Hi Tom, It's a while since I completed my Modulus 86 build and I am here to confess my sins. 
A while back we got a new piece of very nice oak furniture to sit the tv on. It was chosen because it had a deep shelf under plus drawers for bits and pieces and looked ideal for my large pre and power amp. When it came to fitting everything together the Modulus 86 with plugs etc in stuck out a bit so I jumped on a good price for a pair of monoblocks from a small but well respected UK manufacturer (particularly well known for its phono stages). These worked well in balanced mode sat behind my newish speakers - Neat Emotive SX2 - and looked very tidy. I've lived with this combo for quite some while and been more than happy but today I decided to try the Modulus 86 again.
Now, I have no real confidence in my electronic building so half expected it not to work any more but work it did! Not only did it work but it sounded absolutely fabulous. Unfortunately it hasn't shrunk while it's sat upstairs being starved of music. So here's the point of my post. It seems to be I have two options.
1. The furniture gets it - remove some of the back panel and slide the Modulus 86 back.
2. Convert my big box into monoblocks. I'm assuming this would be OK if I bought the same model transformer - 225VA, 230v to 2 x 22v from Airlink and another Power 86. Is it as simple as this and given the extra cost will there be any benefit in going monoblock using long XLR cables and short speaker cables?
For cases I have a couple of nice wooden boxes that would do the job plus some metal cages from some old SMPS supplies. Would putting the cages inside the wood boxes and doing all the earth connections to the cage be OK, with my limited knowledge it seems to make sense. I realise I'm going to have to find some suitable heatsinks to incorporate into the new build if I do go mono.
Cheers, Ian
A while back we got a new piece of very nice oak furniture to sit the tv on. It was chosen because it had a deep shelf under plus drawers for bits and pieces and looked ideal for my large pre and power amp. When it came to fitting everything together the Modulus 86 with plugs etc in stuck out a bit so I jumped on a good price for a pair of monoblocks from a small but well respected UK manufacturer (particularly well known for its phono stages). These worked well in balanced mode sat behind my newish speakers - Neat Emotive SX2 - and looked very tidy. I've lived with this combo for quite some while and been more than happy but today I decided to try the Modulus 86 again.Now, I have no real confidence in my electronic building so half expected it not to work any more but work it did! Not only did it work but it sounded absolutely fabulous. Unfortunately it hasn't shrunk while it's sat upstairs being starved of music. So here's the point of my post. It seems to be I have two options.
1. The furniture gets it - remove some of the back panel and slide the Modulus 86 back.
2. Convert my big box into monoblocks. I'm assuming this would be OK if I bought the same model transformer - 225VA, 230v to 2 x 22v from Airlink and another Power 86. Is it as simple as this and given the extra cost will there be any benefit in going monoblock using long XLR cables and short speaker cables?
For cases I have a couple of nice wooden boxes that would do the job plus some metal cages from some old SMPS supplies. Would putting the cages inside the wood boxes and doing all the earth connections to the cage be OK, with my limited knowledge it seems to make sense. I realise I'm going to have to find some suitable heatsinks to incorporate into the new build if I do go mono.
Cheers, Ian
I prefer to use short speaker cables and longer interconnects to reach the amplifiers.
That compromise seems to suit a bigger variety of hook-ups than using short interconnects and long speaker cables.
Going to mono-block simplifies the wiring.
A wood (non metallic enclosure) is good enough to hold the items together.
Three warnings.
Make sure it can't catch fire in event of a mishap, low fuse value helps a lot.
Connect the major metallic part to Protective Earth. This is what helps to blow that fuse in the event of a mishap.
Be thorough with RF interference attenuation.
That compromise seems to suit a bigger variety of hook-ups than using short interconnects and long speaker cables.
Going to mono-block simplifies the wiring.
A wood (non metallic enclosure) is good enough to hold the items together.
Three warnings.
Make sure it can't catch fire in event of a mishap, low fuse value helps a lot.
Connect the major metallic part to Protective Earth. This is what helps to blow that fuse in the event of a mishap.
Be thorough with RF interference attenuation.
Power amps need airflow, so having them on a shelf with no back is possibly not a good idea. Monoblocks behind (or in my case under) the speakers is the best compromise as the balanced input of the Mod means long interconnects are not an issue and the power amp has an easier time of it. Audible? Unlikely.
And then I decide to build M-86 Monoblocks ;-)
Progress Report:
Note: All prices quoted in $C
Boards for 1 M-86 monoblock (conventional PS, M-86) are in hand. Need a second set for the second monoblock amplifier.
Against Tom's probably excellent advice, I have purchased "boutique" resistors for parts of the circuit that are in the Signal Path. I just like to use certain parts that I am comfortable with; "known entities" if you will. They are not exotic by any means. Total Cost (for 2 M-86's plus extras for the parts bin) $14
A number of ancillary parts are in hand, things like the IEC inlet, for example.
I have not yet purchased the remaining elements of the BoM for 2 amplifiers. Along with some other parts for other projects, will be about $180 at Mouser Canada. Pencilled in for March.
My transformers are at my Customs Broker awaiting clearing, should be in my hands perhaps Wednesday.
The raw metal needed to construct the enclosures have been priced out online, but I have two metal suppliers here in town that can also fill the order. I will be pricing out their equivalents probably next week, and will be buying sometime after 1 March from one of the three.
I have purchased some tools that I had not anticipated needing prior to this project. For example a ceramic crucible and tongs, which along with Sodium Hydroxide and a Butane torch, I will use to prepare the 18Ga magnet wire. Yes, I will be wearing eye protection. I looked into buying a solder pot, but the prices were just unjustifiable in my opinion.
