STA1 + amp vs K-12M - diyAudio
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Old 28th February 2007, 07:23 AM   #1
raffir is offline raffir  Canada
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Default STA1 + amp vs K-12M

Hi.

I'd like to put together some sort of tube kit. I'm considering either the K-12M or the STA1 preamp, which I'd couple to something like a Sonic Impact amplifier or possibly a Gainclone. I'm planning of building a kit because I haven't built anything in a while, and have never built anything with tubes, so would like a simple path for getting my feet wet.

I like the idea of the STA1 because it includes the front panel, which I could then avoid building. Also, I could couple it to a separate power amp, and then have two pieces of equipment, allowing me to upgrade one or the other. Also, I could use a solid state frontend, for what it's worth (I listen to all sorts of music; everything from Bach to heavy metal, and I understand that SS amps are better suited for some; correct me if I'm wrong).

The K-12M is supposed to sound great, and I wouldn't have to buy another piece of equipment. However, this would mean, presumably, that I couldn't add a different preamp later. This would also mean that I'd be using tubes for the output stage (see parentheses above).

I'll primarily be using some kind of computer for output, but I'd also like to listen to records. I'm not sure if this means I'll be needing a separate phono stage no matter what I choose.
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Old 28th February 2007, 02:44 PM   #2
Sherman is offline Sherman  United States
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If you build the STA-1 and intend to use it for a hifi preamp you need to build the STA-1 LG version. The regular version is a high gain device more suited to microphone/PA/guitar.

I also didn't see where the front panel was included with the STA-1 (I didn't get one with my kit a couple years ago either ).

As for the K-12, it has a rated output of 8 watts. A Sonic Impact into 8 ohms is maybe 10 watts. No audible difference in volume there.
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Old 28th February 2007, 08:40 PM   #3
raffir is offline raffir  Canada
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The advantage of using a SS frontend is that I could presumably add a larger, more powerful one at some point (although right now, bookshelf speakers are about as large as I can fit, so it's a bit of a moot point). When I referred to the advantages of a SS frontend, I meant specifically the impression I've gathered that they may be "faster:" I'm not sure if that's an issue or not.

Would either one work for both record players and normal lines-out, or would I need a separate phono stage no matter what?

You've built the STA1? How does it sound? With what kind of amplifier have you matched it?

On further inspection, it does not come with a front plate. How unfortunate. Perhaps I'd just best build the K-12M instead. Can I match the K-12M with a separate preamp?
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Old 28th February 2007, 09:04 PM   #4
gofar99 is offline gofar99  United States
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Greetings, Since I have both an ST1A and K-12, I'll pass along my thoughts. I didn't care much for the ST1A. You are correct it doesn't come with a front panel, just the board and parts. My sense was it wasn't as linear (flat response) as other alternatives. I didn't need the tone controls so there was excess circuitry to muddle things up. I couldn't get it to sound like I thought it should (maybe just my preferences) I use a Velleman 8021 SS preamp now. It has a phono section and drives the K-12 very well. My K-12 is much modified and if you care to see the details look on the diyaudioprojects.com site. There are several K-12s on it. The basic k-12 is a nice sounding tube amp. IMO The most cost effective alteration is to replace the coupling caps. The K-12 does a good job driving my speakers (MTM from Dayton). I also have the SI Super T's. They work well and have a sound similar to the tube amp. Not quite as listenable to my ears though. A very similar amp T10.1 is now on the market and may be better than the SI. It gets good raves and is nicely made. See 6moons site. At about $120US it has to be a buy. SI is according to recent info defunct so the Super Ts may be history.
Hope my ramblings are of use.

Bruce
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Old 1st March 2007, 02:11 PM   #5
Sherman is offline Sherman  United States
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I built the STA1 a couple years ago as a preamp for a pair of SE KT88 monoblocks I was building. The kit consisted of the circuit board and parts including the potentiometers for the volume control and tone controls. I put it in a Bud chassis I had and supplied the power switch, HT delay switch, input selector switch and all the jacks and other connectors.

When I first fired it up it had a LOT of hum, far too much to be listenable. I tried rearranging some things in the chassis with no success. I then changed my grounding scheme also with no change. Finally I changed the heaters to DC and that solved the problem.

Another mod, listed on the Lighthouse Electric site is a change to one of the caps in the tone control section. The standard value has way too much bass boost. After that it was a pretty nice sounding preamp.

I've since changed to using a "passive preamp" with remote control for the monoblocks so I'm not using the STA1 any longer though I've had thoughts of resurrecting it in another form.
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Old 1st March 2007, 04:25 PM   #6
gofar99 is offline gofar99  United States
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Greetings, Mine had the same hum problem and I solved it the same way with DC heaters and revising the ground scheme. As a thought it might me worth the expense to get the SMPS that Lighthouse sells for around $60. It will do the B+ and DC heaters. Could save a bunch of grief.

Good listening
Bruce
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Old 1st March 2007, 07:27 PM   #7
raffir is offline raffir  Canada
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Sounds like the STA1 may be more trouble than it's worth.

How's the K-12M for all types of music? I literally listen to everything from Holst to Black Sabbath (I guess that only spans about 80 years, but still...)

Otherwise I guess I'd consider building the STA1 with a modified Super-T frontend. I've always wanted to try something with tubes, but I guess if SS is the way to go...
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Old 1st March 2007, 09:31 PM   #8
gofar99 is offline gofar99  United States
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Great question, open to many answers. I personally like tube sound for everthing. But it isn't the do all for everyone. Some limitations esp regarding the K-12. If you don't have very efficient speakers there probably won't be enough power to play as loud as you might want. I get around that by using a pair of 15" subs that are self powered. I crossover at 50 and let my main speakers (Dayton MTMs) roll of naturally at roughly 45. I use no boost or equaliztion and the sound is excellent. With the subs doing the power hungry stuff the mains and K-12 are plenty suficient. A plus for tube amps in general is the way they overload. They don't hard clip when overdriven. They tend to go into a compression sot of mode. This is part of the reason that many musicians like them. SS stuff driven hard often sounds horrible when it clips. The MTMs run about 88 db/w and my room is about 200 square feet in size. If your room is much larger it will eat up more sound.

Bruce
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Old 1st March 2007, 10:39 PM   #9
raffir is offline raffir  Canada
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I can see building a sub at some point. My room is tiny right now; this is for a bedroom. I'd like to build a phono stage at some point, so I guess it comes down to the K-12M vs. the Super-T as a frontend right now.
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Old 2nd March 2007, 04:56 PM   #10
gofar99 is offline gofar99  United States
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Greetings, Both are good, the cost of the K-12 will be a bit higher. IMO either will serve you well. And as an update or improvement over the Super T, I believe I would give serious consideration to the Trends Audio TA10.1 It retails for about the same as the Super T and from all accounts is even better. It would be my personal choice for a couple of reasons, first the company isn't defunct, second the construction seems better and as a clincher I seem to recall seeing a recent 6moons review on it that was favorable, so it is probably quite good.

www.trendsaudio.com/EN/Product/TA-10_desc.htm

Keep us all posted on how it works out.

Good listening
Bruce
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