OK, thanks, then I will continue to not ruin your thread.
I attached a pic of my tubelabs se #45 amp.
The power tranny is in the chassis, back left corner in picture.
In case you're wondering, these are actually #46 tubes with an 4 to 5 pin adapter.
I had a breadboard version, will see if I can dig up a pic of that, which was really quiet, no hum. When I moved it into the chassis shown, hum showed up.
In the breadboard, power tranny was in the front of everything, in the front left.
I have tried adding some strips of magnetic shielding material on top of the power tranny, but based on comments the field is going around my material, was wondering why it didn't seem to make a difference.
Any suggestions for making a housing? What material to use that isn't too expensive?
I'm thinking about moving the power tranny outside the box, and see if it helps. Might even try a 2 box solution. Would move it to the left of chassis, left of the rectifier tube.
Pic rotated when I imported. My references are if the front was facing towards you.
Randy
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You can use a VT25 (=10Y), 801A for TT and a VT25A for oxide. Don't believe the stories Ale and Andy tell you, those valves are way better than what they say.
And Geoff, pictures of your amp do help others attempting similar challenge.
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I built a Vacuum Tube Audio PH16 tube phono preamp from a kit and did some upgrades along the way. Sounds better to me than a $2500 Ayre phono preamp I used to own. Several raving reviews on the Internet.
Web site is: tubes4hifi home page
Web site is: tubes4hifi home page
Don't despair. I've had about 15 out of 18 01A that respond well to rejuvenation. Those beauties are quite difficult to work with, requires very high impedance plate load but simply sound georgeous. For me the 10Y is the king of the hill while the 01A is the princess of finesse.
EM fields couple,what under normal conditions goes unnoticed. Because of distance fields weaken, so the effect drops under the radar. It is a fact none complete shielding weakens the coupling, think about the heads of a taperecorder for instance. Shure, for optimal result there must be several layers of different (magnetic) properties so the energy is soaked. Just like isolation of airborn energy.
And here’s the picture I forgot to post on my blog!
Amazing result on this incarnation of the 2P29L in hybrid mu-follower!
Great job again Geoff
I have a construction question. I saw this picture today,
It appears that this company mounts stuffs on a piece of wood and then stuff the whole structure inside a metal case. Only need to drill 4 metal holes. Drilling wood holes is so much easier than drilling metal. Any downside?
It appears that this company mounts stuffs on a piece of wood and then stuff the whole structure inside a metal case. Only need to drill 4 metal holes. Drilling wood holes is so much easier than drilling metal. Any downside?
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Modushop by Hi-Fi 2000 | Contenitori per Elettronica | Electronic Enclosures | Hi Fi Chassis
Buy amplifier chassis and get free shipping on AliExpress - 11.11_Double 11_Singles' Day
And similar. You'll find one I'm sure. (Hopefully these fit into your budget). I tried a big flat, very nice looking all aluminum case for my father (he builds a Class AB tube amp with KT150s), it arrived and we were stunned by the quality and precise craftmanship of that case. A simple cheapo Chinese case from Aliexpress. If machines are set well, they can produce quality stuff too. I'd give it a try.
It was something very similar to this one. I also bought a small standing case for my little cheapo fun-project ("what can a $1 class D 25W amp module do?")
Something like this, with different default cutouts. I packed in 2 good-old Russian military grade transformers from my father, a graetz bridge, 2 big LOW ESR 10k uF caps, ceramic caps and the 2 little Class D modules themselves (these here) .. now they cost a little bit more lol The set sound amazing (compared to its price of course, but absolutely okay otherwise for 'kitchen listening' when my wife is cooking something Anyway... you should try one of these cases.
That unshielded toroidal tansformer and the PCB just above it.
But there're others too, non-toroidals, with somewhat bigger stray. Despite being a beginner I would never use such a placement.
That unshielded toroidal tansformer and the PCB just above it.
Despite being a beginner I would never use such a placement.
I agreed that his layout is a bit strange.
Does anyone in Hungary or EU make a cheap 8k:50 (12.5:1) output transformer good for 5 watts output at reasonable bandwidth? If so, you could make a super-simple single-stage OPT-coupled amp that could sound quite good, and for cheap too.
