Modulus-86 build thread

[geraldfryjr]

Dipping an Antek transformer would require you to unwrap all of the insulating Mylar tape that is on it.
There are about 4-6 layers of the stuff and you can forget about putting it back on unless you are even more patient than you were taking it all off!!

There is also a layer of tape in between each winding layer as well as one around the laminate core.
The chances of getting any varnish past the the First winding layer is slim to none!

Been there done that!!

FWIW

jer

 

[AndrewT]

Dipping an Antek transformer would require you to unwrap all of the insulating Mylar tape that is on it.
There are about 4-6 layers of the stuff and you can forget about putting it back on unless you are even more patient than you were taking it all off!!

There is also a layer of tape in between each winding layer as well as one around the laminate core.
The chances of getting any varnish past the the First winding layer is slim to none!

Been there done that!!

FWIW

jer

Agreed, but it is an option that I thought should be mentioned, rather than ignored.

 

[udoitall]

While it's good to know about the option of dipping a transformer, it sounds well beyond my skill set. I'll contact Antek and see what they say.

I've ordered a variable bench power supply which I can use to test the amplifier in the meantime.

In the interests of due diligence, here is an audio clip of what the buzzing sounds like.

 

[tomchr]

I hope you find a better power supply than the Korad I picked up a while back. See my results here: http://www.diyaudio.com/forums/equipment-tools/264622-korad-power-supplies.html

I ended up with two HP 6643A supplies instead. Considerably more expensive than the Korad, but also considerably better performance.

~Tom

 

[maty tinman]

Hi from Spain

I am very interested about Tom's gainclone but but I will wait for it to finish developing the PCB with LM4780

Why? my KEF Q100 have 86 dB/w/m at "8 Ohms".

If you continue having troubles with the transformer (first contact with Antek) then you have DC on the mains like me. The best solution is to add a DC blocking / blocker.

After researching the various solutions available I chose the best according to my judgment.

PCB for DC trap/blocker/filter for toroidal transformers (toroids)

-> PCB for DC Trap Blocker Filter for Toroidal Transformers Toroids | eBay

DC trap/blocker/filter for toroidal transformers (toroids) - fully assembled

->DC Trap Blocker Filter for Toroidal Transformers Toroids Fully Assembled | eBay

 

[rob g]

Finally assembled the boards and tried them out. It lives! This is my first amp build and I didn't have to redo anything! Yet.

I was bitten by the bug in the Mouser system (see Post #334) which causes two connectors and a capacitor (per channel) to be missing; watch out for this if you order the Power86 and the Modulus86 BOM together from Mouser.


.........it played music, and pretty well.

Now the questions:
1) The transformer has an annoying buzz. I had to put my ear close to it to localize the source, but it's audible in the room. I'm hoping this will go away when I bolt it down in a chassis. This is audible without connecting the Mod86 boards; it's not through the speakers, it's directly from the transformer.

3) The sound volume was relatively low. This may be because of my cell phone being the source. But even with the volume on the cell phone turned up all the way, the sound was , well, a quiet listen.

4) I had the feeling that the vocals were somewhat recessed and the instruments somewhat forward, especially the bass. Again, the source, the speakers and the room are far from ideal, but perhaps someone has some explanation independent of these.

And what would a report be without pictures of the war zone. Gentlemen, feel free to comment, criticize, but do avoid direct abuse...

Thanks,
recently started on my build, still waiting for some components.
I was missing a couple of connectors too. I haven't soldered up the power board yet, perhaps I will also be missing those cap's. I will report to Tom in this thread if I am.

The output volume will seem relatively low as the amplifier gain is set a little lower than most Hi-Fi amplifiers, you can increase at a cost of worse sound to noise ratio) but even if you increase this by 6dB you should not hear any audible hiss, unless your ear is right up against the loudspeaker.

The cell phone will have weedy output, coupled to the low gain structure and maybe insensitive speakers? you shouldn't expect mega levels.

