HD650 Returns!

The repaired HD650 arrived very well packed back from Syntec earlier this week. Only had a chance to quickly test them out now, and they are working. I think they also replace the metal tension straps, as they fit a more firm now. Quick thoughts the bass is so much more firm! Anyway, more to come late, and a comparative review with the DT880 and the AD700.

Front Panels Arrive

Probably one of the few companies with excellent service around, the panels ordered from Front Panel Express arrived today in very good condition and packaging. No damage, everything as designed.
This was to aid in the construction of the chassis and the mounting of the tube sockets. But creating a standard cut-out on the panels, I can drill an oversized hole in the timber chassis, without excessive precision, and these tube panels can be mounted on the inside. That way, reducing the cost of large custom cut panels and maintaining the timber chassis look that I like.

The cut-outs were sized for the CMC Teflon sockets. You will see these floating around eBay, Internet and many of the Hi-fi stores. Good quality, but definitely not a premium product. Some of the machining is a little rough, but still excellent value for money. See how well they fit into the panel, and with a 3mm thick panel, the top of the socket is near flush. But at around US$10 each, you can't go wrong!

The order consisted of tops plates for; 1 Bottlehead Crack/Speedball (with a 9 pine and octal), 2 Dual 9 pin plates (one for the D3a build, and another as spare), and 5 dual Octal plates (two for the ST70, two for the D3a and one spare).
See the photos.

HD650 Status

Just got a call from Syntec, informing me that they reviewed the cans and confirmed that the left speaker assembly has a short in the coils, and it will be replaced. They also confirmed that they will match with the existing right capsule. They also confirmed that the repairs are being done today, and will ship once payment has been confirmed. So, except for a slow start, they seem to be all over it, which is good. The cost is in the order of AU$175, including return courier, which is reasonable.

Looking forward to getting them back, burning them in again, and then doing some comparisons with the other headphones.

Modifications to Elekit

Recently had the chance to review the components and check that all the parts were present and accounted for. There was only one very minor issue, in that one of the screws was indicated in the manual as having 6  numbers, but shipped and only requires 5. A minor error, otherwise, all parts in excellent condition. On examination of the PCB, I noticed that the through holes were very small. Indeed, none of the after-market capacitors or resistors leads will fit through the holes. I emailed Victor and confirmed that I need to very carefully enlarge the holes. He recommended a hand drill for the process. So, off to the hardware store to find a small pencil drill bit and a matching small diameter drill bit. Hopefully I can begin the through hole enlarging process in the next few days. (HT58RCWVRAK9)

RCA Command 5751

With the Ear+ amp settling down very well, I decided it was time to swap the driver tube. Currently, it had a cheap and cheerful Sovtek 5751. When I initially bought the amp, I also purchased a single RCA Command Series 5751 from Audio Tubes. This tube could be described as having black plates, double Mica with a halo getter. This tube has probably 40 to 50 hours on it when it was last used with this amp.

A caveat, I loosely call this a review. I only have two 5751 tubes, and my comments are based on a single session where I listen to the same set on the same equipment. The only difference being the tube. The Sovtek has the date code 01 07. The testing conditions are:

• Music: (Small set) Missy Higgins, Coldplay and Jason Mraz.
• Source: Mac Pro with Apple Lossless format created with MaxCD.
• Maple Tree Audio Ear+ with Tantalum, Blackgate, Auricap and Caddock MK132 upgrades.
• Output tubes RCA 12B4A.
• Headphones: Beyerdynamic DT880 (600 ohm).

Some initial thoughts. Volume difference between the two are about the same, with the RCA being a little louder. The soundstage with the RCA is much wider and more spacious than the Sovtek, which feels a little cramped. The instruments appear to have more room to move and mix and are less segmented. When the music passages become more complex, detailed and louder, the Sovtek starts to lose definition on the various parts, they blend into one. The RCA, on the other hand, maintains their individual identity and one can still place and hear each instrument as part of a whole.

Vocals are a little darker and more recessed on the Sovtek. The overall balance seems to be more bass heavy, and the midrange is somewhat smaller and 'behind' the rest of the music somewhat. The sound is more engaging and warm. There is a real tactility to the guitar strumming and female vocals with the RCA compared with the Sovtek. With the RCA is is really a wonderful balance as it is more forward and present centre stage, where it should be. This also applies for the strings line on the track 'In My Place', much more delicate and what strings (synthesised or real) should sound like.

