Carver Config Question

[mr3putt]

Hello

I am a newbie to the board.

Caught the Audio bug as a salesman for Tech HIFI in 1978

Started out with a baby Sansui receiver and a pair of Ohm "E"s.
Migrated to a Marantz 2285B and a pair of JBL L-100s

My current system includes
Carver HR-895 Receiver
Carver TD 1770
Carver SA/D-490T
Technics SL-QD33 Turntable
2 JBL L-100s
4 NHT SB1 speakers

Don't know if this is the proper forum for a config question but here goes....

I have the JBL's as my primary speakers running off of the Carver at 8ohms.
I was running the NHT's through an Adcom GFS-4 speaker switch (2 pair) as secondarys running at 4 ohms in parallel. I like it loud and cooked the receiver.
OOPS
While the amp is in the hospital I was thinking about bridging the NHTs perhaps purchasing a Carver TFM-15cb. Can the TFM-15cb support 2 sets of 8ohm speakers running in parallel (4ohms)concurrently in bridge mode without cooking?

Thanks to all

 

[BalancedXLR]

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[mr3putt]

Absolutely NOT! In bridged mode the impedance is cut in half right off the hop. With an 8Ω load the amp "sees" 4Ω. Your scenario would be 2Ω. That poor 15cb will be next to let the magic smoke out :yes:

Bummer

This config looks to be gettin a bit pricey.

 

[mr3putt]

Would a device like a speaker impedance matching switch help?

If so would I need separate volume controls?
One for the primary...one for the switched secondarys.

 

[mulester7]

Absolutely NOT! In bridged mode the impedance is cut in half right off the hop. With an 8Ω load the amp "sees" 4Ω. Your scenario would be 2Ω. That poor 15cb will be next to let the magic smoke out :yes:

.....look again, Balanced XLR....he's going to try to run, "two sets" of 8-ohm speakers, with "all 4 8-ohm speakers" paralleled off the bridged amp, "one channel"....we're talking Magic Smoke within about 30 seconds cranked, if even that long.....

 

[BalancedXLR]

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[mr3putt]

I glossed over the 2 "SETS" and saw his 4Ω figure (which after re-reading is wrong BTW). The 4Ω nominal load bridged scenario that I thought he was doing would tax that amp like I said but a 2Ω?!?! Remember the amp will be seeing 1Ω in that case OMFG!

So if I follow this correctly.

Pre/out to the secondary is seen by the primary as 4 ohms.
2 pairs of 8 ohm speakers hanging off the secondary amp would then be seen as 2 or 1 ohms?

I am confused.

Thanks for any help.

 

[BalancedXLR]

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[mulester7]

To calculate resistance in a parallel circuit we use the formula 1/Rt = 1/R1 + 1/R2 + 1/R3 + ....and so on. Speakers are not purely resistive so we use the speakers nominal impedance to calculate the nominal load. So lets plug in your 2 "SETS" of 8Ω speakers (4@8Ω)
1/Rt=1/8 + 1/8 + 1/8 + 1/8
1/Rt=.5
Rt=1/.5
Rt=2Ω (Bridged amp cuts that in half so your amp would see a 1Ω load)

.....BalancedXLR, you're sharp as a tack and know your stuff....

.....Mr3Putt, about all you can get away with in this scenario is NOT bridging the amp with two 8-ohm speakers paralleled on each side of the 2-channel amp....even then, the Carver 2-channel amp will be put to the test as the actual impedence probably experiences dips below 4 ohms....try this and let us know what you get....don't feel slighted, what you get should be good....but then again, it all boils down to what you get from the speakers being paralleled....speakers that are very descriptive and somewhat bright can go to tinny sounding with overbearing highs with them paralleled....even though an amp can handle such a situation, the ears will probably become taxed with the overbearing tinny over-brightness, and listening fatigue will come all too soon....and, listening fatigue usually indicates a possible hearing loss if continued....it all boils down to the speakers used when paralleling as the natural ohmage of the speakers changes toward authority full-range....my 6 main's regiment speakers dictate that I "not" do any paralleling of speakers or bridging of amp channels, and that's just the way I want it to remain at "natural" ohmages for the desired chamber "presence"....one last time, it all pertains to the speakers used and the ears listening to them when paralleling speakers....best of luck to you, Sir.....

 

[BalancedXLR]

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[mulester7]

Well I missed the "sets" part originally so maybe sharp as a tack thats been dropped on the concrete once

.....well, you could be like me and be judged sharp as a bowling ball....hey, we're all in this thing together.....

 

[mr3putt]

Thanks to both of you for your input.

It turns out that the proposed configuration will postion the secondary amp in a non-bridged state.

I will be using an RCA "Y" cable from the HR-895 PRE/OUT and connect it to both the AMP/IN of the 895 and the AMP/IN of the secondary amp.

I am told that this method bypasses the bridged impedance to 4 ohms issue.

My bad for any confusion....
This has been a learning experiance.

 

[BalancedXLR]

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[mr3putt]

Your terminalogy of bridging caused all the confusion. Ok what your proposing now is a whole new ball game if I'm following you correctly. Your not bridging the TFM-15 but simply tapping into the preout/main in loop of the 895. Alright this makes more sense. So yes you will be fine with your last hookup description. You can have speakers on the 895 and the TFM-15. FYI, bridging an amp refers to combining both channels with one being inverted. The amp has to either be capable of bridging or the signal has to be inverted by other means.

I confused the **** out myself too.

Thanks for your help