The Multi Amp aka Dynalo Mk2

[Pars]

Kerry,

What is your impression of the Alpha pot since using it? Taking a quick look I didn't see anyway to get the TKD 601 and the Alpha to play nice together on the same board. If it wasn't for that damn tap or the way they did the pin order on it...

[cspirou]

Wanted to let everyone know that my Song Heui GB is now open to everyone. There is a limited number of pots so a large request is not likely to be honored but I will try to get you at least one. I am coming up with a testing setup to make sure that even if you only order one that it's a functioning one. I also have a TKD GB going if anyone missed the previous one.

[luvdunhill]

I think it would be cool to actually remove the amplifier circuit from the board and make it modular - plug-in boards for the amplifier section and maybe even the PSU.

Would there be interest in something like this down the road?

[kevin gilmore]

how very threshold

benefits, one channel gets trashed, replace it, disadvantages, board costs

 

[cspirou]

1 hour ago, luvdunhill said:

I think it would be cool to actually remove the amplifier circuit from the board and make it modular - plug-in boards for the amplifier section and maybe even the PSU.

Would there be interest in something like this down the road?

Like the headamp GS-X? Isn't the regular Dynalo Mk2 + GRLV pretty modular already?

[mypasswordis]

The headamps are modular, but regular Dynalos are not.

An interesting idea would be to lay the amp sections on their "sides" and have them plug in to a horizontal main board, like RAM on a motherboard. The main board(s) would have I/O stuff (input and output jacks and all that jazz).

Or you could go full HC and do something like Ayre, with a single milled aluminum chassis breaking everything up into sections and all the boards laying on their sides.

[palchiu]

Kerry,

What are these trasistors Q1~4/Q13/Q14 you recommand to uesd ?

Thanks for you sharing your beautiful dynalo to us.

Pal

[JoaMat]

May I help?

Q1/Q3/Q13 - MMBTA56

Q2/Q4/Q14 - MMBTA06

[palchiu]

4 hours ago, JoaMat said:

May I help?

Q1/Q3/Q13 - MMBTA56

Q2/Q4/Q14 - MMBTA06

JoaMat, thank you!!!

 

[cspirou]

What purpose do these holes serve? Are they for PCB standoffs?

[Kerry]

They were in case we wanted to shield things.  They are not required.

[FallenAngel]

What's the TL;DR on settings? 3 trimpots, what should be done with them, measured where and adjusted how?

Thanks.

[Pars]

take a look around this post

 

[FallenAngel]

Need more TL;DR than that. Like measure X resistor and adjust TP1 until 0v.

[sbelyo]

Does anyone who ordered a set of Dynalo boards want the little adapter board that is part of the gerber?

[mwl168]

14 hours ago, FallenAngel said:

Need more TL;DR than that. Like measure X resistor and adjust TP1 until 0v.

The 3 trim pots on each channel adjust the output DC offset. You want to get the offset as close to 0V as possible reference to ground. The adjustment needs to be made without the servo engaged.

If you are using the TO92 version boards, the pot next to the LED by the power connector affects the output of both phases while the 2 pots in the middle of the board each adjust one phase of the output. I first adjusted the pot next to the LED so that the inverted and non-inverted output offset are fairly evenly spread in reference to ground, I then adjusted the pot on each output phase to bring the offset close to 0V. The goal, when you done adjusting, is to get the DC offset between the two output phases as close to 0V as possible. This is very tricky work due to the constant thermo drift so experiments and patience will be needed.

There are quite a few related discussions in this thread if you have not already read them.       

Edited October 20, 2016 by mwl168

[FallenAngel]

On 20/10/2016 at 5:52 PM, mwl168 said:

The 3 trim pots on each channel adjust the output DC offset. You want to get the offset as close to 0V as possible reference to ground. The adjustment needs to be made without the servo engaged.

If you are using the TO92 version boards, the pot next to the LED by the power connector affects the output of both phases while the 2 pots in the middle of the board each adjust one phase of the output. I first adjusted the pot next to the LED so that the inverted and non-inverted output offset are fairly evenly spread in reference to ground, I then adjusted the pot on each output phase to bring the offset close to 0V. The goal, when you done adjusting, is to get the DC offset between the two output phases as close to 0V as possible. This is very tricky work due to the constant thermo drift so experiments and patience will be needed.

There are quite a few related discussions in this thread if you have not already read them.       

Thanks my friend. I had thought so but really wanted a clear and direct answer like this.

After 15 minutes of setup, I've gotten both boards to about 0v. The second was MUCH harder for some reason but it looks good now.

[Pars]

Were the transistors matched? If not, getting to 0V without the servo could get touchy. Even matched, it might not fall perfectly into place.

[RudeWolf]

You won't get a real zero with most DMM's and that's really not needed. My rule of thumb is to stay below 5mV at all times and be done with it. Just watch that warmup doesn't stray too sideways and you should be okay. Also - when adjusting with servo opamps in place, always measure the opamp output pin rather than amp output.

P.S. What's the current standing with PCB design on the mini-dynalo? Maybe it would make sense to make the PCB wider so it fits readily available cases? And add standoffs for guys wanting to mount it with screws.

Edited October 24, 2016 by RudeWolf

[JoaMat]

IMO it's fairly easy to build a nice case for this board without the need for standoffs.

[Pars]

Also, I don't think you want the board to slide in the slots present in these cases, but instead want the board to not touch the sides. There are some traces (including AC) very close to the board edge.

[cspirou]

8 hours ago, JoaMat said:

IMO it's fairly easy to build a nice case for this board without the need for standoffs.

I would prefer it. All the parts on the front panel are fine sticking through without attachment. This means I wouldn't need to worry about the front panels holes being a little too big and I don't need to worry about the top, bottom and sides being exactly 6.8", I can afford to have something a little bit longer without penalty.

However this is mainly an issue when shopping around for a stock case. Something custom made shouldn't be too much of a problem.

[Pars]

I sent an email to Context Engineering regarding their 6008H-8.5N case (8.5" long) and whether they could cut them to 6.8" (or 6.840") for this application.

I have not followed up with them yet.

Quote

Hi Chris,
 
Thank you for your interest in our aluminum splitbody enclosures
 
Yes we can cut to your required length, but since we do not do any machining hear the lead-time can be 6 plus weeks after receipt of order and it also depends on the qty.
 
If you would like us to work up a quote for you, send your required depth, quantities you need quoted, also if you need a finish.  We offer the natural aluminum, and various colors of anodize finish, we also offer custom machining, and silkscreen and laser etch for any artwork you may need
 
If you should have any questions, do not hesitate to contact me
 
Regards,
 
Lucy del Real
 
Context Engineering
1043 Di Giulio Ave
Santa Clara, CA  95050
PH: (408)748-8676
Direct: (408)764-8214
Fax: (408)748-8683
Email: [email protected]
Website: contextengineering.com

 

[sbelyo]

is it 6.840 " in between the back of front and rear plates?

[Kerry]

I designed them at 6.80" and just measured the actual board at the same.

Components should keep to the same dimensions.  I just measured the pot face to the XLR input and it seems to be at 6.8" as well.