KG Balanced Dynahi build discussion thread

508 posts in this topic

Posted (edited)

Now that the PCBs are finding their ways to us -Balanced Dynahi Builders-, I think that it's time for starting a build discussion thread for this beloved amplifier.

The purpose of this thread is to create a place for builders to discuss all topics related to the build of this amp (parts, constructions, troubleshooting...), to share experiences and to consolidate the information and discussions about this project.

Schematics of the Balanced Dynahi and the associated Power Supply by KG.

Background information about the original KG Dynahi can be found here.

Based on the preliminary BOM posted by Lil Knight earlier, an updated version for the Dynahi and the associated power supply, including Mouser parts numbers for the not yet specified parts in the preliminary BOM can be found in the attachment.

For the resistors, Vishay-Dale alternative parts numbers are added for people who like to use Vishay-Dale resistors.

Happy building. cool.png

BALANCED DYNAHI_BOM.xls

Edited by Vortex

Share this post


Link to post
Share on other sites

Posted

Is there an equivalent to this amp in the commercial world?

Maybe a Headlamp Gilmore XXX or something?

FWIW, I'm kind of interested in building this now to drive my new cocobolo Grados.grin.gif

Share this post


Link to post
Share on other sites

Posted

FWIW, I'm kind of interested in building this now to drive my new cocobolo Grados.grin.gif

What about a DynaToob biggrin.png

AFAIK there is no commercial equivalent to the Dynamite

Share this post


Link to post
Share on other sites

Posted

The Bamaslama, true KG madness! anpopcornyi7.gif

Did that design ever see the light of day?

The thread just petered out. I just read the start and finish. Not start to finish...

Share this post


Link to post
Share on other sites

Posted

I have updated the first post with a BOM including Mouser parts numbers for the not yet specified parts in the preliminary BOM posted by Lil Knight earlier.

Share this post


Link to post
Share on other sites

Posted

Thanks vortex, for starting this thread.

Guys, newb here but Im eager to learn so Id appreciate any help. Right now I'm acquiring the parts for the Dynahi but I'm having some issues. When you look at the BOM and this layout(http://gilmore.chem....u/dynahibal.jpg) you can see there are two capacitors (470 uF/50v) Yet on the amplifier board itself there are six places for capacitors 470 uF / 35 v. Can anyone tell me which ones I need, preferably with a part number?

And my second question, would it be a good thing to spent a bit more for higher quality parts or should you strictly follow the BOM with its part numbers?

Share this post


Link to post
Share on other sites

Posted (edited)

You are correct that the final Dynahi PCB is a bit different than the layout under that link.

The PCB indeed has place for 6 capacitors: 3 on the positive rail and 3 on the negative rail.

These are local filter capacitors, the amp will work fine with 1 or 3 capacitors on each rail.

Since the amp is feeding by ±30V DC rail voltages, the used caps need to be rated at a higher voltage than 30V.

Capacitors rated at 35V (minimum) or higher (50V, 63V) can be used, as long as they fit the board.

Some examples of 470µF capacitors are:

Panasonic FM (Digi-Key P12400-ND)

Nichicon HE (Mouser 647-UHE1J471MHD)

About spending on higher quality parts, there is no general answer for that.

For the active parts (transistors/JFets), you have to follow the specified parts (or alternative parts in some cases).

For the passive parts (resistors, capacitors, volume pot…), one can go for boutique parts, but as long as they fit the board of course. (things you have to find out yourself)

Edited by Vortex

Share this post


Link to post
Share on other sites

Posted

One little note about the parts list for the power supply board.

As most of you already know, the PS board consists of a ±30VDC section and a lower voltages (3.3V, 5V and 12V) section.

The ±30VDC PS is used by the Dynahi. The lower voltages are only necessary if you are going to use relay-based stepped attenuator (for example: KG stepped attenuator or AMB δ1 stepped attenuator…). Otherwise you can skip the lower voltages section.

More precisely, the following parts can be left out of the PS:

Bridge Rectifier for 18V AC section

LM7805 - 5V regulator

LM7812 - 12V regulator

Murata 3.3V DC converter

1x 4700uf/63V capacitor

3x 1000uf/25V capacitors

Share this post


Link to post
Share on other sites

Posted

Awesome. Thanks for your time Vortex, that is some useful information to me. I think it is wise to be sticking to the more basic parts for my first build.

Share this post


Link to post
Share on other sites

Posted

I have a bunch of 1/4w PRP resistors for a Dynahi build (s/e) if anyone wants them I'll let them go really cheap. You'll just need to pick up a set for the second half if you're building a balanced one. gone

Share this post


Link to post
Share on other sites

Posted

Has anyone started stuffing (or touching smile.png ) the Dyna PCBs yet?

I was busy today and this is what my boards now look like.

The small things on the back are stacked KG stepped attenuators (for balanced use) and a LCDuino-1 processor.

Still lots of (case)work to do...

Afbeelding885.jpg

Share this post


Link to post
Share on other sites

Posted

Nice work!

Your project is evolving rapidly, cant wait to see the finished goods.

