Another Amek Tac Scorpion overhaul!

[Eliani]

You're a better man than me.  I would just match 4 resistors and call it a day.

That's exactly what I ended up doing! It was to hard setting the trimmer I bought to the optimal value! In a next revision, if I ever need it, I will implement the CMRR trim with the series resistor!

I'm going for the calculated 5.9k with 220pF should get me around 122kHz... close enough to 120.938Hz!! I get where I was mistaken. in Jeff's schematics it says -3dB corner frequency is 120,938Hz... Europeans use comma's before decimals, so I naturally thought low-pass!!

 

[craigaudio]

Brilliant thread thank you for taking the time to be so detailed. I'm very interested in some boards, but having pretty much no electronics skills. I'm learning a lot re-reading this thread and online info. I do have a good tech however and am not alien to an iron.  Any plans for some audio samples?

 

[Eliani]

Brilliant thread thank you for taking the time to be so detailed. I'm very interested in some boards, but having pretty much no electronics skills. I'm learning a lot re-reading this thread and online info. I do have a good tech however and am not alien to an iron.  Any plans for some audio samples?

Thanks for the interest! Yes I've got sampels in my mind, but I'm away from home for a job in Holland. I'll post some next week!

 

[bluezplaya]

VERY COOL STUFF! I'm in the market for a recording console and have found a local TAC Scorpion that I may buy. If so, I'm definitely interested in some of your boards as well as the Langley upgrade boards from Colin. I'm very interested to hear about the master section summing mod too. I just picked up a Tascam MS-16 1" tape machine and have decided to get back in to recording (for personal use) but this time around I'm going all analog and primitive. I'm sure the Scorpion will be a great sounding console with mods.

Adam

 

[Eliani]

VERY COOL STUFF! I'm in the market for a recording console and have found a local TAC Scorpion that I may buy. If so, I'm definitely interested in some of your boards as well as the Langley upgrade boards from Colin. I'm very interested to hear about the master section summing mod too. I just picked up a Tascam MS-16 1" tape machine and have decided to get back in to recording (for personal use) but this time around I'm going all analog and primitive. I'm sure the Scorpion will be a great sounding console with mods.

Adam

Thank you Adam!!
The scorpion is a great platform for a custom modded console! I've just ordered another 10 gar1731 DOA's from Jeff to complete the first 16 channels with the El-252_Rev003 differential receiver. If you get the scorpion a would be happy to provide you with the necessary details, boards/kits/whatever you need! I'll be smoothing out the kinks into a Rev004 revision, but if you do not mind a slight pin offset you can get the Rev003 boards cheap!

The master summing mod is just Jeff's 2-ACA-Bo wired to replace the original summing amp and fader booster. Again, I would be happy to help you on how to wire one in yours! I'm thinking about modding the groups in a similar fashion with different DOA's so you can group single channels through a specific setup to give it some flavor!! Can't wait to get it finished...

As for the scorpions' looks...
I've used 200B knobs for all the API-receiver channels with Gar2520 opamps, 8 channels in total, and there will be 8 channels channels with Gar1731 opamps in the receiver with soundcraft 200 knobs, or if I can find them more 200b's!! I'm not convinced the Langley channel knobs look their best, I'll have to find something else for them!!

 

[critterkllr]

Just curious if you could describe what kind of improvement was made  over the stock circuit when you installed Jeff's 2-ACA-Bo board. Was it a big difference?

 

[bluezplaya]

Just curious if you could describe what kind of improvement was made  over the stock circuit when you installed Jeff's 2-ACA-Bo board. Was it a big difference?

Ditto. I'd like to know how it sounds.

 

[Eliani]

I couldn't say if the 2-ACA- really improves the original circuit. It rather changes it from a not badly working  summing amplifier into a world class yet vintage circuit. I never liked TL0x chips in any circuit, but I liked everything I built with discrete opamps and transformers. I found, although that's a personal opinion, that this modification transformed the clean but cold, characterless sound from the TL072 into warm but bright and dirty... For me this was an improvement for sure!!

I could say the same about my discrete API-style line receivers I built! The original pre-amp has no musicality, sound harch, low on headroom, and the line-inputs run through the same circuit, thus could not be called a true unity gain line receiver. The Langley upgrade pre-amps are a great adition to the channelstrip, but it's still a padded down line-input running through your preamp, and although sounding spectacular compared to the SSM2015, again it's that TL0x that I do not really like in there. The 2520-style line receiver adds a certain kind of gritt to the signal.

 

[Eliani]

Not really a great test, levels are off to low, and not the same on all tracks, on the other hand, all gains are at minimum.

https://soundcloud.com/eliani/ribbon-gtr-original-channel

https://soundcloud.com/eliani/ribbon-langley-pre-1

https://soundcloud.com/eliani/ribbon-gtr-2520-2

https://soundcloud.com/eliani/ribbon-gtr-1731-2

 

[bluezplaya]

I bought it today!!  I am the proud, second owner of this board. It was bought brand new in 1986 from a local church and they have had it in their smoke-free sanctuary all these years! First thing I checked out was the PSU. Dirty as hell. I'll be ordering  caps for that. The fan is a Radio Shack fan and it is noisy. Need to replace that. I'm now about to check out the master module and see if it has been recapped recently. The PFL meter lights stay on constantly, and so do the meter lights for #7 buss. Any suggestions?

 

[bluezplaya]

Yeah, this thing is a time warp from 1986. Just checked the master, aux, group, and an input module. It looks brand new and clean as a whistle, minus some light dust inside the frame. No recap on ANYTHING. Looks like I'll be starting the process of recapping the PSU and Master module.

