My approximation of how much this would weigh was a little under shot. I put all of these parts on a scale this morning and, with the SP10, it’s 106lbs. Spent the afternoon getting all of the individual sections ready to become one homogeneous plinth. After all of the layers were cut to match one another; using a pattern bit and a router, I put a continuous layer of resin between the sections and clamped them all together. I’d intended to use a set of Isoacoustics Gaia 3 that I already had as footers, but this will be too heavy for 4 feet and six is out of the question. I’m going to have to rethink that.
The last couple days have seen a bit of progress on my Plinth build. I decided to go with Teak for the top of the plinth and Gabon Ebony for the armboard. At this point I’ve fully embraced the built up plywood construction and opted to leave the plies exposed on the armboard as well. I had originally planned to not do an armboard, but I think I’d regret that decision later. At this point I’ve dry fitted all of the parts to work out how I want to do the tonearm wires, which can be more fiddly than normal with these arms. I also need to work out where I’ll install the connectors, which will be mounted in a wood plate similar to what I used for the SP10’s umbilical.
Follow-up on my DIY phono reamp. To recap, I've been using the original PP999 schematic, and the changes suggested by a user @ another forum, to construct my own phono preamp. I've been working on the circuit board design for a month or so, this is about my fourteenth revision. I'm using the software I normally use for other CNC projects, sort of adapting it to making very rudimentary circuit boards via isolation routing. Today was the first time I cut/stuffed/soldered one and powered it up, a sort of proof of concept. I figured it may work, or may not, or could work but be a noisy mess. So I was thrilled when I turned the gain on my preamp up and discovered that the phono preamp is equally quiet as the PP999 (maybe even a little more quiet), and it wasn't in any sort of enclosure yet. My original goal was to build a design with lots of loading options (capacitance as well as resistance, maybe adjustable gain as well). But I wanted to make sure I could match the PP999 performance before going any further. First pic is of the assembled board running on my system, the 2nd is stuffing the board (still needed to add the TLE2426). Anyone familiar with the schematic may notice I don't have any input loading caps (there is a place for them, they are not installed), and I added bypass caps for the 100uf electrolytic capacitors (why not?). The DC jack is center, the next two jacks on the inside are INPUTS and the outside jacks are the corresponding OUTPUTS. The third pic is the solder side, I still have to clean this (still messy from soldering). This is also the first time I've used liquid tin to treat a board. I wasn't sure what to expect, next time I will do a better job prepping the copper substrate (sand it with some ultra fine). A photo of the enclosure I'll use for this can be found earlier in this thread.
Today I cleaned-up the solder side of the board, and made a rear panel (just using the same copper clad I used to make the preamp board), and test fit everything. Forgive the black thumbscrews, I'll find better screws later, I just knew those were M3 because I use them for something else and know their size, and I don't want to use flat-head screws here. So now I can move onto designing the second board that will achieve the loading options, and fit in this same enclosure.
Nice work Phil. Have I got the purpose of the TLE2426 right - that it takes the positive & negative rails and creates a separate ground? If so, what happens to the negative rail? It terminates to pin 8 (?) on the chip and that's all? *edit: oh, or does it create a bipolar supply out of a single rail?
Yep. I'm using a 24vdc power supply now, an inexpensive (but decent) switcher that has a right-angle DC plug. This worked nicely with the PP999, as the DC jack is on the side. I also have a 24vdc linear wall wart with a straight DC plug that I can try now that my DC jack is on the rear of the phono preamp. I don't know that I'll be able to detect any improvement as the phono preamp is already impressively quiet (thank God!), but it is worth a try. But that TLE2426 is pretty neat, allowing flexibility in power supplies.
Can anyone school me on switches that may possibly be suitable for switching capacitance/resistance in/out of the loading, while the preamp is powered up? I'm not even sure this is doable, or if I can expect loud/possibly damaging (to the preamp) transients. In a perfect world, though, I'd be able to make these adjustments at moderate-low volumes. If that isn't doable, I'd still like switches that have decent contacts that will last a long time and I'd either lower the gain or turn off the preamp altogether. I'd prefer PCB-mounted (if possible) toggle switches. I'd like DPST so each switch handles both channels. I'm picturing about 8 of these on the front of my preamp (s0 not too physically large). And my budget is definitely of the beer variety. Domestic, in fact.
A switch which is specified as "make before break" is what you need. I don't have any specific switches off the top of my head though.
