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First DIY amp FINISHED - 300B SET - works!
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Author:  massina218 [ 18 May 2010, 17:35 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

My intent was to pass on, to anyone who might care, that I hadn't noted any RFI with my ears. I don't own a scope, yet, just music. Didn't mean to push anyone's button, just indicating I hadn't had an audible issue.

John

Author:  Bennybuis [ 18 May 2010, 18:57 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

Hi everybody,

a smps is a good way of heating tubes, if you are not able to build a noise free amp using smps on the heaters, you are probably just not able to build a noise free amp, period. As for myself I do prefer a voltage controller and a solid state psu, that is how I heat my OddBlock, of course noise free, even on high sensitive headphones with load resistors, and those are very unforgiving, you hear everything.

Author:  mwhouston [ 18 May 2010, 20:06 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

Nice build. What I do when I have finished the amp is grab related or near clumps of wire and place a small zip tag around them. It makes it look just a tad neater. But I beleive this free-style or 3D wiring is the best. Problem is you need the 3D glasses to work it out (lel)!
Attachment:
KitAmpUnderSmall.jpg

Author:  sampleaccurate [ 18 May 2010, 23:45 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

massina218 wrote:
My intent was to pass on, to anyone who might care, that I hadn't noted any RFI with my ears. I don't own a scope, yet, just music. Didn't mean to push anyone's button, just indicating I hadn't had an audible issue.

I got my scope out of storage today and I've been poking around my amp. Everything I see that's ultrasonic is EXTREMELY small in amplitude. It looks like broad band noise from no particular source and it's still there with the amp unplugged from the wall but still working off the capacitors. Seems to me as soon as I unplug the amp all this EMI should disappear, but I see no difference.

Neither do my ears hear any.

Sampleaccurate can now be quoted: "SMPS passes the test".

One good thing I found, one of the stages is not biased properly - the clipping is highly asymmetrical, so the amp is capable of going much louder once I fix this. The positive voltage goes 3 or 4 times higher above the x axis than the negative goes below before clipping.

I'll track that down tomorrow.

Author:  sampleaccurate [ 18 May 2010, 23:55 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

mwhouston wrote:
Nice build. What I do when I have finished the amp is grab related or near clumps of wire and place a small zip tag around them. It makes it look just a tad neater. But I beleive this free-style or 3D wiring is the best. Problem is you need the 3D glasses to work it out (lel)!

Thanks. I agree about the glasses - I was starting to go cross eyed looking at the wires!

I actually bought a bunch of mini zip ties for just that purpose. Once I work out the bias issue and the amp is "final" I'll neaten it up.

Author:  mwhouston [ 19 May 2010, 00:01 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

sampleaccurate wrote:
mwhouston wrote:
Nice build. What I do when I have finished the amp is grab related or near clumps of wire and place a small zip tag around them. It makes it look just a tad neater. But I beleive this free-style or 3D wiring is the best. Problem is you need the 3D glasses to work it out (lel)!

Thanks. I agree about the glasses - I was starting to go cross eyed looking at the wires!

I actually bought a bunch of mini zip ties for just that purpose. Once I work out the bias issue and the amp is "final" I'll neaten it up.

Good part is the zip tags are cheap so if you have to cut them away and re-apply there is no huge cost issue.

Author:  sampleaccurate [ 19 May 2010, 02:13 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

Scoping it out:

Image

Did I mention this amp sounds great?!

Author:  cheap-Jack [ 19 May 2010, 09:50 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

sampleaccurate wrote:
Everything I see that's ultrasonic

sampleaccurate wrote:
It looks like broad band noise from no particular source

HI.

What bandwidth is yr scope?

FYI, RFI powerline filters handle RFI well beyond 100MHz. The powerline filters (made in England) I installed on the dedicted powerlines (125V & 250VAC 60Hz) for my audio rig, provide max insertion loss of 52dB at 32MHz & 36dB at 100MHz.

As my picky ears find anolgue programmes, e.g. vinyls & tapes, sound more musical than any digtial sources, which include DVD-audio 24bit/192Khz mastered soundtracks, I just can't buy the idea of SMPS for my audio amps. Good soldering knowhow does not warrant better music listening.
They are 2 different things all together.

As I already said, SMPS is a technically smart way of heating tubes, but not a wise way to do so musically. Otherwise I would have done do years back.

"If the facts don't fit the theory, change the facts"....

c-J

Author:  azazello [ 19 May 2010, 11:44 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

People talk that with AC heating muzically is better with more dynamic/!! :headphones:

Author:  sampleaccurate [ 19 May 2010, 12:03 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

azazello wrote:
People talk that with AC heating muzically is better with more dynamic/!! :headphones:

I guess I'm just one who has to hear it for myself. I have yet to hear an explanation for AC heaters sounding better other than uneven electron flow in directly heated cathode tubes due to one side of the heater being at a different potential than the other, but considering the heater voltage is only 5 volts on the 300B and the plates are at over 300v I just don't see this being a problem. The hum from AC on directly heated cathodes is probably far worse than any alleged degradation in sound from using DC. Again, I could be wrong!

Edcor is 8 weeks behind on orders. I purchased 3 sets of transformers this morning. One CXPP100-MS-10K set for my GM70 Oddwatt, and two sets for an ECL85 based oddwatt to try out, including a cheap WS8-140 set of line matching transformers to compare against their GXPP10-8-10K.

Now I've got 6-8 weeks of waiting. :shock:

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