Kenwood KA-701 upgrade

[quantaloop]

Recently, I was listening to Cohen's last album using my TT at a fairly high volume (Kenny KA-701 volume knob was almost set at noon position), on a EPI 100 stack (2 pairs) . Amp started to clip on and off quickly. Turned down the volume and everything was fine. Still, quite annoying and now I fear I could damage the amp or speakers, if it's not already happened. So I guess I do need a bit more power to drive that stack? Some AKers did suggest recently I would ideally need more power to make those speakers shine.

Also, I recently goy my hands on a pair of Image Concept 200 (pre-Energy). I'd like to really drive them with a solid receiver/pre and PA to do them justice. I'd like to get my hands on a Kenwood KR 9600. I prefer receivers to power amps if only for their good looks... but please let me know if you feel this is not a good choice, or if you have alternatives to suggest.

 

[turboyam]

The KA-701 has been clocked at close to 100 real wpc, so it is not anemic.
Are you sure all of the pots and switches are all clean?.

 

[quantaloop]

Are you sure all of the pots and switches are all clean?.

I had it serviced last summer, so I'm hoping that yes, everything is clean.

 

[Binkman]

Clipping is the result of an unstable condition. Can be impedance load and speaker db quality. Study up on the 1watt per meter speaker over wattage required. i.e. the amp and speakers are basically in the same ball park. Speakers with higher wattage ratings require more wattage. simple.

note also speaker wattage is additive. driver a+b+c = total watts x2 for two speakers.

 

[turboyam]

Try driving your speakers with the attenuator switch ON ( -20DB), and
the volume pot all the way to 0 DB (if tolerable), and see if it's still clipping.
Try a line level source too (tape, CD, or else)...

 

[quantaloop]

note also speaker wattage is additive. driver a+b+c = total watts x2 for two speakers.

According to Human Speakers, the EPI 100 are "very conservatively rated" to bed able to handle 12 to 50 watts rms. Doubling this, then, to 24 to 100 watts? And being "very conservatively rated", according to HS still, the speakers could take up to twice this amount. So what, 48 to 200 watts?

Now, stacking the speakers, I'm figuring they become 4 ohms instead of 8 ohms nominal (HS lists the EPI 100 as 4 ohms DC and 8 ohms nominal). The Kenwood KA-701 manual specifies that the power output at 4 ohms is 100 WPC. There is also a note in the section about speaker connexion that reads : "If a single pair of speakers is to be used, each speaker must be rated at 4 ohms or more. When two pairs of speakers are connected (A+B), each speaker must be rated at 8 ohms or more."

Please enlighten me if I'm all wrong!

 

[blhagstrom]

Kenny KA-701 volume knob was almost set at noon position), on a EPI 100 stack (2 pairs)

You are pushing the edge with the gear you have.

You may be able to squeeze a little more out with some refurbing but to truly get to the next level, you will need a bigger system. At least a stronger amp.

 

[roger2]

8 ohms "nominal" is a very general designation. The fact is that speaker impedance varies significantly across the audible frequency spectrum. Meaning that an 8 ohm nominal speaker will be less than 8 ohms for some frequencies. And when two such speakers are in parallel, the resulting load will be less than 4 ohms for some frequencies. Your amp does not like that, especially when cranked up.

You probably have not done any damage to your amp or speakers as the KA-701 has some type of limiting circuitry.

If you want to push your speakers harder, you need a stronger amp as blhagstrom said.


EDIT: tweeters are often the first thing to go when driving speakers hard, so listen to them to verify no damage to speakers. You can hold something (pillow) over the woofer or between the woofer and tweeter (board, rigid insulation, etc) to help isolate the tweeter while doing a listening test.
.

 

[quantaloop]

If you want to push your speakers harder, you need a stronger amp as blhagstrom said.

That's what I was hoping to do. I have my eyes set on a Kenwood KR-9600... 160WPC. A decent option?

 

[roger2]

That's what I was hoping to do. I have my eyes set on a Kenwood KR-9600... 160WPC. A decent option?

Well, blhagstrom has much broader experience, relevant to giving you a good answer to that question, than I do. KR-9600 is certainly more beastly than KA-701. But I am not sure that either is the best option for 4 ohm loads.