I am estimating total cost for the raw metal to build two enclosures to be perhaps $C 120 ($US 90). For the most part, the enclosure will be made of 0.500" (13mm) 6061 aluminum. Exactly what the cosmetic elements will comprise of is still undecided, but the intention is to look like a finished hopefully commercial-quality product rather than as a prototype.
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Johnny, I not sure you need all that exotic stuff to handle magnet wire -- I assume you're trying to remove the 'enamel' coating in order to tin the ends.. I've always had good luck using a hot-ish soldering iron to melt the goo and then tin the copper. It helps to carefully do a bit of scraping with an X-acto knife, being careful not to ding the wire.
I just use a utility knife to scrape off the enamel. You can get special tools for it, but scraping generally works well enough.
As far as mono block vs stereo build: As quoted above, I don't see a lot of advantage in going for a mono build. The main advantage is that you get to shorten the speaker cables. This means less resistance in series with the speaker and, thereby, higher damping factor.
If you're comfortable with the additional expense, by all means go for a mono build.
I don't see a problem with putting the amp on a shelf as long as there's plenty of air flow around it. If it's inside a cabinet, having an open back or lots and lots of ventilation holes in the back are needed.
Wood vs metal: I'm more of a metal worker. I like aluminum. 6061-T6 is awesome to work with. Wood works too, but I'm usually limited by my ability to work with it and my tool selection, so I tend to not go that route much.
If you do go the wood box route, follow Andrew's advice above.
Tom
As far as mono block vs stereo build: As quoted above, I don't see a lot of advantage in going for a mono build. The main advantage is that you get to shorten the speaker cables. This means less resistance in series with the speaker and, thereby, higher damping factor.
If you're comfortable with the additional expense, by all means go for a mono build.
I don't see a problem with putting the amp on a shelf as long as there's plenty of air flow around it. If it's inside a cabinet, having an open back or lots and lots of ventilation holes in the back are needed.
Wood vs metal: I'm more of a metal worker. I like aluminum. 6061-T6 is awesome to work with. Wood works too, but I'm usually limited by my ability to work with it and my tool selection, so I tend to not go that route much.
If you do go the wood box route, follow Andrew's advice above.
Tom
I'm just about to case up my 86p amps. Monoblocks in wanbo goldmund clone cases. Enough space to fit a second 86p should I choose to bridge them at a later date.
https://m.aliexpress.com/s/item/327...r-case&spm=2114.40010208.4.38.nvnkny#autostay
https://m.aliexpress.com/s/item/327...r-case&spm=2114.40010208.4.38.nvnkny#autostay
Dang! Nice chassis. That should certainly be ample heat sinking.
Don't plan for bridging. The LM3886 is not all that well suited for it. You can bridge an 8 Ω load, but not a 4 Ω. One of these days I really need to add a page to my Taming the LM3886 series that explains that.
Tom
https://www.aliexpress.com/item/180...id=029bb4c2-cb08-4e7e-b2b8-5b8636009842&tpp=1
As monoblocks, traffo and PSu board on one side amp board on the other
As monoblocks, traffo and PSu board on one side amp board on the other
There should be enough room for one Power-86 and one Parallel-86 board on the same side of the chassis. Plunk the transformer down in the bottom so the chassis is evenly loaded.
Putting the amp on the opposite side from the power supply is about the worst spot as the supply wiring gets to be the longest that way.
The Modulus-86/286/Parellel-86 don't care that much about the power supply. They can handle any droop across the wiring just fine. However, a Class AB amp draws current in half-cycle pulses so the currents in the supply harness tend to be pretty nasty. While the Modulus/Parallel aren't super sensitive to this, it would seem prudent to limit the amount of crud that you allow the supply harness to radiate.
I hope this makes sense. It's a multi-variable optimization problem (like any other engineering challenge).
Tom
Putting the amp on the opposite side from the power supply is about the worst spot as the supply wiring gets to be the longest that way.
The Modulus-86/286/Parellel-86 don't care that much about the power supply. They can handle any droop across the wiring just fine. However, a Class AB amp draws current in half-cycle pulses so the currents in the supply harness tend to be pretty nasty. While the Modulus/Parallel aren't super sensitive to this, it would seem prudent to limit the amount of crud that you allow the supply harness to radiate.
I hope this makes sense. It's a multi-variable optimization problem (like any other engineering challenge).
Tom
You of course are right that the job can be done differently, and at lower outlay. Others interested in taking on a Modulus-86 build can always use some cost cutting tips, I'm sure.
"All that exotic stuff" cost me $C 8.63 [$US 6.59] and about a month's wait from China. The butane torch is from my tool box and the Caustic Soda (Sodium Hydroxide) is a component of my usual chemical stockpile.
There are other uses for the equipment besides this little project. I have some tonearm wire that will need tinning, for example, and that does require a touch that the soldering iron trick or some emery paper probably won't work with. There are others. Besides, I have never felt that buying tools constituted a waste of money.
In other words, I am OK with it, as I am with the added cost of constructing monoblocks. I like a dual-mono construction in a stereo amplifier, and two chassis is not much more cost wise as a % of the overall build and offers more area for dissipating heat.
I'm not approaching this as a proper engineer would (one who designs a project so as to spend only as little as is absolutely necessary) ... I'm doing it like an amateur who wastes a lot of money making unwise but harmless choices, because I like it that way. And the final product will almost certainly still manage to be a bargain, despite my foolish approach. The only question mark is how much of a bargain, and for that I'll need to do some listening.
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