-Explorer line from SKF is their low noise and vibration choice. Actually did not found such in SKF selector, whil eseet his at Nagravox offer… strange.
I heard in May 2023 at a friend’s home (sadly, but not a friend anymore…) the Braun L710. I was surprised by the concert feeling, by the atmosphere what that thing did. The guy had been saying this for over a year, how good the Brauns are and I ignored it. Maybe the fine details are not the best, but the overall sound pressure and the natural and honest acoustics dazzled me. And not just me, 2 of my other friends (they are still my friends) heard the same. One of them purchased that damn thing and proved that we were not wrong. Is a fantastic speaker if fed with good material. So I purchased the Big Brother L810 (more bass, but the same mide/tweeter)! 150EUR+60EUR post after some negotiations. Condition, nearly horrible, but I classified it as fixable. (Fix laminate errors, repaint, bend back grill… replace 50uF electrolytic caps, new connector, ect…)
On the video before any fix, but: This is the sound that I was looking for. I find it flawless, and straight to the point. Perfect for Rock, but I loved jazz also on it. In level of joy, this is the first time something that close to my loved Tannoy Chatsworth. A big recommendation to these speakers. Very unlikely that they are tun with high-end source or amp, so very likely even the seller has no idea how good these damn things are.
Kudos for AVS forum for the crossover pics. Schematic of L710 and L810 seams to match, except C6, which is 3.3uF(L810), 4.7, 5.1 or 5.6uF… (L710), but here the high driver is the reason LC2 (L710)–> LC3 (L810).
“The cabinets are encased in 1,5mm Formica which forms the rigid structure over the large sub straights. Remove the Formica and you will ruin the sound.” So I propose to take care of it, even if in bad condition.
Note: Kangoroo measurements pics are from L710!!! Base on pics the L710 kangoro elevetes the unit with 19cm and tilts it with 10degree. The L810 elevation is 12cm and tilt is 13degree. The Brown wood laminated speaker is an L810.
I have no idea what caps were put once by somebody. The may even original as they look like Arco (used by Tannoy), but grinded down and wrapped in textil.
The cabling improvement is a shame. Not my work.
The 15uF for the bass is closer to the “Gold” crossover design, wondering if this may be factory value.
The 3120 as many other DIY-er realized has a value of ~3.3mH and not 1.2mH as at many places suggested.
However in the tone boards I would ommit all Tantals and use the more cost effective Muse electrolytes. But is well documented, so suggest it as start.
Studer #41.99.0106 (RF516), ID 5 x OD 16 x W6, Ball Bearing D=5/16×6 (QTY: Tape tension L+R 4pcs), only 5mm thick is available!!! With 1mm shrim, itn works
Studer 41.99.0105 Ball Bearing D=8/22×7 Qty 2+2pcs for Spooling Motor EZO6082Z
Studer 1.020.840.09… 1.020.840.10. 1.020.820.06. head block
Since a long time I was confident that eliminating feedback from loudspeakers, my military box was terrible. Tried out crazy ideas like the Ikea lack, which is even worst. Played around with lifting, isolations, but no improvement. The last push was from Zsolt Bodnár (72 audio) to be not lazy and build a stand. (well was lazy to just borrow sizes from him, thx ) Here are some pics and guide for other lazy DIY-ers, who just need the last drop to build such. The result is very good for turntables or tube amps where microphony could be a problem.
BOM with 40×20 closed steel profile:
2pcs 250mm, cut on both side in 45degree on the 40mm sides
2pcs 500mm, cut on both side in 45degree on the 40mm sides
2pcs 430mm, cut on one side to 45 degree one the 20mm side
1pcs 500mm cut on both side to 45 degree on the 20mm side
I was using a nice Lenco PTP (pics here where I sold: https://avx.hu/forum/viewtopic.php?p=2669729#p2669729 ) with Fidelity Research 24 tonearm, till the owner/designer/diyer of 72 audio – Zsolt Bodnár – showed me that there is way of improvement at my frontend. He brought a DIY turntable with Dual 1219 roots and his tonearm built in small series with some MC and MC trafo (72 audio).
The tonearm is a miracle, which just works due to its simplicity. This blog entry shows in pictures what to do with the Dual 1219 to improve sound quality to finally be on the same page or better as Garrard, EMT, SP10, or my PTP. (I know just the PTP with proper experience, so handle this now as my strong belief) So ideas are not from me, I just try to have the same sound again in my chain that I got demonstrated by Zsolt:
Step 1 Remove everything from the chassis. Part you have to keep is the chassis(14), spring leg (78-82) the turntable (3-6, 16, 17) speed setting components (8-12, 101-115) and the motor (116-125), the motor switch is not mandatory, but feel free to keep it (parts 130-135, but you need to cut and bend the switch lever to make it constantly on). User manual to see assy and identify part numbers, motor electronic schematic is here.
Step 2. Close the holes with car body repair filler (is epoxy based) and sand it down with water proof sandpaper (water helps to not fill up the pores while sanding ) 200-400 sandpaper is fine. At the speed setting knob, add a 29mm coin exactly centered to the middle shaft hole (the 2 slot is not centered! Do not worry. if one seems to be more away than the other. You can see this in the bottom right of the next pic)
Step 3 Paint or add leather to look nice (The one in the picture is used by Porsche).
