mwhouston Posted December 13, 2015 Posted December 13, 2015 As I posted above I have been rolling between three amps. I have my Beymas now working well with my 250W IRS Class D amp. But it has so much gain I can barely turn up my preamp. From the preamp the electronic Xover passes bass (100hz and under) to my stereo sub-woofer amp. But if I can't turn up the preamp the subby amp does not get enough signal to drive the subbies to a balanced level. So today I added a 28 step step attenuator to the Class D power amp. Now I can set a volume level on the power amp and crank the preamp up enough to feed more signal to the subby amp. Sounding good. 2
mwhouston Posted December 19, 2015 Posted December 19, 2015 Checkout the latest Silicon Chip there is a two stage tube preamp kit there. All on one pcb, generates HT from a chip and has very low distortion and noise figures. Does have NFB but some of my tube preamp builds with NFB sound excellent. A good summer project. 1
Guest PsiGen Posted December 22, 2015 Posted December 22, 2015 Hi everyone! I am going to build a pair of speakers you can see in the rendering I've made recently. This is my second project so I will have a lot of questions and need a lot of help I hope you will enjoy the process as I am going to post it from time to time. Drivers: Scan-Speak 26W/4867T00, SS 15M/4624G00, SS R3004/662000 And stacked ply wood of course:)
mwhouston Posted December 22, 2015 Posted December 22, 2015 Still experimenting with the IRS 250W Class D amp the high efficiency Beymas. As in the above posted I have padded down the tweeter by -7db. The Xover point is 1600hz. But thinking about it all frequencies from 1600 up are padded down. I wanted a little more air from the tweeter. Thinking about an "L" you have a series and a parallel resistor. By shunning the series resistor with a 2.2uf quality signal cap I have effectively raised all frequencies from about 10k and up, up a few 2db. It worked and and now there is just a little more sparkle in the higher frequencies. Strangely double bass also sound better, richer.
Tony ray Posted December 22, 2015 Posted December 22, 2015 That's a lot of speaker PsiGen, I like it. 1
Tony ray Posted December 22, 2015 Posted December 22, 2015 Mark I cannot see the tweeter in your pictures. I am confused is the Beyma concentric? 1
Guest Posted December 22, 2015 Posted December 22, 2015 (edited) Ok, the sound lounge after 18 or more weeks The pile of gear (Junk as the Wife says) is in service as the room has stopped raining crap all over the gear. The room is to be "detailed and fitted out" as time goes on (back burner as the system works) Sub was commissioned yesterday and integrated into the Horn system. A Monarchy Amp joined the Team of gear to perform class A duty on the Compression Drivers in my PSE144. Amazing system, very happy with it and the room. Phenomenal is a word a Mate used. PS Remember there is a thumping great 5500Wrms 16 speaker stereo rig in the other end of this room. The silly phone photo shows sort of how the room ended up Edited December 22, 2015 by Guest
betocool Posted December 22, 2015 Posted December 22, 2015 @@125dBmonster, your avatar is in your picture.
Guest Posted December 22, 2015 Posted December 22, 2015 @@betocool Yea but had to be moved from the speaker as it was a perp, for the only reverberation for anything in the room. Room can run up to punishing 120dB+ levels without even a door rattle. The dog on the other hand, needs sorbathane to sit on.
mwhouston Posted December 22, 2015 Posted December 22, 2015 Mark I cannot see the tweeter in your pictures. I am confused is the Beyma concentric? Yes think Tannoy. It is a 2" titanium and Mylar tweeter. 1
Guest PsiGen Posted December 22, 2015 Posted December 22, 2015 Hi everyone! I am going to build a pair of speakers you can see in the rendering I've made recently. This is my second project so I will have a lot of questions and need a lot of help I hope you will enjoy the process as I am going to post it from time to time. Drivers: Scan-Speak 26W/4867T00, SS 15M/4624G00, SS R3004/662000 And stacked ply wood of course:) Now I am really worried about "splitting" problem when using trans-lam technique. My first pair of speakers ended up with several splits in different locations. So now I am looking for a good solution to avoid that...
mwhouston Posted December 23, 2015 Posted December 23, 2015 A fellow SNA member was looking for a volunteer to assemble a Bottlehead amp kit he had bought. I put up my hand and took on the job. I didn't realise there was the Speedball upgrade (three cct. brds) and bases which required prepping and finishing and a top plate needing paint. There was nothing I haven't done 100 times over I just didn't expect it. Fortunately the owner of the kit compensated my efforts so all is good. I'm not showing the top of the amp yet because I am keeping the colour a surprise. The base (came as four pieces of wood (oak I think) I prepped and spray varnished. I didn't come up well so I re-sanded and this time besswaxed. Much better as you will see in time. For the top plate I use a 320 grit, then etch primer and finally Epoxy Enamel spray. The paint probably takes a month to full dry but you can work with it two days later. Im pleased with the colour. I would not recommend the kit for a beginner. Way too hard, very cramped to work on and lots of very fragile and small parts. BUT I must say the amp sounds fabulous. I used a pair of 32 ohm closed back DT770 and was very impressed with bass. I listened to the amp for a few hours to check nothing was going to fail. Apart from the tranni getting very hot all appears well and the unit looks very smart on its blond deep base and contrasting top plate. I would recommend the kit even with the speedball upgrade. The kit uses transistors and diodes to make a constant current source (I think). The transistors are metal canned and were NOS 2N2222 and others. The leads were even a little rusty. Adds to the sound. Complete images will follow once the owner has received the amp. 4
Green Wagon Posted December 24, 2015 Posted December 24, 2015 I didn't realise there was the Speedball upgrade (three cct. brds) and bases which required prepping and finishing and a top plate needing paint. Gotta love the suprise buttsecks jobs you get now and then.................... 1
mwhouston Posted December 24, 2015 Posted December 24, 2015 Gotta love the suprise buttsecks jobs you get now and then.................... Fortunately I had been down this road of DIY so many times. It was all good in the end.
