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Anxious to glue it back onto the power supply, I did not wait long enough for the lacquer to dry. I used a stack of magazines to support the face plate with the power supply face down, weighing on it, while the glue on the other side dried. When it was done, I realized that the magazine page stuck to the face plate. The paper caused the lacquer to come off in some parts. What a bummer.

I ended up having to redo this. I didn't want to sand off the surface again, so this time, I layered a couple of mica blue and lacquer it off. So much trouble for such a small job... Guess I was not patient enough... Luckily the quick job did not have too adverse a result. ;)

First, a big thank you to Francis for being an accommodating host for us at the shootout. He recently had his Shanling CDP modded by a local guru to have the opamps working in class A. It was wired to use this stage with XLR connections and single ended connections via RCA will rely on the CDP's in-built tube buffer stage.

When it was my turn, with the same track played, there was this nasal vocal that emerged from the speakers... something was not right. I knew that there was nothing I could do if the preamp was at fault... I did not bring any tools and was definitely not in the mood to troubleshoot even if I brought tools... I told Francis that we should move on and bring in another preamp. By the time I was finished unhooking my preamp, I was perspiring as the air conditioning by then, was not as cold... There were more than 10 people in the room.

Later, Nick and William suggested that either I have some loose part due to transporting it to the location or it could be clipping. I told them that my bias for the 5687 was at -2.1V. Nick was guessing that it could be that the CDP's tube buffer had gain in it, which is not uncommon of the chinese designs that he came across. I thought it was a possible hypothesis. I was just disappointed that the audience did not get to hear the preamp. I was most interested to know if it lacked "speed", as that was the general comment about the tube preamps... unmatched for vocals, but lacked speed. The mercury rectifier and the shunt regulated supply should satisfy any "Need For Speed" fans. A quick A/B was done at some point in time to check if the 24/96 upsampling vs the normal red book had any effect on the sound as the Shanling CDP had a remote controllable feature for this. One guy was asked of his opinion and he did not have any reply at first, when the feature was explained, he said something like the 24/96 was better or something... I phased out and did not pay much attention at this point... I disagreed quietly as I could not discern any noticeable difference... not strikingly huge anyways... and not in the few seconds of A/B switching.

I tend not to be too judgemental when it comes to music. There are always generalisation that certain stuff cause certain sound. I think the DIY guy especially, should be open when approaching different topologies and implementation. In the same vein, most commercial gear people seem to have this unspoken discrimination of folks who build their gear. It is almost always in the same breath as low cost. I wonder how many of them would know that Tamura is used by Air Tight, Sun Audio, etc. Tango is used by Wavac, etc. Lundahl is used by Manley, VAC, etc. Some parts used by the DIY guys will rival those used by the commercial companies. In fact, it may in some instances, trend into the esoteric and exotic range.

When the solid state preamp brethren were playing, I gave them lots of leeway in their sound presentation. However, I felt most of them just seemed too bright and shrill sounding in the treble regions for extended listening. I immediately want to leave the room or find refuge from the assailing soundwaves... Nick echoed similar sentiments. Saying that the tube folks will not adjust to this type of sound well. I was also surprised that the Densen preamp (which the owner said had a SGD3k price tag when new) exhibited almost the same shrillness. I used to own the Densen Beat 100 integrated and found that it was quite a nice piece of gear. But it really required warming up to sound the best though. I'm not sure if that preamp was already warming up prior to being played in the system or my ears (or age have caught up) have slowly grown used to something not as <span style="font-style:italic;">exciting</span> in the higher frequencies.

Unfortunately, I had to leave early as I had to bring Lucas for his lessons. So I promptly packed my stuff, thanked Francis and said my good byes to people I knew. On my way back, I was thinking that my system could be too tuned to my chain of equipment. DAC was a passive I/V unit, which had lower than the normal 2v RMS output. Maybe that was the reason why it did not clip the preamp... but 2.1V bias point would mean an input swing of 4.2V, and should be sufficient for any decently built gear...