I've found that it's easier to find a suitable configuration switch in DPDT format rather than DPST. Just don't use the second output. I've also found switches to be far more expensive than I'd like them to be. Anyway, I'm assuming you want a right angle pin style for attaching to your PCB. Many of these type don't seem to have threaded bushings either. Another annoyance. Here is a non-threaded version. I'm not sure if the height will be an issue. https://www.digikey.com/en/products/detail/e-switch/100DP1T2B4M7QE/1803090 Or the threaded version. More expensive! https://www.digikey.com/en/products/detail/e-switch/100DP1T1B1M7QEH/4027499
Thank you, you're confirming what I seem to be finding on my own. So I guess I'll go with DIP switches. That's okay, I can still make windows in the front panel to access the switches, it will just be slightly less convenient. I flipped the silicon 180-degrees, which allows me to swap inputs and outputs (inputs now on outside, outputs on inside nearer DC jack). This made possible routing everything w/o requiring any jumpers. The center DIP switch will control the gain (I'll have four gain settings, just need to determine optimum gains/resistor values) and the two outer DIP switches will control L/R capacitance (100, 220, 440, 440pf, approximately) and resistance (I'll likely use values similar to the Muffsy valyes).
It begins. I'm just starting a build to replace my current 300B SET which drives my HF horns. I found these two nice NOS Triplet meters on Ebay and although they were quite pricy, they have the original vintage look. They will be mounted vertically somewhere to continuously indicate current - because. They are pictured connected to my current SET and nicely showing 60 milliamps. I also have two Edcor output transformers on order, but as is usual with them, they won't arrive for several weeks. All of the signal capacitors will be NOS original military spec oil-in-paper types containing those wonderful, extremely toxic PCB oils which I'm sure add to the sound in nice, toxic ways. The B+, filament and bias power supplies will probably be external in another chassis or rack mounted. My current amp already has an external filament supply. The B+ will be extremely heavily filtered as in my current amp to eliminate noise from the very sensitive horns. The circuit itself will use a 6SN7 input (one half for each channel) which feeds another 6SN7 (one for each channel) operated in cascode in order to get enough loop gain to use negative feedback if I want to. The output tube will be 300B or 2A3. The Edcor output transformers will have only 4 Ohm output taps since I'm running 4 Ohm diaphragms these days, and if I do use an 8 Ohm diaphragm, running them off a 4 Ohm taps will decrease distortion. There will be two controls for bias adjust for the left and right channels and left and right gain controls. These will be actual gain controls rather than 'volume controls' since they will be trimming negative feedback. The amp's form factor is in the air. I'm leaning toward going vertical in a recessed/terraced type layout, but I'll see. The transformers will probably be painted with black wrinkle paint.
It’s been slow progress the last few weeks on my SP10 build, but I’m finally getting there. Went with an ebony veneer on the armboard and finished the whole table in 10 coats of a low sheen urethane. Still need to add a ground connector, but for now the wire coming through my plate will have to do. The motor itself is attached with long all tread through the plinth and nuts and washers in recessed holes on the bottom of the plinth. The other thing I’ll be doing is building another base for my isolation footers to mount to and my level spikes to sit firmly on.
Project, upgrade a £20 ebay Philips CD723 Cd Player. (props to lampizator as the source of the ideas here) This is one of the last cd players that Philips produced. It has a VAM1201 transport which is about as good as they get and a tda1525 dac chip which is called Bitcheck in marketing speak. It's a very advanced dac with continuous calibration and sounds very fast and energetic. I think its a mixture of mulitbit and bitstream. This is the internals, not a lot there! The mains psu and audio board, top left is psu stuff with the big filter caps, top right is the TDA1545 dac chip just an 8 pin dual in line. Bottom centre is the audio output, op amp chip is a JRC4560. The dac is a current output device and it feeds direct to the opamp, the output from the opamp is then converted to dc by just one coupling 47uf cap so there's only one cap in the audio output whereas a lot of other players may have more than one which isn't as clean. The main filter caps have been replaced with much bigger 6800 uf. The area circled in green is where the signal muzzing mute transistors have been removed. There is a slight noise at turn off that's the only penalty. The area in blue is where the tiny yellow/orange signal muzzing filter capacitors (that look like resistors) have been removed these filter off high frequencies, but destroy atmosphere. Removing them just means hearing everything. Bottom middle the opamp is now a Burr brown opa2134 and the opamp coupling and power caps are now top of the range Nichicon KZ Muse, as black gate are no longer available. Overall a nice player that hasn't jumped once and now sounds unleashed, unveiled. The player was £20, opamp was £6 and caps were approx £10. (I didn't change the diodes for quieter Schottkey as the board tracks are very thin and its easy to run into problems with unsoldering and resoldering thick diode legs.) Thanks, if anyone has any other suggested changes please feedback!
