[Yggy]

Did my research on coupling capacitors and ordered a matched pair of V-Cap CuTF 0.22uf 600VDC from HifiCollective in the UK for 300 GBP.

https://www.hificollective.co.uk/content/cutf-090-022uf-600vdc-v-cap-cutf-capacitors-matched-pair

Availability seems to be more problematic with Duelund. The Cast DC copper 0.22uf 630VDC was a 6 month wait at HifiCollective and wasn’t stocked by PartsConnexion.

The Cast DC silver version was only in stock at PartsConnexion and would have cost about 800 GBP with import taxes in the UK.

There is a Cast DC copper pair on eBay China but the seller has no feedback and delivery was 3-4 months.

https://www.ebay.co.uk/itm/Duelund-...2349624.m46890.l49286&mkrid=711-127632-2357-0

Might be worth waiting for or could be a fake. Hard to tell. Decided not to take the risk.

Apparently, Frederick Duelund made this rectangular pair himself. Could be amazing and better than current production but I wasn’t willing to take the risk on this either. The higher 0.47uf would be fine as far as I could tell, the VDC is the key metric to match at 600-700.

https://www.ebay.co.uk/itm/Rare-Fre...2349624.m46890.l49286&mkrid=711-127632-2357-0

I understand V-Caps sound better out of the box than Duelunds and the upgrade benefit is skewed slightly more towards clarity than musicality.

https://www.isakusphere.com/audio-hifi/audio-reviews/capacitor-review/

 

[Yggy]

I took the fabric pads off my Sennheiser HD-540 Reference headphones, removed the disintegrated foam inserts, cleaned the headphones and cable with lens wipes, washed the fabric pads in warm water with soap powder, rinsed them, dried them on the HA-300’s transformers, and clicked them back in with new HD-430 foam inserts.

They look and smell as good as they sound now. The neutrality, clarity, and detail is stunning. Comfort is superb because they are so light. Completely different sound signature to modern TOTL headphones. Thinner, fresher, lighter bass, and heavenly treble. Literally, a breath of fresh air after the clean-up.

 

[Whitigir]

Interesting amplifier ! Do we have the specs for the Input and output transformers disclosed

 

[111MilesToGo]

Interesting amplifier !

Very interesting indeed. Looks like it could be ”my dream“ for my high-impedance headphones, the Sennheiser HD 800 S and the Beyerdynamic T1.2. One can dream …

 

[dadracer2]

Very interesting indeed. Looks like it could be ”my dream“ for my high-impedance headphones, the Sennheiser HD 800 S and the Beyerdynamic T1.2. One can dream …

I have the HA300 mk1 and it pairs with the HD800S better than any other amp I have heard or owned. There is something truly magical happening with the midrange whereas the bass and treble are merely excellent.

 

[Yggy]

There is a 600ohm HD250 closed back on eBay, but you need to find a new earpad for this one. Let's see whether you like the HD540 before we try other options. I have collected 600ohm version of HD540Gold, HD540 and HD250. I happen to like the HD250 more then the other two.

I bought the 600 ohm HD-250 for USD 300. I figured I might as well because I really liked the HD-540 and I have two NOS pairs of HD-430 pads to put to use now after salvaging the fabric pads on the HD-540. The ones I bought from the Amazon UK Sennheiser store have the plastic clips on the back. I’m not sure about the other NOS pair the HD-540 seller is sending to me.

600 ohm Linear 1s look to be much rarer than 300 ohm Linear 2s, I can’t see any other pairs for sale. The HD-250 on eBay looked to be in excellent condition apart from the pads.

Two questions. Have you tried / do you use the HD-540/HD-250 with upgraded cables? I was thinking of a 4 pin XLR Stefan Audio Art Endorphin. I had an Equinox with my HD-650s years ago and it was brilliant, it made me a believer in the value of premium cables. My K1000s have a hard wired Equinox and that’s one of the reasons I bought them. My only reservation is that premium headphone cables tend to skew sound signatures and the beauty of the HD-540 is its purity and neutrality.

Does the HD-540 Reference gold sound better than the Reference 1 to your ears or is the value in the more upmarket look (for the 80s!) and more collectible presentation box. Based on what I’ve read, they are sonically identical / very similar but I can see they have a different cable / 6.35mm gold termination, for example. What do enthusiasts think?

 

[Andykong]

I bought the 600 ohm HD-250 for USD 300. I figured I might as well because I really liked the HD-540 and I have two NOS pairs of HD-430 pads to put to use now after salvaging the fabric pads on the HD-540. The ones I bought from the Amazon UK Sennheiser store have the plastic clips on the back. I’m not sure about the other NOS pair the HD-540 seller is sending to me.

600 ohm Linear 1s look to be much rarer than 300 ohm Linear 2s, I can’t see any other pairs for sale. The HD-250 on eBay looked to be in excellent condition apart from the pads.