I wonder if the transformer hum is being exacerbated by the resonant cardboard box. Sympathetic resonances can be strange. It may indeed disappear when bolted down in your amplifier chassis with the rubber damper in place.

Consider that if you do not have a loudness function or equalizer changing the balance of sound on your phone (so we assume it is set flat) then the sound quality you describe is down to the original recording, or the loudspeakers in the room. The amplifier comes way, way down the list if it is a competent design.

The quality of the sound will probably be entirely down to the balance of the loudspeakers and their position in the room.
After the recording itself the loudspeakers are by a country mile the component that makes the greatest contribution to the quality of the sound, assuming a competently designed amplifier (and source component) is in the mix loudspeakers (and room) contribute massively (almost entirely by themselves) to the colouration of the signal.

The contribution to the sound quality (for the real world differences, not audiophilia nervosa) the part the amplifier plays is extremely minor, but it is there. it's all important of course but what you describe is not down to the amplifier (unless we've all been duped!).

 

[tomchr]

I recently started on my build, still waiting for some components.
I was missing a couple of connectors too. I haven't soldered up the power board yet, perhaps I will also be missing those cap's. I will report to Tom in this thread if I am.

I have an email in with Mouser on the issue of missing parts. It's a pretty clear bug in their system. I'll let you know of their response. Meanwhile, double-check that you get the correct number of capacitors (C9 in MOD86 R1.0; C10 in MOD86 R2.0) and 3-terminal supply connectors. This is only relevant if you order from two Mouser projects at the same time - so Power-86 and Modulus-86. Those ordering from one project only should get the correct number of parts.

~Tom

 

[Domi_78]

Hello everyone,
All equipment ordered has arrived. Now the final assembly phase.
- The first electrons should pass into the amp by tomorrow ...

Visible cables (mains and input signal) will be limited to those going through the pass-son to front panel and to rear panel.

 

[rob g]

Hi Tom,
Thanks.
I did combine the copied part BOMs and as a result I have four parts missing.

I actually completed soldering the mainboards one of the nights last week. Fully populated.

However I am missing C1 and C2 (for the Power 86 PSU not mainboards) from my Mouser order.
That is
R82EC3100AA70J Kemet | Mouser

Also I only have two 651-1714968 (J1 & J2) left so was considering hard wiring for power 86 end only. If you could get Mouser to recognise an issue with the orders and send the missing components to correct the orders that would be great. I realise it will be up to us as customers to claim this.

 

[Domi_78]

Hello everyone,
... Visible cables (mains and input signal) will be limited to those going through the pass-son to front panel and to rear panel.

Oups !!!
- "pass-son" is a bad translation from french to english, "grommet" is better !!!

 

[udoitall]

Hi from Spain

....
If you continue having troubles with the transformer (first contact with Antek) then you have DC on the mains like me. The best solution is to add a DC blocking / blocker.

After researching the various solutions available I chose the best according to my judgment.

PCB for DC trap/blocker/filter for toroidal transformers (toroids)

-> PCB for DC Trap Blocker Filter for Toroidal Transformers Toroids | eBay

.....


DC trap/blocker/filter for toroidal transformers (toroids) - fully assembled

->DC Trap Blocker Filter for Toroidal Transformers Toroids Fully Assembled | eBay

.....

Thanks for the detailed info, Maty. I have contacted Antek, let's see what they say. If no resolution, I will try your suggestion.

 

[rob g]

Hello everyone,
All equipment ordered has arrived. Now the final assembly phase.
- The first electrons should pass into the amp by tomorrow ...

Visible cables (mains and input signal) will be limited to those going through the pass-son to front panel and to rear panel.

Domi,
I see a piece of metal that currently blocks the path to the LM3886s. How are you going to attach the heatsinks to the LM3886s?
They need to be flush mounted across the entire surface of the chip.

