Description
The Stepped Attenuator Kit is all about making a Master Volume Control that allows Precise Balanced Control of the signal level, while having the least possible affect on the sound quality of the signal. The result is an amazing amount of clarity, and that is because most analogue volume pots inject a small amount of distortion, that you wouldn’t even know was there, until you hear the difference – and then there’s no going back!
The attenuator works so well, because it has only one resistor in the signal path and one resistor to ground that diverts or shunts a portion of the signal to ground. And that’s how it got it’s official name of a “shunt attenuator”.
***PLEASE READ – The output impedance of the devices you intend to plug into your Stepped Attenuator will determine the resistor set you choose to build. For most builders Set “B” will be the most practical. Any questions, just send us an email and we’ll lend a hand right quick.
Set A – Low Input Impedance (1K ohm) – suitable for low output impedance devices like DACs which are typically under 100 ohm. This give you a safe 1:10 ratio. To check if your device is suitable for this Set, check your manufacturers specifications, and if your device shows an output impedance of 100 ohms or less you should be good.
Output impedance will vary depending on the step resistor selected, but typically at low volume it will be ~12 ohm, mid ~150 ohm and high ~2kohm.
Set B – Medium Input Impedance (10K ohm) – suitable for devices that have an output impedance of 1K ohm or less. This includes all of our Kit Preamps and most other devices. To check if your device is suitable for this Set, check your manufacturers specifications, and if your device shows an output impedance of 1K ohm or less you should be good.
Output impedance will vary depending on the step resistor selected, but typically at low volume it will be ~150 ohm, mid ~510 ohm and high ~2.7kohm.
The Stepped Attenuator comes as a Full Kit that includes all parts and an unfinished Solid Cherry Wood Plinth, Finished 3/16″/ 5mm Aluminum Top Plate and 2mm Aluminum Bottom Plate.
We’ve carefully selected every part and component. From the quality 1/4w 1% resistors and dual gang 24 position switch to the solid Cherry Wood Plinth and Hand Brushed Aluminum Top Plate, to the solid anodized aluminum volume knob.
Build Information will include the Resistor Set work sheet, and also a Build Series of Videos is available on YouTube under Mellow Tone Kits.
The videos are the Build Manual.
Sound Signature: Clean and Clear, with Very Low Distortion.
System Compatibility: Set “B” is designed to drop in just before or after one of our Control Preamps Kits, with the Preamp volume set to max, the volume pot is mostly out of the signal path, but then presents ~100k ohm load to whatever is input. The best thing to do is to try it before and after the Control Preamp and see what you like best.
Build Complexity: Medium Plus – if you already make stuff, and are a thoughtful careful person, who can focus for an hour – You Can Build this Kit Amp. The one tricky aspect of assembly is you need to have good soldering skills (the switches have very tiny solder tabs). So this kit is not for the beginner who is still learning good soldering skills (try a monoblock first – they’re a lot easier to build).
Size: 7″w x 13″d x 4.75″h (17.8cm x 33cm x 12cm), 4lbs/1.8kg
Shipping Extra (to check on rate, make an account, place item in cart and go to check out page).
Discount Codes – don’t work on Kit Amps – the margin is too tight to offer discounts.
Stepped Attenuator Resistor Set A dB Chart
Stepped Attenuator Resistor Set A Worksheet
Stepped Attenuator Resistor Set B dB Chart
Stepped Attenuator Resistor Set B Worksheet
Fun Fact: There are many different ways of setting up the resistor Sets, but we already knew that we liked the log (logarithmic) Alps volume pot settings in our preamps. So we ran a test signal through one of our preamps and made a plot of our regular listening positions on the Alps and then transferred that information into the second most complex spreadsheet we’ve ever developed (the Universal Kit Phono Preamp was even more complex). And then with some minor tweaks we had “Set A & B” and wow it works perfectly, the steps land exactly were you want them to.
horaciojervis (verified owner) –
Jim,
This kit took me approximately 6 hours to compete, working on and off across three days, not including the time it took to finish the wooden chassis. I’ve spent the last 10 days listening to it for several hours per day. For reference purposes, the following is the equipment I’m using: Soundsmith cartridge, VPI turntable, Bob’s Devices SUT, Manley Chinook phono preamplifier, PrimaLuna EVO 300 preamplifier, 45 tube SET monoblock amplifiers,100dB open baffle speakers with full range drivers, and of course, the Mellow Tone Stepped Attenuator Kit with the Set B resistors.
Initially, I had the stepped attenuator positioned between my phono preamp (91 ohms output) and control preamp. Later, I found it really sounded best positioned between the control preamp(256 ohms output) and my amplifiers.
I played around with my phono preamp’s gain options, and took the SUT in and out of the chain. In the end, I simply preferred the sound with the SUT and the 65dB of gain with the 0.4mV cartridge.
Consequently, because of this higher gain, and my speaker’s sensitivity, I’ve done as you suggested, and lowered the control preamp’s volume pot until it’s “trimmed” to my liking. I am typically setting the attenuator to its 9th step/240ohm or 10th step/300ohm, and adjusting the preamp’s volume pot accordingly. I will play around with this more. I like the idea of being able to max out the preamp’s volume control(“removing” it from the circuit) and simply use the attenuator to adjust the volume. I am assuming that being able to do this, would result in getting the maximum benefits the attenuator has to offer.
My rig is pretty transparent and open sounding, with a deep soundstage, including good height, width, and precise imagining, along with a palpable holographic presence. The stepped attenuator kit has simply refined this presentation. Improving, and making all the important bits better. This has not been a subtle change, but the kind of improvement that is “in step” with a significant preamp or cartridge upgrade. I honestly am astonished at the difference this has made (perfectly matched resistors in a simple circuit design!). Keep in mind that my preamp sports the well regarded 100Kohm Alps Blue Velvet motorized potentiometer, arguably no slouch. For me, with my gear, the stepped attenuator is better.
My first reaction was that adding the attenuator was like cleaning my eyeglasses when I thought they were clean, and then being surprised by their subsequent clarity. Except the attenuator is better, because it offers more than just clarity, delivering greater detail, tighter focus, increased sound staging, improved presence and body.
The other aspect that has delighted me, is that adding the attenuator either before or after the control preamp did not add any noise. I realize that it is a passive device, yet I’m impressed and happy that it is dead silent, especially when running my phono preamp into it; zero grounding issues.
I have enjoyed absolutely everything about this kit. Building it was a blast (soldering the resistors to the attenuator was my favorite part), the instructional videos are very well done, and the kit itself feels like a quality product, the cherry wood frame and metalwork are substantial, elegant and attractive in their simplicity.
Thank you for the time, effort, and detail both you and Charles put into these kits and videos. Also, thank you Jim for taking all this time to work with me, provide consultation, offer feedback, read my long emails, and for being patient and kind with me. Much appreciated.
This has been a really worthy investment, money well spent, and a great education and learning experience. I’m glad I found you guys.