I posted this recently in reponse to a thread in the Apeks forum - reposting it here for future reference, and also because I can be a little more frank since this isn't the manufacturers forum.
If someone else is interested or has done something similar for other popular brands, maybe a mod can put a sticky with a link to the individual threads?
==========
Apeks regs can be a bit confusing is that their regs are largely retailed as first and second stage pairs, referred to by the model name of the second stage. As you can see from some of the posts above, it's not clear whether people are talking about a first or second stage or a pair, and if a pair, then which first stage. Then there are the series. So let me try to make it a little clearer:
Series:
T, TX, ATX, XTX: Basically these are the evolutions over time, with the current series (XTX) starting around 2007 IIRC. Most of the below first & second stages were available in each series, some exceptions being the Flight and Tek3s which only evolved after the start of XTX. To add to the confusion you can still buy new ATX series in some models/markets; NOS I think
First stages (http://www.apeks.co.uk/products/prod...rst Stages):
US1, US4, UST - these are all nsealed (for use in warm, uncontaminated water). 1 & 4 refer to the number of Low Pressure or LP (which Apeks like to call medium Pressure or MP) ports. T means it has a swivel turret
DS1, DS4, DST - [D]rysealed for use in cold and/or contaminated water. 1 or 4 LP ports, the T has a [T]urret to allow the LP hose ports to turn
FSR, FST - Both sealed, both have 4 LP ports, no turrets. Higher end regs/better performance deep. FST has replaceable ARCAP valve seat
Tek3 - dedicated left & right handed doubles regs for better hose routing
Flight - ultra-lightweight travel reg, not suitable for cold water or extreme depth
Most of the above are available from the factory in DIN or yoke fitting and also with the useless Status gimmick and as the equally-useless (IMO) dedicated Nitrox (CE regs) models (which in the EU come with an M26 DIN thread) - with the exception of the Tek3s. Most ATX series first stages had one 1/2" LP port (which doesn't perform any better at all) with the rest of the LP ports the 'standard' 3/8" size
Second stages (Apeks Products - actually this page is a mix of seconds and pairs):
20 - basic warm water reg, has cracking pressure adjustment
40 - same as 20 but with a heat exchanger, so suitable for cold water
50/100/200 - same as 40 but with breathing resistance knob. Only other differences are cosmetic between them
Egress - low profile octo crap; just bungee an ATX40 instead
Flight - matching second stage, has proprietary tool-free hose fitting (which I don't like) so only works with Apeks hose
Again most if not all of the above are or were available in T, TX, ATX and XTX series. T/TX were big and heavy. XTX have interchangable wide/narrow exhaust Ts and you can reverse the venturi to make the hose route from the left, they also have a different purge button. 20/40/50/100/200 can all be converted to each other by swapping or retrofitting the various knobs etc
Pairings (these vary a bit from market to market eg US and EU but are typically as follows):
XTX20 - UST or US4 first stage
XTX40 - DST or DS4
XTX50 - DST
XTX100 - FST
XTX200 - FSR
Flight - Flight
Tek3 - L&R firsts come with pair of XTX50 seconds, and hoses inlcuding 7' primary, and necklace for secondary
The other firsts - DS1, US4 etc - usually come as single units. DS1/US1 are designed for drysuit inflation so no need to pair them
All clear now? Good
If anyone has any additions/corrections - I'm not very familiar with the early T/TX series - please update, thanks!
If someone else is interested or has done something similar for other popular brands, maybe a mod can put a sticky with a link to the individual threads?
==========
Apeks regs can be a bit confusing is that their regs are largely retailed as first and second stage pairs, referred to by the model name of the second stage. As you can see from some of the posts above, it's not clear whether people are talking about a first or second stage or a pair, and if a pair, then which first stage. Then there are the series. So let me try to make it a little clearer:
Series:
T, TX, ATX, XTX: Basically these are the evolutions over time, with the current series (XTX) starting around 2007 IIRC. Most of the below first & second stages were available in each series, some exceptions being the Flight and Tek3s which only evolved after the start of XTX. To add to the confusion you can still buy new ATX series in some models/markets; NOS I think
First stages (http://www.apeks.co.uk/products/prod...rst Stages):
US1, US4, UST - these are all nsealed (for use in warm, uncontaminated water). 1 & 4 refer to the number of Low Pressure or LP (which Apeks like to call medium Pressure or MP) ports. T means it has a swivel turret
DS1, DS4, DST - [D]rysealed for use in cold and/or contaminated water. 1 or 4 LP ports, the T has a [T]urret to allow the LP hose ports to turn
FSR, FST - Both sealed, both have 4 LP ports, no turrets. Higher end regs/better performance deep. FST has replaceable ARCAP valve seat
Tek3 - dedicated left & right handed doubles regs for better hose routing
Flight - ultra-lightweight travel reg, not suitable for cold water or extreme depth
Most of the above are available from the factory in DIN or yoke fitting and also with the useless Status gimmick and as the equally-useless (IMO) dedicated Nitrox (CE regs) models (which in the EU come with an M26 DIN thread) - with the exception of the Tek3s. Most ATX series first stages had one 1/2" LP port (which doesn't perform any better at all) with the rest of the LP ports the 'standard' 3/8" size
Second stages (Apeks Products - actually this page is a mix of seconds and pairs):
20 - basic warm water reg, has cracking pressure adjustment
40 - same as 20 but with a heat exchanger, so suitable for cold water
50/100/200 - same as 40 but with breathing resistance knob. Only other differences are cosmetic between them
Egress - low profile octo crap; just bungee an ATX40 instead
Flight - matching second stage, has proprietary tool-free hose fitting (which I don't like) so only works with Apeks hose
Again most if not all of the above are or were available in T, TX, ATX and XTX series. T/TX were big and heavy. XTX have interchangable wide/narrow exhaust Ts and you can reverse the venturi to make the hose route from the left, they also have a different purge button. 20/40/50/100/200 can all be converted to each other by swapping or retrofitting the various knobs etc
Pairings (these vary a bit from market to market eg US and EU but are typically as follows):
XTX20 - UST or US4 first stage
XTX40 - DST or DS4
XTX50 - DST
XTX100 - FST
XTX200 - FSR
Flight - Flight
Tek3 - L&R firsts come with pair of XTX50 seconds, and hoses inlcuding 7' primary, and necklace for secondary
The other firsts - DS1, US4 etc - usually come as single units. DS1/US1 are designed for drysuit inflation so no need to pair them
All clear now? Good
If anyone has any additions/corrections - I'm not very familiar with the early T/TX series - please update, thanks!
) But you can get the same performance out of the DST. The TEK3 are for people who think that Tech diving is spelled TEK. The routing is average at best. Plus any damage to the ports means you're up ye old creek sans paddle as you can't just seal them off and turn the reg over.