Share this post


Link to post
Share on other sites

Posted

Very Nice! What are your plans for the enclosure? :)

Share this post


Link to post
Share on other sites

Posted

Looks nice Vortex. Did you need to make any changes to the lcduino to work with KG's attenuators?

Share this post


Link to post
Share on other sites

Posted

Very Nice! What are your plans for the enclosure? smile.png

To keep things simple, I will go for something relative cheap and easy to get.

Probably this one or… this one. Both are made in Europe, so shipping cost is not a big issue.

The Dyna PCB’s are designed for this kind of enclosure. cool.png

Share this post


Link to post
Share on other sites

Posted

Looks nice Vortex. Did you need to make any changes to the lcduino to work with KG's attenuators?

I have not tried it out yet (will do soon), but I think that LCDuino will have no problem with KG attenuators.

For the processor, it’s just an 8 bits relay-based stepped attenuator (like any others from the same family).

Only point that needs attention is the 12V PS for the relays on KG attenuator boards.

Share this post


Link to post
Share on other sites

Posted

Looking good :)

Share this post


Link to post
Share on other sites

Posted

Has anyone started stuffing (or touching smile.png ) the Dyna PCBs yet?

I was busy today and this is what my boards now look like.

The small things on the back are stacked KG stepped attenuators (for balanced use) and a LCDuino-1 processor.

Still lots of (case)work to do...

Afbeelding885.jpg

Well work even faster, as I always look forward to seeing your final products! :)

Share this post


Link to post
Share on other sites

Posted

silkscreen error on the dynahi power supply board.

The resistor labeled as 40k for dual tracking should be 20k.

schematic is correct.

Share this post


Link to post
Share on other sites

Posted

notice to people doing the dynahi power supply boards.

If you are using the lm4040, make sure you buy the 10 volt versions.

Otherwise you end up with the biggest +/-15 volt around :D

lt1021 definitely a better part, and not a lot more money if you buy from digikey.

Share this post


Link to post
Share on other sites

Posted (edited)

Thanks for the note on the Dynahi power supply board, Kevin. cool.png

I just wanted going to ask you about that resistor labeled 40KDT (40K for dual tracking).

There is also another resistor on the power supply PCB labeled 10KLO (on the negative rail section), which I couldn’t find in the schematic. (I’m using the schematic you have posted ).

Also, The value of R15 on the schematic is 10K.

To my opinion, R15 = R5 = 20K ? (correct me if I'm wrong or overlooked something)

Edited by Vortex

Share this post


Link to post
Share on other sites

Posted (edited)

On the power supply board, do not populate Q9,Q10,Q24,Q14,Q15,Q26

While it works great on the bench with dummy loads, when you try to power it up

with a real amplifier, the current limit comes up so fast that those transistors pop.

Likely need 1k ohm series base resistors on these, or the next size up in transistors,

something in a to92-mod case.

edit:

andy/steve have a working balanced dynahi now, a few teething issues...

Hopefully he will post the pictures he sent to me.

second edit:

only board from the group buy not tested now is the balanced dynafet board.

(obviously the most complicated of the dynamics)

Edited by kevin gilmore

Share this post


Link to post
Share on other sites

Posted

After some trial and error, we got the Dynahi to make music. And it sounds fantastic – prefer it to my balanced Dynalo with my grados (although it was built for Andy’s LCD-2). The following is what I learned in the process.

There are a few discrepancies in the PS silkscreen as compared to the schematic:

-R9 and R20 are 5K in the schematic and 10K in the silkscreen.

-R15 is 10K in the schematic and 20K in the silkscreen.

In both cases I followed the silkscreen. When powering up the amp boards the PS was blowing transistors. So I removed Q24, Q9, Q10, Q15, Q14, and Q26 (as per Dr. Gilmore’s suggestion), and populated 10KLO (left 40KDT unpopulated).

With this configuration I was able to power up both amp boards.

Initially I had a little trouble biasing and removing the offset in the amps. After some experimentation I got the offset down to 0. There was about 470 ohms across R1/R4 resulting in about 80 mv across the 20 ohm resistors. It ran really hot (about 60C on the heatsinks after about 15 minutes). To try to lower the heat I replaced R1 and R4 with a 680 ohm resistor and preset RV1 and RV2 to give 500 ohms across R1 and R4. This gave about 75 mv across the 20 ohm resistors. Still ran really hot. The problem is that my heatsinks have horizontal fins (as you can see from the photos). They don’t dissipate enough heat. Until these are replaced I’ll need to use a fan. Now to start building a case!

Many thanks to all involved with this project - looking forward to listening with Andy’s LCD-2s!

post-1195-0-84030300-1318874749_thumb.jppost-1195-0-01520200-1318874769_thumb.jp

Share this post


Link to post
Share on other sites

Posted

For those of you that bought the 2sa1349 from Electronix (in the bom) are they verified to be real?

If anyone has extras, I'm looking for just 2

Share this post


Link to post
Share on other sites

Posted (edited)

There is a missing resistor on the gates of the fets from the drive transistor, requires a cut on the circuit

board and attaching a 1k resistor. schematic updated.

like this

http://gilmore.chem.northwestern.edu/dynapowerfix.jpg

Edited by kevin gilmore

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now