Later in the day, when I was heading to Novena with my family, I got a call from Nick, informing me that my preamp should be fine as the problem of the nasal voices is back to haunt every gear they tried! I then recalled Francis saying that the CDP was modded and was running hot into class A. I guessed it could be due to that. It exhibited thermal runaway. That was just a conjecture. Not sure what really happened... cos the opamps were biased into class A and that should only affect the XLR connection. Why would RCA connected preamps be affected as well? No idea... but the guys were playing LP instead and seemed to be having fun.

I concluded that either I should raise my bias point, or don't lug such tailored stuff over for shootouts when the possibility for mismatch would be great. Oh, and I just listened to my system... it's working... no nasal voices.

Some pics here... from my iPhone.

Took out a diaper box and turned it into a suitable packing for a preamp shootout that will take place next week.

With 10 different preamps and many participants, it will not be meant as a definitive "best preamp" knock out, but more of an excuse for some audio nuts to get together and experience the different types of preamps available at the venue. It's a mix of commercial and DIY preamps. I think the results would be interesting.

The PS-2 shunt regulator was nicely fitted into the preamp. I contemplated fitting it into the power supply chassis, but gave up thinking of how to mount it. When I built the PS-2 on the heatsink, I was thinking of mounting it via a screw onto the back of the preamp. That's how it was done in the end.

But looking at the power supply, I wanted to rebuild it with a proper transformer as the one being used now outputs a B+ of 350vdc. The shunt regulator will be very hot dropping 200+ volts. And it turned out that I had one odd R-core transformer that was shipped wrongly to me when I ordered transformers for the 6T10. This also presents the opportunity to build a chassis that looks similar to the preamp.

I ordered the aluminium from Superfix as usual. Collection was done on the same day I placed the order. When I got home, I checked the dimensions and to my dismay, there is some excess on the metal. 3mm is not easy to file off... especially if there is a long length. I tried to do so initially and it was a tough job just to file off 2 surfaces. I then decided that I should get a Jig saw.

It's the first time I went to Homely Hardware Superstore at Ubi Cresent. It's almost like Home Depot and I had much fun there, picking stuff to buy. I ended up with a Makita Jig Saw and other stuff.

I also got some e-nuts, screw covers and stuff from Yong Seng Screws at French Road. The most I ever spent on screws... The screw cover set is not cheap. $4 for a set of 4 screw covers and mounting flange. I bought 10 sets of 4. The e-nuts were $20 for 100 pieces. I think I'm nuts... but I have a total of 3 chassis to build. One for power supply and 2 for the 6T10. My previous builds used wall plugs instead. Not very tight after may rounds of opening the panels.

The 3/4" MDF were bought from Ban Heng Long Trading at 11 Syed Alwi Road. They cut to the mm. Nice. ;) The jig saw was really nice. Opening the IEC inlet on the 3/4" MDF never was so easy. It's like a sewing machine for men! Trimming the excess off the aluminium was also effortless. Next time I should order my aluminium with at least 5mm excess so that trimming is easier.

I made sure that MDF was drilled carefully when putting the e-nuts in. First a pilot drill with 3.5mm, then 6.5mm. 6.5mm is the best diameter to use at the sides of the MDF. I tested it for grip and made sure the MDF does not split when the e-nut is screwed in place. Alignment is important. So I drilled the holes on the aluminium first, and then overlay it on the MDF and used a dot punch to punch the mark on the MDF for the e-nut position. The aluminium pieces were drilled 1mm larger so that I have some freedom to align the MDF and top and bottom aluminium. I got an auto dot punch when at Homely, and it is very accurate. It is spring actuated and is much more expensive than a normal dot punch. $16 each I think, but well worth the investment.

Finishing spray on the top and sides are Mr Hobby Super Clear lacquer. The front plate and rear MDF are sprayed with Tamiya Metallic Mica Blue to match the preamp.

