No Respect! The Kenwood KA-7300

[bbopman1]

I Wonder what a KA 9100 would actually bench at? Factory specs are 90 per ch. @ 8 ohms, @ 0.03 THD...

 

[bbopman1]

To Echo Wars..Thanks for all your posts!...PS: Have you ever bench checked a KA 9100?...just curious..its rated at 90 per channel @ 8 ohms...Ive read somewhere on here that someone benched it at 117 per ch?..

 

[EchoWars]

By Bench at, do you mean actual full power based on 1kHz power from a warmed up amp or do you mean per FTC regulations:

Pre-condition at 1/3 power a half-hour or so to get it really hot
check power output
report power bandwidth into specified load at specified max distortion levels with specified channels running.

First one, maybe 125 watts

second one maybe 94.5 wpc both channels driven, 20-20kHz into 8Ω with less than 0.03 THD.

Why, for God's sake, would we want to duplicate the FTC tests? Subjecting a 30+ year-old piece of unrestored audio gear to this regimen could very well be the end of it. Not recommended, in a big way.

To Echo Wars..Thanks for all your posts!...PS: Have you ever bench checked a KA 9100?...just curious..its rated at 90 per channel @ 8 ohms...Ive read somewhere on here that someone benched it at 117 per ch?..

Maybe. Sounds about right. Been too long since I had a 9100 on the bench.

 

[legal eagle]

The pix are gone :tears:

 

[EchoWars]

ImageShack tends to do that. When I still have originals, I re-upload them. Unfortunately, those 7300 pics have disappeared.

 

[wsissons]

Echo nice work the 7300 looks alot like my hk 930 in the amp section and I love the twin power supplys......bet that kenny does sound nice......

 

[tomasvalpara]

consult

hi guys

somebody have problems with the bass & trebble adjustements ??

thanks !!! ,)

 

[DaWoofer]

I forgot it had them

 

[ManyMoonsAudio]

May start a new thread here.

 

[bill1956]

Nice...love the series

 

[Eargasmike]

My Kenwood KA 7300 which I bought new in 1977 is starting to fade in/out

Can someone help me?
My Kenwood KA 7300 (export model http://www.thevintageknob.org/kenwood-KA-7300.html) which I bought new in 1977 is starting to fade in/out on the right channel only. I am new to the Nashville area and am only qualified to transport the unit for professional attention... I do love the sound and want to restore the sound... I have tried working all the knobs to ensure clean contacts, but that doesn't help and all the switches sound good.
Thanks for any suggestions!

 

[ManyMoonsAudio]

Terry Dewick is in your back yard......

Here he is...

 

[ken.nelson]

May start a new thread here.

Looks like your in Tulsa. I live on Lake Eufaula. Longtown by #9. Nice to meet someone with my interest nearby. Do you have a shop in Tulsa?

 

[ManyMoonsAudio]

Collinsville. Nice to meet you as well.

 

[700cmt]

I have a couple of KA 7300's both are needing some professional care . Im not sure if im going to keep them or have them repaired. Terry has done some work for me in the past. =)

 

[lasminit2]

Wow that KA7300 seems so uncluttered compared to the KA8300 I had. The 8300 sounded nice but needed frequent attention (a couple of trips to Terry DeWick). It is interesting that the 7300 has separate transformers while the 8300 did not.
As long as we have delved into so many of the Seventies KA series, do you guys like the KA8100? It appears to have a very clean internal design.

 

[claneg]

KA7300 pre power supply

Hello guys,
I was reading EW fine words on how good the 7300 preamp section is, so I decided to get one 7300, knowing how right are EW words. Last night I spent some time looking at the 7300 schematic, and noticed that the preamp/control sections are supplied buy a very basic regulator: a resistor and a zener, like what happens in the entry level X550 series. Since in the X100 series uses a more complex regulator, my doubt is: might be that such a simple regulator is one of the reason of the KA7300 preamp better sound (compared to the 7100)?

Kind regards,

Claudio

 

[EchoWars]

Sometimes simplicity is good. To be more specific, there's nothing in the preamp that would benefit from a more tightly regulated supply (essentially because the current draw of the preamp is pretty constant).

 

[anderslober]

EW....great restore, man.......I was wondering.....what is that servo for? What is the advantage of it?
Would you share specs/construction?
I have had many integrated amps......but, I always seem to go back to my Kenwoods(Ka9100/ka8300). That HAS to mean something!

 

[EchoWars]

The servo is there simply to monitor the DC level at the output of the power amp (acts as an integrator), and to supply a correcting signal at the input stage to keep the offset as close to 0V as possible. Nothing mysterious, they've been around for years. The 7300 has no offset adjust, so I wanted to experiment with a servo to see how well it worked.

I do not have the specific circuit I used in the 7300, but the general form of a corrective DC servo is below. If an opamp is used that has sufficiently low bias current, the cap and resistor on the non-inverting input are not necessary, and it can be tied directly to chassis ground.