New amp(s) for RF7 MKII

[psg]

someone on another forum said he thought it was strange to put a big metal bolt here, but I know know if that really does anything. Does anyone here know?

It's keeping the heavy transformer from busting loose, my A21 has the same setup.

No interference with magnetism and so forth then? Standard procedure? I wouldn't be surprised. If this were an issue, it would have been easily bypassed.

[dtel]

Wanting to try some tubes is understandable but what is wrong with the vintage Kenwood KA 1100-D (160W/ch @ 8 Ohm , 450W/ch @ 2 Ohm) your using now ?

You may not get a better sound from some of the amps mentioned, some of the vintage amps are very well made and have a really nice sound. What is it with the Kenwood that your not happy with? New does not always mean better.

Just asking.

[willland]

someone on another forum said he thought it was strange to put a big metal bolt here, but I know know if that really does anything. Does anyone here know?

It's keeping the heavy transformer from busting loose, my A21 has the same setup.

No interference with magnetism and so forth then? Standard procedure? I wouldn't be surprised. If this were an issue, it would have been easily bypassed

My NAD T773 receiver has the same thing. Something needs to hold those heavy toroidal tranformers in place.

Bill

And my B&K EX4420 amp.

[russ69]

No interference with magnetism and so forth then?

Purely mechanical.

[psg]

Thanks all. I am reassured.

[tillmbil]

Is this just a two channel system? I have had way better luck with tubes and Klipsch speakers myself, but that is just my opinion. If you are gong to stay with SS I would reccomend B&K. I had an ST202 for a long time and to me it sounded the best with Klipsch as far as SS goes. The B&K Sonata series is really good if you are wanting to spend more dollars. I also loved my McIntosh amp,but it was the MC402, go figure. I had the MC 2505 but it did not impress me. ON the other hand the MC240 really puts out some juice for a tube amp.

.

[Wim M]

Wanting to try some tubes is understandable but what is wrong with the vintage Kenwood KA 1100-D (160W/ch @ 8 Ohm , 450W/ch @ 2 Ohm) your using now ?

You may not get a better sound from some of the amps mentioned, some of the vintage amps are very well made and have a really nice sound. What is it with the Kenwood that your not happy with? New does not always mean better.

Just asking.

Indeed my vintage amp never let me down in 22 years, so it must be a quality amp. But now I think he lacks overall definition, especially on the RF 7II's. It might also be a cable problem, I'll try to fine tune this.

This doesn't mean the Kenwood can retire []

[Wim M]

Is this just a two channel system? I have had way better luck with tubes and Klipsch speakers myself, but that is just my opinion. If you are gong to stay with SS I would reccomend B&K. I had an ST202 for a long time and to me it sounded the best with Klipsch as far as SS goes. The B&K Sonata series is really good if you are wanting to spend more dollars. I also loved my McIntosh amp,but it was the MC402, go figure. I had the MC 2505 but it did not impress me. ON the other hand the MC240 really puts out some juice for a tube amp.

.

For now it's just a two channel system. Now I'm looking for a 2 channel power amp, or 2 monoblocks. So it can be easily integrated in a future multichannel system. What is meant by the term: SS?

I don't think B&K and Emotiva products are available in Belgium (Europe)

I recently heard a Mcintosh amp (MA 7000 - integrated amp) which sounded really nice, great definition and soundstage, the only problem was the price label. In our country I think Mcintosh products are fairly expensive. The MA 7000 costs in Belgium 10.000 euro which is 14.400 US D. ...

[tillmbil]

SS stands for Solid State as opposed to Tubes. There are many 2 channel amplfiers that can be bridged Mono. Adcom, older units like Hafler, McIntosh etc. Not familiar with what is available in your area, but I have had good luck when buying tubes from Germany so possibly having somthing shipped overseas could work.

[Wim M]

1) one A 21

2) two A23's: mono bridged

3) two A23's: one A23 for each speaker but bi-amped.

Can somebody give me some advice?

1) Entirely sufficient (unless your room is HUGE)

2) Even more sufficient, enough for a huge room. Do you really need that much power? Ok, too much is just enough when it comes to ss power, but on the other hand, a single A21 should reach ear blistering volumes before running out of steam.

