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DIY Simple Active Preamp

Passives have a couple of problems. The input impedance is the sum of the pot resistance and the input impedance in parallel with the unused portion of the pot.

That makes the input and output impedance variable.

A preamp should have a high,10k Ohms or more, input impedance and a low output impedance, best less than an ohm.

The buffer does what it should do as a preamp.

In addition, some amps need an active circuit to drive them. Well, what I mean is they sound better with an active circuit driving them.
 
Ahhhh. OK, now I'm with you. That should have occurred to me, perhaps nightshift has fried my brain more than I had estimated.
 
Grainger49 said:
Passives have a couple of problems. The input impedance is the sum of the pot resistance and the input impedance in parallel with the unused portion of the pot.

That makes the input and output impedance variable.

A preamp should have a high,10k Ohms or more, input impedance and a low output impedance, best less than an ohm.

The buffer does what it should do as a preamp.

In addition, some amps need an active circuit to drive them. Well, what I mean is they sound better with an active circuit driving them.
Click to expand...

Passive need a robust drive from the sources to work well.

Sent from my SM-N900V using Tapatalk
 
What are the power requirements for ssp preamp ie. max voltage and max current consumed?
How much gain can we get from this or it can only be used as a buffer only?
What are better options for opamp ICs, seems its working with many opamps?
 
LME49990 is what I am using now. With adapters of course. (brown dogs) TINY soldering was actually fun! There are a LOT of different chips to try, so try them in your system. They all have their own personalities and sounds. What will sound best to you may not sound good with my system components / speakers.
Lot's of info around the middle of this thread. Just look about.
Voltage is 18Vdc. Unsure of the mA draw.............chip dependent also.
Gain is chip dependent, this is NOT just a buffer like the Pass B1. That said, I use this with the DCB1 and can switch in in and out of series for added Db. Doesn't really change the sound much when it's in the chain. This is a VERY clean PreAmp.
 
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Can I use an 18 VDC wall wart instead of the 9V batteries? I have a bad habit of leaving the pre on & draining batteries. Also- how can I safely add a second output?
 
Scott , you can build a simple power supplywww.audiokarma.org/forums/showthread.php?t=538253 which doesn't use transformer and run on wall wart.

Regards
Sachin
 
Thanks for that, Sachin. I guess I forgot about the simple PS. I built the SSP a couple years ago but just put it back in service using my "optivol" LDR volume control.
 
Now that I've gone back & read the whole thread, I should have the PC board for the simple PS around here somewhere, bought it when I got the Lightspeed Volume control board that I never built. I'm blaming CRS disease!
 
sachin,
I have no doubts that there are experienced engineers on this board that could design a good quality opamp. It's the fabrication of the chip that's prohibitively expensive.
Even if we could, there is no guarantee that it wouldn't sound like cr_p.
PM inbound.
Ron
 
sachu888 said:
Does anyone have experience with Burson Audio type Opamps? A Hifivision member posted a SSP review with Burson Audio opamps here http://www.hifivision.com/preamplifier/57775-burson-supreme-sound-dual-opamp-review.html
Those Opamps are costly. Can we design our own opamps?

Regards
Sachin
Click to expand...

The Burson Supreme uses 2SA970 transistors or copies as Toshiba hasn't made them for years. Ironically they are the same transistors used in the input stages of the CA640P. The AD797 phono stage easily beats out the modded 640P IMHO.

I wouldn't say that just because you use transistors you automatically improve the sound, the reason we use op amps is they offer great performance in a small easy to manage package. The AD797 for example offers noise figures only found in the very best transistors.

I did make a Pass B1 preamp with matched 2SK170 JFET's (one of the best) and didn't like the sound, that's where the SSP came in, to me it sounded more rounded, the B1 seemed to dissect the sound too much. YMMV.

Here's a good read from DIYAudio on the Burson:

http://www.diyaudio.com/forums/analog-line-level/234675-ics-get-hammered.html
 
Thanks Philips,

I did not know the details. AD797 HQMC phonostage is great. Few of my friends preferred it over with Pass Pearl2, MS Phonomena etc. Unfortunately I still couldn't find a LOMC which can fit into my budget :no:
I am enjoying my CNC phonostage since day one :thmbsp:

Regards
Sachin
 
HypnoToad said:
I did make a Pass B1 preamp with matched 2SK170 JFET's (one of the best) and didn't like the sound, that's where the SSP came in, to me it sounded more rounded, the B1 seemed to dissect the sound too much.
Click to expand...
I found default B1 sounds very dull and changes original sound signature.
So from inspiring from others,I tried modifying and results were better than original resistor value.
http://www.hifivision.com/diy/21036-pass-b1-158.html
 
sachu888 said:
... Can we design our own opamps?

Regards
Sachin
Click to expand...

IMHO: I highly suspect that you would find that there are waaaay too many variables to making DIY opamps. Many of these variables can be controlled, or compensated for, by design, manufacturing processes, quality control, etc, at larger plants - but also at higher prices. "Commercial" opamps must exhibit similar characteristics and performance (within tolerance) or the manufacturer would soon be out of business.

If you and I worked side-by-side, using parts and components ordered from the same batches, and built "identical" opamps, I would be very surprised if more than 2 out of ten would exhibit the same set of performance characteristics. If we then put them into SSPs we built using the same parts, how many of them do you think would "sound" the same?
 
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Instead of trying to make your own op amps you could just make a preamp using transistors.

Eg:

design4.gif
 
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