When you compare power ratings you should use the number that is stated as "xx watts per channel, 20Hz-20kHz, 8 ohms both channels driven". Compare apples to apples. The 100w figure you quoted for the KA-701 is at 1kHz and 4ohms. Another thing to make note of is the increase in the ratings given at 4 ohms vs 8 ohms (usually at 1kHZ). In some amps this inrcease is significant. In both of these amps, not so much.

Be aware that the increase in perceived volume is not 1:1 linear with respect to amplifier power. In other words, a 160wpc amp will not produce 2x the volume vs a 80wpc amp. I believe 2x power gives you something like 3db more volume.

If you can get a good deal on that KR-9600, and it is healthy, it wouldn't hurt to try it. It may give you enough more vs the 701 to satisfy you. It is possible (I am not stating this as fact) that the 9600 could be more comfortable with a 4 ohm load, or that its limiting circuitry may not be as tightly wound as the 701's. I can say that the KA-9600 is highly regarded and that there is a lot of helpful documentation in the AK Kenwood forum for this model.

 

[bigaltx24]

If you want to run a 4 ohm load, buy an amp that can easily handle a 4 ohm load. I've never liked running vintage receivers on 4 ohm loads even if they are rated for it. If you want to run a 4 ohm load to high volume levels get a power amp that's 4 ohm rating is double it's 8 ohm rating. Look at amps like Carver, Adcom, Yamaha M**, Crown, etc they're built to handle the high current draws encountered with 4 ohm loads.

 

[quantaloop]

I'm starting to think I'll just steer away from stacking. This is but an experiment. I want to buy a receiver that's going to be versatile enough to test many different speakers over the years. I think I will turn to my Image Concept 200, simple 8 ohms load, but need quite a bit of power. Will keep my eyes opened for these big receivers!

 

[blhagstrom]

Too many unknowns to be specific and it sounds like you are aiming for a different goal.

Testing different speakers.

Again, it is not clear what you intend, but fwiw, I have a friend that was a speaker flipper and to demonstrate speakers he had large gear. His main demo system was a good CD player, a good preamp and a big Pioneer power amp (M90?). The power amp had been "repaired" at some time in his ownership by someone. It wasn't quite right and I tore it apart and cleaned up the relays and found a bad part, resister I think.

The point being, to really "test" something, everything you use needs to be 100%.
To test speakers at high output, you want big power.

And, speakers will sound different with different power levels of amps.
50wpc, 100wpc, 200wpc seem to be the places where speakers can sound much different above and below.

 

[quantaloop]

Too many unknowns to be specific and it sounds like you are aiming for a different goal.

My goal kinda changed in the last few hours as I am thinking. I was first hoping to get an amp that would be ok with the EPI stack - but it seems like I would need to specifically get an amp capable of handling a 4 ohms load just to make it work. So now I mostly want something (ideally a receiver, for aesthetics reasons rather that audio ones - without compromising too much) that will make my Image Concept 200 sound right. However, I do not intend to keep the Concept 200 forever. I will want to try something else in the future. I guess what I wanted to say was that I didn't want a receiver to just to make the stack work, but primarily the Concept 200, then other speakers I might acquire in the future.

 

[blhagstrom]

SO, good sound, big sound, current gear but ready for other gear, receiver, 4 ohm capable.

Sort of.

Right?

Easiest answer, a monster receiver in good electronic condition.
I recommend a properly restored unit. Recapped, with all known "funky" fiddly bits replaced/upgraded, amps adjusted properly.

BOAT.
(Break out another thousand).

If you are prepared to pay-to-play at the $1000-$2000 level, then you are not ready to play.

Luck

 

[roger2]

Don't rule out the KR-9600 because of any comments I made. Compared to your current amp it would likely be a significant step up for driving the stacked EPI's.

... it seems like I would need to specifically get an amp capable of handling a 4 ohms load just to make it work...