The bass seems to be much firmer, balanced and better controlled on the RCA. On the Sovtek, though the balance favours the bass more, it just feels like it is a little lazy. The guitar licks have more precision about the sound, and seems to be better controlled with the RCA. The very soft guitar plucking on 'Hardest Part' seems far more refined with the RCA and defined. With the Sovtek, you could hear it, but it just sounds more like a metal wire being plucked, rather than a guitar string.

Overall the Sovtek doesn't have the life or energy that the RCA does. It sounds a little flat and a little boring. The Sovtek brings the impression that the music is just music, whereas the RCA brings a dimension that is missing with the Sovtek that draws you into the music, where it is no longer just music.

The Sovtek currently retails for $19.95 at Tube Depot and the RCA Command at $94.00 at Audio Tubes. Is the RCA tube more than four times better? Do I hear four times more detail? Well, I am not sure it is four times better. It is definitely better, but the quality of improvement is very subjective. The pre-disposition that a more expensive product must be a better product, always comes into mind, and with such a price premium and associated folk-lore an, it is sometimes difficult to clearly define what it is that is better, and by how much. That is, to put a price on the improvement.

For me, the differences between the Sovtek and the RCA comes down to me wanting to continue listening and not stopping. The Sovtek doesn't really give me a compelling reason to continue listening. It is just not that engaging. I could compare the change in tube as the same as the HD650 on the Crack to the DT880 on the Ear (Sovtek). The RCA tube brings the Ear+ setup to a similar level of addiction as the Crack/Speedball with the HD650.

Would I pay the difference again? Yes. As far as tube life, ageing and the frequency that one needs to change tubes, I think that $94 is a wholly worthwhile upgrade. Would another tube cheaper perform better? Quite possibly. But until I obtain a few other samples, that question will remain unanswered. But for now, I will keep the Command in the Ear. It just sounds better.

Arrival of Elekit TU882R

This arrived in the mail today, via EMS in very good condition. Thanks Victor. The box was well packed and appeared to suffer no damage from transit from Japan to Canada to Australia. The box itself, was packed extremely well. You have to hand it to the Japanese, they really do know how to do their packaging. Without peeling apart the various bits of paper protection, everything appeared in very good order.

One of the nice things about getting it packaged like this, is the sense that you are really buying a branded product. Most of my other kits have arrived in an unbranded box, in lots of sealed plastic bags, all put into a shipping box. Un-boxing this, feels like you are un-boxing a camera, a laptop or something really special. I know this is a little silly, but there is something tangible and exciting about un-boxing something like this for the first time. Everything so well packed, each item has its place and order.

Haven't had time to open up and check all the components yet, but the three main things seem to be present. 240V transformer, chassis parts and output transformers. Victor was kind enough to send me the English manual just after purchase, which has allowed me to review it quickly to start building the amp in my head. It appears that everything has arrived, and is in good order and in the specifications as requested (namely 240V).

I will have a few more things to say about the manual and the components later. But I have ordered a set of replacement resistors (Shinkoh Tantalum and Amtrans Carbon Film, all from Japan, seems to fit the bill of this Japanese amp) and will be using some Mundorf Zn Tin foil capacitors as the coupling capacitors. If there is sufficient space, I might place a few low value teflon or PIO capacitors as bypass for the main PSU capacitors. Apart from those, I took the risk and ordered a TKD 2CP-601S 100k stepped attenuator. No idea if this will fit, but I have so many other projects, it will find a home eventually. Apart from those three items, I do not plan to make any more changes to the components.

The main question on my mind, or of issue, is that this amp has negative feedback. It takes the output from the highest impedance tap and brings it back to the cathode of the first stage (or input stage) of the 5670. No idea how this will affect the sound. But in the past, I have avoided the use of NFB designs, but thought it'd be good to include this to see its net effect.

If I get time over the next few weeks, I will start the checking and cleaning processes. Once everything has been cleaning and thoroughly checked, I will being to assemble and hopefully, within 3 to 4 weeks, this will be fully complete. I will be definitely posting progress photos and notes as I go, and once complete, hope to give some feedback comparing this with my other two operating amps.