Edcor in the USA makes such a transformer:
EDCOR - XSE10-8K
Perhaps a triode-wired D3a or Soviet-era 6Zh52P into such an OPT? 6S45P?
I used a triode-wired 12GN7A and it's working quite well. It has only 6dB gain after the step-down, but that's enough for my needs.
The design could not be simpler.
Audio is a volume control on the input, triode-wired pentode with cathode bias (fully bypassed), into the above-mentioned Edcor output transformer.
Power supply is solid-state rectified 500VCT 150mA EI core transformer, choke-input with a common stage of RC decoupling, and then one more RC decoupling per channel. Target Ebb is about +180V DC. Heater supply is 6.3V AC, elevated to +30V with a simple resistive voltage divider. Somehow I managed to wire it cleanly enough that there is no audible hum, none at all.
Easily point-to-point wired (no PCB necessary).
I can post a schematic and a picture of my little monster after I get home. I built it into a discarded amp chassis, so it's not pretty. But it's functional.
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Edcor in the USA makes such a transformer:
EDCOR - XSE10-8K
Perhaps a triode-wired D3a or Soviet-era 6Zh52P into such an OPT? 6S45P?
I used a triode-wired 12GN7A and it's working quite well. It has only 6dB gain after the step-down, but that's enough for my needs.
The design could not be simpler.
Audio is a volume control on the input, triode-wired pentode with cathode bias (fully bypassed), into the above-mentioned Edcor output transformer.
Power supply is solid-state rectified 500VCT 150mA EI core transformer, choke-input with a common stage of RC decoupling, and then one more RC decoupling per channel. Target Ebb is about +180V DC. Heater supply is 6.3V AC, elevated to +30V with a simple resistive voltage divider. Somehow I managed to wire it cleanly enough that there is no audible hum, none at all.
Easily point-to-point wired (no PCB necessary).
I can post a schematic and a picture of my little monster after I get home. I built it into a discarded amp chassis, so it's not pretty. But it's functional.
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Schematic of my little monster, attached.
I use it to drive Sennheiser HD650 (actually Massdrop HD-6XX) and Fostex T50RP. It drives the Sennheisers better, but it can drive the Fostex cans to satisfyingly loud volume.
I have an Objective2 amp to compare. I find the O2 sounds more sharply detailed, and of course its bass response is more authoritative ('faster', 'punchier') and sounds like it goes lower in frequency. I find the little monster sounds smoother, a bit darker in the highs, generally more mellow. But it does not sound woolly, fuzzy or 'slow'. Just a tad 'dark', which I actually like. That could be the sound of the OPTs, which are cheap (about $25 USD each) and probably have limited bandwidth compared to $100+ OPTs.
I use it to drive Sennheiser HD650 (actually Massdrop HD-6XX) and Fostex T50RP. It drives the Sennheisers better, but it can drive the Fostex cans to satisfyingly loud volume.
I have an Objective2 amp to compare. I find the O2 sounds more sharply detailed, and of course its bass response is more authoritative ('faster', 'punchier') and sounds like it goes lower in frequency. I find the little monster sounds smoother, a bit darker in the highs, generally more mellow. But it does not sound woolly, fuzzy or 'slow'. Just a tad 'dark', which I actually like. That could be the sound of the OPTs, which are cheap (about $25 USD each) and probably have limited bandwidth compared to $100+ OPTs.
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I'll bet those Electra-Print OPTs would perform better than the Edcor OPTs I used. The step-down ratio of the 8k:50 Edcor OPTs is 12.5:1, while the step-down ratio of a 5k:100 transformer is more like 7.07:1. That means you would probably get more gain from the same circuit if using a 5k:100 OPT. That would be nice.
I think the primary inductance of the Edcor OPTs is only about 8H. If your OPTs have a much higher Lpri, then you should get better low bass response. I found I get good-enough bass response using 12HL7, but it didn't work with triode-wired 6J9P (rp of that triode is too high).
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I think the primary inductance of the Edcor OPTs is only about 8H. If your OPTs have a much higher Lpri, then you should get better low bass response. I found I get good-enough bass response using 12HL7, but it didn't work with triode-wired 6J9P (rp of that triode is too high).
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