all versions.