3) Doesn't make sense; you're giving the highs way more power than needed. Due to the high crossover of the RF-7's, the amp driving the bottom inputs is doing all the work, and the money spent on the amp for the highs is an extravagance. I'm cheap, and given the marginal, perhaps imperceptible benefits of passive bi-amping, this one just seems like a stupid idea. If you need more output, get a more powerful amp, or follow suggestion number two.

When a 2-channel power amp is mono bridged, the amp sees the speaker at half of its nominal impedance. The parasound site states that a single A23 can deliver a 45A peak current. Is it correct that when you bridge the A23, it can deliver 90A peak current to a single speaker?

I'm just looking for an amp which can deliver warm, rich, powerful and dynamic sound at low levels. If it can reach ear blistering levels, that's OK but that's certainly NOT my primary concern.

[Ski Bum]

When a 2-channel power amp is mono bridged, the amp sees the speaker at half of its nominal impedance. The parasound site states that a single A23 can deliver a 45A peak current. Is it correct that when you bridge the A23, it can deliver 90A peak current to a single speaker?

I'm just looking for an amp which can deliver warm, rich, powerful and dynamic sound at low levels. If it can reach ear blistering levels, that's OK but that's certainly NOT my primary concern.

Assuming the amp has the ability to generate that current and dissipate the associated heat, then yes, you are correct. Keep in mind that speaker impedance is not constant, so that's just a guestimate. This will put more stress on the amp, a strong argument for simply choosing a more powerful amp to begin with.

You keep using terms like 'warm' and 'rich', which makes me think 'tubes'. Not necessarily trying to steer you that way, the A23 is an outstanding amplifier after all.

[Wim M]

Perhaps one more item... damping factor.

The damping factor is the ability of an amp to drive and control a speaker, especially difficult loads. A decent explanation can be found here:

http://www.crownaudio.com/pdf/amps/damping_factor.pdf

A few weeks ago I mentioned that I had a demo at our place with 2 mono bridged NAD C275BEE's.

The NAD site states a damping factor for their C275BEE of >180

Parasound states a damping factor for their A21 and A23 of 1100 and 800.

Perhaps the low damping factor of the NAD (compared to the Parasound) can explain why bass performance was so poor on the Rf7 II's?

Do you consider the damping factor as an important issue, as far as 'choosing an amp' is concerned?

[Wim M]

I already thought about tube amps. I mentioned it to the NAD-guy and he said that tubes have also serious disadvantages. He said that tubes fade out like conventional light bulbs and that they should be replaced every 300 hrs. If this is correct they should be replaced at least once a year!

[Ski Bum]

Do you consider the damping factor as an important issue, as far as 'choosing an amp' is concerned?

Not really. Amps like the A21, A23, and even the NAD have such high damping factors that they all would have an iron grip.

Perhaps the low damping factor of the NAD (compared to the Parasound) can explain why bass performance was so poor on the Rf7 II's?

Maybe, but I suspect it's more due to the Parasound being the more powerful amp, able to better sustain power during demanding bass heavy passages than the NAD's 'powerdrive' trickery can muster. Keep in mind that the damping factor would have to be much, much lower than either of these to make a difference, and that in such a case, the amp with the lower damping factor would likely sound more boomy and bassy than the one with a high damping factor.

[Ski Bum]

I already thought about tube amps. I mentioned it to the NAD-guy and he said that tubes have also serious disadvantages. He said that tubes fade out like conventional light bulbs and that they should be replaced every 300 hrs. If this is correct they should be replaced at least once a year!

That's not exactly true. Some amps are easy on tubes, where driver tubes can last for years, even decades. Others push them to their limits and use them up faster. It all depends on the particular amp.

Something tells me that the biggest disadvantage from the perspective of the NAD salesman is that he has no chance for a commission.

[Wim M]

I haven't heard any of the Parasound amps yet. Just read very nice comments on reviews and forums.

But I already found a dealer who has the Parasound P3 pré, A21 and A23 power amps on demo. The only problem is that he has no Klipsch speakers. He mailed that he can do a demo on Kef Reference 205. Though, I hope it can give a good impression of the capabilities of the amps.

I won't have time to get to the Parsasound dealer for at least 3 weeks, cause I'm rather busy at work (poor me...)

