I inherited this late 70's receiver from my father, it's a Kenwood Eleven GX
Anyways, being rather new to the hifi scene I have yet to acquire any gear except for my old vintage stuff that I really don't consider hifi (I've always collected vintage gear, ranging from PA and recording gear, to relics of the "bigger is better" period of the 70's and 80's). Now, considering the fact that I'm only 22 years old, I'm going to guess that a couple of you may actually know more about this amp than me, but recently I discovered while pulling it out of storage that it has two sets of RCAs on the back. One says AMP IN, and the other says PREAMP OUT. It has always had a jumper going between them, and I had never really thought about it, but I decided that there could be a possibility that the amp would be on a whole different circuit on a whole other board within the receiver (remember I come from a generation where everything is mashed together, you know, save money and space and put it on a single board!). Needless to say within the case I found a complete and separate stereo amplifier!
So, here is my dilemma. I've always cared for the sound of the particular amp, even though it is solid state I would say it has a warm quality. However it has always been noisy, at least by the standards of modern and even vintage hifi. As I started playing with it I discovered it was the preamp circuit that was the cause of over 95% of this noise!
I did this by running the PREAMP OUT into another amp of mine, but I also discovered by doing this that a lot of the warm quality I described followed. So I decided to run straight out of my laptops USB D/A into the AMP IN, and control the volume using my laptop. What I found was a very quite amp, not nearly as warm, but much more detailed, and very likable! However I also found two problems...
First is that low frequency response seems to have suffered, not in quality, but in quantity. The built in preamp has a little 5 band graphic equalizer, and I've always noticed that I've had to crank the low and high frequencies to get it to sound flat (yes I know what flat should sound like, I'm new to hifi, but I have degree in music and recording tech. hehe, I'm just saying I'm not your typical teen looking for piercing highs and thumping lows...)
So I decided to plug the preamp back in but turn off the eq, and what I found was a very muddy sounding amp. My theory is the preamp sounds muddy so they give you an eq to fix it. Without the preamp I find no attenuation of high frequencies, and in fact they are very clear and focused, but the low end tends to roll off a tad early. This isn't a huge factor for me, the low end frequencies are there, and actually much improved over the use of the preamp. It's just they are a little quieter than I'd like.
The second, problem is that it seems that one of the channels is slightly louder than the other, I only seem to notice it at low levels. This is something I never noticed when running it as a complete unit, with the preamp plugged into the amp with the jumpers. I don't know what could be causing this issue, but that's what I have you guys for!
Alright, now for the choices...
1. I could put it all back together and leave it as it is, it's either not worth my time, or would be better left as part of my collection as it is, all original, and wait until I have the money to build a new amp (something I plan to do no matter which choice I choose).
2. I could attempt to do a full restoration of the entire unit, with help from you guys, clean up the noise as best I can, and use it as a total package, even though it's got tons of "features" I will never need or use, and is way too big for my current living space.
3. I could remove the amp circuit from the unit, do a full restoration and/or modification of just the amp circuit with help from you guys, recase it, and build an external passive preamp to control volume and select inputs with.
So, now I'm looking for responses from you guys! Questions, comments, opinions, rude remarks, and utter sarcasm, they are all welcome! I don't really need another project, but I do need a decent playback system for as little as I can do it. I've already decided to rebuild my old technics sl-1500 that is part of my collection, as I have recently discovered a love for the sound of vinyl. I don't know how far I'm going to take that, but it may end up with a new plinth and a DIY tone-arm. I am also building a cd player out of a playstation as I gave my favorite cd player to my mother to replace her old one, and have yet to find one I care for as much. And now I am finding myself not happy with any of the amps I have on hand. I will eventually be building an amp from scratch, but that must wait as speakers take the first priority as far as money goes, as they are what I need the most.
Anyways, thanks for reading my terribly long thread, I hope you tell me what you think!
-Justin
Anyways, being rather new to the hifi scene I have yet to acquire any gear except for my old vintage stuff that I really don't consider hifi (I've always collected vintage gear, ranging from PA and recording gear, to relics of the "bigger is better" period of the 70's and 80's). Now, considering the fact that I'm only 22 years old, I'm going to guess that a couple of you may actually know more about this amp than me, but recently I discovered while pulling it out of storage that it has two sets of RCAs on the back. One says AMP IN, and the other says PREAMP OUT. It has always had a jumper going between them, and I had never really thought about it, but I decided that there could be a possibility that the amp would be on a whole different circuit on a whole other board within the receiver (remember I come from a generation where everything is mashed together, you know, save money and space and put it on a single board!). Needless to say within the case I found a complete and separate stereo amplifier!
So, here is my dilemma. I've always cared for the sound of the particular amp, even though it is solid state I would say it has a warm quality. However it has always been noisy, at least by the standards of modern and even vintage hifi. As I started playing with it I discovered it was the preamp circuit that was the cause of over 95% of this noise!
