Sawtooth Posted May 13, 2011 Share Posted May 13, 2011 (edited) The following 2 band active eq was fitted in my G&L L1000 passive bass when I bought it. It still has the original volume pot, switch and jack. There is no brand name printed anywhere, the only information I can offer is that it has 'korea' on the chips and '50k Mexico' on the pots. (I can add serial numbers if helpful). I'd love to know what brand or even model it is and have searched for similar looking pics but had no luck, do either the board or pots look familiar to anyone? Thanks. (Edit: topic description) Edited May 14, 2011 by Sawtooth Quote Link to comment Share on other sites More sharing options...
icastle Posted May 13, 2011 Share Posted May 13, 2011 That's going to be a hard one to identify as it was added after market and any helpfull markings are going to be on the pcb... which is now buried under the potting. It's been well though out though - I like the idea of having the two op amps in sockets on the top where they can be replaced without throwing the whole unit away. Quote Link to comment Share on other sites More sharing options...
Sawtooth Posted May 13, 2011 Author Share Posted May 13, 2011 Thanks for your quick response. I don't know much about active preamps. Potting - is that the black coating? Op-amps - are they the chips? Is there anywhere I can learn a bit more about this subject please? From what you say, does the quality 'look' any good? (I know this is a silly question really!) I suppose I was thinking about maybe changing it, but I guess I should find out what it is first. Quote Link to comment Share on other sites More sharing options...
icastle Posted May 13, 2011 Share Posted May 13, 2011 [quote name='Sawtooth' post='1230437' date='May 13 2011, 09:11 PM']Thanks for your quick response. I don't know much about active preamps. Potting - is that the black coating? Op-amps - are they the chips? Is there anywhere I can learn a bit more about this subject please?[/quote] Sorry, yes the two chips are op amps - each one has two amplifiers in it (giving you seperate amplifiers for bass, middle, treble and volume). Potting is that black resin stuff - underneath that there is a circuit board with passive components (resistors and capacitors) on it. Things are usually potted to make it difficult to copy designs. [quote name='Sawtooth' post='1230437' date='May 13 2011, 09:11 PM']From what you say, does the quality 'look' any good? (I know this is a silly question really!) I suppose I was thinking about maybe changing it, but I guess I should find out what it is first.[/quote] Well it 'looks' ok. It's neat, well thought out and someone has gone to the trouble of potting it. Quote Link to comment Share on other sites More sharing options...
Sawtooth Posted May 13, 2011 Author Share Posted May 13, 2011 Great, thanks for your informative help. Hopefully, it may look familiar to someone else, who's seen something similar looking. Cheers, Dave. Quote Link to comment Share on other sites More sharing options...
Dood Posted May 13, 2011 Share Posted May 13, 2011 Just out of interest, do those two op-amps say 4558 on the top? I can't quite see. If they are, they are a generic op-amps - ( a pair of 741's in a package for all the geeky types) So my guess is that it's a fairly old preamp - because there have been a lot of advances in both performance and power consumption since they came out. The same Op amps appear in an old combo I have which is well over ten years old, as a guide. It is possible to upgrade the chips - as iCastle has pointed out they will pop out and with a bit of investigation I'm sure it'd be easy to find out what the latest incarnation of a quality pre op-amp is. I recall names such as TL072, LF353N, OPA2xx, NE553x, LT1358(?) from waaaay back - most will just slot straight in - but it'd be hard to make a 100% definite choice without seeing knowing the schematic - though my major hunch looking at the lack of stuff on the board is that it's probably a gain stage and baxandall bass treble network - a very obvious method and used a great deal in active circuits. Given what we can see, if you decided to upgrade to an up to date preamp I am positive you will notice a big difference in Bass sound. Quote Link to comment Share on other sites More sharing options...
icastle Posted May 13, 2011 Share Posted May 13, 2011 [quote name='dood' post='1230535' date='May 13 2011, 10:48 PM']Just out of interest, do those two op-amps say 4558 on the top? I can't quite see. If they are, they are a generic op-amps - ( a pair of 741's in a package for all the geeky types) So my guess is that it's a fairly old preamp - because there have been a lot of advances in both performance and power consumption since they came out. The same Op amps appear in an old combo I have which is well over ten years old, as a guide. It is possible to upgrade the chips - as iCastle has pointed out they will pop out and with a bit of investigation I'm sure it'd be easy to find out what the latest incarnation of a quality pre op-amp is. I recall names such as TL072, LF353N, OPA2xx, NE553x, LT1358(?) from waaaay back - most will just slot straight in - but it'd be hard to make a 100% definite choice without seeing knowing the schematic - though my major hunch looking at the lack of stuff on the board is that it's probably a gain stage and baxandall bass treble network - a very obvious method and used a great deal in active circuits. Given what we can see, if you decided to upgrade to an up to date preamp I am positive you will notice a big difference in Bass sound.[/quote] Now you say it, yes, I reckon I can see 4558 on those op amps. The TLE2272 is the latest version of the 4558. Quote Link to comment Share on other sites More sharing options...
