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A Very Compact Hybrid Amp - Page 24

post #346 of 2213
TimJo, wow that tube hole is very tightly packed in there. You must have spent an awful lot of time measuring. Any tips you want to share? I wanted the tube hole bigger to let some heat escape, as I have vent holes in the bottom as well. It still does get too warm (IMO) and I may have to open up more holes on top.

cfcubed, yep I remember those protectors. I thought about using them, but since I mounted the PCB in the top slot, and the caps are right on the case, I don't think I have room for nuts on the underside. Unfortunate, but true.

What is your source level output range? Mine is ~2Vrms max. I'm using my DT150 @ work which is 250 ohms right now (my other headphones like ATH-M50 or M-Audio Q40 are much more sensitive), and I can't get the knob to 9 o'clock with the "loudness enhanced" recordings of today. The RK097 seems to noticeably break up between 7-8 o'clock. I have to turn down my source. I'm using a 12AU7 variant (6189) with 120 ohm series resistors. Perhaps populating them in R18 affects the output signal more?
post #347 of 2213
Quote:
Originally Posted by holland View Post
< snip > yep I remember those protectors. I thought about using them, but since I mounted the PCB in the top slot, and the caps are right on the case, I don't think I have room for nuts on the underside. Unfortunate, but true.
If the top panel is thick enough I'd consider just drill/tap it & use short screws for the tube ring, thus nothing pokes below top panel (cut off screws to fit). If you've no taps just buy a single tap kit (e.g. 6/32 - has correct bit + tap) & use a drill on slow to drive the tap. Something to consider...

Quote:
Originally Posted by holland View Post
What is your source level output range? Mine is ~2Vrms max. I'm using my DT150 @ work which is 250 ohms right now (my other headphones like ATH-M50 or M-Audio Q40 are much more sensitive), and I can't get the knob to 9 o'clock with the "loudness enhanced" recordings of today. The RK097 seems to noticeably break up between 7-8 o'clock. < snip >
Shoot! I forgot that I "mp3gain - album normalize" all my files to 90db.... This could explain why its less of an issue for me... That process kicks down the volume uniformly to mitigate horrible effects of the "loudness war". I use like 225kbs/VBR/Stero MP3s.
Alex knows best WRT using R18s for output resistors
post #348 of 2213
Quote:
Originally Posted by cfcubed View Post
If the top panel is thick enough I'd consider just drill/tap it & use short screws for the tube ring, thus nothing pokes below top panel (cut off screws to fit)
Good idea! I'm glad you thought of it for me.
The CE cases are not as thick as Hammond belly plates, but should be thick enough to use a 1/8" screw with small protrusion.
post #349 of 2213
This looks excellent, love the design. I'm looking forward to building one or two once its all finalised.

Will the PCB gerber files be made available at all? I can get them fab'd quite cheaply locally and could make some available to other Australian's wanting to make it.
post #350 of 2213
Quote:
Originally Posted by holland View Post
TimJo, wow that tube hole is very tightly packed in there. You must have spent an awful lot of time measuring. Any tips you want to share?
Well, I think you hit it on the head. Careful measuring and I tend to move up drill sizes slowly. After centerpunching, I usually start with a 1/16 bit, and then move up in sizes a little at a time allowing each subsequent pass to center itself in the prior hole. Once I hit 1/4" then I use a stepped bit which keeps things centered as well. That being said, it also is dependent on how my luck is running - sometimes it doesn't work out perfectly. Luck was on my side on that tube hole.
post #351 of 2213
I've had fairly good results with the Irwin Unibit step bit. It seems to be a bit more ridgid and doesn't flex like the smaller bits, and thus stays centered a little better. I am using them on a small table top drill press. I still punch the metal to get things started. I want to shop for a press with less slack to keep the bit from wandering, and now I lower the bit and put a fair amount of pressure then flip the power on.
post #352 of 2213

Another CTH lives !!!!

Okay, she's all finished now !!!

I am loving this amp and so far I am really digging the sound. The thing is so small and easy to move around I'm blown away that it sounds this good. The amp is dead quiet, with only a little hiss when the pot is maxed. One thing I have noticed is that the volume can be a bit louder than I am used to, but with no fatigue, just more detail with amazing control. It is probably just that I am so used to the Millet tubes that I am experiencing the benefits of higher end audio tubes for the first time, and I am liking it. The servos are great as well because it means rolling tubes is so easy. Last night (and right now) I'm trying out a CBS 7730 (gold pins and black plates) and the results are quite good.

I used the longer Hammond case so I could fit a Blue Velvet pot, and I mounted the taller components on the bottom of the board. Several of the 1" caps were just a little too tall to fit in the case, so I drilled some holes in the bottom plate. I also added a 4-40 screw under the tube socket before soldering so that I could have a standoff between the board and the bottom plate. The tube socket is in contact with the top, and the standoff supports the board underneath, so there is no flexing to the board when rolling tubes in or out. I added four holes directly below the voltage regulator, and a row of 'exit vent' holes along the top of the back panel. The case is barely warm with only this minimal venting - largely because the tube itself is completely out of the case.

Here are a few pictures of the amp. I added one next to my iPhone for an idea of how small this thing really is...
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post #353 of 2213

That's sharp. I really like it. You've obviously done this before
post #354 of 2213
Are schematic and project details avaiable?
post #355 of 2213
Quote:
Originally Posted by Giuss View Post
Are schematic and project details avaiable?
Details will likely be available soon - after the rest of the prototype builds are finished and feedback incorporated.
post #356 of 2213
The second round of 10 proto boards are getting near to being completed. It will be up to Runeight to decide when he's ready to take it to the next phase. He and Cfcubed have done a great job on it, and most of the issues that have come up were self inflicted. Runeight has a great web resource that he will make available when he's ready. Full schematics will probably not be made available, after he got burnt on the SOHA project. He's broken it up into sections that can be used for diagnosis, but not for replicating the full board..
post #357 of 2213
Quote:
Originally Posted by MrSlim View Post
The second round of 10 proto boards are getting near to being completed. It will be up to Runeight to decide when he's ready to take it to the next phase. He and Cfcubed have done a great job on it, and most of the issues that have come up were self inflicted. Runeight has a great web resource that he will make available when he's ready. Full schematics will probably not be made available, after he got burnt on the SOHA project. He's broken it up into sections that can be used for diagnosis, but not for replicating the full board..
Second round?

I thought our boards were the first round?..I would be interested in picking up one more board if anyone is not using theirs..
post #358 of 2213
Thread Starter 
They were. There are no boards currently available. We are working on this. Getting more boards is easy, but supporting kits is a little harder.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #359 of 2213
Quote:
Originally Posted by runeight View Post
They were. There are no boards currently available. We are working on this. Getting more boards is easy, but supporting kits is a little harder.
right..i understand..however, i seem to have most of the parts with me now..so whenever the more boards become I would be happy pick one up..this amp is soo good..I love it..my first tube amp ever.

can't wait to show it off at the upcoming meet here in Portland..
post #360 of 2213
Is the BOM looking like it can all be sourced from Mouser?

And would it be possible to be PM'd a copy of the BOM? I'm just finalising a large Mouser order for some other projects, and it would be great if I could add the parts required for this to be ready for when PCB's are available, as shipping to Australia is expensive

Anyway the design looks great, very well thought out. Looking forward to building one.
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