I did this by running the PREAMP OUT into another amp of mine, but I also discovered by doing this that a lot of the warm quality I described followed. So I decided to run straight out of my laptops USB D/A into the AMP IN, and control the volume using my laptop. What I found was a very quite amp, not nearly as warm, but much more detailed, and very likable! However I also found two problems...
First is that low frequency response seems to have suffered, not in quality, but in quantity. The built in preamp has a little 5 band graphic equalizer, and I've always noticed that I've had to crank the low and high frequencies to get it to sound flat (yes I know what flat should sound like, I'm new to hifi, but I have degree in music and recording tech. hehe, I'm just saying I'm not your typical teen looking for piercing highs and thumping lows...)
So I decided to plug the preamp back in but turn off the eq, and what I found was a very muddy sounding amp. My theory is the preamp sounds muddy so they give you an eq to fix it. Without the preamp I find no attenuation of high frequencies, and in fact they are very clear and focused, but the low end tends to roll off a tad early. This isn't a huge factor for me, the low end frequencies are there, and actually much improved over the use of the preamp. It's just they are a little quieter than I'd like.
The second, problem is that it seems that one of the channels is slightly louder than the other, I only seem to notice it at low levels. This is something I never noticed when running it as a complete unit, with the preamp plugged into the amp with the jumpers. I don't know what could be causing this issue, but that's what I have you guys for!
Alright, now for the choices...
1. I could put it all back together and leave it as it is, it's either not worth my time, or would be better left as part of my collection as it is, all original, and wait until I have the money to build a new amp (something I plan to do no matter which choice I choose).
2. I could attempt to do a full restoration of the entire unit, with help from you guys, clean up the noise as best I can, and use it as a total package, even though it's got tons of "features" I will never need or use, and is way too big for my current living space.
3. I could remove the amp circuit from the unit, do a full restoration and/or modification of just the amp circuit with help from you guys, recase it, and build an external passive preamp to control volume and select inputs with.
So, now I'm looking for responses from you guys! Questions, comments, opinions, rude remarks, and utter sarcasm, they are all welcome! I don't really need another project, but I do need a decent playback system for as little as I can do it. I've already decided to rebuild my old technics sl-1500 that is part of my collection, as I have recently discovered a love for the sound of vinyl. I don't know how far I'm going to take that, but it may end up with a new plinth and a DIY tone-arm. I am also building a cd player out of a playstation as I gave my favorite cd player to my mother to replace her old one, and have yet to find one I care for as much. And now I am finding myself not happy with any of the amps I have on hand. I will eventually be building an amp from scratch, but that must wait as speakers take the first priority as far as money goes, as they are what I need the most.
Anyways, thanks for reading my terribly long thread, I hope you tell me what you think!
-Justin
yeah having things on separate boards is kinda nice isn't it. maybe not quite as compact, but much more intuitive. also easier to troubleshoot stuff. you and i are basically from the same generation and i love vintage stereo's as well. it is amazing to hear the sound quality they were able to achieve back then.
if you don't want to go with the full blown resto route (which would undoubtedly be the best yet most expensive and time consuming way to go) you could try to debug the noise and balance problem on their own. you did say the amp sounds nice as is. visually inspect all the capacitors in the entire unit, especially the electrolytics. an aged or leaking bypass or reservoir cap, for example, could easily be the cause of the noise injection. the balance problem could be related to the volume control pot ... often the symptom of an aged vol control pot is a weak channel, especially at low listening levels as you describe. every vintage stereo i have worked on has needed that pot replaced because it wears out with use.
if you don't want to go with the full blown resto route (which would undoubtedly be the best yet most expensive and time consuming way to go) you could try to debug the noise and balance problem on their own. you did say the amp sounds nice as is. visually inspect all the capacitors in the entire unit, especially the electrolytics. an aged or leaking bypass or reservoir cap, for example, could easily be the cause of the noise injection. the balance problem could be related to the volume control pot ... often the symptom of an aged vol control pot is a weak channel, especially at low listening levels as you describe. every vintage stereo i have worked on has needed that pot replaced because it wears out with use.
I vote for a restoration/hot rodding. Go through the receiver and replace components that are known to go bad over time, like electrolytics. However, use better quality parts. One thing here would be to replace any eletrolytics that are in the direct signal path with polypropylene caps if possible. They are larger, but have a much more linear behavior to audio(AC) signals. I would recommend finding the schematic for the receiver first, that will help greatly in your resto/improve.
Peace,
Dave
Peace,
Dave
First thing i'd do without question - replace the main power supply capacitors - the two big ones in the middle. This should improve things overall a lot.
Leolabs said:
I don't know that I want to retain the original circuitry. But, I do know that I am on a budget, and of the amps I currently have at my disposal this one sounds the best. If it can be made to sound better though I am all for it!
gain said:
I fell in love with vintage gear because it is what made me fall in love with music, my dad always had a large collection, as he slowly got rid of it, I gained much of it, then started adding bits and pieces myself. Sadly I've recently been forced to get rid of a lot of it due to space constrictions, as I said even this amp in it's current state is to big for my current space.
