D-AOC PCBs - the building and help Thread

[ilfungo]

thanks but I do not understand ....
Kuby says:
"Change the input transformer from 10k:10k to 600:10k. Can be the same like the output transformer. 1:3 is cool, too.

600Ohms is high enough to be driven from any professional gear from the last 60 years. The changed transformer will give you additional 12dB gain at the input which you might really need as the compressor needs to be driven hard. It will also marginally improve the noise figures as a side effect due to the lower resistance. "

you advice 10K: 10K?
thanks

 

[syn]

thanks but I do not understand ....
Kuby says:
"Change the input transformer from 10k:10k to 600:10k. Can be the same like the output transformer. 1:3 is cool, too.

600Ohms is high enough to be driven from any professional gear from the last 60 years. The changed transformer will give you additional 12dB gain at the input which you might really need as the compressor needs to be driven hard. It will also marginally improve the noise figures as a side effect due to the lower resistance. "

you advice 10K: 10K?
thanks

Yes I use 10k:10k and the rest are Kubi mods.

"600Ohms is high enough to be driven from any professional gear from the last 60 years."

Yes it is, but some  dislike the way it sounds. A lot of pro equipment uses AB output driver stages which will
introduce a (unpleasent) higher crossover distortion when loaded with 600ohm (higher THD as well) .
To conclude yes they can drive 600ohm but they were designed with 10k loads in mind.
I use Lavry Blue D/A to DAOC and don't miss any volume. Outputs are  UTC A24 15K : 600ohm.
Oh- and i use 10uF Ampohm PIO caps at the output (so not ALL Kubi mods  ).
The other source of distortion is too hot signal to the input tube. With 1:4 that is more likely to happen then
with 1:1. I think 1:4 more applies to the 1 vactrol only situation.
just my 0.2c

 

[ilfungo]

Thanks Syn
I have 2 edcor XSM 10k: 10k I try and tell you what happens
thanks

 

[j.frad]

I use my daoc unbalanced with kubi's mods because I felt the edcor were not consistent enough (one gave me no bass, and aftre replacing one both didn't sound the same...).
I will put transformers back when I get really goos ones, my cables are short anyway.
The makeup is usually all the way up but I have no problems with levels.
When mastering I calibrate to converter sensitivity to run at lower levels to preserve headroom and I can still get it to compresse with no problem.
I hope it helps!
jules

 

[ilfungo]

news ...
I changed the input 600:10 k with 10K: 10K and ...
much better for the signal edcor but I can not have a sound that satisfies me
you know you recommend inexpensive alternative?
Thanks

 

[Hank Dussen]

Why not try the Lundahl LL1540? Can be wired as 1:1 or 1:2.
Lundahls are supposed to sound clean and correct and these are not to expensive.
They're often sold here for around 30 euros.
Maybe try here: http://www.groupdiy.com/index.php?topic=40845.msg506206#msg506206

 

[syn]

See that you use a proper termination resistor (r101)
for the input transformer. It is hard to find inexpensive
but good high impedance transformer.Lundahl is good.

 

[ilfungo]

Thanks Hank Dussen
thanks syn....

See that you use a proper termination resistor (r101)
for the input transformer. It is hard to find inexpensive
but good high impedance transformer.Lundahl is good.

What do you mean by correct value ?
Edcor XSM 10K: 10K (from Bom = 15k) is correct?
Thanks

 

[syn]

it depends on the transformer you are going to use.some will be happy with 15k
some will be less happy.you have to decide what  transformer are you going to use
and then the termination network. the other way around will not work.

 

[ilfungo]

Edcor XSM 10K: 10K

how can I calculate it?

thanks

 

[syn]

Use RMAA. Use o.scope. Do search, plenty of info on the forum.
For 10k:10k the obvious choice is 10k resistor. start from there if you like.
Transformer will reflect that value to the primary, so source (output of your DAC)
will see 10k load and will be happy with it.
I don't know anything about edcor transformers.
Best

 

[kambo]

i am going through parts, i have most parts in stock,  PCB will be here soon
i think i am gonna have unbalanced out option, but like the drive the last tube stage , and have an additional
output control right at the unbalanced output...

should i use unbalanced attenuator calculated for 600ohm,  or 10K
or
should i order a good quality 1/2w pot, 10k, or 1k (as used with some balanced equipment)
cheers

 

[ilfungo]

someone managed to change the vactrol attack and release?
I built two LA4 and changing a resistor from 82k to 150k has changed the response of vactrol.....(slow attack and release)
Can you tell me what resistor is is in DAOC?
Thanks

 

[dagoose]

someone managed to change the vactrol attack and release?
I built two LA4 and changing a resistor from 82k to 150k has changed the response of vactrol.....(slow attack and release)
Can you tell me what resistor is is in DAOC?
Thanks

Hmm.. that would be nice indeed.
Anyone?

 

[ilfungo]

???

 

[[silent:arts]]

someone managed to change the vactrol attack and release?
I built two LA4 and changing a resistor from 82k to 150k has changed the response of vactrol.....(slow attack and release)
Can you tell me what resistor is is in DAOC?

???

please compare your LA4 schematic with the D-AOC schematic and let us know if you find any difference

 

[ilfungo]

Thanks [silent: arts]
comparing the two schematics suggests that  common resistor is:
R102 (DAOC)
R13 (LA4) from 82k to 150k ( slow attack and slow release)
vactrol datasheet  saw that changing the value of resistor can change the response....
you think it might be right?
Thanks

 

[[silent:arts]]

good comparison

funnily it is even 8K2 vs 82K

I would say this resistor is your playground.
if it worked in your LA4 fine, if it works in the D-AOC  ???
you will find out

 

[ilfungo]

I would try using a POT
if it worked we would have a real control of attack!?
thanks

 

[[silent:arts]]

I doubt this mod will do any change to any timing, not in the LA4, not in the D-AOC, but what do I know.
compare it to the LA2 schematic, one part of this resistor is switchable - how is it labeled?