• 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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I'm a noob to diy audio, I built my first Gainclone a few months ago and a pair of speakers using the WR125s. I want to build a tube amp, and have done a TON of searching. I've read a lot of you all's suggestions, and the K-12M seems like it might be the best for my budget. I'm willing to spend about $250, and I think thats about how much I'll end up spending after the modification

The Wr125s are only 85.6db efficient. Will the 8 watts be enough? I know very little about tubes, and have only listened to them a few times. A friend of mine's dad is a guitar player and has a recording studio and he loves tubes, he says he likes it better when the tubes are hot, is this true with music listening, and not just guitar? Would the amp have to run hot to power the speakers at normal listening level, or maybe a little above normal listening volume? I'm 17, and am about 10 feet away from my speakers when listening and sometimes like to turn up the volume a little high.

Do you all think this is a good kit for me?
I'm willing to MAYBE take up to $300 but I would prefer not to.

Thanks,

Josh
 
gmilitano,

Timn8ter told me about your site, I read it earlier today actually.

I was talking to Planet10 earlier today and he recomended the K-502 due to different tubes which he says are more well known. In the furture I'll build some new speakers, but I recently built the WR125s and wanted to try them out with tubes. I'd really like to do a tube project, but I just don't know which will work best and sounds the best. Planet10 also recommended the ASL Wave 8s which look very nice, but I don't have a preamp, but I was thinking maybe combining the two and adding a pot.

gmilitano, I have a pair of B&W 602's that are 91db, those would work well, but personally the wr125s sound better. Could I listen to the WR125s and the 8watt tube atleast at normal listening volume?

Thanks,

Josh
 
edjosh23 said:
...The Wr125s are only 85.6db efficient. Will the 8 watts be enough?...
Thanks,

Josh

Josh,
I also built one of these amps and did the modifications on Voltsecond's site. (Many of them were done already on the version of the board I got, including ceramic tube sockets.)

When finished I used it for a couple of months with a pair of Advent/1 speakers. I believe the Advents are about 87-89db/w/1M. If your room is smaller or you don't plan on listening at ear-bleeding volume 8W might be enough for 85dB speakers. Meaning if you listen to acoustic music, chamber music, most jazz etc. you should be OK. But... if you like to occasionally blast head-banging music you'll probably be disappointed.

Remember that 3dB increased efficiency in your speakers is almost like doubling your amp's power. I would recommend building the amp as a first tube project and then build some efficient speakers to go with it later on.
 
frugal-phile™
Joined 2001
Paid Member
edjosh23 said:
Wr125s are only 85.6db efficient. Will the 8 watts be enough?

At the rated power this gives you 94.6 dB at 1 m at clipping. tube amps typically compress instead of hard clip so there might be a bit more headroom than that.

That is fairly loud... it now depends on how loud you listen, how compressed the music you listen to is, and how big your room is.

It is a very good starter kit... add a copy of Morgan Jones "Valve Amplifiers" and away you go on a journey into tubedom.

dave
 
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All 4 amps mentioned (there are 2 versions of the antique electronic supply amp) use tubes with a triode section & pentode section. They use one of the triode sections as a gain stage, the other as a concertina phase splitter, and then the PP output stage. This is a classic design.

I have a couple old Viking amps (one 6BM8s, the other ECL86) that are the same topology. They are going to be resurrected but i will wire the triodes in a differential phase splitter with a CCS on the cathodes.

Something like this http://www.diyaudio.com/forums/showthread.php?postid=552739#post552739

dave
 
Dave,

I was reading through your posts on these amps. So if I have it right, the S5 K-12M uses 11MS8 tubes, as does the AES K-501 monoblock, and the AES K-502 uses the 11BM8. These tubes appear very similar, 1 triode + 1 pentode.
You probably know what I am going to ask: what's the Tim-the-Toolman bigger tube to cram in there to hot-rod it? Assuming of course one can live with swapping things around for heater voltage, etc.
 
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leadbelly said:
You probably know what I am going to ask: what's the Tim-the-Toolman bigger tube to cram in there to hot-rod it? Assuming of course one can live with swapping things around for heater voltage, etc.

You'd have to worry about plate & cathode loadsand current draw on the trafo, but the ECL86 is probably your best candidate... 12-15W as opposed to the (nominal) 8W from the others.

You also have to deal with the different filament voltages...