 

[Eliani]

I bought it today!!  I am the proud, second owner of this board. It was bought brand new in 1986 from a local church and they have had it in their smoke-free sanctuary all these years! First thing I checked out was the PSU. Dirty as hell. I'll be ordering  caps for that. The fan is a Radio Shack fan and it is noisy. Need to replace that. I'm now about to check out the master module and see if it has been recapped recently. The PFL meter lights stay on constantly, and so do the meter lights for #7 buss. Any suggestions?

Congrats on the purchase!! Again, this is a great basis for modification due to the modular design of the channelstrips, and separated i/o patch. I would have liked to have a slightly larger master section, although it does what it needs to do.

I've read on several ocassions that the stuck LED's is a known scorpion issue.  No idea how to resolve this problem. I've got a custom meter-bridge one for every channel, built up from several original scorpion pcb's... The scorpion meter bridge is built up from a 8, or was it 10, channel pcb's with the led modules stuck to them... Colin used to carry new metering modules, but I think he doesn't sell them anymore...  I was thinking on replacing mine with better ones... More on this later on... ;-)


As for having a good condition console, you should be happy! Mine has been tampered with a lot, and although that "previous owner" might have had a plan, he screwed up a lot in this little scorpion!

 

[craigaudio]

I bought it today!!  I am the proud, second owner of this board. It was bought brand new in 1986 from a local church and they have had it in their smoke-free sanctuary all these years! First thing I checked out was the PSU. Dirty as hell. I'll be ordering  caps for that. The fan is a Radio Shack fan and it is noisy. Need to replace that. I'm now about to check out the master module and see if it has been recapped recently. The PFL meter lights stay on constantly, and so do the meter lights for #7 buss. Any suggestions?

Congrats on the purchase!

My colleague who I had loaned mine to just brought it back. Sounds like you got a good one, as did I. MINT condition, I re-capped the power supply, master section and 2 channels with added Langley line mods. Was going to do the full 16 until I heard about Eli's mods. After checking the sound cloud page, if I can afford it, I'm going with Eli's stuff. Sounds fantastic.

Eli, any chance I could get some wav's of  the audio files to put into ProTools so I can A/B direct from my convertors please? I can already hear the difference on Soundcloud but I could do with hearing them A/B'd properly. I know you're busy so no rush.

 

[Eliani]

My colleague who I had loaned mine to just brought it back. Sounds like you got a good one, as did I. MINT condition, I re-capped the power supply, master section and 2 channels with added Langley line mods. Was going to do the full 16 until I heard about Eli's mods. After checking the sound cloud page, if I can afford it, I'm going with Eli's stuff. Sounds fantastic.

Eli, any chance I could get some wav's of  the audio files to put into ProTools so I can A/B direct from my convertors please? I can already hear the difference on Soundcloud but I could do with hearing them A/B'd properly. I know you're busy so no rush.

Craig!

One more thanks for the appreciation!! I'm really busy taking a short vacation with my girls!

 

[bluezplaya]

Congrats on the purchase!

My colleague who I had loaned mine to just brought it back. Sounds like you got a good one, as did I. MINT condition, I re-capped the power supply, master section and 2 channels with added Langley line mods. Was going to do the full 16 until I heard about Eli's mods. After checking the sound cloud page, if I can afford it, I'm going with Eli's stuff. Sounds fantastic.

How does your board sound after the upgrades?

 

[Eliani]

How does your board sound after the upgrades?

I'm pretty sure it sounds great! Clean but withouth real caracter... I recap the mastersection and PSU first and did 4 channels langley mic pre upgrades next. But after rethinking my setup I was thinking it would be better, for me at least, to keep my preamps 500 series based and build a decent line receiver. After switching to Jeff's 2-ACA-Bo I knew I wanted to go for the 2520 based input. Only because Mitsos pushed me towards the differential receiver, I would have gone for something trimable. It was not until later I figured out that I need to set my levels "In The Box" and use unity gain inputs...

I'm playing with the idea of building an API 2520 based ADAT converter!! I'm already testing ADAT Receiver chips and DA converters... It would be cool to fit 32 channels of line drivers and output Iron in a box..!

I'm working on replacing my metering with more accurate LED bargraphs (they are dead cheap! 18$ for 50 pieces of 12 led's) and LM3916 chips. I just need to figure out how many bars of LED's can fit the metering slots... Hmm interesting days!!

 

[Eliani]

I remembered opening the metering bridge for the first time and finding a big mess... so I slammed it shut and didn't look at it again. Now I've got this 25 LM3916 driven bargraph design in my head and I needed to have a look at one of the original PCB's...

There's two PCB in my metering bridge, for a clean setup for 24 channels... the rest is that big mess I found..!!

There's 8 meter buffer PCB's for a total of 32 channels... I don't think these are supposed to be in there originally... I guess the previous owner needed them as he took the metering point right at the channels PFL point. I guess that would be a good place to start. But would I need another buffer as the LM3916 datasheets tels me there's little to non influence on the original circuit because of the internal buffer...?

Anyway, 24 led bargraphs (2x12) would fit the Telefunken slots, I would like to run 3x LM3916 in cascade to drive the bargraphs.

 

[Eliani]

Depending on how much time there is left in the day after taking care of the kids and working as a full time sound-engineer at the start of the Belgian/Dutch summer festival-season, I try to use that time as useful as possible! Today I managed to find the offset on my Differential sub-board... one pin was off by 0.05 inch which made it slightly less easy to fit onto the main PCB! I've  finished Rev004 of the PCB....

 

[Eliani]

So I'm in the progress of ordering the Rev004 batch. Does anyone need some boards?
I'm thinking €7.5 each, €5 each from +10 pieces upwards excl VAT and shipping.

 

[bluezplaya]

I'm interested in 4 of the boards.