Hi everybody,
I found that SL-10/CAS-1 for a good price, and they work very well! I use them with my Infinity Quantum 3. I'll recap them later, since I spend too many time and money to recap/refoam/fix the Infinities.
Now, my problem is that volume control is too sensitive: on first position it's already too loud. (I use a NAD C521).
Is there something wrong, or do I have to build an attenuator? Also, I have too much bass and subs, but maybe it's a Quantum 3 characteristic...
What do you think?
I found that SL-10/CAS-1 for a good price, and they work very well! I use them with my Infinity Quantum 3. I'll recap them later, since I spend too many time and money to recap/refoam/fix the Infinities.
Now, my problem is that volume control is too sensitive: on first position it's already too loud. (I use a NAD C521).
Is there something wrong, or do I have to build an attenuator? Also, I have too much bass and subs, but maybe it's a Quantum 3 characteristic...
What do you think?
Those have pretty standard gain characteristic, and the SL10 has an audio
tape pot, so unless they have been modified, you shouldn't have this as
an issue. Also, as I recall the SL10 did not have a stepped pot.
tape pot, so unless they have been modified, you shouldn't have this as
an issue. Also, as I recall the SL10 did not have a stepped pot.
Try this after each CD line output, with R1=10k, and R2=1k.
http://www.electronics-tutorials.ws/attenuators/attn8.gif
If it works better, you may need a different volume control.
wow, I have to check that! I opened it when when I returned from shop, just to check if something had been modified, and I just remember the "threshold" caps and a big volume pot in a sealed plastic case.
I do it and I return to you. thank you!
I do it and I return to you. thank you!
I restored an SL10 back in 2010 and wrote about my experience here:
http://www.diyaudio.com/forums/pass-labs/162305-restoring-threshold-sl10.html
I discuss a couple of different ways of reducing the gain in that thread.
I posted several pictures of that restoration here:
Threshold SL-10 preamplifier schematic and an introduction - www.thresholdlovers.com
---Gary
The line stage has about +28dB gain, so it's no wonder you have gain to burn on CD.
The volume control is 22k, so if you replace the 1k in series with it with a higher value,
that will burn some of the excess gain. To reduce the overall line stage gain to +14dB,
change the 1k resistors to 86.6k (or a near value), using 1% tolerance parts.
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Here is:
The pot is ok, 22K, not stepped but "detended", as says the schematic.
First, I'll try my SME/Garrard/Ortofon 540 MKII, and check if the gain is also a problem. Then I will probably change the serial resistors if needed.
Later I'll change the caps for Elna Silmic II , and maybe others low values for styroflex or something... A lot of suggestions on internet.
Do I have to re-set the trims? What is the procedure?
The pot is ok, 22K, not stepped but "detended", as says the schematic.
First, I'll try my SME/Garrard/Ortofon 540 MKII, and check if the gain is also a problem. Then I will probably change the serial resistors if needed.
thank you, I found your posts about... very helpful!
Later I'll change the caps for Elna Silmic II , and maybe others low values for styroflex or something... A lot of suggestions on internet.
Do I have to re-set the trims? What is the procedure?
Ok, I finally replaced the 18K2 with 4K7. It's a bit better, but It's still loud on second position... Maybe I will add the divider mod.
Next step will be to recap everything...
Last owner build a device which can be called "idiot proof delayed switching module" (with two LM555 and two e-relays). Do I really have to wait 60'' before switching on power amp? Would 30'' be enough?
Next step will be to recap everything...
Last owner build a device which can be called "idiot proof delayed switching module" (with two LM555 and two e-relays). Do I really have to wait 60'' before switching on power amp? Would 30'' be enough?
one BC517 , one (DT) relay , cap and resistor is all you need for turn on muting
if needed at all
even 5sec is plenty
if needed at all
even 5sec is plenty
I can set time, there is a trim...
I made a caps list, just have to order now.
And what about the trims?
I made a caps list, just have to order now.
And what about the trims?
power up , let it settle one hour , open , set output offset with trimpots
close the lid,let it sit again for one hour , repeat procedure until you have steady minimal output offset
close the lid,let it sit again for one hour , repeat procedure until you have steady minimal output offset
Ok,
-I've changed elkos on both SL-10 (Silmic II) and CAS-1 (tantalums for Silmic II and Nichicon FG). There is a big difference, although I couldn't describe it, excepted that I recovered some lost bright... I let the 6 big 6900µF for later, I spend too much money for now.
-I set offset as described by Zen Mod. I measured about 1mV.
-I cleaned big Waters volume pot (see post #8): in fact, it is a stepped attenuator! on each detent the brush stops on a pad, which is connected to the the resistive material by a track. The brush never touches the resistive material (conductive plastic). I forgot to make pictures, but have a look on this. It's a modular system easily demountable by layers. After clean, I have no more cracks.
But after that, I still have a small hum on left channel. I noticed it after changing the feedback resistors, but maybe it was already present before. It comes from SL-10, after volume. Any idea?
-I've changed elkos on both SL-10 (Silmic II) and CAS-1 (tantalums for Silmic II and Nichicon FG). There is a big difference, although I couldn't describe it, excepted that I recovered some lost bright... I let the 6 big 6900µF for later, I spend too much money for now.
-I set offset as described by Zen Mod. I measured about 1mV.
-I cleaned big Waters volume pot (see post #8): in fact, it is a stepped attenuator! on each detent the brush stops on a pad, which is connected to the the resistive material by a track. The brush never touches the resistive material (conductive plastic). I forgot to make pictures, but have a look on this. It's a modular system easily demountable by layers. After clean, I have no more cracks.
But after that, I still have a small hum on left channel. I noticed it after changing the feedback resistors, but maybe it was already present before. It comes from SL-10, after volume. Any idea?
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Since CD was still too loud, I added 56K on Aux1 inputs (I had 0.1% handy...), now it's correct, and it's ok with other sources (phono and DAC).
I re-soldered some components, and the hum disappeared.
The system is ok for now, maybe one day I'll change PSU caps.
Thank you for your help!
I re-soldered some components, and the hum disappeared.
The system is ok for now, maybe one day I'll change PSU caps.
Thank you for your help!