As far as the known problems go, as far as I can tell the noise issue has to do with the preamp, so can I assume you are saying I should keep this together as one unit and not gut the main amp circuit out of it? The weird thing is that the balance issue is only noticeable when bypassing the preamp. I switched cables, I switched channels, I've tried everything, but it seems to be the amp itself. So, what could be causes of this?
Also, the amp circuit has no pots at all, it's just a raw power amp with no attenuators or anything. Because of this I actually just picked up the parts I need to build a cheep little passive volume control/input selector, so we'll see how that works.
dave_gerecke said:
I'm kinda leaning your way Dave but am torn between attempting a full restoration, or simply restoring and hot rodding the amp circuit. And if I only restore and hot rod the amp circuit should I leave it in the original unit, or re-case in into a new smaller case that makes the amp more usable?
jaycee said:
Ok, so a dumb question, is there any "upgrade" for these? Or should I just replace them with ones of the same values and type?
Either way if I decide to restore the amp circuit all electrolytic capacitors will be replaced, and those in the signal path will be upgraded. Hopefully this would help the low frequencies out. Otherwise I may have to find a schematic for a diy adjustable low shelf filter or something.
I guess the question is, to gut, or not to gut! And, if I choose to gut, where would be a good place to start looking for the schematic for this thing?
-Justin
Hello despot, Sorry it took a few days to get back to you, I got distracted.
So here's a thought for the main power supply filter caps. Replace them with a similar value, making sure that the voltage rating is as high or higher than the original caps. Then bypass these with some polypropylene and ceramic caps.
The other thing you may want to do that is relatively cheap that will cleanup the sound is to look at the schematic and find the coupling caps between the amplifications stages. Chances are they are electrolytics, so they should be replaced anyway. Replace these with some polypropylene caps, if there is enough space to fit the poly caps. They tend to be larger than the same value electrolytic.
If you do go the route of removing the power amp section and using it by itself, I would suggest that you document all of the connections,etc. Then if you decide to put the power amp section back into the receiver, it will be much easier. Personally, if the receiver is working, I would keep it together. I would only recommend gutting it if it isn't working.
Peace,
Dave
So here's a thought for the main power supply filter caps. Replace them with a similar value, making sure that the voltage rating is as high or higher than the original caps. Then bypass these with some polypropylene and ceramic caps.
The other thing you may want to do that is relatively cheap that will cleanup the sound is to look at the schematic and find the coupling caps between the amplifications stages. Chances are they are electrolytics, so they should be replaced anyway. Replace these with some polypropylene caps, if there is enough space to fit the poly caps. They tend to be larger than the same value electrolytic.
If you do go the route of removing the power amp section and using it by itself, I would suggest that you document all of the connections,etc. Then if you decide to put the power amp section back into the receiver, it will be much easier. Personally, if the receiver is working, I would keep it together. I would only recommend gutting it if it isn't working.
Peace,
Dave
dave_gerecke said:
Alright, so I took your advice Dave and left it together. I put the behemoth into my system in place of my Yamaha receiver which I've always thought sounded cold. Well, before I could even replace any caps or anything I've started having issues with either one or both of the channels dropping out. I'll have to troubleshoot it to see if its the amp or the preamp, but if it's the preamp section I may just go back to the original idea of gutting it out.
Does anyone know where I could find a schematic for this unit?
-Justin
Hello Justin, Have you tried using contact cleaner on the pots and input connectors. With equipment of that age, it's quite possible that they are dirty. This can cause dropout on channels. It is also possible that something else, more major, is wrong.
I did a quick google search and wasn't able to find the manual for this for free, but I did find companies that advertised manuals for sale, perhaps they can help. It's also possible that some other kind soul here on diyaudio has this schematic.
Good luck,
Dave
P.S. This receiver didn't come with the schematic. Strange, that was pretty common with the Japanese equipment in the 70's.
I did a quick google search and wasn't able to find the manual for this for free, but I did find companies that advertised manuals for sale, perhaps they can help. It's also possible that some other kind soul here on diyaudio has this schematic.
Good luck,
Dave
P.S. This receiver didn't come with the schematic. Strange, that was pretty common with the Japanese equipment in the 70's.
So far it seems to act like there is a loose connection somewhere internally, where it is located I have yet to find. I'll probably start seriously looking over the weekend. I'm not too distraught, and if the problem is in the preamp section I probably won't bother as there is alot going on there with the equalizer, RIAA phono pre, tuner, and other tape outs and level controls. If it is in the amplifier section I have no doubt I can fix it, but I am curious what I can do to help the bass response. If I had a schematic this whole thing would be a tad easier I suppose.
-Justin
-Justin
Eleven GX
I've got the original manual if you need a copyu of it. I bought mine in Okinawa in 1979. It still works great. I matched it up with two HPM100 Pioneer speakers, sounds good.
DZ
I've got the original manual if you need a copyu of it. I bought mine in Okinawa in 1979. It still works great. I matched it up with two HPM100 Pioneer speakers, sounds good.
DZ
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