I posted my build a while ago and at the time it still had an unsatisfactory relay attenuator from eBay. That has now been replaced with a very good (though tricky to solder, being all SMD) relay attenuator by Neutrality, of this forum, so I've attached a couple of final build photos. I've been listening to the amp for a while now and it sounds very good, completely noise free and very neutral, and the 0.1% thin film resistors used in the attenuator makes for a perfectly preserved stereo field. Thanks Tom, it's been a pleasure building your design, I've learned a lot along the way. And for other builders, I highly recommend Neutrality's attenuator as a great complement to the Modulus86.
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That's been my experience as well. Most throw money at me and go away. That's a pretty nice arrangement, actually, but I do like seeing the build pictures. Special thanks to those who post their build pictures in the various threads.
Tom
Attached are pictures of a Modulus-86 4 way build I just finished. I used a case and PS from a 2 way 25 watt Class A amp I had which I will use as an excuse for any sloppiness
. It was a pleasure to build these boards. The BOM was a big time saver, the boards are top quality, and the documentation extensive and very helpful... and so it Tom.
Objective Review: My Oscilloscope / signal generator/ distortion analyser (USB Analog discovery 2) is no match for the Mod-86. At first I was disappointed because I was measuring distortion that was lower than any other amp I had seen but not that much different. Tom pointed out it was probably my test equipment and sure enough my signal generator has harmonic distortion at -70 db.
There is a lot of discussion that many amps have "low enough" distortion so there is no point in the Modulus-86 ultra low numbers but I don't agree. While many amps look pretty good at 1 Khz and high power I like to look at 250 mW at 20 Khz. No amp I have had does particularly well (usually 20-30 db worse performance than @ 1 Khz). While I make no claim to hear past 14 Khz I have found the less distortion at low levels and at 20 Khz the better I like the amp. The Modulus-86 measures much better than any amp I have ever had (even though I can't completely measure it).
The main purpose for this 4 way build is for a "summer amp". I have a tri-amp system and was running El-34 triode strapped mono block amps on the mids and a class A on the highs (MOSFET for bass which is staying put). There is no doubt that 4 MOD-86 run WAY cooler than a Class A and two tube mono blocks.... somewhere around 400+ watts cooler and with more power as well.
Subjective Review: I built two MOD-86 first and used them on 1 channel and my old amps on the other channel and switched back and forth with some mono recordings I had. Knowing full well about bias and sighted testing I still believe I could ABX between the two. The MOD-86 were both more detailed and smoother. I especially liked the vocals and guitar tone... I usually miss my tube amp on the mids during the summer but not this summer. After listening I bought two more MOD-86 and completed my 4 way build. I will be selling off some amps this summer as well.
Bottom line I am a happy customer.
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Attached are pictures of a Modulus-86 4 way build I just finished. I used a case and PS from a 2 way 25 watt Class A amp I had which I will use as an excuse for any sloppiness
Very cool. Thank you for sharing!
Good to hear. And you're welcome.
Welcome to the club.
I need to resort to special tricks and use a precision oscillator to measure the distortion of the Modulus-86 with my APx525. The '525 is the second-best audio analyzer in the world. The $32k+ APx555 is better and might be able to resolve the THD of the MOD86 (both the MOD86 and the APx555 THD is around -125 dBc).That's what I've found as well. If the THD vs frequency rises significantly, I perceive the amp as harsh and straining. If the THD remains flat vs frequency - even if it's approaching audible levels as it is on many tube amps - I find I like it much better.
In the end, there's no substitute for precision.
Awesome. I'm glad the build worked out well for you.
Tom
Good to hear. I've opened up for preorders of the Guardian-86 and ISS (Intelligent Soft Start). Preorders will ship before my upcoming vacation.
Tom
Very cool, congrats on the new product line!
You said the Guardian-86 is "mono construction" meaning that two are required for a 2xMod-86 with a single Power-86, correct?
BTW - the "Buy it now" button on the Guardian-86 page doesn't go anywhere, though I was able to figure out the pre-order URL without too much difficulty.
And some of us just linger....
Hey... Works for me.
Thank you.
You are correct. If you prefer a stereo version, I'll have the Guardian-686 available in mid/late July. It'll feature two Guardian-86es on one board. It can be used with balanced/bridged/BTL amps, such as the MOD686, or in a stereo MOD86 build.
If you've built your stereo MOD86 as a sort of "dual mono", i.e. with the two outputs on opposite sides of the chassis, you'll likely find the Guardian-86 easier to work with.
BTW - the "Buy it now" button on the Guardian-86 page doesn't go anywhere, though I was able to figure out the pre-order URL without too much difficulty.
I changed that last night. If you hit reload in your browser you'll get a Buy it Now button that works. As you pointed out, you can also find the Guardian-86 (and ISS) in the Solid State section of my website.
Tom
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Ah, gotcha - thanks, yes, must have had it cached.
Well, now I'm conflicted. For the specific case of a stereo Mod-86 is there any reason (layout, BoM cost) to prefer the Guardian-686 vs 2 Guardian-86s or vice versa?
EDIT - think you were editing as I was replying. Thanks, that answers the question.
The BOM cost of one Guardian-686 will probably be $1 less than the BOM cost of two Guardian-86. You might save $5 on one board vs two. Nothing earth-shattering (and subject to change). I won't know the board pricing of the Guardian-686 until I have a quote from my manufacturer ... which requires a layout to submit to quote.
I'd let the chassis layout drive the decision.
Tom
I'd let the chassis layout drive the decision.
Tom
Oh, I'm planning much more than a kludge. I've already approached ModuShop about drop shipping and similar sundry details to see if I can make a Modulus chassis available.
I'm thinking 2 x MOD686 + 2 x Mean Well RPS-400-27 + ISS + Guardian-686 in a 3U Mini Dissipante for the Vancouver Island DIY Fest in August.
Tom
I'm thinking 2 x MOD686 + 2 x Mean Well RPS-400-27 + ISS + Guardian-686 in a 3U Mini Dissipante for the Vancouver Island DIY Fest in August.
Tom
You have two kidneys for a reason...
Honestly, I don't know yet. I need to know what to stuff in the box before I'll know what to charge.
I agree. I did the math when I built my 4xMOD86 amp (that you saw at the Audio Fest two years ago). With heat sinks from HeatsinkUSA and raw aluminum from Online Metals, just the raw materials would set me back about 2/3 to 3/4 of the cost of an eBay BZ4309 chassis - including the cost of shipping the chassis from China to the US via DHL. There's no way I'd be able to build a chassis and have it anodized for less than the cost of the BZ4309. I subsequently discovered ModuShop/HiFi2000. Their 2U Dissipante is similar to the BZ4309, but of much nicer construction. Last I checked, the shipped cost of the 2U Dissipante was on par with the BZ4309, and with ModuShop I don't have to deal with eBay.
Did DIY Audio Store ship from the US or did they drop ship from Italy?
Tom
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Read. Comprehend. It's a skill.
I just answered my own question: Chassis Shipping Information – diyAudio Store
DIY Audio Store drop ships the chassis from Italy.
Tom
I just answered my own question: Chassis Shipping Information – diyAudio Store
DIY Audio Store drop ships the chassis from Italy.
Tom