Long Weekend Summary

It was a good audio weekend for me. I got over five hours of good listening sessions over the three days. During this time, I spend listening to both the AD700 and the DT880 with the Ear+. The sessions were both enjoyable and allowed me to take stock of the projects that I have going, and focus my efforts on those which can be fulfilled as quickly as possible. The Ear+ performed well over the weekend, with no playing up. I did notice that this amp gets very hot, even the chassis and the wood side panels. This is probably due to there bring no ventilation at all in the chassis. There are no air vents, holes, slots, etc, where air can cool the transformers and diodes. The two transformers are completely enclosed in the steel box above, and thus rely purely on the black case being cooled. This is something that should be addressed if, and when, I rebuild the amp.

The Headphones

Being able to compare both sets, with similar amount of burning in, on the same system was enlightening. The method I used to test was not very scientific, nor very systematic. Very simply, I listen to various music on each one for about and hour and then swapped. No scientific A-B testing, but a lot of the music was common between each session. Both headphones have had at least five hours of burning in, and both have experienced the full works of Handel’s Messiah and the four Coldplay albums during the burn-in. Some initial findings.

• Bass is firmer and better controlled on the DT880.
• Generally more detailed on the DT880.
• Sound is more open, possibly a larger sound stage on the AD700.
• More depth to the music in terms of extension of frequencies and layering on the DT880.
• More engaging, vocals more addictive on the DT880.
• A little flat or boring on the AD700.
• Overall musical presentation on the AD700 seems to be more ‘dynamic’, and more balanced with the DT880.
• Comfort was better with the DT880. It had even pressure between the headband and each headphone. A light, constant pressure, which was quite comfortable.
• Comfort on the AD700 was a little different. No pressure on the head via the 3D wings. The headphone itself had pressure at the lower end, and very little on the top of the headphone. Overall, comfortable, but a little strange to get used to.

Comparing the two headphones, whose price difference is double, is probably not a fair comparison. However, when I listen to the AD700 it was enjoyable and musical. It was only when it was replaced with the DT880 that the AD700’s limitations were made apparent. However, I could not complain about have either headphones in my inventory. They do present the music in a different manner, and perhaps in a complementary manner.

In the future, I plan to write reviews based on each amp used with different headphones and each headphone used with different amps. This can begin once the HD650 have been repaired and returned. To this, I plan to add a pair of Grado’s and maybe a few more from AKG, Denon or Audio Technica.

When using the Ear+ amp with the AD700, the volume control was around 50% to 70% range depending on the program material, and with the DT880 it was between the 70% and 100% range. Obviously, not a great match with the DT880. With the 600 ohm version, I’d suggest that there just isn’t enough voltage at the headphone terminals. The Hammond 119DA used in the amp has a ratio of 600:8, which may be a little too high to provide enough voltage. They seem to work well with the HD650 (from distant memory), but it struggles to get enough volume with the 600 ohm DT880.

Projects

Having the time to review the stock piles of components, PCB and project ideas has led me to the following conclusion. There are three projects that have are fully funded with all components on hand, that require assembly and chassis work. They are, in no particular order:

1. D3a Headphone
2. K and K ST70 Upgrade
3. Aikido 5687 PCB Headphone 

The Aikido build is something that I had time to dig up and check over, ensuring that I had all the necessary components. The only items missing for the above three projects are the chassis work and the large output coupling capacitor for the Aikido 5687. I do have a pair of Solen 47uF MKP on hand, which would work well with 300R plus headphones, but given I have the AD700, and plan on a pair of Grados, it may make sense to budget in a large pair (say 200uF plus) to allow them to be used. To expedite the construction, I have ordered a number of custom aluminium panels from Front Panel Express. They are basically a small panel with cut-out for the tube sockets. This then allows me to cut the timber chassis without exact precision (i.e., oversized hole). Preserving the convenience of metal panel, on which most of the circuit can be assembled with stand-offs and tag boards, and keep my aesthetically desired timber external.

During this time, I also took the opportunity to order the replacement active components for the Crack. To piggy back on the order, I also topped up on the Neutrik headphone TRS plugs, some additional heat sinks and enough active components to make another Speedball.