Not necessarily so. If you were committed to a 4 ohm speaker load, and wanted to fill a large room at high sound levels for extended periods, then maybe you would want to look at some other amp options. But it would not be fair to say that KR-9600 can not "handle" 4 ohm loads. In particular, compared to KA-701 (that you know) which is rated 100wpc @ 4ohms @ 1kHz only; KR-9600 is rated 200wpc @ 4 ohms @ 20Hz-20kHz. It is easier for an amp to produce power at 1k than across the entire audible frequency spectrum. Big difference in those ratings, not only double the power, but also producing that power over the entire audible range instead of just at 1k.

In addition to that, KR-9600 was made during what could be considered the height of the vintage era and a time when Kenwood was putting out its best stuff. Around 1980 most consumer grade audio gear took a step backwards. KA-701's first year of production was 1980. And...there have been posts questioning the limiting circuitry of Kenwoods x01 series, some suggesting that it activates too easily. A situation which possibly you are experiencing, I couldn't say for sure though. There is just a lot more to it than power ratings alone.

The point is, if you have KR-9600 on your personal radar, please don't rule it out based on a few comments/opinions. It might rock that EPI stack, and make your Concept 200's sing. Of course, any purchase of vintage is risky. Price vs condition/functionality always needs to be considered.

 

[Blue Shadow]

I'm curious about this discussion and the OP's comment that got folks answering the way they have.

quantaloop, you said " Amp started to clip on and off quickly. " This is using one technical term, Clip, that may be applied to your situation in a non-technical manner. Clip is reaching the limits of amplification and the signal wave is clipped on the top and bottom, something that when done excessively, will lead to a harsh sound on solid state electronics and eventually damage tweeters, but the sound continues. You indicated that the amp would ----on and off quickly. Is this the amp not playing, then playing, then not playing in rapid succession? If so, although the load is marginal, the amp should be able to drive it to very loud levels. If it can not, maybe there is something wrong with the protection circuit of the amp, needing a bit of freshening. You said the amp was worked on but if it worked and the amp was just serviced not rebuild, tired components might not have been found or some may have gotten old since then.

A little clarification, what do you mean the amp would ______ on and off quickly, please fill in the blank. Use as many words as needed to make it clear to us.

How loud are you able to play the stacked 100s? Have you tried them in series instead of parallel connection? This will lead to a 16Ω load and the high voltage needed for 4Ω work will be much less and possibly not cause the problem. Of course, the amp won't make quite as much power so there are trade-offs. but I think that amp should rock with a 4Ω or higher load as it is not a low powered unit.

 

[turboyam]

I'm curious about this discussion and the OP's comment that got folks answering the way they have.

quantaloop, you said " Amp started to clip on and off quickly. " This is using one technical term, Clip, that may be applied to your situation in a non-technical manner. Clip is reaching the limits of amplification and the signal wave is clipped on the top and bottom, something that when done excessively, will lead to a harsh sound on solid state electronics and eventually damage tweeters, but the sound continues. You indicated that the amp would ----on and off quickly. Is this the amp not playing, then playing, then not playing in rapid succession? If so, although the load is marginal, the amp should be able to drive it to very loud levels. If it can not, maybe there is something wrong with the protection circuit of the amp, needing a bit of freshening. You said the amp was worked on but if it worked and the amp was just serviced not rebuild, tired components might not have been found or some may have gotten old since then.

A little clarification, what do you mean the amp would ______ on and off quickly, please fill in the blank. Use as many words as needed to make it clear to us.

How loud are you able to play the stacked 100s? Have you tried them in series instead of parallel connection? This will lead to a 16Ω load and the high voltage needed for 4Ω work will be much less and possibly not cause the problem. Of course, the amp won't make quite as much power so there are trade-offs. but I think that amp should rock with a 4Ω or higher load as it is not a low powered unit.

Agreed, as i said, this is not an anemic amp, and has been regularly tested @ 100 wpc 20 to 20 000hz both channels driven.

 

[Blue Shadow]

@quantaloop Can we get an update on the clip on and off that your amp was doing?

 

[quantaloop]

@quantaloop Can we get an update on the clip on and off that your amp was doing?

Thanks, Blue. You are absolutely right. I did use the wrong term. What I wanted to say was that the amp started turning on and off intermittently very quickly. NOT clipping. The amp was set to 11 o'clockish and was running the stack in parallel while playing the TT.

You are right, the amp was mostly cleaned and DeOxited, but that's it.