Cheap Valve Kits (such as this one)... Are they worth the effort? - diyAudio
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Old 21st February 2011, 01:07 AM   #1
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Default Cheap Valve Kits (such as this one)... Are they worth the effort?

Hi,

As a new-comer to DIY audio endeavors, I am trying to gauge whether or not it's worth purchasing any of the cheap Chinese kits that can be found on auction sites. I have attached a schematic and a couple of pictures from a listing found here, which is particularly cheap. Is this item worth the effort as a foray into tube buffers or will I simply be building something that's as good as useless in a decent system? I'm not hugely interested in starting right at the hi-end and will enjoy a journey of building and improving.... however I certainly don't want to start of with items that I will find useless in 6 months time.

I have finished stuffing the boards of a pair or MyRef RevC mono-blocks and I'm looking for a front end to match to them. Some have reported success with tube buffers here and I thought I'd look into it.

If the example given here is a waste of time (even with some upgrades), are there any cheap kits that are worth the effort? Failing kits altogether, where should I look as a good starting point into tube pre-amps or buffers?

Thanks everyone, your input is greatly appreciated.

Tani.
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File Type: jpg 6N3 tube buffer from china.JPG (63.1 KB, 227 views)
File Type: jpg 6N3 tube buffer from china2.JPG (105.7 KB, 225 views)
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File Type: pdf 6N3 tube buffer BOM.pdf (39.0 KB, 14 views)
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Old 21st February 2011, 03:20 AM   #2
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It looks fairly simple. I don't know why you want it, or what function it would be intended to perform. Looks like separate input gain controls for each channel, then a cathode follower will a bit less than unity gain to the output.

Frankly, I'd just replace the entire thing with just the two gain controls. And building such a circuit from scratch (not a kit) is almost a trivial exercise, either what you have shown or what I have suggested.
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Old 21st February 2011, 03:50 AM   #3
toufu is offline toufu  United States
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Why not get a decent kit like the aikido and be done with it?
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Old 21st February 2011, 04:08 AM   #4
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The aikido was one I was looking at, knowing that it gets rave reviews and many fans... I guess I was wanting to have a play around at a lower cost to start with, but like I mentioned, I'm not interested in rubbish...
Might just save up and go with something decent like the aikido.

Thanks.
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Old 21st February 2011, 06:10 AM   #5
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Quote:
Originally Posted by taniknight View Post
I have finished stuffing the boards of a pair or MyRef RevC mono-blocks and I'm looking for a front end to match to them.
The only thing I added to (my) MyRefRevCs was a good potentiometer, CD player and speakers.

Sounds great!

I don't see the need for adding a buffer between the CDP (or CDP/DAC) and the MyRef.

If you've just finished stuffing the boards, you still have a way to a finished amp....don't stop just because it sounds good on that breadboard!


There aren't all that many complete kits out there with decent parts and instructions. By that I mean something similar to the Heathkits of yore.....all the parts, great instructions, chassis, faceplate, knobs, electrical cord, fuse,...the works. Most 'kits' these days leave the most difficult parts completely up to the builder - stuffing a board is really quite easy and fast.

If you want a tube project perhaps something from Bottlehead would be a good intro..though in a totally different price range, at least it would have resale value if you did reasonable job on the build.

There's a Bottlehead kit in the mail to me right now; I'm looking forward to it.

PS: Stay away from the Chinese EL34 SE amp kit unless you want to do a fair bit of 'independent building' (throwing the instructions in the garbage...cutting...filing..)

Last edited by VictoriaGuy; 21st February 2011 at 06:18 AM.
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Old 21st February 2011, 11:07 AM   #6
DF96 is offline DF96  England
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Would you like to add a little noise and distortion to your music? If so, buy the kit.

By the way, it is astonishing how much circuitry they have used so that they can get away with using a cheap 12V transformer: back to back voltage doublers and amplified capacitors for the fairly low HT, and a separate regulator for the heaters (presumably to keep diode switching noise at bay). Maybe all this circuitry is intended to impress the unwary?
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Old 21st February 2011, 09:15 PM   #7
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The comments on this schematic confirm my suspicions, though as a learner in a field, I'll always ask for help for fear of passing over something through assumption. While I knew that this kit was never going to be something great, I guess I was hoping it would be worth the $25.... but if it does nothing positive to the sound then forget it.

VicGuy: I am more skilled in mechanical design and assembly than I am with circuits, so the MyRef will not stay wired like a rats nest for ever, guaranteed. I'm just experimenting before designing a chassis, as it will use a lot of hand worked timber and cosmetic metal finishes and I don't want to go to all the effort and end up wanting to alter it's contents.

Your comment regarding the lack of truly complete kits is encouraging, as I am toying with the idea of supplying chassis kits in an effort to stop DIYers from having to use cake tins. There are universal type chassis kits available but they are completely devoid of artistic flair, in stark contrast to the wonderful sounds that the builder intends it to reproduce. It may never happen but I hope I'll have enough time to pursue the idea.

Anyway, enough rant. I'll continue listening to the MyRef with nothing but a Salas RIAA and a pot and maybe look at building some speakers instead....

Thanks everyone.
T
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Old 22nd February 2011, 03:28 AM   #8
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T-
Sounds like you will have a great-looking project when it is wrapped up!
For my Myref (#1) I added a power switch and LED on one end of the front panel, and an input selector (A/B) at the other end. In between, just the volume pot. The input selector is useful for me- saves some cord switching.

Really, the MyRef sounds so good that I'm glad I didn't put anything else in the box with it (I was thinking DAC at one point). I think the MyRef will stay around a lot longer than the DACs and other bits I have here....

Your idea about chassis kits is an interesting one.... you could offer a variety of woods, different feet, knobs etc to put some variety in the offerings. (You've got access to lots of interesting domestic woods, from what I see your guitar builders using.) Aluminum (aluminium to you?) top plate and back plate would be fairly easy for most hobbyists to drill/machine. Provide the IEC AC inlet cutout....provide a perforated bottom cover.
If you do the wood machine work properly, you could flat-pack it for purchaser assembly. Bottlehead do this with their (very simple) boxes.
Good luck!
PS- It sounds like you are an adept woodworker. For a nice complex speaker project, check out Planet 10's Fonkens. I built a pair and they sound fine.
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Old 22nd February 2011, 04:21 AM   #9
doorman is offline doorman  Canada
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http://www.transcendentsound.com
not exactly "cheap", but less than many a set of speakercables or IC's!
Happy hunting
Don
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Old 22nd February 2011, 07:51 AM   #10
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Quote:
Originally Posted by doorman View Post
http://www.transcendentsound.com
not exactly "cheap", but less than many a set of speakercables or IC's!
Happy hunting
Don

Bruce Rozenblit is one of the 'good guys' in my book.
I should try to scratch up the $$ to buy one of his kits......
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