JBL 308P and 708P

[Spannko]

I’m going to try disconnecting the earth inside the speaker rather destroy an expensive power lead.

[FairPlayMotty]

Careful Sparrko!

[markiteight]

I’m going to try disconnecting the earth inside the speaker rather destroy an expensive power lead.

Do you have "cheater plugs" available to you? Here in the U.S. we can get adaptors that convert 3 prong leads to 2 prong, eliminating the ground. This is a chap and easy way to experiment with the grounding of your components without (semi-)permanently altering anything. They work perfectly on my HAKAI. I'm just not aware if such a thing exists for plug designs other than that used in North America.

[FairPlayMotty]

I’m going to try disconnecting the earth inside the speaker rather destroy an expensive power lead.

Do you have "cheater plugs" available to you? Here in the U.S. we can get adaptors that convert 3 prong leads to 2 prong, eliminating the ground. This is a chap and easy way to experiment with the grounding of your components without (semi-)permanently altering anything. They work perfectly on my HAKAI. I'm just not aware if such a thing exists for plug designs other than that used in North America.

I'm sure they can be bought on the internet. However, in the UK I'm positive they'd be viewed as non-compliant with BS1363 and result in prosecution for a UK manufacturer or seller. There are plugs in the UK with a plastic earth pin (ISOD) but they're only allowed for a two cord appliance.

[lejonklou]

Dangerous for any other device connected to them?

A proper mains ground will minimize the duration of the catastrophe.

Let's assume the power supply in a 308 breaks. The likely scenario is that it stops drawing any current. Then it will be dead and nothing more will happen. Mains ground or not won't matter.

Assume that it instead short circuits. Then it will draw lots of current and its internal fuse will likely blow. The central fuse of your mains will likely trip as well. Mains ground or not won't matter.

Assume that live mains for some reason gets connected to the chassis (the metal part on the back of 308). Now that's where a mains ground will make the central fuse trip at once, which is great. But the live mains will also transfer to the signal ground, as they're connected in the 308, so the other units of your system will break as well. Power supplies will die and the circuit boards fry. The mains ground makes this scenario short, cutting the power. But likely no unit that is connected by signal ground will survive. Without mains ground, this frying will continue until some unit draws enough current to trip the central fuse. Or tracks/wires melt and disconnect the units, leaving the 308 isolated and with mains power still connected to its chassis.

In this last scenario the mains ground really helps. Although it appears unlikely that the live wire should connect to the chassis, such things have happened (incorrectly designed and assembled unit / someone having manipulated the amp and not attached the live wire properly, so that one day it comes loose and falls against the chassis). So here's where I have to say: Always keep your units grounded! It's safer.

[lejonklou]

Would it be generally beneficial to cut the ground cord in the power strip..?

No! Apart from safety, the system sounds better when it's grounded.

[tokenbrit]

I’m going to try disconnecting the earth inside the speaker rather destroy an expensive power lead.

Do you have "cheater plugs" available to you? Here in the U.S. we can get adaptors that convert 3 prong leads to 2 prong, eliminating the ground. This is a chap and easy way to experiment with the grounding of your components without (semi-)permanently altering anything. They work perfectly on my HAKAI. I'm just not aware if such a thing exists for plug designs other than that used in North America.

I'm sure they can be bought on the internet. However, in the UK I'm positive they'd be viewed as non-compliant with BS1363 and result in prosecution for a UK manufacturer or seller. There are plugs in the UK with a plastic earth pin (ISOD) but they're only allowed for a two cord appliance.

Maybe use something like this (if there's a way to get them in the UK without violating standards/someone being prosecuted) to convert the 308 to take a 2-pin power cord with regular UK plug?
https://www.amazon.com/Adapter-Vellcon- ... 06XXWNNYH/

[Spannko]

Disconnecting the earth inside the speaker is much more complex than I imagined. The power socket is soldered directly on to a pcb and I don’t want to do anything which isn’t reversible.

[Defender]

Disconnecting the earth inside the speaker is much more complex than I imagined. The power socket is soldered directly on to a pcb and I don’t want to do anything which isn’t reversible.

than the only way I see is cutting the plug from two standard power cables and use a screw on one and leave the ground open.
Or disconnect the ground on the socket of the strip.
In European power plugs you can tape the earth but in your case that might create a mess if the tape keeps sticking in the socket in the end.
Heat shrink it maybe?

[David Neel]

I did this for my Hakai by taking a power strip with a non-moulded plug, and removing the earth lead from the plug. I then filled the other sockets on the strip with childproof covers to remind me not to plug anything else in.

[Spannko]

I did this for my Hakai by taking a power strip with a non-moulded plug, and removing the earth lead from the plug. I then filled the other sockets on the strip with childproof covers to remind me not to plug anything else in.

Good idea!

[David Neel]

I did this for my Hakai by taking a power strip with a non-moulded plug, and removing the earth lead from the plug. I then filled the other sockets on the strip with childproof covers to remind me not to plug anything else in.

Good idea!

But, see Fredrik's post above...

[Lego]

Have you checked settings at the back or could your KDS be a bit ropey ?

There’s a small gain switch. Not sure what it should be on though. I’d have to plug them back in to experiment.