Step 4 Assy it back. Do not forget to clean and oil with sewing oil all bearings and moving parts. I see the debates to use single 40W or multi 5W20… probably all works, but self need to test which the best, maybe the tackier 40W. (inside the motor there is one hidden bearing, you will need to take it apart) The height of the driver motor wheel helps to set the speed knob to the middle(side screw-118 fixes, top screw -116 aligns height) Add bitumen-based sound absorber (car HiFi shop, 2mm with a thin aluminum carrier), to compensate for weight loss and eliminate vibrations (add double on the tonearm side to compensate asymmetric plate weight) Oh and you will need a hook to fix part 103 (spring of the idler arm) somewhere. I fix the hook with the the bitumen plate, I simply put it under it, while hook comes out.
Step 5, Polish the running surface till it mirrors. (the top of the left pic is a mirror)
Step 6 Add a heavy wooden plinth. The aim is that there is no feedback from the loudspeaker, while resonances are well suppressed. Think about using a wall console!
Step 7 Get 50Hz 230V clean power source. Less, than 60 Watt type, so something built for turntables . Should be with the precise clock to eliminate wow, flutter, or speed deviation. Should operate with LOW THT Sinus. Should drop the voltage to minimize motor vibration. 110Volt is enough. That will help that motor gets not hot. Ensure that chassis has protection earth!
Step8: Plinth. 5 layer CNC formed 6pcs 18mm plywood.
Can give you not painted one for 180Eur+ship cost. Mail me at r.bakos.gyorgy at gmail.
Note: Dual 1219 has a really bad bearing. PTP or Lenco is way more advanced. Motor vibration is enorm, but it gets very well suppressed with the motor holder. The plate has also audible noise while rotating as the motor. I think the side idler helps a lot with the direction to eliminate this. Overall: Very hard to believe this is better than my PTP, but listening confirms it. What comes from the loudspeaker is not bearing the listed flaws.
“And now it’s time for … no, not for Telesfor, but for probably the biggest sensation of this year’s exhibition, i.e. the Hungarian Popori Acoustics electrostatics, which, together with the 72 Audio electronics, caused such a stir in the lobby that most of the interlocutors were unanimously inclined to consider them the best sound in the Sobieski, with which I do not intend to argue, because it was indeed a phenomenal musical feast. Maybe the bass did not go very low, but it was energetic and tight enough not to show signs of slimming, while the rest of the band stunned with its resolution and speed. Big and well deserved applause!”
I recently upgraded with magnet bearing. Bought an 20mm-10mm/3mm N35 magnet from Aliexpress. Drilled up one with 11.6mm in lathe with using Dremel.(dust is cancer! Avoid it while work.) For bottom you need 4-5mm (if smaler, then take N48 or bigger) I sourced this: https://neomagnet.hu/Neodimium-gyuru-magnes-23x10x5-mm-N35
In the previous blog entry, I tried to show how to connect a generic turntable to the amplifier to avoid hum. This time I show my chain and how I connected it and eliminated hum completely.
Brief schematic is:
Important to keep MC transformer more than 0.5meter away from amplifiers transformer. If not possible, try to rotate it to find the dead ar where the magnetic field is not causing humm.
As you can see there is no loop, nothing is connected via more the one cable. I am thinking to connect the tonearm to the MC transformer housing but found no need yet for this as this was already very quiet.
The output transformer has ~4ohm output! (3.7Ohm to be more specific)
You need to connect the speaker for this mode between the 8ohm positive (which will be the “new” GND) and between 16ohm positive (will be the “new” 4ohm +)
Measurements + Pin out:
The below current mirror choke, along the Rodenhuis book, should be something similar, just split, (S6-S6a, S4-4a). While resistance is similar, the 8H is –> ~ 60H!
My grandfathers home was in the 2nd world war located in the highest part of the village, so the Wehrmacht has choosen their house to setup the radio. In 1944 when the Russaian army was closingm they decided to flee, so left a complete AM radio there. My father was using the tubes as radio amateur (DX), but those times are over and now I have the tubes in my hand to build an SE amp.
Tried to check if Tube can operate in Triode mode (G2 on Anode, G3 on K or A). Well, yes an no. Issue is that G2 is extremely hot, having 20% of the Anode current, while the maximum rating of G2 is 200V. So putting it on anode is driving it crazy (can the tube do 70Watt or more with 600V on Anode and G2–> Yes… Do not try at home, guess it kills the tube) .
Max shirmgitterspannung ist 200V Schirmgitterverlustleistung 5W Kathodenstrom 150mA Anodenverlustleistung 30W
I am still unsure if my aim is to build an triode SE amp with ~250V-350V anode, while trying to limit G2
or
Pentode operation with Anode to screen resistor as NFB. G2 = 240V, Anode = 350-450V, G1= -25 – -30V (need to set 85mA – 90ma Ia)
Feedback: plate to driver plate, 10%, simple cathode bias
Driver: C3M
Power Transformer nktes for me:
400 (A)–> 320V AC 0.5A, assume 50V DC drop while filtering… 240 (G2)–170V AC, (assume no drop…) 12V-15V (G3)–> 9.5-11.63V AC (assume 1V drop while filtering) -28.1V (G1)–> ?….
Philips AG9015 
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