critterkllr
Well-known member
Eliani said:
Keeping fingers crossed for a time machine!
Another Amek Tac Scorpion overhaul!
- Thread starter Eliani
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Keeping fingers crossed for a time machine!
bluezplaya
Well-known member
Mmmmmmmmm.....! Inductor EQs! So how much would the 1512 boards be? And I'll bet they'll sound way better than the SSM2015s.
bluezplaya said:
Let's say around €3 each for test-boards only!! No parts, no shipping included... max a couple test boards per person and for a limited time only. Pin-setting is the same as the API2520 boards, Just the gain-pot will have to be wired, and probably swapped too... but I would need to look into that again, as it's been a while since I built myself a 1512 pre-amp...
bluezplaya
Well-known member
I finally got around to building four of the GAR 1731 opamps and tested the first one out on the S1000. So, it works, but at a very low signal level and the gain does not work. I was not aware, so rereading through the thread I learned that I will need to rewire or replace the gain pot. Can you tell me what I will need to do that?
I listened to some mp3s through the modded channel next to a stock channel and the EQ really thumps! Overall it does have a slightly more pronounced and beefier midrange.
I listened to some mp3s through the modded channel next to a stock channel and the EQ really thumps! Overall it does have a slightly more pronounced and beefier midrange.
critterkllr
Well-known member
bluezplaya said:
That doesn't sound right. I had a similar issue with my first channel and the opamp was messed up. It should be the same level as your other channels when the gain knob is at noon.
bluezplaya said:
The Diff.Rev00x boards are not meant to be used with any gain pot in place, they are Unity Gain Line receivers. If there's to little signal in your track, use the XLR input instead of the Jack-input, or remove and bridge the PAD resistors!!
jensenmann
Well-known member
I don´t want to rain on your parade, Eliani. But simply throwing API into a circuit doesn´t make everything necessarily better. I once refurbished and modded a Scorpion for a friend. I left the bad and ugly SSM2015 in and modified the circuit around it to make it perform better. The result was that the owner sold his API preamps because they found no more use.
Your circuit suffers of mediocre CMRR. If that´s of no significance then go ahead. If it matters then the stock SSM performs better. In certain surroundings technical parameters do matter because they translate into percieved sonic quality. Not everything can be justified with "if it sounds better then..."
Just my 2ct
Your circuit suffers of mediocre CMRR. If that´s of no significance then go ahead. If it matters then the stock SSM performs better. In certain surroundings technical parameters do matter because they translate into percieved sonic quality. Not everything can be justified with "if it sounds better then..."
Just my 2ct
bluezplaya
Well-known member
What exactly did you do to mod the circuit around the SSM2015?
bluezplaya
Well-known member
And I'd be interested in trying the THAT 1512 board. It would be a cheaper and easier build than the 2520.
critterkllr
Well-known member
jensenmann said:
I'm curious about something; So, you would say that the absolute best sounding gear specifically relates to it having the highest CMRR?
It's great that a previous customer enjoyed your modded preamps so much they decided to get rid of their API preamps. That is really what we're all after. Whatever sounds the best to the end user is the best.
As for the argument that the API line input circuit is going to sound worse that modding the stock circuit, I'm not sure how to go about that without getting into subjective territory. Perhaps you could elaborate on your mod and possibly how to improve on the API circuit? Have you tried the API circuit mod?
jensenmann
Well-known member
critterkllr said:
No, I never said that.
critterkllr said:
I didn´t compare the SSM to the API. The owner did that. You´re right, though, percieved soundquality is highly subjective. But like I said. Depending on the scenario technical parameters turn into better or worse circuit behavior, hence soundquality.
jensenmann
Well-known member
bluezplaya said:
There´s an input filter which I opened up a bit to get rid of HF phaseshift. Then I modified the supply around the chip. There´s some small ceramics across the rails next to the SSM. I replaced these with 100uF electrolytics + bypasscaps. Then I modified something in the network around the SSM, but since it´s many years ago I don´t remember exactly what that was. Of course I recapped everything (usually with larger value caps), added bypasscaps to all electrolytics and replaced all chips downstream. In the end it´s the sum of everything I did which lets the SSM perform better. And it does help to keep the EQ engaged even if not in use since the SSM doesn´t like to see much load at it´s output. The EQ circuit works as a buffer for the SSM this way.
jensenmann said:
I've read a lot of your old posts regarding the Scorpion mods you performed. I'm not a true electronics engineer, rather an enthousiast. All the projects I did so far are built on trial and error. I took the original API differential circuit and tried it with succes on one of my S1000 strips.
But I am a true audio engineer, and to me this is exactly why I prefer Analog audio including the theoretical imperfections.
jensenmann
Well-known member
Rereading my first post let´s me think that it sounds a bit harsh. It´s not meant this way. I only wanted to add the CMRR thing for the record. No offence intended. And I´m totally with you about the beauty of DIY to tailor everything to fit one´s needs.
jensenmann
Well-known member
That´s not so easy done in this scenario. Depending on how things are connected to your input it will represent different impedances to the source on + and - inputs. Transformers of course will handle this problem great. But that may not be an option here.
With opamps it could be done by using a circuit like in the latest revision Urei 1176 with two ampstages. Both amps are connected via their - inputs. That means they will show the same impedance to the outside on the + and - inputs of the inputjack, no matter how things are connected. Trying to get a circuit like that based on 2x 2520 footprint DOAs will not fit due to space. You could try to do skip on the 2520 footprint and do a new layout with both DOAs on a single PCB. That´s a lot of work though.
IMHO there are many other corners cut in that desk, which can be adressed for improvments. The input stage being only one of them. Improving other aspects can result in better sound, too, without having to go the long way of designing a new PCB with all the trouble involved which comes along with it.
With opamps it could be done by using a circuit like in the latest revision Urei 1176 with two ampstages. Both amps are connected via their - inputs. That means they will show the same impedance to the outside on the + and - inputs of the inputjack, no matter how things are connected. Trying to get a circuit like that based on 2x 2520 footprint DOAs will not fit due to space. You could try to do skip on the 2520 footprint and do a new layout with both DOAs on a single PCB. That´s a lot of work though.
IMHO there are many other corners cut in that desk, which can be adressed for improvments. The input stage being only one of them. Improving other aspects can result in better sound, too, without having to go the long way of designing a new PCB with all the trouble involved which comes along with it.
critterkllr
Well-known member
jensenmann said:
What kind of input transformer would do the job? Is it a simple 600:600 that would do it?
jensenmann
Well-known member
10k:10k