For the power supply, I reused the 50H chokes and the current regulator. Topology used is the RCA83 -> 50H choke -> 56uF GE oil capacitor -> 50H choke -> Mundorf 47uf+47uF capacitor. This then goes to individual PS-2 shunt regulators for each 5687 tube at the preamp. I changed the 2 LM317 on the regulator to a LT1085 in TO-3P package. The output of the regulator has a OS-Con 100uF 20V capacitor. The series resistor is connected by a pair of screw connectors. This is done so that if I use my power supply for other preamp builds, all I need to do is vary the current to the tubes being used. Of course, a PS-2 would be in future preamp builds to vary the B+. ;)

I learnt a lot from this rebuild especially in the chassis construction portion. It was a fun build, and now I will be ready for a preamp shoot out with 9 other preamps after Chinese New Year. This would be fun.

More pics here.

This preamp was working well since it was built. There were a couple of mods done since then, namely, the Feedforward Shunt Regulator, and also the DACT 50K Stepped Attenuators. I was re-looking the design especially from the perspective of my entire chain, and thought I should try out a different operating point.

What I had in mind was to do a -2v bias. This meant removing one LED from each section of the 5687 and also adjusting the B+ voltage. I also wanted to try John Broskie's PS-2 solo design. I intend to reuse the 10M45S on the Feedforward Shunt Regulator and also the heatsink for this modification.

I went to Koba and got some 1% 10R and 1R resistors, Wima and Rifa capacitors, a pair of LT1085, and a pair of BI Technologies 7276 - 10 turn 50k potentiometer to be used to set the output voltage. I also threw in my Mundorf 47+47uF capacitor and bought a pair of 240R Kiwame resistors from AHFartaudio for the PS-2. All these goodies would make any power supply green with envy. ;)

The PS-2 solo worked like a charm upon power up. With a 10 turn potentiometer, it was very easy to dial in the voltage on the plate of the 5687. With this potentiometer, the working output voltage range would be from 50vdc to 250vdc. Next steps are to mount the regulator into the chassis, along with some minor wiring.

You probably want to get John's PCB for the PS-2 instead of hardwiring.

More pics here.

i've been wanting to try out a stepped attenuator for a long time. i even got a kit from someone that is bare, with all the various resistors unsoldered. it took some time to understand which resistor value pair goes where for that ladder stepped attenuator. i saw a posting on echoloft selling a used DACT CT1 50k stepped attenuator and did not hesitate in getting it. the CT1 was installed onto the 5687 preamp last night. i had to drill a larger opening for the shaft to be put in. i also had to drill a smaller hole to accommodate the small stud on the CT1 which prevents the entire attenuator from moving around. then came the desoldering of the previous 100k Alps Blue and soldering of the connections onto the CT1. earlier this evening, i played various cds thru the preamp via the UCD180AD class D power amp that is already hooked up to my speakers. this was not my usual setup to evaluate changes, but with the UCD180AD as the amplifier and the rest unchanged, transparency was the first that strike me. i had the opportunity to listen to some esoteric setup over the Chinese New Year holidays. i brought along a cd for comparison. i thought the Snow Rose 3 - Milan Rose cd was particularly close mic-ed as this was evident in my setup. i was surprised that the atmosphere was not so easily felt in other setups that i listened to during the holidays. the CT1 kept this feel still, but i would need to compare it with my DRD amps. this would be for another day as I went through cds and cds... from Frou Frou to Madeleine Peyroux to more familiar cds such as Ryuichi Sakamoto's Cinemage. more pics here

finally the feedforward shunt regulator design taken from John Broskie's blog is incorporated into the 5687 preamp. it is now providing dc with minimal noise to the circuit, biasing the tubes at 22.2mA per tube. will try to post a hand-drawn circuit of the implemented circuit later. more pics here.

