525 build thread

[DAN_000]

Hey Peter,  I readed your BOM and is IC meter is marked as LM391X , but, there are differents law on this IC.
LM3914 Linear Version
LM3915    3 dB/step, 30 dB range
LM3916 Audio VU Version

and, what about DCR in original analog meter ?  any 391X is HIZ buffered. Maybe we can add a resistor in that place?
Best!

 

[benlindell]

Crappy n00b question. I've order 2 sets of caps now, and keep getting the wrong casing of WIMA caps, which ones should I have gotten?

Also wondering which LM391X chip people used? I assume the Audio VU one?

-ben
http://www.benlindell.com

 

[benlindell]

just finishing up my 525s and had a few quick questions to double check before I blow it up.

1. the output transformer termination mod. what is the best/most popular way of doing this? leaving the 600ohm resistor off or leaving it there and no jumper or do I have this all messed up.

2. the optional 10pf cap (C4) doesn't need to be jumped if not there correct (read the schematic and that looks to be true but just wanted to double check)

those are it for the moment.

thanks guys

-ben

 

[peter purpose]

Hey Peter,   I readed your BOM and is IC meter is marked as LM391X , but, there are differents law on this IC.
LM3914 Linear Version
LM3915     3 dB/step, 30 dB range
LM3916 Audio VU Version

and, what about DCR in original analog meter ?  any 391X is HIZ buffered. Maybe we can add a resistor in that place?
Best!

I use 3916. Try what you will Dan.

 

[peter purpose]

Crappy n00b question. I've order 2 sets of caps now, and keep getting the wrong casing of WIMA caps, which ones should I have gotten?

Also wondering which LM391X chip people used? I assume the Audio VU one?

-ben
http://www.benlindell.com

Look at the pcb footprint. It's small, with a 5mm spacing.
See above.

 

[peter purpose]

just finishing up my 525s and had a few quick questions to double check before I blow it up.

1. the output transformer termination mod. what is the best/most popular way of doing this? leaving the 600ohm resistor off or leaving it there and no jumper or do I have this all messed up.

2. the optional 10pf cap (C4) doesn't need to be jumped if not there correct (read the schematic and that looks to be true but just wanted to double check)

those are it for the moment.

thanks guys

-ben

1. Do it as in the instructions, or leave it out altogether.
2. correct.

 

[T1M0N_5]

hi
are those kits still available?

timon

 

[peter purpose]

I have a few of most things.

 

[memestudio]

Hello,
has someone tried to install an input transformer instead of the discrete op amp? Maybe a Lundahl 1540 or a Neutrik will work... http://www.neutrik.com/fl/en/audio/210_197961/NTL1_detail.aspx
They are small, so probably it is possible to place them on the 525 board.
Ciao
Fabio

 

[substitute]

Hey, I wanted to ask about the trimmer values.  The closest I can find is 50k, 2k, 5k, from mouser, I'm figuring these can be adjusted to the appropriate values.  Is this correct?

 

[substitute]

for the record, Peter said those trimmer values should be cool.

 

[benlindell]

Finished my first one tonight, haven't had time to calibrate it, I'm just super happy it didn't blow up when I first turned it on. It's squeezing and the in, out and less/more knobs are all working perfectly. There seems to be a little bit of difference on comp and limit, can't tell the difference in the releases.

Two things right of the bat:

1. The In and out button makes a bad scratch noise after it's been pressed in, any thoughts.

2. Peter shipped mine with a 100k pot for the attack, so I thought I'd try to make it work without any mods that have been put out, it doesn't do anything Did anyone find the most reliable mod to work for the attack knob?

I'll get a chance to calibrate it some time this week.

thanks

-ben
http://www.benlindell.com

 

[peter purpose]

1. The In and out button makes a bad scratch noise after it's been pressed in, any thoughts.

2. Peter shipped mine with a 100k pot for the attack, so I thought I'd try to make it work without any mods that have been put out, it doesn't do anything Did anyone find the most reliable mod to work for the attack knob?

1. Are you saying you have a continuous sratching noise when switch engaged, or a momentary?
2. You're going to have to do the mod. It's only a couple of trace cuts and a bit of wire.
I still haven't tried it, but I beleive Greg has. Small/miniscule range though.

peter

 

[benlindell]

1. It's a momentary scratch after the button is pressed, both in and out.

2. So even with the attack mods there is just a small variation of attack?

thanks

-ben
http://www.benlindell.com

 

[Greg]

2. So even with the attack mods there is just a small variation of attack?

That was my experience. Fantastic compressor but the variable attack (so far) is a bust.

 

[peter purpose]

I blame Joe Malone.. ;D
Ben, try a snubber on the switch if it bugs you.

 

[benlindell]

I'm kinda fresh, how do I do a snubber?

 

[substitute]

if you go to the drip site (dripelectronics.com) and download the instructions for his la2a there's some info and diagrams of snubbers.    I don't know how specific you need to be with the values though.

 

[SIXTYNINER]

very cool project

 

[kazper]

I've been pondering over the Attack issue since I'm in process of finally finishing up my 4 units.

In looking at the attack as it sits and appears it end up like this...?

Attack Time = 3.8 ms with the 38K (R5) and 100n cap.
Add the 10 K pot full value for a total Resistance of 48K we get 4.8 ms of Attack.
Using the optional 100 K pot + R5 we get 13.8 ms of attack.

Using a 330n cap we increase them to
38K =12.5 ms
48K=15.85 ms
138K =45.54ms

I'm using this calculator..
http://www.cvs1.uklinux.net/cgi-bin/calculators/time_const.cgi

I think peter originally designed this attack from Joe from JLM audio's post #18 on this thread http://www.groupdiy.com/index.php?topic=61.0

Overall I'm thinking that placement of the RC is the key factor, because of the added resistance of R5... so

The attack of the UREI 1176 is said to be 20-800 micro seconds, which is what were trying for in this circuit I believe.

Could you reorient the configuration of the parts to be something like the following?

Fet to junction (to other resistor) then 10K pot in reistat form, Cap(to Gnd), 38K (R5). This would provide Attack circuit from 0-1ms or 0-1000 micro seconds. Would this work just by moving the RC around? Would it be benifital to have a small resistance in front of the pot, say 200R...?

What would the effect be of the Fet with the cap straight to ground when the pot is adjusted to zero?

Sorry for all the basic question, I've been looking at lots of schematics to see what was done in other products and designs and came up with a few questions and ideas on how to make this work

Kaz