So you'd be looking at fairly major surgery... might as well buy some budget Hammond iron (or find an old donor amp -- my preferred methodology) and build from scratch. And if you are that far, you could consider just using EL84s + an approproprite input tube (you are no longer tied to the one in the bottle)

I can't recall whether the WAVE 8 is point-to-point, but the circuit board in the others -- althou making it fairly easy to build -- also discourages tweaking. Note: the WAVE 8 should be considered a pre-assembled kit amp (as it much of the ASL stuff) -- there are some things that need changing pretty quick.

dave
 
K502 owner

Hi, I built a K502 amp a few months ago and have been very impressed with the sound, it is my first tube amp also. I upgraded the capacitors & most resistors, and power cord on it and think it sounds great. I listened to old Cd's and was impressed by the sound quality and detail not heard before. Now I would say I would be willing to spend more on a new tube amp in the future. I have 88db tower speakers with twin 6.5" woofers, one 4" mid and one 1" tweeter on each, and it plays plenty loud, I don't even turn it up more than half way. Your speakerswill probably sound ok at moderate levels, but it will probably leave you wanting to upgrade those, too, because I am wondering how much better this amp will sound with better speakers now.
 
Thanks,

James_b, well, now that i convinced myself of spending more, I'm not sure what other kits there are in my price range that will offer more power.

Right now I'm looking at this route I understand point to point is better but, this is a neat concept, and might be the reason why they sell, and rip off people like me, but I wanted you all's oppinoin, obviously if I went with 300B tubes I'd be way over my budget, I haven't reasearch the prices of the other tubes.

The 6L6 is reasonably priced as are the kt88s
the EL34 are somewhat cheap also
the 300Bs, are a little over priced, depending on how much the other stuff in the amp will cost, I found a pair for $169 and thats the cheapest so far

I did a lot more reading and actually understand te tube concept (I'm sooo happy, no homework for once).

I definately have not ruled out the K-502 idea, but I was hoping that with, about 3 times the price I could get more. :D Any other suggestions for amps?

Thanks,

Josh
 
edjosh23 said:
Right now I'm looking at this route I understand point to point is better but, this is a neat concept, and might be the reason why they sell, and rip off people like me, but I wanted you all's oppinoin, obviously if I went with 300B tubes I'd be way over my budget, I haven't reasearch the prices of the other tubes.

Point-to-point might be better sonically (or so some might argue...), and it does make it a tad easier for modifications. I think the main reason why most DIY valve amps are built PTP is that the circuits aren't too complex, and not many can be bothered designing and etching a PCB themselves. I wouldn't worry about the PCB since it makes things so much easier to wire up.

The driver circuit looks okay, and should be able to drive any of the valves listed there reasonably. Phase-splitting with the input transformer will add extra cost to your amp though.

The Sowter transformers specified will cost US$130 in addition to the US$58 for the PCBs. So far that's US$188.

edjosh23 said:
The 6L6 is reasonably priced as are the kt88s
the EL34 are somewhat cheap also
the 300Bs, are a little over priced, depending on how much the other stuff in the amp will cost, I found a pair for $169 and thats the cheapest so far

I would forget about 300Bs, if I were you - especially since you need four. They're nice, but with a US$500 budget, you might end up having to sacrifice on other things (like the output transformer) to pay for them. 6L6/807 or the many, many variants can be had quite cheaply even as NOS (i.e. old stuff sitting in a warehouse for decades). I would start with one of the tetrodes or pentodes first, depending on which you can find easily and affordably. Anyway, this thing was designed to be "universal".

4x EL34 will cost around US$45
2x 6SN7GT will cost around US$17.90
2x Hammond OPTs are about US$100

So we've used up $350.90, and now have to add a power transformer, chassis, sockets and maybe a few other parts like RCA sockets etc. So you could probably do it for under $500 without too much difficulty.

edjosh23 said:
I did a lot more reading and actually understand te tube concept (I'm sooo happy, no homework for once).

:D
 
Ooo, I like the mag 1515, the THD is a lot less than what was showing up with the universal amp. I saw an article when reading tubez for noobz, about a Magnovox amp. 15watts is much more promising than the 8watts, and I must say the design Idea seems a lot better to me than the K-502 or the K-12M.

What about the tube upgrade? Sovtek EL84M (Matched Quad JAN GE 6EU7 (for either amp) , This is $60 more, I could probably come up with $60 somehow, but is it worth it? This also pushes my budget of $500 to $550, then to $610 with the upgraded tubes. This kit looks really promising.

I've done some research on the Wave 8's, which look really nice, and inexpensive enough to where I could build those and myabe a preamp, but they have been discontinued, and I like the idea of almost 2 times as much power for my new speakers.

Thanks a lot,

Josh
 
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