Welborne Remote Stepped Attenuator - It Works!!!
I have one of these mentioned in the title, and when I tried to use it many years ago I remember having a problem with the first step, which was too loud, even using the various options provided. I also remember having power supply problems as it needed a 5v source, but was in a Aikido pre-amp with a minimum 24 volt source. I used a 9v battery, reduced with an LM317, after I tried using the 24v source that made the whole thing overheat.
But aside from the operational issues, has anybody used one of these successfully? And how did it sound? It can't be worse than the scratchy pots I'm using now, could it? Welborne claimed that you may be able to squeeze better sound out of a resistor attenuator, but that it could stand with the best of them. He was also not very well regarded by the audio community, so I take that with a grain of salt.
I'm looking at it again because those scratchy pots are just driving me crazy, the dual mono is a pain to get right, jumping up and down from the couch to center the image, and my phono input has too much gain compared to the others. Plus, it is remote control, something that I appreciate when I use my Oppo player as a source, but can't with the phono. I haven't played a CD in 9 months since I upgraded my turntable.
Any thoughts?
Update:
After taking it apart, checking the resistances, setting the first step, and overall screwing around with it, it seemed that everything was in order. Today I put it all back together, and then wired it into my Aikido pre-amp. It worked!!! I even got the first step low enough for my tastes, below conversation level for when you want it that soft. That just required switching in the 25k series resistor for a total of 34k. I can also try 5k or 10k, which I will.
The problem is the power supply, but this isn't the remote's fault. I had put a 9v battery with an LM317 regulator to get the required 5v. That works great except that the battery only last for about an hour
I guess the regulator draws current even when it isn't doing anything. I have more than a few wall wart power supplies around, I'll find one that's suitable.
The other thing I discovered is that the tubes in the Aikido weren't what I thought. I'd have sworn I had 6GM8 Bugle Boys in it, but when I pulled them out to give myself some room to work I saw they were GE. Then I recalled seeing a batch of tubes in a drawer next to the pre-amp that I thought were 6922s, but they were the bugle boys. I put those in instead. It isn't a night and day difference so I won't say they sound better. I didn't realize I was so clever to buy an extra set when they were still cheap, $20 for a quad. Last I checked people wanted big money for these.
I have one of these mentioned in the title, and when I tried to use it many years ago I remember having a problem with the first step, which was too loud, even using the various options provided. I also remember having power supply problems as it needed a 5v source, but was in a Aikido pre-amp with a minimum 24 volt source. I used a 9v battery, reduced with an LM317, after I tried using the 24v source that made the whole thing overheat.
But aside from the operational issues, has anybody used one of these successfully? And how did it sound? It can't be worse than the scratchy pots I'm using now, could it? Welborne claimed that you may be able to squeeze better sound out of a resistor attenuator, but that it could stand with the best of them. He was also not very well regarded by the audio community, so I take that with a grain of salt.
I'm looking at it again because those scratchy pots are just driving me crazy, the dual mono is a pain to get right, jumping up and down from the couch to center the image, and my phono input has too much gain compared to the others. Plus, it is remote control, something that I appreciate when I use my Oppo player as a source, but can't with the phono. I haven't played a CD in 9 months since I upgraded my turntable.
Any thoughts?
Update:
After taking it apart, checking the resistances, setting the first step, and overall screwing around with it, it seemed that everything was in order. Today I put it all back together, and then wired it into my Aikido pre-amp. It worked!!! I even got the first step low enough for my tastes, below conversation level for when you want it that soft. That just required switching in the 25k series resistor for a total of 34k. I can also try 5k or 10k, which I will.
The problem is the power supply, but this isn't the remote's fault. I had put a 9v battery with an LM317 regulator to get the required 5v. That works great except that the battery only last for about an hour
I guess the regulator draws current even when it isn't doing anything. I have more than a few wall wart power supplies around, I'll find one that's suitable. The other thing I discovered is that the tubes in the Aikido weren't what I thought. I'd have sworn I had 6GM8 Bugle Boys in it, but when I pulled them out to give myself some room to work I saw they were GE. Then I recalled seeing a batch of tubes in a drawer next to the pre-amp that I thought were 6922s, but they were the bugle boys. I put those in instead. It isn't a night and day difference so I won't say they sound better. I didn't realize I was so clever to buy an extra set when they were still cheap, $20 for a quad. Last I checked people wanted big money for these.
