I’m a DIY guy and have either built, upgraded, or modified most of what’s in my system, and it’s always a pleasure to see such nice clean work as you did in this passive pre. 🔊😊🎶👍
Hi Jim, after twenty audio equipment builds I would have no problem soldering those 48 resistors to that selector switch, but it would be tedious. Another way to create the kit version would be to mount the resistors to a prepared pcb. The selector switch could be fly wired to terminals on the board. It wouldn't look as cool, but it would be easier for most to solder.
Yup that's a valid approach and we thought about it (well Charles did), but I was lead on this design and I went with what I thought would be the best assembly method - none of them are ever going to be perfect or a lot of fun to assemble, but the resulting sonic improvement is absolutely stunning, so well worth the effort! Fun fact, after installing the prototype attenuator in our main listening system we couldn't take it out again, that's how much of an improvement it made, particularly to the clarity of the signal. Charles observed the single largest improvement was the low frequency bass notes, which went from slightly muddy to noticibly firm and well defined.
@@HoomanR17 unfortunately it's not practical to design for 3 inputs, at least not the low noise circuit topology I like to use. When we design a new Kit we have the sonic performance as a priority, then the features that 90% of users will need, then aesthetics.
@@mellowtonekits4932 Thanks for your explanation. I understand the criteria for your design. Correct me if I'm wrong, but isn't the input # just the difference between going from a DPDT switch to a TPDT switch, or is it the case that the brand/quality switch that you use doesn't come in that flavor?
@@HoomanR17 correct the switch type we use is limited to DPDT and where would you even put a 3rd pair of RCA jacks? We have a multitude of source signals and whenever we run out of inputs we just swap one out. Otherwise we'd need a dozen inputs, which would basically be a patch bay. And that's not something I'd want even in our main critical/test system - though the idea has merit!
Hi Jim, if I wanted to use this stepped attenuator before my integrated tube amplifier that has an 100k pot and turn that pot all the way up. How would my input impedance be affected?
@@garyvitrano8362 good question, IF your volume pot is a passive device like a blue alps or 99% of all pot ever made (till recently when manufacturers started switching to chips) then whatever the impedance of the pot is, that's the input impedance of the amp. So in your case 100k ohm, even when the pot is fully open. You can actually measure this, with the amp off, use an old rca patch cord, strip back one end to a centre conductor and ground shield, connect both to a volt/ohmmeter, switch to ohm function and Bob's Your Uncle.
Wow, the Alps sounds better with digital, I think that is fascinating. I have to say, I love watching you and your son inventing all these great products. Still waiting for that headphone amp, -- wink, wink, wink. By the way, my uncle is named John, actually.
Yes, but when you realize how complicated the digital side is, it's not surprising that you would have a totally unexpected interaction. I've been so impressed with our analogue side that I've spent thousands building up our vinyl collection - almost all of the new purchases are records that were pressed before 1982. Even though I'm doing digital development work, I honestly don't ever expect it to come close to our all analogue tube side. And not surprising the very best records ever pressed were all done on all tube gear, even the cutting lathes were running on tubes! And If Charles didn't want a sexy headphone amp chassis we'd have the Kits Shipped already! But have no fear my job this week is to do development work on the new chassis design.
This came really timely, as I have been looking for/into a passive pre for my system for a couple of weeks now. Some comments, and questions: I would use this to bypass both the pot and the selector switch on my amp (crap quality). I would only connect my turntable and DAC, and for the DAC input I would actually like to bypass the whole attenuator and just use the "preamp" as a selector (I use digital control on a PC for that anyway). How would you wire that? Remote control would be a must for me. I hope to see you come up with something cool there :) LDR's - Have you ever looked into those, tried something built around it yourself, or have any thoughts to share?
Coming up with a remote control that doesn't muck with the sound is unlikely, which is why none of our gear has any of that kind of stuff in it. But we're taking a look to see if something can be built that both meets our requirements for uncompromised sound and allows people to control the volume without ever having to get up. I have no (zero) idea as to what an LDR is. The way the stepped attenuator is designed does not allow a complete bypass, I'm not sure what the point of that would be?
@@mellowtonekits4932 Thanks for replying! The point of the bypass would be to avoid another attenuator in the signal path when using the DAC, and just have direct to amp input. Since I want to eliminate the selector switch in my amp and have only 1 input there. Workaround would be setting the attenuator to max when using the DAC then. Edit: Actually, if I just reverse the order and move the switch to the output side, I can wire 1 input directly to the switch, the other input to the attenuator, and Bobs my uncle? LDR, light dependent resistor. A design around those would leave a very short signal path, but would also require some electronic control. So arguably not a true passive. Oh, and reagarding your question on soldering 21 resistor pairs, I would say that sounds like a fun evening :)
@@brianhowe2078 we design everything in house from first principles. Some would call us old school, but honestly I don't care, so long as we achieve our primary goal, which is great sound and almost as important, our second which is affordability.
