DIY Super Simple Preamp

[vin_eme]

Sachin,

as i mentioned earlier to balance the output impedance of LSA, i was having a tough time. And i figured out the culprit, which was the 100k pot. It didn't have the exact reading for 2 legs. One was 110k and other leg was 102k. So due to this difference, the bias voltage to the LDRs were varying and the overall output impedance had a mismatch. Had a tough time hunting down the 100k in SP road, finally found a couple of them, checked on the resistance, one leg was 99.4k and other was 99.2k. I connected them back and Viola!, have a balanced output from both channels.

~cheers

 

[josephjohnt]

Hi Vincent,
Where do we get good pots and RCA sockets in SP Road?
Thanks

 

[gopib]

@josephjohnt . he got them from HK...some posts above...

 

[josephjohnt]

My bad, wanted to enquire about the pots and not knobs.

 

[vin_eme]

Pots are very difficult to source. You can get them at below

1. Pankaj electronics
2. Vishal
3. Kanchan Electronics
4. Keltronics

The kurling kind of shafts are very difficult to get

cheers,

 

[omishra]

Sachin,

as i mentioned earlier to balance the output impedance of LSA, i was having a tough time. And i figured out the culprit, which was the 100k pot. It didn't have the exact reading for 2 legs. One was 110k and other leg was 102k. So due to this difference, the bias voltage to the LDRs were varying and the overall output impedance had a mismatch. Had a tough time hunting down the 100k in SP road, finally found a couple of them, checked on the resistance, one leg was 99.4k and other was 99.2k. I connected them back and Viola!, have a balanced output from both channels.

~cheers

This problem should not come. This LSA designed to take care of tolerance of stereo pot. Each wiper is attached to both channel either series or shunt. So both series or shunt gets same voltage from attached carbon track of pot and this expecting same current for matched LDRs of series/shunt. Any cheap, highly mismatched 100K stereo pot will do.

The LDRs are matched very closely and could be managed equal volume level at 10'o clock volume setting (considered lowest volume at 7'o clock position). If you feel difference then Exchange positions of LDR 2,4 (in case mismatch at low volume and 1,3 for mismatch at high volume) 5% mismatch is anyway expected.

While adjusting trimmers I remove audio wires and feed (+5V, G) supply to audio 'in' of both the channels on LSA board and measure respecting output for balance with changes in trimmer 1/4 turns in each opposite directions. I measure output voltage at output terminals and not resistances.

 

[adie]

hi sachin hv made payment to ur ac. will soon be entering ssp club.

 

[vin_eme]

Sure Om, in fact i was doing the impedance matching with input audio wires removed. But am not able to explain with changing the pot, i am getting 5% deviation at extremes and 2% at mid. So am not sure what was causing it in my previous pot with a big deviation.
But overall am happy with this change. I don't want to touch the soldered LDR's again since resoldering heat will cause the LDR characteristics to change. So i better leave it as it is. Thanks again for explaining Om.

 

[santhosh]

Hi Vincent,
It looks as good as expensive commercial product:clapping:
Regards,
Sachin

Sachin, I saw it last week and asked him what it was and which brand. Apart from SSP, he also has a source selector in the same box.

Very good DIY Vince!!

 

[omishra]

But overall am happy with this change. I don't want to touch the soldered LDR's again since resoldering heat will cause the LDR characteristics to change. So i better leave it as it is. Thanks again for explaining Om.

+1, Yes.
Don't solder/desolder LDRs unnecessarily.

You are always welcome.

 

[exljp]

Over the weekend, completed the soldering. Now I have to source remaining parts such as volume pot, connectors etc
https://plus.google.com/u/0/photos/...lbums/5796809657705719201/5796809661272666402

 

[omishra]

Over the weekend, completed the soldering. Now I have to source remaining parts such as volume pot, connectors etc
https://plus.google.com/u/0/photos/...lbums/5796809657705719201/5796809661272666402

Could not see the photo album, it seems you haven't made it public.

 

[atozguy]

Hi Dude,

I am buying EMOTIVA power amp UPA-2 but not going for a preamp now due to budget constraints. Please let me know whether this SSP can be used directly with UPA-2 or does it require additional electronics. I have PC (without sound card) and have a lot of FLAC format audio. Also have Denon DCD510AE as Source.

Regards
Gopinath J

 

[sachu888]

Hi Dude,

I am buying EMOTIVA power amp UPA-2 but not going for a preamp now due to budget constraints. Please let me know whether this SSP can be used directly with UPA-2 or does it require additional electronics. I have PC (without sound card) and have a lot of FLAC format audio. Also have Denon DCD510AE as Source.

Regards
Gopinath J

Hi Gopinath,
yes it can be used with Emotiva.FM Murli N is using SSP with Emotiva Power amp.You can PM him for audition since he is from Chennai.

Regards,
Sachin

 

[spirovious]

Finally it worked.After talking to O.Mishra & Hari,I changed Batteries from Hiwi to GP,also re-soldered all point & yes its working.I was told that it cant run Headphones,but it can.I was wondering the same,why cant as input(D2X out)to SSP could drive & after connecting SSP there was no reason to get output lowered.I will check if it can be used as Headphone amp(low powered).Now everything sounds clean,but Bass reduced than I get directly from D2X out.

 

[rams1977]

Hi DIY Geeks... Went to FM Murali sir's house with my Norge 2060. Compared with SSP and stock preamp in 2060. Results are jaw dropping. Amazing soundstage, Imaging and seperation. Amazingly tighter bass. clean trebles and airy vocals. We even compared with emotiva setup. In fact he was of the opinion it sounds better than emotiva setup except for the transparency in which emotiva can't be beaten. He has been kind enough to get my amp modded with the this SSP. Like mentioned earlier Norge owners can benefit from this mod. I will post my impressions after listening to the modded amp.

 

[gcpraveen]

This is my first diy, I had done my soldering and setup. There was some loose connection between -V and G. For sometime preamp was working. After that it stopped, now when i measured with multimeter I am not getting voltage between -V and G again (+V and G shows some voltage). I do not know what to do, Help required plz...

Thanks,
Praveen.
sent from SGS2 skyrocket.

 

[omishra]

This is my first diy, I had done my soldering and setup. There was some loose connection between -V and G. For sometime preamp was working. After that it stopped, now when i measured with multimeter I am not getting voltage between -V and G again (+V and G shows some voltage). I do not know what to do, Help required plz...

Thanks,
Praveen.
sent from SGS2 skyrocket.

Some pictures will help. Till the time you sort out power supply line, remove OPAMP carefully and keep aside safely. Then we can help you with pictures in place.

 

[sachu888]

Hi Praveen,
Please measure voltage on Batteries,sometimes they drain very fast.There must be some loose contact in your power connection,please check that.

Regards,
Sachin

 

[spirovious]

I had some issues,but the Batteries were culprit.I use GP one & every thing works good now.