i've actually got this board done up before i shifted. that must have been 3 or 4 weeks ago. i was even comtemplating putting it into my 5687 preamp the day before NoiSing07 so that i can demo the preamp with the regulator. good thing that i did not... it took many attempts before i got it to work. most of the time, i burnt resistors as i forgot where the ground of the board is cos it was sooo long and i did not mark the board with symbols. i also killed quite a couple of 10M45S chips. it seems that even though it is sourcing 10mA, heatsinks are still required on the chips. it seems that the regulator added a sense of scale and resolution to my soundstage. it is easy to pick out details... very resolving. also, the bass seems to have benefitted by being more controlled and detailed. not quite sure how to put it, but i would say that this is worth the effort. perhaps other HV regulator designs would produce the same effect? the circuit is based on Jon's feedforward shunt regulator. parts are swapped below as mentioned: 1. first dropping resistor after B+ as 1k2 10W instead of 309R 2. second dropping resistor after B+ as 2k2 10W instead of 614R 3. B+ is 290V, between dropping resistors is 228V and 136V (L channel)/140V (R channel)

The much anticipated event on the local audio calendar is finally here... NoiSing07, on 8th September 2007. Not having a NoiSing in year 2006 surely must have created a void as the displays in NoiSing07 is easily the best of the 3 we had so far. The venue was Republic Polytechnic. We had two rooms, one on level one, the other on level two. Accoustics was to die for. In my opinion, Level two had the better of both rooms. It is meant for panio practice. Fully treated even on the ceiling. This room was dedicated to Solid State gear. On level one, we had the tube gear, and easily the larger crowd of both rooms. This year, we only had one full range single driver speaker, represented by the famed Freastrex driver, courtesy of Willam Ang. We had quite a few preamps, two Audionote M7 designs, one other that I'm not too sure of, two Akido preamps, a Sakuma Tube buffer using 211, and my 5687 with Tamura output transformer. The main eye candy is the speakers... Ken helped setup the electronic crossover to enable a three way system using his Dukane plasma tweeters, Maxonic fieldcoil horns, 340hz Azura with TAD2001, Karlson bassbin with 18" JBL drivers, 15" Altec BR box... For the actual list of components, take a look at the echoloft posting. Both rooms had great sound. I was impressed by the ML preamp in the Solid State room, with a virtual control from the laptop. Eusof's (Synthesis) Vifa speakers, although bookshelves, turned out to be a beast to tame when we heard the solid state amp happily clipping away. It produced astouding sound when driven at moderate volume. Had to do a double take to be sure that the Orions are not playing. The 3 way setup at the tube room was equally astounding, given the 5 mins tuning of crossover by Ken. There was a distinct lack of amplifiers. I thought Ken joked with me when he mentioned that he was waiting for me to bring amps. All in all, a great way to spend a Saturday. Really enjoyed myself there. Unfortunately I was not able to stay all the way till 6 odd. Kudos to the organizer (Johari) and all those who helped in this event. Mervin (MB) did a fine job by helping us book the rooms at Republic Polytechnic. A big clap for all those die hard DIYers who brought their geat to RP! The morning rain was not enough to stop us! More pics here.

The anticipation of this moment since early this week... i pulled together my horses and men for this session. The other source is a Marantz CD50 using a TDA1541A dac. My 5687 preamp, d3A/VV302B DRD amps and my Diatone PM610MB speakers were called to duty. Sequence of A/B is always PS1 first, followed by CD50 for each track. Discs used are 1 - Plastic Flower from Op4, Lena Park (Korean Artist), 2 - The Power of Love Songs CD1, Fish Leong (Malaysian Artist), 3 - The Hong Kong Hifi show CD (2007 I think), 4 - You'll Hear Better Songs and Memphis Tennessee from Early Hours (Hybrid SACD), Eleanor Mcevoy. Impressions are that the PS1 presents a lower output voltage to the preamp, the bass is rounder and not as profound, soundstage is less deep, and it has a more mellow presentation when compared to the CD50. It also seems veiled in comparision, with the CD50 giving a cleaner and clearer sound. Perhaps after the mods, it will be better... I can only keep my fingers crossed.