The goal is to complete all three projects by Easter this year, which is in late April. All the chassis timber work will be done at once as well as the assembly. I am estimating that it’d take the better part of a week or evenings and a few day sessions to complete all three projects. The ST70 mod and Aikido will probably be the quickest, given it has a PCB based construction, making all the wiring and soldering much faster.

Future Projects

Having the opportunity to take stock of the current headphone amps and planning on the next stage. What I would envisage is having one amp of each of the major topologies to be able to evaluate and compare how they perform. To that effect, I have come up with the list of the final assemblage of headphone amps. With each of the project, I eventually plan to have a page dedicated to each of them, providing information, schematics, photos and possible upgrades.

1. Transformer coupled. D3a project. All parts collated, awaiting chassis assembly and build.
2. Parafeed transformer anode coupled. To be determined, most likely a clone build of the Espressivo or L’espressivo and another link here.
3. Parafeed transformer cathode coupled. Maple Tree Audio Ear+, completed.
4. OTL. Bottlehead Crack and Speedball, completed. Awaiting repair of RHS Driver CCS.
5. Aikido OTL. All parts collated (except output coupling capacitor), awaiting chassis assembly and build.
6. Tube/Mosfet Hybrid. Mini Max Millet, completed.
7. Transformer coupled with negative feedback. Elekit TU-882R kit ordered, awaiting delivery and assembly.
8. Ultimate Headphone Amp. After the completion and analysis of the above amps, an uber-no expenses spared amp based on the design and headphone that best meets my needs and suits my taste. I am hoping that the D3a would be that amp, but until it is built and compared, this project is still the ultimate goal.

With regards to stereo amp projects, as mentioned before, they are taking a back seat to headphones for the time being. This is primarily due to the lack of appropriate space in the current house and young kids. But for the moment the project on the cards are:

1. K and K ST70 Build 8W. All parts collated, awaiting chassis assembly and build. I should start referring to this as the Class A, fully differential push-pull triode amp.
2. Ultrapath DRD45 1W. All parts collated (some have been scavenged for the projects above), awaiting replacement parts, chassis assembly and build.
3. F2a amp 6W. 4 tubes on hand and sockets, everything else not yet sourced. Yet undecided on whether it’d be a SE or Class A PP design.
4. Future 32W Tube. Unknown design, topology and tubes complement at this stage, but planned.

HD650 Servcing Update and the AD700

After sending the HD650 up to the service department via courier on Wednesday, I have heard nothing back. Not even a courtesy email to say that it has arrived and in the queue. So I called up the service department today to request an update. Was notified that it has arrived and it is in the queue, which is two weeks long. Generally, I am not too concerned about things like this, but given the expense of the headphones, I would've expected at least a courtesy call or email to let me know that it has been received and that it is in the queue for however long it needs to be. Not the best customer service in my opinion here.

Last night I had the chance to put some music through the AD700. Had around one hour with them using the Ear amp and listening to my standard test set of music. Initial impressions are that; bass is a bit shy and mids quite forward or pronounced. The highs wasn't opened up, felt a little closed. The balance was more towards the mid range, and it was quite 'in your face', so to speak. But nothing overly offensive so far. The music overall was quite enjoyable, but the fit of the headphones not as much so. Whilst I found that the 3D wing system did end up being very light on the head, and placed very little pressure on the skull, most of that weight was transferred to the sponge ear surrounds. This, along with my larger then average ear, made it a little uncomfortable to wear. But, I trust that over time, both the sound and the wear will get better. And no, it did not sound worse because it was purple, and yes, it is still purple....

More headphones and revived the EAR

After experiencing the problems with the left channel of my Crack, and getting no assistance from the Bottlehead forum, I decided that I just need to replace all the active components (transistor and diodes) on the left driver channel CCS. The components themselves are quite cheap, but I will end up paying far more for postage. And thus, I will wait until I can piggy back this onto another order. Earlier this week, I took the time to pack and send my HD650 back to the Australian servicing agent, Syntec, for repairs. I specifically mentioned that if the left driver needed to be replaced, that to make sure it was matched to the right. Not sure how things will go, buy you'd think for a $500 plus headphone, they'll take the care to make sure it is repaired correctly and back to factory specifications.