[KanedaK]

Joop,

Welcome to the forum.

I think the dealer suggestion of bridged NAD C275BEE's is a super idea. Those amps are pretty potent even the conventional way.

Bill

I have to disagree... quite why you'd want to use 400watts amplifiers on speakers that are above 100dB sensitivity leaves me perplexed. I mean, MOST of the times, you will be using LESS THAN ONE WATT. While it's good to have some headroom, it's also good to know that THE BIGGER AN AMP, THE MORE LIKELY IT WILL SOUND MEDIOCRE UNDER 1 WATT (except maybe some very high-end or ClassA or no-feedback designs).

I use LaScalas and my power amp is 120watt/channel (wich is already overkill). According to the vu-meters (wich, of course, only give "average" readouts but still) I'm around 0,01watts at night, max 1watt in daytime (I have neighbours and 1watt is LOUD, 10watts shakes the house and brings the cops at the door... the remaining 100+ watts are just headroom.

While it's true that you need some power (i'd say current) to keep those 10inch woofers in check, IMHO 400watts is really, really overkill. If I were you I'd look for a less powerful, more upmarket option, possibly second-hand. Or save some money, buy only one NAD power amp and save some money for good cables and / or music.

Just my two cents. 400watts amps are made for sluggish unsensitive speakers, not for horns...

[Ski Bum]

... quite why you'd want to use 400watts amplifiers on speakers that are above 100dB sensitivity leaves me perplexed. I mean, MOST of the times, you will be using LESS THAN ONE WATT. While it's good to have some headroom, it's also good to know that THE BIGGER AN AMP, THE MORE LIKELY IT WILL SOUND MEDIOCRE UNDER 1 WATT (except maybe some very high-end or ClassA or no-feedback designs).

I use LaScalas and my power amp is 120watt/channel (wich is already overkill). According to the vu-meters (wich, of course, only give "average" readouts but still) I'm around 0,01watts at night, max 1watt in daytime (I have neighbours and 1watt is LOUD, 10watts shakes the house and brings the cops at the door... the remaining 100+ watts are just headroom.

While it's true that you need some power (i'd say current) to keep those 10inch woofers in check, IMHO 400watts is really, really overkill. If I were you I'd look for a less powerful, more upmarket option, possibly second-hand. Or save some money, buy only one NAD power amp and save some money for good cables and / or music.

Just my two cents. 400watts amps are made for sluggish unsensitive speakers, not for horns...

I'm part of the choir you're preaching to (except for the cables part [:|]). For the fortes I have about ~6 watts of SET juice on tap, and even that can get to ear-shattering levels. And I happen to own a C372 which I've also tried on the Klipsch, and frankly prefer the SETs by a wide margin. The NAD is used primarily to drive some inefficient M&K studio monitors (4 ohm, something like 85db/w/m), a far better use for that amp.

The Parasound amps that Joop is considering are biased for class A output for the first several watts. They DO sound good at low levels. Kinda pricey for this ski bum, but they are indeed excellent amplifiers. Joop wouldn't be making a mistake by getting one. I would agree that he likely would never need all the power of even that, and more power, i.e. bridged amps, is just overkill.

Isn't there some saying among those stricken with the audio gear addiction along the lines of "I spent all thay money to learn I didn't need to spend all that money to get great sound." Multiple bridged C275's or A23's would be an expensive lesson indeed.

[CECAA850]

I don't know about the Mk II's but the original RF-7's have a nasty impedance dip down to around 2.8 Ohms. Lesser amps run out of steam trying to drive them, I don't care what the sensitivity is. I drove mine originally with a 120 WPC HK and then went to 300 wpc QSC amps. The difference is noticed WAY before you hit 10/10'ths.

[Wim M]

I have 2 amps: a Denon PMA 1500 (2x70w@8ohm) and a vintage Kenwood KA-1100D (2x160W@8ohm). The difference between the two (on the RF7MKII's) is remarkably. The more powerful amp drives the RF7's with more ease, greater soundstage, greater dynamics, better definition, at low 'easy listening' levels. This has nothing to do with blowing of roofs or upsetting the whole neighbourhood.

I must agree: no matter how many watts an amp can put out, it's the first one that counts. But it's my opinion that the more powerful an amp is, the better the first watt will be.