LM3886 w/ tube front end DIY project

Niteshade · « **on:** 11 Mar 2010, 02:56 pm »

Mariusz and I are sponsoring what looks to be an excellent DIY project with a unique board which has dual LM3886 chip amps, built in filters & rectifier and a 6DJ8 tube front end. I like the board's design and it should prove to be a good hybrid amplifier.

Materials required:

1] The board, as shown on Ebay: http://cgi.ebay.com/Excellent-2-X-LM3886-6N11Tube-Audio-Amplifier-Board_W0QQitemZ190377477809QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2c5361c6b1

2] A 56v transformer with center tap (Similar, but not over voltage can be used.) Note: About 3 amps or more would be nice. Good one: http://cgi.ebay.com/28Vx2-200VA-Toroid-Transformer-DIY-HiFi-Power-Amp-Kit_W0QQitemZ370271245773QQcmdZViewItemQQptZBI_Circuit_Breakers_Transformers?hash=item5635e2d5cd

3] Either a 6.3v or 12.6v (w/ center tap) transformer for the 6dJ8's filament supply Note: 1 amp or more. It's overkill, but they're inexpensive. Example: http://www.radioshack.com/product/index.jsp?productId=2102702

4] A decent sized heat sink

5] Mounting hardware for the heat sink

6] RCA's and 5-ways

7] Project box: fairly large- to make it easy to work on.

Project cost will be under $200.00, depending on what parts you purchase.

Something to consider: Keep your old hard drive! They're made from thick aluminum and can be used as heat sinks!

Just thought of this today. A little work might be necessary to make it happen- but it's doable.

NOTE: I will go through this project step by step in about three weeks.

face · « **Reply #1 on:** 11 Mar 2010, 03:14 pm »

I already have one of those Ebay tube/chip amps sitting here, I'll be following this.

shadowlight · « **Reply #2 on:** 11 Mar 2010, 03:26 pm »

Looking forward to it. Are you planning to provide links for all the parts that you plan to use/upgrade as part of the process, like the case, volume pot, etc?

Thanks

Mariusz · « **Reply #3 on:** 11 Mar 2010, 03:27 pm »

I want to thank Mr. Blair and few others for their willingness and drive to undertake these kind of projects. Projects which are not only budget sensetive but also make it easier to understand how audio components work and how to improve your skills as a hobby builder.

Looking forward to this and future projects on Audio Circle.
Projects which in my opinion are in great demand but for some reasons missing.
I am sure there are many regulars on DIY forums but I do not see why we can't have it here as well.

Ones again thanks Blair and looking forward to this DIY project.

Best
Mariusz

Niteshade · « **Reply #4 on:** 11 Mar 2010, 03:38 pm »

I will modify the original post as reliable parts locations are found. The 12.6v transformer can be found at Radio Shack. The parts I am making the amp from will differ in appearance, but operate the same way. I purchased some of the parts from different sources THEN realized I should have looked for more generic components that are easy to find repeatedly.

The differences are technically negligible.

etcarroll · « **Reply #5 on:** 11 Mar 2010, 07:48 pm »

This looks like a fun project - looking forward to the updates as they come in.

Niteshade · « **Reply #6 on:** 19 Mar 2010, 12:46 am »

The board is in. No instructions with it!

Not only are there no instruction with it...the board is miss-marked!

The good news: It appears to be built well and the design looks good.

[Image from Ebay seller]

It is marked as taking a 52 volt transformer, not a 58 volt model as in the diagram. I will email him regarding this issue. The outputs might be miss-marked as well. I know it is difficult to mark things on PC's. I am positive it can all be resolved. The soldering is perfect! It uses the isolated LM3886 IC's which are easier to mount.

Niteshade · « **Reply #7 on:** 19 Mar 2010, 01:30 pm »

I have a question for everybody: The electrolytic capacitors can be upgraded. However, since this is a double sided board- it's not going to be easy. The caps they're using are low computer grade and have a lifespan of 1-4 years.

The trick to taking these out: You cannot desolder them! The solder is used as a heat transfer medium that can wick up to the top side. Solder cleanup takes place after the part has been removed.

Since the leads cannot be clipped from the top-side, the legs have to be heated one at a time from underneath. The capacitor(s) has to be gently pulled from side to side (left, then right, etc..) until it is free of the board. Your iron cannot be too hot or board damage will occur. The tip has to always be clean.