I have been unhappy with the performance of the MiniMax Millet with the Beyer DT880. It is not due to the fidelity of the system. But for me, it lacks the life that the Crack had, the engagement with the music and the vocals. The sound wasn't harsh, it was a little clinical, but for me, it was just a little boring and not engaging. So, in need of a better amp, I decided to dust off my Maple Tree Audio Ear+ all tube headphone amp. This hasn't been used for around 2 years, and has been sitting in various cupboards during that time.

The main reason why I had put the Ear+ inthe stroage cupboard was primarily hum. When I last used it around two years ago, I did not have the time to diagnose and fix the problem. So, with the other amps available to me, I decided to shelf the amp. Bringing it out of the closet, checking the internal workings, I made sure that nothing strange has happened since I last used it. Putting in the basic tubes, Sovtek 12AX7 and RCA for the 12B4A and 12BH7, I fired it up with a pair of cheap headphones, just in case. Low and behold, sound, but only on the left side. After sound jiggling around the tube sockets, I coaxed stereo sound. The fact that I had to do that to get stereo sound, was another reason why it was shelved. This most likely points to a cold solder joint or a faulty tube socket somewhere. I guess I do have to spend some time under the chassis to reflow the joints.

Once confirmed as working okay and stable, I plugged in the DT880. First, the sound was quite soft. The volume control had to be almost 75% up before I get decent levels of output. Perhaps it is due to the higher 600R impedance of the headphones, and that the amp can't deliver enough voltage. Not sure why, maybe it wasn't designed to driver such a high load. But nonetheless, there was music. Further, the hum that I remembered was gone. Perhaps it was a different house, with different equipment plugged in and different wiring [read less dodgy]. Or it mayhave been something else completely. I was just glad that there was no hum. This is something I think I can't live with. When hum can be heard, it is just not acceptable.

Comprade to the Crack on the DT880, the hum levels were lower. But then there is a difference between DC heaters for the Ear+ and AC heaters for the Crack. Maybe all DC heaters are in order.

To listen to this all tube headphone amp after the MMM was a telling story. First, it wasn't as dynamic, or articulate as the MMM. However, it was full of life, it was engaging and it made me want to listen to more music. The balance in low, mids and high was different. There was more emphasis on the mids, but the highs were still very delicate. The bass was present, and quite controlled and to my ears, a nice balance to the overall sound. This is the direction in sound that I am looking for. I think my quest is to find a headphone amp combination that does deliver of all the qualties that I desire. Some from the MMM, some from the Crack, some from the Ear+ and some that I don't know about yet.

Also arriving in the mail recently, was the Audio Technica AD700. A low impedance open back headphones. I got them off eBay for a decent price. The packing appears to be stock from Japan, and it is made in Taiwan. The first thing I noticed was that it was purple! The second thing I noticed was that it was still purple! Yes, this is a purple pair of headphones. Now as someone who appreciates design, I am not sure that purple is the right colour for headphones. However, looking at the overall design and packing, it is a nice overall design package. But still, not sure if it is the right style for the headphone audiophile market.

Some unboxing photos below, no time yet to plug them in yet. I tried them on quickly to see how this '3D wing' would fit and feel. Overall, the pressure on the head is very light, a lot less than either the DT880 or the HD650. They feel like they are almost going to fall off your head. The 3D wings also make it feel like they will slip further down your head. Now, I am sure that there are ways to adjust this, and reading the manual will probably help. But I was in a rush, and will explore this a little more later.

More photos below, I have place the DT880 side by side, and you can compare the difference in size and colour. The Ear amp and MM are also in the background. In terms of fit and finish, it is not at the DT880 level, which itself is better then the HD650. Of all three, I'd say that AD700 is a little rough compared with the other two. Especially when you run your fingers over the top of the grill. You can feel the slight stamping burrs and uneven edges on the AD700. With the other two, it is just smooth metal. Of the two, the DT880 wins easily in my eyes with the build quality. However, to compare a $150 headphone to a $400 pair is not necessarily fair either.

This weekend is a long weekend in Melbourne and I plan to spend some serious time with the two amps and the two headphones. Hopefully provide some meaningful comments about the different setups and gear.

Softone Transformers Arrive

Excellent customer service, fast shipment, well packed and very nice packing. Check out the unboxing photos.