Green Wagon Posted December 24, 2015 Posted December 24, 2015 Fortunately I had been down this road of DIY so many times. It was all good in the end. Haven't we all ? When I do the 'lids lifted' of the classe audio I'm currently working on you'll enjoy the fun of the Schrodinger varistor in it. Now, wheres that buttlube
mwhouston Posted December 27, 2015 Posted December 27, 2015 An EL84 amp I built a few months back was originally fitted out with a 5U4 rec tube. I really wanted to use a Sophia Princes 274B "bubble" mesh plate. While inspecting the amp today I realised I had mixed the schematic of two versions of the amp. To bring it more in line with one I changed the blocker resistor to the EL84s and while I was at it checked the total current draw. As it turned out it was well below what the Sophias can carry. So I dropped one in. The big bubble tubes sure look the part and the filaments glow right through the plates. At night they are very impressive looking and I think an excellent sounding rec tube. Glow images to follow. I'm putting up this amp ("Tamarisk") for sale. 3
Owen Y Posted December 27, 2015 Posted December 27, 2015 That's a nice build MW. EL84s sound good, almost invariably. You prob already know this but.... I think the 274 drops a quite a few more volts than a 5U4 which is a lowwww impedance rectifier. Also the 274 should be used with a small (10uF?) C1, if using C input filter - whereas the 5u4/5Z3 etc can handle 40uF. Cheers, Owen Dark Lantern blog - http://darklanternforowen.wordpress.com/ 1
mwhouston Posted December 27, 2015 Posted December 27, 2015 (edited) That's a nice build MW. EL84s sound good, almost invariably. You prob already know this but.... I think the 274 drops a quite a few more volts than a 5U4 which is a lowwww impedance rectifier. Also the 274 should be used with a small (10uF?) C1, if using C input filter - whereas the 5u4/5Z3 etc can handle 40uF. Cheers, Owen Dark Lantern blog - http://darklanternforowen.wordpress.com/ Lately all my tube power amps, which always have tube rectification, have a 4uf Russian paper and oil first cap. They are always choked after the first small caps then 47uf, limiting resistor then 100uf. This allows me to use a mesh plate if the current draw is under 90ma. And yes I lost about 10V more but that's OK. Edited December 27, 2015 by mwhouston
Owen Y Posted December 27, 2015 Posted December 27, 2015 I always use PSUD (Duncan amps) to model PSU ripple & behaviour. And it's worth checking the RC pass freq (online calculators again) - for good bass ;-) Cheers, Owen Dark Lantern blog - http://darklanternforowen.wordpress.com/ 1
Tony ray Posted December 28, 2015 Posted December 28, 2015 (edited) An EL84 amp I built a few months back was originally fitted out with a 5U4 rec tube. I really wanted to use a Sophia Princes 274B "bubble" mesh plate. While inspecting the amp today I realised I had mixed the schematic of two versions of the amp. To bring it more in line with one I changed the blocker resistor to the EL84s and while I was at it checked the total current draw. As it turned out it was well below what the Sophias can carry. So I dropped one in. The big bubble tubes sure look the part and the filaments glow right through the plates. At night they are very impressive looking and I think an excellent sounding rec tube. Glow images to follow. I'm putting up this amp ("Tamarisk") for sale. Hi Mark, what timber did you use. it looks like two different kinds and at a guess I would say Blackwood and Jarrah. Also looks recycled. Looks great by the way and what sort of finish do you apply ? Edited December 28, 2015 by Tony ray
mwhouston Posted December 28, 2015 Posted December 28, 2015 Fortunately my tube amp building mate, Don, is as good with a saw as with a soldering iron. It's Spotted Gum. Don does all his bases with this wood. I get the raw base then prep and finished as the mood takes me. The finish can be beeswax, estapol or a can of 20 year old varnish which will expire one day. It's about how I feel on the day what finish I apply. Even Tung oil or cedar oil. 1
Guest Posted December 28, 2015 Posted December 28, 2015 (edited) Amp Build on the table again @@awty yep still the same one but everything is mounted now, ready for solder, had to post the SS here Houston is dominating with the tubes. Edited December 28, 2015 by Guest
mwhouston Posted December 31, 2015 Posted December 31, 2015 I thought I would try to beat the world record for putting a cct. brd. together from scratch. It took 1:20. I had two problems, I put a cap in a wrong hole and had to wick it out and a pin got stuck in one of the standoff. Now for the PS.
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