 

[tomchr]

Mouser ordering issue

Would those of you who had issues with missing parts (supply connectors and C9 (MOD86 R1.0) or C10 (MOD86 R2.0) or C1, C2 (PWR86)) in your Mouser orders please forward your Mouser Invoice numbers to me via PM or email so I can pass them on to Mouser?

The issue you are experiencing has been reported by other Mouser customers as well. They're working on fixing it. To assist them in fixing the issues, Mouser asks for the invoice numbers that were affected by the bug.

Thanks,

~Tom

 

[Domi_78]

Hi rob g,

Domi,
I see a piece of metal that currently blocks the path to the LM3886s. How are you going to attach the heatsinks to the LM3886s?
They need to be flush mounted across the entire surface of the chip.

The thickness of the double bottom is inserted in the aluminum profile that serves as a heatsink and as a side of the case. On the pictures, it can be seen that the cooling area of the LM3886 "obscured" by the double bottom does not exceed 15% of the total area.
For the record, the power supply is -/+ 28V, so the maximum power dissipation is 18 watts and the output power is 28 watts into 8 ohms. That will be OK.

 

[rob g]

Domi,
Thanks for the additional pictures.
With the additional picture of the heatsink (above and below) I think the combination will be fine, provided you can make the contact surface area nice and even, a flush fit.
It looks like a smart build. I'm just using a regular aluminium Hi-Fi case for the Modulus amplifier unit I am making for my Dad.

 

[rob g]

Would those of you who had issues with missing parts (supply connectors and C9 (MOD86 R1.0) or C10 (MOD86 R2.0) or C1, C2 (PWR86)) in your Mouser orders please forward your Mouser Invoice numbers to me via PM or email so I can pass them on to Mouser?

The issue you are experiencing has been reported by other Mouser customers as well. They're working on fixing it. To assist them in fixing the issues, Mouser asks for the invoice numbers that were affected by the bug.

Thanks,

~Tom

Done,
Thanks Tom.

 

[udoitall]

Bad AC discovered and finally, listening!

Would those of you who had issues with missing parts (supply connectors and C9 (MOD86 R1.0) or C10 (MOD86 R2.0) or C1, C2 (PWR86)) in your Mouser orders please forward your Mouser Invoice numbers to me via PM or email so I can pass them on to Mouser?

~Tom

Thanks, Tom, sent via email.

Now, to report some progress. Evidently, the AC supply upstairs in my house is worse than the supply downstairs. When I plugged my build into a socket downstairs, lo and behold, the transformer stopped buzzing. I plugged in a more respectable source than my cell phone, and wow, what a sound! I listened to the amp for a long time (well, until the heatsinks became uncomfortably warm).
and I found the sound, well, superbly clean and totally non-fatiguing.

For a comparison, I swapped it out with an SMSL SA-50 (TDA7942) amp and an Onkyo SV515Pro, keeping the same source and speakers. Here are my subjective observations:
SA-50: Clean sound, but the higher frequencies seem artificially bright, and one tires of the sound after a while.
Onkyo SV515: Mellow sound, pleasing to the ear, but the sounds seem packed together somehow.
Mod86: Clear as a bell, great separation between instruments, completely non-fatiguing, the sounds are all well defined, but not harsh in any way. A winner.

Well done, Tom.

 

[soongsc]

You make it sound like a Goldilocks adventure.

 

[soongsc]

Hi rob g,

The thickness of the double bottom is inserted in the aluminum profile that serves as a heatsink and as a side of the case. On the pictures, it can be seen that the cooling area of the LM3886 "obscured" by the double bottom does not exceed 15% of the total area.
For the record, the power supply is -/+ 28V, so the maximum power dissipation is 18 watts and the output power is 28 watts into 8 ohms. That will be OK.

Looks like an interesting layout, how does the bottom the board is mounted on secure to the chassis? Just plug it?

 

[udoitall]

You make it sound like a Goldilocks adventure.

Forgive me for not being sufficiently jaded.