I think the KDS is OK because it makes the LS5/9’s sound pretty musical. I thought it might have a fault after it was thoroughly demolished by a Källa at David Neel’s, but now I’ve got used to the lower performance again it’s OK.

I inadvertently bought wrong XLR cables ,female instead of male ..I used male/adapter s and there was low hum coming through and the sound was terrible

[FairPlayMotty]

Measure twice cut once comes to mind......

[snatex]

Has anyone compared the powered monitors from Neumann (KH120?) or any other brands to the JBL 3 and 7 series? I picked up a used pair of LSR305P for my office and they are shockingly good for the price.

[FairPlayMotty]

Has anyone compared the powered monitors from Neumann (KH120?) or any other brands to the JBL 3 and 7 series? I picked up a used pair of LSR305P for my office and they are shockingly good for the price.

See Jajo's comment on page three of this thread.

[FairPlayMotty]

Has anyone compared the powered monitors from Neumann (KH120?) or any other brands to the JBL 3 and 7 series? I picked up a used pair of LSR305P for my office and they are shockingly good for the price.

The 305s are shockingly good for the price. The 308s are shockingly good irrespective of price. It's a shame that a second version was launched.

[snatex]

Has anyone compared the RCA vs XLR inputs on the 305/308 series?

@FairPlayMatty Thanks for pointing me towards the @jajo post about trying some other brands of monitors. It was helpful, but I didn't see any discussion about Neumann, a German brand with a great reputation. If anyone has tried Neumann monitors please share your thoughts.

[ThomasOK]

Has anyone compared the RCA vs XLR inputs on the 305/308 series?

@FairPlayMatty Thanks for pointing me towards the @jajo post about trying some other brands of monitors. It was helpful, but I didn't see any discussion about Neumann, a German brand with a great reputation. If anyone has tried Neumann monitors please share your thoughts.

The 305/308 don't have RCA connectors. I would guess you mean the 1/4" TRS connector (similar to the larger headphone connector). I haven't seen anybody comment on it. I'm not overly fond of how that type of connector makes contact but I can't say whether it sounds good or not.

[snatex]

Has anyone compared the RCA vs XLR inputs on the 305/308 series?

@FairPlayMatty Thanks for pointing me towards the @jajo post about trying some other brands of monitors. It was helpful, but I didn't see any discussion about Neumann, a German brand with a great reputation. If anyone has tried Neumann monitors please share your thoughts.

The 305/308 don't have RCA connectors. I would guess you mean the 1/4" TRS connector (similar to the larger headphone connector). I haven't seen anybody comment on it. I'm not overly fond of how that type of connector makes contact but I can't say whether it sounds good or not.

Oops. Yes. That is what I meant. I am running Linn RCA's and using these RCA/TRS adapters to go into the 305:

https://www.amazon.com/gp/product/B08TP ... UTF8&psc=1

Was curious if going to some canare or mogami XLR's would be an upgrade.

[Discodave]

I have Van Damme XLRs running from Kisto to 308s. Sound good. It was between that and Mogami but needing 2 sets of 6m cables the Mogami was too expensive for me. The Van Dammes were all in £40. Obviously I cannot tell which cable is musically superior but I am very happy with the performance.

Now, I am currently demoing Giella and needed the RCA connections for it with XLR. Managed to procure an adaptor from local music shop that does the trick. Result!! There probably is some form of degredation (again I cannot test this)however, Im not really too bothered and means I can now listen to Giella/308s without paying for 2 x 6m cables that will cost more than the speakers themselves. And it sounds/feels fantastic.

Hope this helps.

[u252agz]

I have Giella Pi running into 308s - it is really very good ( easily good enough for KDS/2 and even Kalla) , and definitely deserve a pair of high quality cables.

If you have found a great pair of inexpensive cables which sound great, there is no need to look further.

I was toying with the idea of Linn silvers - but these are seriously expensive, and I am happy with my lowly blacks.

[tokenbrit]

I have Van Damme XLRs running from Kisto to 308s...

Now, I am currently demoing Giella...

Kisto to Giella? Quite the change... Do the 308s appreciate the difference made upstream?

[tokenbrit]

Something worth knowing about JBL 308 is that they tie signal ground to mains ground. This can be problematic in some systems, causing hum, radio frequency noise and/or degradation of the music.

For instance, I have Källa - Sagatun Mono - JBL 308 at home. All powered from the same grounded strip with SM first, Källa in the middle and 308 last. Sounds great!

If I would add either my Panasonic TV, a HAKAI or a KDS to this system, I get problems...

I meant to ask, do the 708Ps also tie signal ground to mains ground, or is this just an LSR308 'thing'?

Looking forward to Azazello receiving his 708s so that we can get a summary of 3677 -> 308 -> 708 - I'm still intrigued by jajo's reports of the 7s maintaining their musicality across a wider volume range, amongst other benefits.

[Azazello]

Looking forward to Azazello receiving his 708s so that we can get a summary of 3677 -> 308 -> 708 - I'm still intrigued by jajo's reports of the 7s maintaining their musicality across a wider volume range, amongst other benefits.

I would trust Jajo's assessment more than mine. :)