Elekit TU-882R

Couldn't resist the urge, and I pulled the trigger on the Elekit TU-882R tube headphone amp kit. From what I can gather, it is a 5670 baesd design, two stage conventional RC coupled in-between and has a multi-tap output transformer. It also has negative feedback between the output and the first stage. One of the items I like about this kit is that it has multiple output impedance that will allow the use of a range of headphones from 16R all the way through to 600R. This would be a good benchmarking platform to compare different headphones. I purchaed the kit from VK Music. So far, the service has been excellent and I look forward to getting the kit and building in the next few weeks.

Headphone List

Have set up a page to provide a list of known headphones with various key stats. It is my aim to keep it as up to date as possible, and will include as much information as I can find. Please see the link on the right hand column for the link, or here.

Clarity and direction.

After the first initial session with the DT880 and the MiniMax, I ran them through a whole range of music as burning in. This included everything from the full works of Handel's Messiah, to the entire works of Coldplay and Muse. After 10 hours of burn-in, I sat down for another session. Cued up was my now standard testing and auditioning mix. This has a range of music styles that I listen to, and am quite familiar with. I will elaborate on the playlist at a later date.

The result after the first burning in session - bass has firmed up, balance is even better and treble is more articulate. This has made dramatic improvements to the stock cans. The bass that was quite recessed and thin has opened up. The high end has definitely got more definition and clarity. I would say that the mid-range has seen as dramatic improvement as the lower and higher registers. There is no harshness in the sound, and I would not call it ‘boring’. The sound is now closer to my HD650, which has over 500 hours of use. To compare with the HD650, the bass is more controlled, and highs more clear, but the midrange is not as engaging. I can hear now, what others on the Internet have been saying about the differences between the HD650’s and the DT880’s. It does come down to a matter of taste. But any more critical analysis has to be done after at least another 100 hours of so with the DT880’s.

Through using the MiniMax in the last few days, has highlighted a few points of difference with the Crack. Once you get used to it, the MiniMax does sound pretty awesome and is enjoyable thoroughly. But in a direct comparison between the two, I'd have to say that the Crack with Speedball wins comfortably. It is shame that I am having a few issues with the Crack at the moment, but a quite weekend is what is needed to check and test. But I am looking forward to using the Crack again.

Another decision was to abandon the Yamamoto HA02 and the custom Crack build for the time being. With other priorities, it is probably not the best to invest in more headphone amps. Instead, a concerted effort will be made to complete the D3a amp and the ST70 upgrade/new build from K and K Audio (link). So looking forward to coming days and weeks, when I will post more information and progress updates for the two amps. The ST70 project really shouldn’t be considered a ST70, as it uses a brand new driver board and different output transformers. The only similarity is that it uses a KT88/EL34/etc type tube in a push pull arrangement and it also uses the ST70 spec transformer. To complete this amp, I have purchased a ST70 replacement power transformer, and made an order for a pair of Softtone/ICL RX-40-5 (link). Looking through the web page, they look to be a very good performer. The fact that it shares the same footprint as the Tango FX40 makes any future upgrading a snap.

In terms of speaker projects, that has been on the back burner for the last few years, I want to revive it with mating the ST70 clone build with an open baffle speaker. Recently ordered a pair of Fostex F200A for a very good price (in small part due to the excellent Australian dollar!) and this joins my collection of full range drivers. This collection currently made of; Fostex FE207, Lowther DX3, 8” Saba Alnico Green cones and Jordan JX92s speakers. This forms the range of speakers that will be compared in an open baffle speaker. With the ST70 design having around 8-10W, should be plenty to drive the more inefficient JR92s and the F200A. Currently in my head is an open baffle speaker with replaceable baffle panels to allow quick switching and storage of speakers. The baffle design in mind is a U frame. Overall dimensions are; 440mm wide by 940mm high and a side depth of 180mm. This will have 2 identical front baffles, each at 400x400mm, which can be user replaced. In the central part separating the two removable baffles would be rail to allow for tweeter placement. There will also be a fixing point at the top to allow for alternate tweeter placement. This would form a speaker frame/carcass that can allow me to change and match different speakers in different configurations. This could form my primary speaker that can be tweaked and changed easily. Expect more to come with some initial sketches and simulations.

One last item on the wish list is to review my previous posts and clean up the grammar, spelling and links, and make sure everything is working and makes sense. Hopefully this will make this blog more readable, enjoyable and relevant.