• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Would an s5 K-12M kit suffice?

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#61
Thanks Mark, Yea I think the hammonds are all right and Angela Instruments has them for pretty cheap. I can build my own case, I just think that my case designs are bad and simple. I'm thinking of maybe getting the premade top plate (copper) from the website with the holes in it already, just because I would not only need to buy the copper anyway, but have to buy tools to drill the holes for the tubes, I saved the thread about how to drill holes for tubes, but haven't read it yet (probably a pretty good idea). On the pdf has all the parts from mouser and prices from a bunch of place (some wrong) but also tells some modifications, and Dave it actually says on there to stick with 100k or larger (guess I missed that). So my big question is buy the $400 kit or go with the PCB and buy everything by itself? One other option is use tubes4hifi.com and get the $129 PCB with parts + $55 for tubes + $149 for transformers= $333 That means I can use the group buy and get high quality RCA and binding posts for pretty inexpensive. Instead of paying lots of money for tubes4hifi.com to sell me cheaper stuff for more $. I also have to get some hookup wire too, not a problem. It seems to me like tubes4hifi charges a rediculous amount of money for that, because didn't I cover pretty much everything except on/off switch and fuse?

Thanks,

Josh
 
#62
Sounds like a plan. Switch and fuse are in the parts list too. Is that group buy still goin on? I thought it ended. I'd like to get in on that too but thought I missed it! Yep hookup wire is all over the place if you can watch e**y. I picked up a 1000 foot of 22ga solid silver plated teflon for like 10 bucks!

Mark
 
#65
planet10 said:
With appropriate heater rewiring (and a 6.3 V filament trafo) you should be able to just drop in a 6BM8 which is very commonly used in audio circuits (was designed with the express purpose of dual TV & HiFi usage)

dave
Click to expand...

So is the reason for this just you can get the 6BM8 in matched pairs/quads or is there also something else better about it?

And similarly, is triode strapping always successful in getting extra linearity at the price of power, or would these tubes be a poor choice for trying that?
 
#66
leadbelly said:
So is the reason for this just you can get the 6BM8 in matched pairs/quads or is there also something else better about it?
Click to expand...

AFAIK the 11BM8 is simply an 11V heater version of the 6BM8. I've never touched an 11BM8, i've got quite a few 6BM8s -- including new surplus Russian military versions. The Japanese. in particular, really stretch this tube.

And similarly, is triode strapping always successful in getting extra linearity at the price of power, or would these tubes be a poor choice for trying that?
Click to expand...

In theory, my experience hasn't extended as far... i'm real interesting to see if RHing them approaches the best of both world's.

dave
 
#70
what awg do you prefer? What fits well into the PCBs? I dont mind spending more on wire, I'll use all the wire anyway. Most of the stuff on ebay seems toe be silver coated standed wire. I found a few websites, but some are like $12 for 1meter, that is a little much.

Here is one I found, 22awg but pretty inexpensive.

Any other recomendations?

Thanks,

Josh
 
#78
I have the standard version of the Foreplay. It is still in it's original box. I assembled one of the K501s, but something came up and I stopped. I've had them for a year and have just decided to get them out and assemble them. The K501 monobolcks were quite easy to assemble. I think I assembled the first one in less than 2hrs and that was after reading the entire manual and sorting all the parts. Sorting all the little resistors was the hard part...the rest was easy. I also have a plan that I drew up for a wooden case. For the top chassis I bought an aluminum kick plate for a residetial entry door. I plan to cut it to fit the two K501 cases. I bought some new switches at Radio Shack. I need to get a better cord for the k501s because they came with little cheap lamp cords. That is the first thing you should replace. It is the kind of cord that has the wheel in the cord to turn it on. If you plan to build a case for the S5 amp, remember to mount everything on the bottom side of the board except the tubes and transformers. My K501s were of a later generation and have the ceramic sockets. I figured the monoblocks with the Foreplay would provide cleaner sound than the standard kit. I have no idea if that's true and I haven't really seen anyone else who has done this. I've only seen the K501 monoblocks available at one place.

I had forgotten about these amps until I got the speaker building bug again.
 
#79
A friend has a home built foreplay and a factory one (with a few mods -- it is for sale BTW). The Foreplay is excellent value for the dollar. A pretty standard common cathode direct coupled to a cathode follower. Lots & lots of grunt. Not really necessary to drive the K12s or thei ilk, but allows you to build amps that need lots of voltage (ie my buddies ELL80 Spud amp which needs 4+ V to hit full stride)

An externally hosted image should be here but it was not working when we last tested it.


dave
 
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