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Old 22nd February 2008, 06:48 PM   #1
kvk is offline kvk  United States
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Join Date: Jan 2008
Question Help Me Pick Projects, I Can't Decide ???

Completed my HT system, I want to do an audio-only system. Something a little different. I have an old Kenwood receiver and an HK integrated amp not doing much but want something interesting. I want to do speakers and some kind of amp, maybe tubes or maybe chip.

Speakers, thinking I might give the fullrange thing a try. Some ideas--

An fe127e project, one of the plans on the net. Maybe just use scrap plywood in the basement. Advantage is would only cost me $100 (using scrap wood, new wood would be $50-100 more) and would give me a taste to see if I like fullrange speakers. Downside is if I decide I want something more efficient or with more bass down the road, I have to build another project and don't really need two pairs of speakers in every room in my house. Of course, DIY subs is an upgrade path to more bass but not more efficiency.

An fe167e, plans off the net (folded pipe, MLTL or something like that) or maybe spend $25 for BB's plans for the 1600MKII since it's supposed to be a proven design. Cost $250-400 for parts and wood depending on how fancy I wanted it. Advantage is they go pretty deep are getting low to mid 90s for efficiency.

A Hemp FR8c project, basically something a little bigger than the preceding for a bit more cash.

If I wanted to bag the fullrange idea and go two-way, build Pi II Towers. The parts are about $200, add $100-200 for MDF or ply. That gets me reasonably Hi-eff speaker if I have a low power amp but not fullrange.

Amp--

I had initially thought about a BottleHead S.E.X. They look like such nice kits. Downside is at close to $400 it's really pushing my price range. Also, I don't know if even the 90-94db ideas above will be loud enough. Also, there's no real upgrade path from it if I want something bigger.

Build an S5 K-12 8W PP tube amp. Include some of the mods on the net. This would be $150 plus $50-75 or so for a box and mods. That gets me to dabble in tubes. It gets me started with something that's a proven design but also let's me do a bit of DIY by tweaking via some mods.

Build a chip amp like the 41Hz Amp6. Could build with a box and hardware for <$100. Use a passive volume control instead of a pre at least to start. This is cheap. It ain't tube and I kinda wanna dabble in tubes. Of course I could upgrade it by building a tube pre-amp if I wanted (do you really need one? would it help the sound?)

Maybe build a tube pre-amp, maybe from scratch. That would be maybe $150 or so for parts and hardware. Certainly the most ambitious but also the most satisfying route (if I got it to work???). But, just a pre is pretty useless unless I build the above chipamp or maybe use it with my HK amp. The chipamp and then the tube pre is at least an upgrade path. I seriously doubt I'll ever have the money to build a tube power amp.


So what would you pick?


Me, I can read a schematic, solder, understand basic electronics and can understand someone else's design but couldn't design something on my own. I'm moderately handy with tools but no Norm Abram by a long long long shot.
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Old 22nd February 2008, 07:46 PM   #2
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Do my dishes!

Just kidding. If the HK integrated has power amp in jacks, I would say build the tube based preamp to start. The design from Bruce Rozenblit in "The Beginner Guide to Tube Audio Design" is a good beginners tube project. Bruce is the founder of Transcendent Sound.
Tube power amps aren't has hard, or as expensive than you would think. You just have to explore using used components for some of the more expensive items, like transformers.
Another possibility would be to mod the Kenwood receiver to use it has a power amp only, then build an active crossover and your own speakers. Use the power amp section of the Kenwood, along with the HK integrated to setup a two way active loudspeaker design.

Peace,

Dave
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Old 23rd February 2008, 12:36 AM   #3
kvk is offline kvk  United States
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Well the thing about the HK is the pre-amp section is currently crap because all those stupid itty bitty buttons on the tone controls that I never use are dirty and channels cut out. So I was thinking of either cleaning it up or getting a separate pre but I might have another use for it. My HT receiver Rotel RXS1057 does multi-room but only has five amps. If I want to drive the speakers on my deck, I need a two channel amp and that might be the HK.

I haven't been into electronics in about 20 years so I don't have much of a junk box any more. Makes doing things from scrounged parts kinda hard. Maybe I'll hit the garage sales here and there this summer and see what I can find in the way of tools and parts.

Still up in the air. Keep the ideas coming.
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Old 23rd February 2008, 03:27 AM   #4
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Ok, so the HK pre is hosed. Then you are down to the power amp. Again, that's a good option to go for a tube preamp. If you look at the design that I mentioned previously, you will see that it only uses 2 tubes. It doesn't have a phono section, but you can build one of those also. Mr. Rozenblit built the whole thing for around $100. If you were to follow the design of the preamp itself and make modifications to the power supply section to accomodate a different transformer, you could probably build it even cheaper. The other nice thing about Mr. Rozenblits book, is that it is a tutorial on designing tube based audio electronics! Try this website:

www.tubesandmore.com

This is Antique Electronic Supply. They carry parts, tools, books, etc. for old radios, hifi, and guitar amps.

Here's a URL for looking up hamfests in your area:

http://www.arrl.org/hamfests.html

This is always a good place to look for electronics junk. Second hand stores can be good also. We have a place here in Burlington called Recycle North. I've gotten a bunch of old transistor stuff from the 70's from there. ebay isn't a bad place either, but they are screwing around with there GUI, search, etc. and they are starting to get me cranky with them. Look on Craigslist also.
Another possibility would be to use the preamp section of the Kenwood if it is still working. If you decide on a tube preamp, I might even have a transformer and possibly some caps I may be willing to sell, pretty reasonably.
You could also gut either the HK or the Kenwood and use the case and transformer to build a chipamp based on a National Semi LM series power opamp. Something like the LM3875, 3886 or 4780 as an example. They have good datasheets and app notes on their website, and there are a couple of members here on the forum that have businesses making PCB's and kits to build this sort of amp.
In regards to the speakers, I'm just getting back into electronics and audio experimenting, so others will have more opinions on full range designs.
Whatever path you follow, I wish you luck and hope you post pics, etc. when you have things working.

Peace,

Dave
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Old 25th February 2008, 08:24 PM   #5
kvk is offline kvk  United States
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Default SS / multi-way = been there; done that.

I can't get exited doing anything with the Kenwood or HK as I just finished setting up a system with a Rotel receiver and B&W speakers. This hit my max affordability for a SS amp / multi-way speaker system and is pretty nice for music in addition to HT. That's why I'd like the next system to be something fullrange with tube or tube/chipamp hybrid. Why build another one of what I have working nicely.

I'm still vacillating daily on the speaker project. Figure I'll do that first and use it with the Kenwood til I do an amp project.
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Old 25th February 2008, 09:22 PM   #6
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I can understand your desire for something different. If you have a good amount of room in your listening area, you could try a J-Low or Kleinhorn for the designs by Nelson Pass. Check out www.passdiy.com and look for either of these. If these are too big, there is an entire section dedicated to just full range designs here (which you probably already know), with an amazing array of different designs. I think that short term plans make sense. Then do a chipamp power amp design, with a tube based preamp.
Whichever way you go, make sure you report back your results for the rest of us to enjoy and learn from!

Peace,

Dave
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