[dip16amp]

Quote:

Originally Posted by kevin gilmore Real measurements. All under 1 amp load! 33.6 volts rms AC at the inputs of the diodes. 40 volts DC on the first stage rectification cap. 36 volts DC after the lm338 regulators. 30 volts DC after the opa541's.

Good to see that you got the LM338 input voltage down to 40 vdc but that diode drop is quite large. The schottky barrier rectifiers like the MBR1060 have much less voltage drop and I'll have to measure them to compare.

 

[kevin gilmore]

I have decided to add the trimpot to the reference, you can
choose not to populate it if you want.

Both boards will be updated within an hour or two.

 

[intlplby]

Is someone going to start the groupbuy thread?

 

[Edwood]

Calling Mister X................................

OK, after the holidays.

-Ed

 

[MisterX]

Quote:

Originally Posted by Edwood Calling Mister X................................ OK, after the holidays. -Ed

Monday Monday Monday.

 

[dgardner]

We should update the BOM for the two boards and put a some general pricing in for folks.

Here's what I have to far from the BOM listed above:
1) Change 3.57K resistor from 1/4w to 1/2w.
2) Pick a final part number the snubber caps on the rectifier diodes.
3) Put in alternate electroylic caps for both boards.
4) Add precision resistor options.

Any others?

 

[kevin gilmore]

Increased the mounting holes for the 3.5k resistors to make sure
they will take a .5 watt. If the length needs to change too, let
me know. Both boards now updated. The optional trimpot is a 10k.
http://gilmore.chem.northwestern.edu/dynahips.zip
http://gilmore.chem.northwestern.edu/dynahipsbig.zip

I would like 4 of the bigger boards if that is what you are going to
have made please.

 

[dip16amp]

The 3.5k ohm resistors would change to 3.32k ohm for a LM338 output of 36 volts. Maybe change the board silkscreen to say 40 volts on the LM338 inputs and 36 volts on the OPA541 inputs. Those would be the minimum voltages that you are currently running.

 

[ble0t]

Unfortunately, Mouser doesn't have the RN65D (1/2W) series in stock for 3.57k, but I found the KOA Speer (50ppm) with part #MF1/2CL3571F.

As for the snubber caps, the biggest voltage I have been able to find at Mouser in ceramic caps is 50V, which correct me if I'm wrong, seems a bit on the low side? They are Kemet .33uf 50V 10% with part #80-CK06BX334K. There are some 100V film caps made by AVX also...those are part #BF074E0334J. Anyone find anything else?

As for the precision 10k resistors, the part number listed earlier in the thread is also at Mouser and is part #PTF6510K000AXBF. These seem to be just what the doctor ordered

 

[dip16amp]

Quote:

Originally Posted by ble0t Unfortunately, Mouser doesn't have the RN65D (1/2W) series in stock for 3.57k, but I found the KOA Speer (50ppm) with part #MF1/2CL3571F. As for the snubber caps, the biggest voltage I have been able to find at Mouser in ceramic caps is 50V, which correct me if I'm wrong, seems a bit on the low side? They are Kemet .33uf 50V 10% with part #80-CK06BX334K. There are some 100V film caps made by AVX also...those are part #BF074E0334J. Anyone find anything else? As for the precision 10k resistors, the part number listed earlier in the thread is also at Mouser and is part #PTF6510K000AXBF. These seem to be just what the doctor ordered

The temperature coefficient is the main reason for using the precision resistors and the PTF5610K000BZBF and PTF5610K000TZBF does have three times better stability of 5 ppm/c than the PTF6510K000AXBF of 15 ppm/c.

 

[Edwood]

Is it adviseable to use one PSU per Dynahi board for dual mono? Or is it a waste, and not necessary? Or is it only necessary for a DynaMite with four Dynahi boards?

-Ed

 

[kevin gilmore]

picture of the current big board

http://gilmore.chem.northwestern.edu/dynahipsbig.bmp


There is no such thing as excessive. Two transformers, 2 power
supply boards, dual mono... Very nice.

 

[sft]

a wonderful thing:

2 transformers + 2 psu pcbs + 4 amp pcbs + switch
= a full bal. dynamight AND two dual mono dynahies

 

[skyskraper]

christ almighty !¬¬!¬

 

[bg4533]

Quote:

Originally Posted by kevin gilmore with the .2 ohm current limit resistors, the maximum current is about 3 amps. Certainly enough to run a dynomite, but not enough to run speakers. But if you are going to run a dynomite, you really want 2 power supplys for dual mono...

What is the point of a current limiting resistor? Wouldn't it be best to just let the PSU be limited by the OPA541?

If the resistor was lowered to .1ohm would the max current be doubled? Are there any problems with doing this?

Since current is limited it seems logical that the PSU can only take advantage of a certain sized transformer. Is this true? What is the max size that can be taken advantage of given the .2ohm resistors? How about .1ohm resistors? If I am to use a transformer with a current rating of 5A does this mean that without the current limiting resistor the PSU could output 5V?

I am considering integrating the Dynahi with a Gainclone or even using the Dynahi to power speakers directly and think I need more than 3A power.