I would suggest that in the course of looking into cable influence on interface between devices, consider the cable as a lumped load in parallel with the load of the input of measurement equipment if you measure the cable independently, and when you connect the cable to an additional load, that load is also in parallel. Since the cable does have a capacitive nature, it is easy to measure the total capacitance of a cable, then you can calculate the impedance over the audio range. It is possible to measure differential cables this way to see how much imbalance occurs, I am not sure how THAT chip will handles the imbalance of this nature.
If you are designing a driver, you want to check and see how the capacitive load will effect driver stability and also see if the driver can properly drive the capacitive load. This way the overall design possible can be less sensitive to interconnect variation. Consideration would probably be similar to power amp driving capacitive loads.
Neurochrome PCBs
Tom,
Just opened the package and was absolutely delighted with the quality of these boards!😀 I bought a set of your Parallel 86es along with a Power86.
Over the past 5 years I've had PCBs from a lot of places around the globe and these are by far the best I've ever seen. They are solid, finely crafted, and a joy to behold. Worth every cent.
Eventually I'll end up with 8-channels in two separate boxes. Look forward to the build(s) and, of course, bugging you. These days I'm hanging out with relatives in central Germany and probably won't return to the states for several years...during which time I've got you to harass.
I wish you all the best with this exciting venture!
Thanx,
Ronald
Tom,
Just opened the package and was absolutely delighted with the quality of these boards!😀 I bought a set of your Parallel 86es along with a Power86.
Over the past 5 years I've had PCBs from a lot of places around the globe and these are by far the best I've ever seen. They are solid, finely crafted, and a joy to behold. Worth every cent.
Eventually I'll end up with 8-channels in two separate boxes. Look forward to the build(s) and, of course, bugging you. These days I'm hanging out with relatives in central Germany and probably won't return to the states for several years...during which time I've got you to harass.
I wish you all the best with this exciting venture!
Thanx,
Ronald
Very cool. I'm glad to hear that you appreciate my work and effort. Best of luck with your build. Should you need my help, just toss me an email.
Thanks,
Tom
Thanks,
Tom
been long time no see
Hey guys been out of it for awhile...can someone please send some links to the evaluations of the amplifiers
I also wanted to say that speaking of the preamp and amp combo THD stuff ...I read many moons ago that a series of opamps seemed to lower the total THD not raise it ...weird contemporaneity thinking would indicate otherwise...
If you still would like an honest review of your stuff Tom I have very wideband speakers that IMO qualified for proper evaluations
Thank you
Lawrence
Hey guys been out of it for awhile...can someone please send some links to the evaluations of the amplifiers
I also wanted to say that speaking of the preamp and amp combo THD stuff ...I read many moons ago that a series of opamps seemed to lower the total THD not raise it ...weird contemporaneity thinking would indicate otherwise...
If you still would like an honest review of your stuff Tom I have very wideband speakers that IMO qualified for proper evaluations
Thank you
Lawrence
In most cases, a string of op-amps will exhibit higher THD than a single op-amp. There are exceptions, though. In some cases, you might get harmonic cancellation. In other cases, such as with composite amplifiers, you can use a low-THD op-amp to drive down the slightly higher THD of another op-amp. However, to get any reduction in THD, I'd argue that you need an architecture or circuit topology that reduces the THD.
I appreciate your offer. You're certainly welcome to build an amp and review it. Also, should my travels take me past your location, I could bring an amp for you to listen to.
The people who build the amps and take the time to write me with their experiences like the amps.
Tom
Kool Thanks
I am in the Dallas area now ....any of your customers located here that i may contact?
Thanks again
Lawrence
I am in the Dallas area now ....any of your customers located here that i may contact?
Thanks again
Lawrence
If there are, they're certainly free to speak up here or contact you directly via PM.
I've shipped boards across most of the US and quite a bit of the rest of the world. I don't recall specifically if I shipped boards to the Dallas area. If someone pops up, I can ask for their permission to share their contact info with you. I do respect my customers' rights to privacy.
My travels take me to the left coast of the US, so Dallas isn't in the cards for me at this time.
Tom
for Lawrence
Hi Lawrence,
I built the Mod-86 and would say it's the best $300 I've spent on audio.
I've compared it to a UCD amp and both the UCD owner and I thought the Mod-86 considerably "better".
We also compared it to Halcro monoblocks. I thought they had a similar sound though the Halcros had more detail.
And Tom is available for advice and reassurance.
Merry Christmas
tim
Hi Lawrence,
I built the Mod-86 and would say it's the best $300 I've spent on audio.
I've compared it to a UCD amp and both the UCD owner and I thought the Mod-86 considerably "better".
We also compared it to Halcro monoblocks. I thought they had a similar sound though the Halcros had more detail.
And Tom is available for advice and reassurance.
Merry Christmas
tim
Tom
My boards turned up today - really impressed with the speed of delivery as I only ordered these last week, and the estimated delivery time was 4 - 5 weeks (from memory).
The boards are the best quality I've seen; I also had a little chuckle to myself about how you've managed to hide the trace layout from view. And go on you for doing that.
It'll be a while before I can build them (need to buy the parts and find time), however I will report back with results.
My boards turned up today - really impressed with the speed of delivery as I only ordered these last week, and the estimated delivery time was 4 - 5 weeks (from memory).