Very nice! I have been wanting to do similar Lampizator type mods to some cheap CD player as well. Off the top of my head, you could add ferrites to the ribbon cable going to the display and separate out those wires and twist them, and you have plenty of space in there if you want to add another transformer and regulator(s) for just the analog section Probably way finishing returns compared to removing those HF cut caps, muting section, etc. though like you did. Put an old book inside laying on the sheet metal of the case to damp it, and same with on top of the lid.
Thanks for the suggestions, top players to modify are probably the last two Philips which are below, they are easy to mod because they have the short loader which makes extraction of the board easy. CD723 as above, TDA1545 Bitcheck Iout dac. CD753, TDA1549 Bitstream Vout dac. This has internal to the dac opamps so the entire output path can be disconnected and you just wire (VOLL and VOLR) from a close track near the dac through a polyprop or paper in oil capacitor to the rcas. I've done this on a Marantz cd48 but yet to get my hands on a CD753. Not sure why having taken the trouble to onboard the opamps they still run it through all the usual circuitry including the external opamp, I can only conclude that it wasn't worth the effort to redesign.
Project, Rejuvenate some old Mission 771 speakers by recapping. Take the old crossovers out, four screws to remove the binding posts on the back. In blue the old, rubbish bi polar electrolytic capacitors there because they were cheap. Its very easy to unsolder the legs, apply the iron and the legs lift with pliers. Then lever up the caps the glue will give up quite easily. Far right a 4.7uf 50v and middle a dark blue 10mfd (microfarad = uf) 50v electrolytic. Remove the old glue if necessary it should cut away fairly easily with a craft knife. Then solder in the new caps, I heated the solder then introduced the leg with pliers until I found the hole. Apply fresh solder if necessary. The capacitors have been replaced with Jantzen MKT Cap Metallized Polyester Film and (just about the most fun you can have in this hobby) re-glued with hot melt schmoo. There are loads of different makes and models of cap, these were the basic model which are small due to the low 150v rating lots go far higher voltage and bigger. The replacement caps are 4.7 and 10uf 150v don't worry about the voltage rating being more, all caps of this type have bigger voltages than necessary key thing is they are much better capacitors for purpose. Refix the crossovers and try them out, mine took about 30 mins to run in, they sound far clearer than before. Total cost ~£16 with shipping.
Nice job! I love seeing speaker upgrades. If I could humbly suggest, there might 2 or 3 more things you could address without spending a lot of money. The first two are the sandcast resistors. They are notoriously bad sounding, mainly due to the fact they have an inductive component associated with them. A Jantzen Mox 5w resistor would be an upgrade (about $.50 ea) or the Mills MRA5 as a bigger step up. Thirdly, the crossover for this 2 way speaker will be a good bit higher than the 200-300Hz range which is suggested for ferrite inductors. Replacing the ferrite core inductor with an open air inductor would reduce smearing in the midrange by a fair amount. If.....you can find the appropriate value (mH and DCR) in a size that would fit on the board, you could make some improvements there. Lastly you could replace the wire with a high purity copper wire with a teflon jacket. Most of the time the wire used is a basic copper with some sort of poly jacket. All of these are upgrades that will improve the sound of your speaker without breaking the bank.
Thanks for the suggestions, one thing leads to another. If I do all that it'll be a sleeper speaker, maybe. No idea what the inductor values are nothing printed on them and I haven't managed to find a schematic. Almost into designing a new crossover.
I just did a quick search and I couldn't find the schematic either. I'm assuming from your comment you don't have an inductance meter (LCR). A lot of times they are not marked on the actual inductor so I normally just measure them. For the DCR any multimeter should work, just set it to ohms and measure across the 2 leads.....out of the circuit. I saw in another of your posts the resistor values were 3.9 and 4.7. Are you referring to the 2 different resistors on the same board, or the same resistor on the left and right crossover boards? Thanks for the suggestions, one thing leads to another. If I do all that it'll be a sleeper speaker, maybe. No idea what the inductor values are nothing printed on them and I haven't managed to find a schematic. Almost into designing a new crossover.
I'll get an lcr meter would be useful. So speaker 1 has two 4.7ohm resistors, speaker 2 has a 4.7 and a 3.9 strange.
I must admit, that is a bit odd. You might be right in what you said in the other post. This might be hand tweaked to get the 2 to perform the same. Any signs someone else was in there replacing parts? Do you notice a difference in sound between the 2 if you play a mono/same signal into both?