Last edited:
Well, I found the instructions in my pile of DIY project papers, and I'm going to test this thing out again and see if I can get it to work. It says it will provide -35db of attenuation, plus another -6, -12, or -25db with a shunt resistor switched in. I could still never get that first step to be low enough, but I'll try again. I figure that anything good will cost money, and I already have this. It also has a balance control built in, and even if I just use that it would be worth it. Input switching too, but I never found that to be particularly useful when you're using a turntable since you have to get up to take off the record anyway.
A switched attenuator uses fixed resistors to attenuate.
The output is determined by the ratio of the resistors currently switched in.
eg series resistor = 1k, shunt resistor = 9k1 Zin = 10k1, attenuation = 20 log {9k1/(9k1+1k)} = 20log(0.90099) = -0.906dB
switch in at the lowest level and the attenuation is 20log(shunt resistor/{sum of shunt plus series resistor})
eg, 10r for shunt and 10k for series Zin = 10k01 and attenuation is -60.01dB
If there is a Buffer after the vol pot, then you can ignore the loading effect of the receiver's input impedance.
All you need to do, to change the attenuation, is to swap in different resistors.
The output is determined by the ratio of the resistors currently switched in.
eg series resistor = 1k, shunt resistor = 9k1 Zin = 10k1, attenuation = 20 log {9k1/(9k1+1k)} = 20log(0.90099) = -0.906dB
switch in at the lowest level and the attenuation is 20log(shunt resistor/{sum of shunt plus series resistor})
eg, 10r for shunt and 10k for series Zin = 10k01 and attenuation is -60.01dB
If there is a Buffer after the vol pot, then you can ignore the loading effect of the receiver's input impedance.
All you need to do, to change the attenuation, is to swap in different resistors.
I'm going to have to take it apart so I can get at the fixed resistors and measure them. That was part of the problem. There are 3 pcbs stacked with wires running between them and soldered in holding them together. I'm also not sure of how the dip switches are wired to the resistors, whether they add together in series or in parallel or singly switched in. Again, this can be made clear if I just take it apart. There is no schematic and in fact the part #s were obscured on the controlling ICs.
Welborne didn't want anybody copying it, but then provided little support if you had a problem. It was right after I bought the thing that he started taking people's money and not delivering.
Welborne didn't want anybody copying it, but then provided little support if you had a problem. It was right after I bought the thing that he started taking people's money and not delivering.
Last edited:
My experience with this attenuator has been so bad that I believe it is not worth wasting your time on. I am using it now but have ordered and currently waiting for a replacement device.
The software is buggy and needs to be restarted often. Sometimes only one channel works. Sometimes the input changes. The thing is just a pain in the butt! Welborne does not offer much help.
The software is buggy and needs to be restarted often. Sometimes only one channel works. Sometimes the input changes. The thing is just a pain in the butt! Welborne does not offer much help.
The only problem I had in use was the first step, it was too loud. The channels and source always worked. I would check the voltage supplied on your unit, maybe it is not steady 5v as spec'ed. Even the instruction sheet says that it should be regulated. One of my few answers from Welborne was that an LM317 based supply is best, and I drive mine with a 9v battery. I don't know how long it would last because the first step problem was never resolved when I used it last about 6-7 years ago. (I just checked the order date, it was 2006, so almost 10 years now. Also this was right at the time he started getting himself in trouble, although apparently he was always a jerk.)
Last edited:
From input signal to output signal it measures 9.1k, from output signal to ground it measures open, from input to ground measures 9.1k, the series resistor is 9.1k. This is without power, which theoretically only controls the ladder in the IC. When I power it up I still get the same results, even when I use the volume control on the remote to go up and down. These are the only things I can measure, intermediate switchable resistors are hidden as I keep saying.
The one thing I did find though is that the trimpot that sets the first step no longer seems to work. It measures 50 ohms no matter which way I turn the screw, so maybe in testing this out originally I somehow messed up the worm gear. I ordered 2 more just so I could test this theory out. Replacing them requires taking it apart as I've been saying, and I'll see what I can find out.