The boards are the best quality I've seen; I also had a little chuckle to myself about how you've managed to hide the trace layout from view. And go on you for doing that.
It'll be a while before I can build them (need to buy the parts and find time), however I will report back with results.
I say 2-3 weeks for international shipments. Shipping to the EU tends to go a little faster, so probably more like 1-2 weeks. Still, I'd rather say 2-3 weeks and have the buyer be pleasantly surprised when the boards show up early.
Those who need more certainty and precision on the delivery dates can choose tracked shipping (Tracked Packet USA or Xpress Post International Air) during checkout.
That's actually done to minimize the ground inductance. By putting the ground plane(s) on the top side, the inductance of all the ground vias is eliminated. Thanks for noticing, though. 🙂
Tom
Very true. There's more to layout than just connecting the dots. That was definitely a lesson learned on the MOD86 development. I spent quite a while simulating and measuring different prototype layouts to optimize the performance of the MOD86.
Tom
Hi Tom, I just finished my build and it worked beautifully the first time I powered it up. Thank you so much for developing such a state-of-the-art amp for us!
I am using AK4495SEQ direct out to modulus-86. The amp is dead silent and transparent. Now I know if there is something in the music that I don't like, it won't be due to my amp or my dac, it will most probably be due to my source.
I have one suggestion for improving case wiring: if I am to build another Modulus-86 amp, I'd like to order a pair of modulus-86 boards with symmetrical layout, that is, of course, if Tom would kindly offer such an order option.
The reason for this is to optimize case wiring. Currently, my right channel has speaker out jumper very close to back panel, which helps a lot with reducing wiring connection between speaker out and speaker binding post. However, my left channel modulus-86 board has speaker out far away from back panel, requiring at least 9 cm more speaker wiring. To make sure that my two channels are perfectly paired, I had to add an equal length of wiring to my right channel as well. As I use expensive Neotech UPOCC solid core copper wire for internal wiring, this significantly adds up to my build costs while achieving less than shortest signal path.
The same situation exists for power cable connections too.
A symmetrical pair of modulus-86 boards would solve this problem beautifully. This way both my left and right channels will have the shortest possible power and signal path. In addition, I will have much neater case wiring and the lowest build costs as well.
Thanks.
pakultra
I am using AK4495SEQ direct out to modulus-86. The amp is dead silent and transparent. Now I know if there is something in the music that I don't like, it won't be due to my amp or my dac, it will most probably be due to my source.
I have one suggestion for improving case wiring: if I am to build another Modulus-86 amp, I'd like to order a pair of modulus-86 boards with symmetrical layout, that is, of course, if Tom would kindly offer such an order option.
The reason for this is to optimize case wiring. Currently, my right channel has speaker out jumper very close to back panel, which helps a lot with reducing wiring connection between speaker out and speaker binding post. However, my left channel modulus-86 board has speaker out far away from back panel, requiring at least 9 cm more speaker wiring. To make sure that my two channels are perfectly paired, I had to add an equal length of wiring to my right channel as well. As I use expensive Neotech UPOCC solid core copper wire for internal wiring, this significantly adds up to my build costs while achieving less than shortest signal path.
The same situation exists for power cable connections too.
A symmetrical pair of modulus-86 boards would solve this problem beautifully. This way both my left and right channels will have the shortest possible power and signal path. In addition, I will have much neater case wiring and the lowest build costs as well.
Thanks.
pakultra
Awesome. Thanks for sharing. I'm glad you like the amp and that it came together easily for you.
Early in the design process, I did actually consider making a mirrored board. I decided against it for a variety of technical as well as business reasons. I'll keep it in mind for future designs, though. Thanks for letting me know of your preference.
Tom
You could achieve the benefits without Tom having to stock a mirror imaged PCB by mounting the second PCB assembly to the heatsink with the component side down. It would complicate the board mounting and you'd need to wire the board connectors before installing. It would also reduce convective cooling of the LM317/337 heat sinks somewhat and might offend OCD sensibilities but it would allow a symmetrical wiring layout so it's kind of an OCD tradeoff! 😉
Hi Tom, I have a question about my -15V test. When I did the final check as instructed in your document, both of my +15V were exactly +15V, but both of my negative rails were only -14V. This is 1v short of 15V. Why is this so? Does this matter? Will it in any way impair my amp's performance? Do I need to adjust R21 to achieve exactly -15V? If so, what value should I use for the replacement R21?
Many thanks!
pakultra
Many thanks!
pakultra
Sorry Tom, false alarm. Please disregard my previous question about the negative rails.
I measured again, they are now exactly -15.03v, so there is actually nothing wrong. It must have been just a measuring error. I probably forgot to dial down my multimeter's voltage scale to 20V, therefore there were some measuring errors. That's why I only saw -14V last night. Now that I dialed it down to 20v, my meter showed more digits down to .03v.
Again, sorry for bothering you with a false alarm.
I measured again, they are now exactly -15.03v, so there is actually nothing wrong. It must have been just a measuring error. I probably forgot to dial down my multimeter's voltage scale to 20V, therefore there were some measuring errors. That's why I only saw -14V last night. Now that I dialed it down to 20v, my meter showed more digits down to .03v.
Again, sorry for bothering you with a false alarm.