Once you get the hang of it, the upgrade process will go fast. Do it wrong and the board can be destroyed.

Would you folks like a demonstration of this upgrade process?
You are not allowed to blame me IF you do it wrong.

etcarroll · « **Reply #8 on:** 19 Mar 2010, 02:05 pm »

Are you thinking of a live webcast?

Why not post it as a youtube vid?

Either way, I'd be curious to see your technique.

Gene

wushuliu · « **Reply #9 on:** 19 Mar 2010, 09:55 pm »

Quote from: Niteshade on 19 Mar 2010, 01:30 pm

Would you folks like a demonstration of this upgrade process?
You are not allowed to blame me IF you do it wrong.

A demo is a great idea. Some of these kit boards can be a right pita to mod, and you don't realize what approach is best 'til after the damage is done...

Mariusz · « **Reply #10 on:** 19 Mar 2010, 11:13 pm »

Awesome Blair

I am so glad you are in charge of the iron and me ......
well, ........keeping the fingers crossed.

It seems like easy projects can become a nightmare for less experienced, weekend builder.

.......and do not worry about any part upgrade you choose to implement.
As long as it sounds good at the end and otheres can learn from it - the rest is peanuts.

Mariusz

Niteshade · « **Reply #11 on:** 19 Mar 2010, 11:21 pm »

The capacitor upgrades are necessary regarding product quality. Better sound could be a side effect, longevity..absolutely!

Working with double sided boards is a challenge for anybody! I've worked on hundreds of them over the years. That's why I switched to point to point.

My guess is that it will sound good. It has a protection circuit and status LED's. All resistors and solid caps are great quality. The bridge rectifier used is enormous! It has two 10,000uf 'audio grade' caps installed as well. These are clearly all good points!

Niteshade · « **Reply #12 on:** 31 Mar 2010, 10:54 pm »

The capacitor upgrades just arrived from Mouser. I will let you know when the upgrading process begins.

JoshK · « **Reply #13 on:** 31 Mar 2010, 11:01 pm »

Quote from: Niteshade on 19 Mar 2010, 01:30 pm

I have a question for everybody: The electrolytic capacitors can be upgraded. However, since this is a double sided board- it's not going to be easy. The caps they're using are low computer grade and have a lifespan of 1-4 years.

The trick to taking these out: You cannot desolder them! The solder is used as a heat transfer medium that can wick up to the top side. Solder cleanup takes place after the part has been removed.

Since the leads cannot be clipped from the top-side, the legs have to be heated one at a time from underneath. The capacitor(s) has to be gently pulled from side to side (left, then right, etc..) until it is free of the board. Your iron cannot be too hot or board damage will occur. The tip has to always be clean.

Once you get the hang of it, the upgrade process will go fast. Do it wrong and the board can be destroyed.

Would you folks like a demonstration of this upgrade process?
You are not allowed to blame me IF you do it wrong.

Sounds like a good opportunity for making a youtube video.

Mariusz · « **Reply #14 on:** 31 Mar 2010, 11:08 pm »

Quote from: Niteshade on 31 Mar 2010, 10:54 pm

The capacitor upgrades just arrived from Mouser. I will let you know when the upgrading process begins.

Can not wait much longer Blair.

Hope to see some pics along the way. (please)
YouTube would be great but we do understand if it becomes impractical.

Cheers
Mariusz

Niteshade · « **Reply #15 on:** 1 Apr 2010, 04:10 pm »

You Tube is going to be a future project. I have some other surprises on the way as well for virtual auditioning, kits, etc.. AV aids are an asset and can't be ignored.

Mariusz · « **Reply #16 on:** 1 Apr 2010, 04:43 pm »

Love surprises!

So, where are those Easter eggs???????

Mariusz

Niteshade · « **Reply #17 on:** 1 Apr 2010, 05:07 pm »

I dunno where the Easter Eggs are.

A long, long time ago my mom got me this HUGE chocolate hand made Easter egg filled with fudge, caramel & something else- like a white chocolate fudge.

I was only 4 or 5, but still remember it!

Mariusz · « **Reply #18 on:** 1 Apr 2010, 06:21 pm »

LIKE THIS ONE ?????

Mariusz · « **Reply #19 on:** 12 Apr 2010, 12:23 am »

Hello Blair

Any progress on the kit build off?

Mariusz