One thing I did find is that when the voltage dropped below 5v on input due to old batteries, the remote wouldn't turn it on/off. So it does require that 5v.
Edit: I googled "resistor network IC" and now understand a lot more than I did 5 minutes ago. If I knew the part # of the IC used I'd know even more. But in looking, I see there are some DIY designs out there that I could implement myself easily enough, but I guess that's what I already have in my hands, so I want to make this one work.
The one thing I did find though is that the trimpot that sets the first step no longer seems to work. It measures 50 ohms no matter which way I turn the screw, so maybe in testing this out originally I somehow messed up the worm gear. I ordered 2 more just so I could test this theory out. Replacing them requires taking it apart as I've been saying, and I'll see what I can find out.
One thing I did find is that when the voltage dropped below 5v on input due to old batteries, the remote wouldn't turn it on/off. So it does require that 5v.
Edit: I googled "resistor network IC" and now understand a lot more than I did 5 minutes ago. If I knew the part # of the IC used I'd know even more. But in looking, I see there are some DIY designs out there that I could implement myself easily enough, but I guess that's what I already have in my hands, so I want to make this one work.
Last edited:
Ok, I think I have this all figured out. It DID require opening it up, although in the end I didn't need to replace anything. It really made it easier to see what it did.
The series resistor is 9.09k, as I stated. What I needed that was not clear to me is how the shunt resistor works, which is the guts of this thing. It is electronically controlled through an IC, maybe from Maxim but I don't really know. The problem is the first step, and how that gets triggered through a trim pot. The instructions had the turn backwards, it should go full clockwise to zero, then ccw until the shunt resistance jumps to 470k on the first step. It was only when I opened it up that I could see the trace on the board that showed how this was being set by the resistance in the pot. Once the trim pot is set, the up/down on the remote then works in raising and lowering the shunt resistance. How this works on the chip is still a mystery as I don't have a part number. It was erased by Welborne.
What I need to do is measure the steps so I can calculate the attenuation for each. It is supposed to be in .6db steps. I also need to see the impact of the select-able resistors on the whole thing. With all this I can then see what I need to do to get that first step right. Changing the series resistor will change the steps, but that may not matter as I have 60 steps to play with, and I should be able to get plenty loud even if my first step is low.
Of course just trying it would be the best way but I'm short on alligator cables to use to connect everything up. Where is Radio Shack when you need them? There's a blizzard going today in NYC, so I wouldn't be going anywhere anyway. 16 inches of snow at last look, and more coming.
The series resistor is 9.09k, as I stated. What I needed that was not clear to me is how the shunt resistor works, which is the guts of this thing. It is electronically controlled through an IC, maybe from Maxim but I don't really know. The problem is the first step, and how that gets triggered through a trim pot. The instructions had the turn backwards, it should go full clockwise to zero, then ccw until the shunt resistance jumps to 470k on the first step. It was only when I opened it up that I could see the trace on the board that showed how this was being set by the resistance in the pot. Once the trim pot is set, the up/down on the remote then works in raising and lowering the shunt resistance. How this works on the chip is still a mystery as I don't have a part number. It was erased by Welborne.
What I need to do is measure the steps so I can calculate the attenuation for each. It is supposed to be in .6db steps. I also need to see the impact of the select-able resistors on the whole thing. With all this I can then see what I need to do to get that first step right. Changing the series resistor will change the steps, but that may not matter as I have 60 steps to play with, and I should be able to get plenty loud even if my first step is low.
Of course just trying it would be the best way but I'm short on alligator cables to use to connect everything up. Where is Radio Shack when you need them? There's a blizzard going today in NYC, so I wouldn't be going anywhere anyway. 16 inches of snow at last look, and more coming.
I checked the shunt values and they range from 455 up to 25k in increasing increments meant to keep the 60 steps relatively equal. But the other thing I found is that this is a pi pad, there is 9.09k to ground, with dip-switched in values of 5k, 10k and 25k additional if wanted. How does that impact attenuation?
3 years later I'm still using it without a single problem. I haven't even had to replace the batteries in the remote. The best part is that I can sit on the couch and balance the input to dead center, and I have to do that as one side is slightly louder than the other on my amp as my power tube pairs aren't qyute matched.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.