Aleph J build guide for noobs

[pinkfloyd4ever]

^ It's a tight squeeze, but it all fits. Chassis is from China, one of the better ones with the heat sinks as single piece.

What power supply boards are those? One of XRK's PS designs?
Looks like 2 of those are smaller than 4 of the standard DIY Audio supplies, correct?

 

[TungstenAudio]

Those are a couple of Prasi's PSU boards. Check out the Group Buys forum. There's a separate thread for the CRCRC boards. Two of these are definitely smaller than four of the diyAudio store boards.

 

[lonepine510]

1) 18v secondaries will give around 23V rails close enough to 24V
2) I wouldn't bother going with 20V secondaries unless you had 16 Ohm speakers.

Most people haven't even built an Aleph J cause what they have is an under-biased clone, adding more voltage is adding more heat to dissipate in an amp that is going to be hotter than the others.

Obviously if you plan to acount for all of that and scale the amp appropriately then that is a different story, but that's a little above noob level.

Hm. I'm def. a noob and I happened to have picked up an Antek 400 VA 20V secondary (and will use 8 Ohm speakers). I was planning to build the F6... but thanks to this thread thought to build the Aleph J...

 

[2 picoDumbs]

It's not technically difficult but you're not building an Aleph J with 1.5A.
Build it properly get the appropriate size chassis to dissipate 100W per channel at 25C rise above ambient, 30C rise would be ok if you had to go with that.

500VA would have been better for 200W, 400VA is acceptable though.

 

[alanhuth]

codyt: Thanks for the suggestion. Good idea.

 

[13stoploss]

13STOPLOSS et al: We feel your pain. Thats’ why we started this project. But please understand the purpose of this thread. This is not to be the instruction manual. The real benefit of this thread is for the guys building the instruction manual, Flohmann and myself, to ask questions and get feedback on ideas and corrections for the instruction manual. Our intent is that when the instruction manual is finished, you won’t experience the frustrations so many of us have felt. But we’re not there yet. Not even close.

I'm a managing editor and copy editor for the federal government's second largest department, and a former journalist with an MA in Writing. How can I help?

 

[flohmann]

One of my next posts over on the blog is going to be about good building habits (before we dive into the build posts). Here's what I'm intending to cover, let me know if there's more that noobs should know:

• Solder technique: clean your tip, a little solder for heat transfer, heat pads/leads, not the solder
• Clean and measure your parts as you install
• Put down a towel to catch fallen parts
• Continuity testing as you go
• Install parts so that values are legible from the top
• Ground yourself before handling static-sensitive parts (mosfets)

 

[6L6]

All great points!

Neatness counts.

 

[Russellc]

Ohh nice I didn't know about these. I've been wishing Antek would make a 250VA line of toroids for a dual mono Aleph J. Now if only I could find these 250VA Avels for Antek prices.

I just priced Antek, 41 bucks for 300VA 18 + 18, I just scored 2 of the Avel-L shown here, 109 the pair. They are excellent quality (historically anyway) and this is a reduced price.

I have used a lot of Antek with no problems, but I hope these to be better. I was on the fence to go Antek as usual, but at this price I will try these. These are only 250 VA to the Anteks 300 but I feel the difference there to be minimal.

Russellc

 

[Russellc]

One of my next posts over on the blog is going to be about good building habits (before we dive into the build posts). Here's what I'm intending to cover, let me know if there's more that noobs should know:

• Solder technique: clean your tip, a little solder for heat transfer, heat pads/leads, not the solder
• Clean and measure your parts as you install
• Put down a towel to catch fallen parts
• Continuity testing as you go
• Install parts so that values are legible from the top
• Ground yourself before handling static-sensitive parts (mosfets)

Towel on ground is an excellent point. One of my other hobbies concern building firearms and assembling ammunition. The towel on floor is used there to catch all sorts of tiny parts.

I have hardwood floors and it is amazing how tiny dropped items, wires, fets etc can simply disappear!

Russellc

 

[ItsAllInMyHead]

Depending on your scope, you may consider including some amount of personal electrical safety, particularly since this is a mains-wired project. That could be extremely helpful for new builders.

 

[JMacII]

question on the amp PCBs' connection to the speaker posts...

I see the connection for "out" which I take to be the red post. Is the black (-) post just connected to one of the ground connections on the board? So I will have the XLR ground on one ground pad, the black binding post on another ground pad, and then a connection to the star-ground from a third board ground?

I'm planning to have all the ground connections from the power supplies etc. connect at one bolt on the chassis that will also be connected to mains ground.

 

[TungstenAudio]

It is best to separate audio ground from chassis/ mains ground. Your plan for the star ground is appropriate for the audio ground, minus the connections to chassis and mains. The (-) speaker post may be connected to one of the ground connections on the PSU board.
The safety connection from the ground terminal on the IEC power inlet to the chassis should be made with a short wire. There are a couple ways to make the connection between audio ground and the chassis. I believe those have already been discussed earlier in this thread.

 

[JMacII]

So you would suggest mains ground along with transformer shields grounded to chassis at one point, then all the other ground wires connect at another point? Do I connect the audio group to the chassis, or float it, or direct connect the two grounds? I was under the impression that a single ground was preferred. Won’t they all be at the same potential if connected through chassis? Appreciate your help!

 

[2 picoDumbs]

Audio ground is floated using the thermistor, or in other words connected to chassis earth through the thermistor

 

[JMacII]

I’m using the soft start board and wasn’t planning a thermistor. Do I need one? And if not, does that change your grounding approach?

 

[2 picoDumbs]

The soft start has nothing to do with the ground lift thermistor.
These are 2 separate things entirely.
You can use the soft start board, but you still need a circuit ground lift, you can use a thermistor or Wayne's/Jam's ground lift circuit.

 

[JMacII]

The soft start has nothing to do with the ground lift thermistor.
These are 2 separate things entirely.
You can use the soft start board, but you still need a circuit ground lift, you can use a thermistor or Wayne's/Jam's ground lift circuit.

Ok, thank you. I thought the thermistor was used in power on delay, I didn't catch the need for one in the audio ground. From the F6 build guide I see 6L6 using a CL-60 on the audio ground. Am I correct that the softstart replaces the thermisotor(s) on input power?

Then I will need to build a star ground for the audio grounds, and insert the CL-60 between audio ground and safety/earth ground?

Thanks again for helping me through this.

 

[2 picoDumbs]

Audio 0V is connected to chassis earth by a thermistor.

 

[Russellc]

Ok, thank you. I thought the thermistor was used in power on delay, I didn't catch the need for one in the audio ground. From the F6 build guide I see 6L6 using a CL-60 on the audio ground. Am I correct that the softstart replaces the thermisotor(s) on input power?

Then I will need to build a star ground for the audio grounds, and insert the CL-60 between audio ground and safety/earth ground?

Thanks again for helping me through this.

Look at 6L6's BA3 power amp build. He used store soft start board in place of the 2 CL-60 parts normally doing "soft start" duty.

I did the same in my BA3 amp build, and it has worked very well for several years.

Russellc