Sawtooth Posted May 13, 2011 Author Share Posted May 13, 2011 [quote name='dood' post='1230535' date='May 13 2011, 10:48 PM']Just out of interest, do those two op-amps say 4558 on the top? I can't quite see. If they are, they are a generic op-amps - ( a pair of 741's in a package for all the geeky types) So my guess is that it's a fairly old preamp - because there have been a lot of advances in both performance and power consumption since they came out. The same Op amps appear in an old combo I have which is well over ten years old, as a guide.[/quote] Yes they do! (MC?) 4558 (C?) / KOREA / 5A - the print is very small, but I can clearly make out the numbers, the letters less so. [quote name='dood' post='1230535' date='May 13 2011, 10:48 PM']It is possible to upgrade the chips - as iCastle has pointed out they will pop out and with a bit of investigation I'm sure it'd be easy to find out what the latest incarnation of a quality pre op-amp is. I recall names such as TL072, LF353N, OPA2xx, NE553x, LT1358(?) from waaaay back - most will just slot straight in - but it'd be hard to make a 100% definite choice without seeing knowing the schematic - though my major hunch looking at the lack of stuff on the board is that it's probably a gain stage and baxandall bass treble network - a very obvious method and used a great deal in active circuits. Given what we can see, if you decided to upgrade to an up to date preamp I am positive you will notice a big difference in Bass sound.[/quote] Wow, I must admit that most of your information has gone straight over my head but I thank you anyway. You obviously know your stuff and I value your opinion, so, I'm willing to throw a good wedge at a new preamp and would like some help narrowing down my choices. I've done a fair bit of research and have some questions if anyone could help please, is this the right place to ask? Quote Link to comment Share on other sites More sharing options...
icastle Posted May 13, 2011 Share Posted May 13, 2011 [quote name='Sawtooth' post='1230565' date='May 13 2011, 11:31 PM']I've done a fair bit of research and have some questions if anyone could help please, is this the right place to ask? [/quote] At the moment we have topics about getting rid of slugs, soundproofing a garage, redundancy, pizza recipes and getting a Volvo MOT'd... Doesn't matter what you need to know, someone here will have the answer... Quote Link to comment Share on other sites More sharing options...
Dood Posted May 13, 2011 Share Posted May 13, 2011 [quote name='icastle' post='1230578' date='May 13 2011, 11:52 PM']Doesn't matter what you need to know, someone here will have the answer... [/quote] We're like 118... but better - especially numbers! Quote Link to comment Share on other sites More sharing options...
Dood Posted May 13, 2011 Share Posted May 13, 2011 [quote name='Sawtooth' post='1230565' date='May 13 2011, 11:31 PM']Yes they do! (MC?) 4558 (C?) / KOREA / 5A - the print is very small, but I can clearly make out the numbers, the letters less so. Wow, I must admit that most of your information has gone straight over my head but I thank you anyway. You obviously know your stuff and I value your opinion, so, I'm willing to throw a good wedge at a new preamp and would like some help narrowing down my choices.[/quote] Yup MC 4558C - Sorry, I got told the other day by one of my students I kinda go overboard with the detail a bit ha ha ha!!! - ok, in short - the 4558 was like a Ford Escort and you could get a Mercedes version to plug in instead for a more quality ride! - but they're not actually crazy expensive. But that aside - there is a massive choice of preamps on the market from EMG, Seymour Duncan, Aguilar, John East, Bartolini and many more - none of them are bad and will all be a good upgrade. I have experience of some, but thankfully as icastle has said, we have a great collective encyclopaedic knowledge on BC so you'll be sure to get lots of excellent helpful answers! Quote Link to comment Share on other sites More sharing options...
Sawtooth Posted May 13, 2011 Author Share Posted May 13, 2011 [quote name='icastle' post='1230578' date='May 13 2011, 11:52 PM']At the moment we have topics about getting rid of slugs, soundproofing a garage, redundancy, pizza recipes and getting a Volvo MOT'd... Doesn't matter what you need to know, someone here will have the answer... [/quote] ok, thanks. Firstly, this is the bass in question, an '81 G&L L1000. Of course, this bass was originally sold as a passive only option, but I am very interested in exploring the options to upgrade the active circuit already installed (as mentioned above). My reasoning being that the original tone circuit parts are long gone, so why not? I'd prefer to have an active/passive switching option also, much like on the L2000 bass, but want to keep the original 3-way coil switch. I've also got to consider the lack of space in the control cavity as well. One possible option that really interests me is the John East [url="http://www.bassdirect.co.uk/bass_guitar_specialists/East_Preamps_P_Retro.html"]P-Retro[/url] Now, I realise this is designed for a Precision bass, but given the similarity of the control, cavity and jack positions, I thought this may be feasible. I'd have to have the 2 stacked knobs rearmost near the jack output and have the existing front volume knob as a dummy, any thoughts? I've read some very favourable comments (on Basschat) and reviews of this preamp [url="http://www.andrewmckinney.co.uk/ahm/Articles_files/BGM%2055%202010%20P-Retro%20Preamp.pdf"]Andrew McKinney[/url] and heard some nice [url="http://www.bassguitarmagazine.com/index.php?option=com_content&view=article&id=429:p-retro&catid=48:demos&Itemid=102"]demo's[/url] and it seems to tick all the boxes. My only concern is with the G&L MFD pickup, which I believe is quite a high output, resulting in the L2000 active circuit tone controls being 'cut only' (or so I have read). With the P-Retro being 'boost only', in active mode, I wonder if this could be a problem? Would I be better off looking into boost/cut preamps instead? Is there anything I may have overlooked? If anyone can help or enlighten me, or indeed offer other preamp recommendations suitable to my needs, I'd be grateful. Dave. Ps. thanks 'Dood', I see you have replied as I type this. Quote Link to comment Share on other sites More sharing options...
icastle Posted May 14, 2011 Share Posted May 14, 2011 [quote name='dood' post='1230602' date='May 14 2011, 12:33 AM']We're like 118... but better - especially numbers![/quote] ...just as long as it doesn't involve percentages... Quote Link to comment Share on other sites More sharing options...
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