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DIY Simple Active Preamp

The ceramic 0.1uf caps should be close to the power pins of the op amp to help prevent possible oscillation. The larger electrolyitic's can be further away which are for filtering purposes.

As far as op amps go, I do think the change to the more "sensitive" B&W's did make me realize that the AD823 had some harshness in the upper mids. It may not be that apparent when using other speakers. It's probably horses for courses.
 
And actual SSP PCB from me has 0.1 and 10uF tied together near pin 4 and 8. ;)
BTW, its eagle software used and no automatic layout was done.

BTW, in my SSP, AD823 got one channel problematic. It used to come live with a thud after 5 minutes of warming post power ON. I replaced that OP-AMP and its back to normal. Now waiting for LME49720 for a rollout.

Regards,
 
Transformer input

I got my Cinemag transformers installed. It took me a while because I had to separate my chassis ground from my signal ground. But now I understand, finally.

These effectively isolate the input and there is now dead silence, no telltale buzz or hum. I would get that on some sources. I also installed these because I happen to like the sound of transformers.
EDIT: Here's the data sheet.

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These particular transformers want to see a 10kOhm load. Since my attenuator is 20kOhm, I put 20k worth of resistance across the output of each transformer to give me 10kOhm. When I get a chance, I will snip those leads to compare 10k/20k. Cinemag says there won't be much difference, but fairly flat response beyond 20kHz is what you get with 10k. The response will roll off a bit with a 20kOhm load.

No listening impression yet other than these are working properly. I have to tidy up the wiring and then it's done.

I have a lot of old knobs, I like this one:

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HypnoToad said:
I was listening to my HTMCPS that is connected to a Super Simple Preamp and thought their was a little harshness in the upper midrange with my new to me B&W speakers.

I have them going into the power amp section of my Yamaha CR-1020, the pre in the Yamaha is no slouch but everything opens up using the Super Simple Preamp.

I tried swapping the AD823 op amp for a OPA2134, the harshness disappeared but it was too laid back for my liking.

I then looked in my op amp stash and found a pair of LME49710's, they are single circuit version of the LME49720. I put them in a dual adapter an put it in the preamp.

Wow what a revelation, the harshness was gone and the soundstage had widened but is not quite as 3d, but with even more detail. Bass is a little tighter and more extended, voices are much sweeter IMO.

So if you want to try something good give the LME49720 a go, you might be surprised.
Click to expand...

Not one to keep chopping and changing but I removed the DC blocking caps on the HTMCPS and removed the 100k resistors from the SSP and replaced them with 200k. Now the output from the HTMCPS goes from the 47ohm resistor straight to the inputs of the SSP. I also went back to the OPA2134 and things are not only open but very smooth.

It all depends on what you like though, I prefer detail and smoothness not in your face sound.

Next week I may change to something else.:D
 
I need some help with my SSPA build. I got a board from Sachin ( Thank you, sir!) and I have installed the componants using 100uf caps and a LM833N op-amp in place of the AD823 that Mouser did not have. I'm using 2 9V batteries for power with the led indicator and a dpdt slide switch. When I hooked things up, I got no sound at all- no hum, buzz, nuttin. I do have some other op amps on hand, such as OPA 2134,LM4562NA,OPA 2604AP, and a LME49720AP. Should I try swapping to one of these & see if it works? Thanks!
 
You can always test the voltage on the socket to be sure everything is up to snuff before you burn up your opamps. Then dont forget to put the opamp back in the socket. Yup I did that... forgot to put the chip back in the socket = no sound.

Cheers,
Bob
 
That's a good suggestion, Bob. I wish I had taken a picture of the board I got from Sachin before I populated it. There are a few different boards shown in this thread & that's making things confusing!
 
Well, I have 19.2 V between pins 8 and 1 on the socket, #8 being +. I put in my second LM833 & tried it again, still no output. I must have a bad solder joint somewhere..
 
sfox52 said:
That's a good suggestion, Bob. I wish I had taken a picture of the board I got from Sachin before I populated it. There are a few different boards shown in this thread & that's making things confusing!
Click to expand...
Here you go, just replace 10uf caps with 100uF and OP AMP with AD823.

simpleprebrd.png
 
Thanks for the pic of the board, Omishra. I'm good with the 100uf caps , but I don't have a AD823. I will try another type op-amp next- it's hard to see how I could have no signal through either channel at this point.
 
The good thing is there are only ~10 solder joints per channel to check. Did you check for continuity on all solder joints and/or check voltage along the way to see if both sides match?
 
I had not checked this thread for a while and see this project evolved nicely. I dove back in because I got interested in making something similar using op-amps as buffers (maybe 6dB gain on the first) for a VC and a line variable BSC circuit preamp. Nice touch with the transformers. I have a pair of step-up Cinemags that I wanted to use for some passive voltage gain, but the drive and load impedance requirement is a bit steep to use it as such.

az
 
:stupid:Doh! I've found it helps if you hook the outputs to the amp and the inputs to the source!:scratch2: Now I have output one one channel and an open somewhere in the other. As dodog said, it's a good thing there are just a few places to check! Thanks for the help, guys!
 
sfox52 said:
That's a good suggestion, Bob. I wish I had taken a picture of the board I got from Sachin before I populated it. There are a few different boards shown in this thread & that's making things confusing!
Click to expand...

Hi Scott,
There is only one type of PCB for SSP:yes: I hope you will solve this problem soon :)
 
OK, I have it now, I crossed the Left + & - outputs on the board. Stupid mistake #2. My only excuse is that I haven't been breathing solder fumes in a good while.
 
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