Two questions. Have you tried / do you use the HD-540/HD-250 with upgraded cables? I was thinking of a 4 pin XLR Stefan Audio Art Endorphin. I had an Equinox with my HD-650s years ago and it was brilliant, it made me a believer in the value of premium cables. My K1000s have a hard wired Equinox and that’s one of the reasons I bought them. My only reservation is that premium headphone cables tend to skew sound signatures and the beauty of the HD-540 is its purity and neutrality.

Does the HD-540 Reference gold sound better than the Reference 1 to your ears or is the value in the more upmarket look (for the 80s!) and more collectible presentation box. Based on what I’ve read, they are sonically identical / very similar but I can see they have a different cable / 6.35mm gold termination, for example. What do enthusiasts think?

I have bookmarked that HD250 and noticed it was sold at base price, I was wondering whether you have pulled the trigger. HD540 are well known and collected by many, but HD250 are very low profile and didn't draw any attention, so they are hard to find because a lot of users don't know this item has resale value. Yes, 600 ohm LInear one is very rare.

I didn't. I have multiple "original" cables from my HD540s and HD250s, so I convert one of the DIN cable to XLR4 since the cable is not usable with modern gears anyway.

Be reminded the headphone connectors of HD250/540/540 Gold are not identical to HD600/650, the nearest you can get is to get a set of HD600/650 connector and mod them to fit HD250/540. Someone said they can force HD600/650 cable into these headphones, but I didn't bother to try, I worry that once you force a bigger connectors into these antique headphones, you can't use the original cable again, or you can break the connectors accidentially.

If I changed my HD540 and HD540 Gold (both 600ohm or 300ohm) to the same earpad, cable, cotton ring (white) and cotton pad (black), the different is minimal. They might sound different in the very beginning but after 30 years of agin, the premium of HD540 Gold are more related to collection purpose.

I know you'll like these headphones, but I didn't expect you like them so much, so my gut feeling is spot on, agian.

 

[Yggy]

AK, if you get the chance to try the HD-540 on the FiiO M17 DAP, you’ll be very impressed. The M17 is slightly warm, lush and bassy, the best headphone I’ve tried it with so far is the HE1000SE, because it’s the opposite of the M17 sound signature but doesn’t lose any of the HE1000SE’s amazing detail. The M17 slightly warms up the HD-540 and shines a light on its bass more than 300b tubes can but it’s still incredibly neutral, pure, and linear. I’ve been listening at 72 on the volume dial (out of 120) plugged into my Ifi iPower Elite 12v PSU and 90 on battery only. Really looking forward to hearing how the HD-250 sounds with the HA-300 and M17.

 

[Andykong]

Interesting amplifier ! Do we have the specs for the Input and output transformers disclosed

Unfortunately, we don't disclose or discuss our product at components level, once we start these topics, we'll need to deal with many questions, and a lot of them will mislead other consumers, especially when some users are over sensitive on quantifiable parameters. If you look at my response to 6SN7 replacement qurestion, you'll notice that I tried very hard to cover my ass when I compile that response, and not all forum/community are muture and reasonable like HeadFi, you can imagine how difficult this can developed into if we took them lightly.

Please accept tour sincerely apology, we prefer to stick with our policy on this practise.

 

[Yggy]

Be reminded the headphone connectors of HD250/540/540 Gold are not identical to HD600/650, the nearest you can get is to get a set of HD600/650 connector and mod them to fit HD250/540. Someone said they can force HD600/650 cable into these headphones, but I didn't bother to try, I worry that once you force a bigger connectors into these antique headphones, you can't use the original cable again, or you can break the connectors accidentally.

Yes, my view too. I’m going to bin the cable upgrade idea unless I find something genuinely made for HD-540/HD-250.

I know you'll like these headphones, but I didn't expect you like them so much, so my gut feeling is spot on, again.

I love the HD-540! They look and feel so ordinary but sound extraordinary. I thought I’d die wearing Susvaras but since discovering the HD-540, K1000, and 4 screw HE-6 I’ve realised that headphones don’t always get better across decades, they are just different! Sound signatures are as much about fashion as technology.

 

[Andykong]

Yes, my view too. I’m going to bin the cable upgrade idea unless I find something genuinely made for HD-540/HD-250.

I love the HD-540! They look and feel so ordinary but sound extraordinary. I thought I’d die wearing Susvaras but since discovering the HD-540, K1000, and 4 screw HE-6 I’ve realised that headphones don’t always get better across decades, they are just different! Sound signatures are as much about fashion as technology.

Well, I happen to own K1000, HE6 (not the 3 screws version, but a very old shop demo) and a complete family of HD540/540G/250 linear 1, so I do recognise what you have experienced, but I come to a different conclusion.

I have shared my view on this subject briefly HERE. In short, I put refinement, empathy, emotional involvement , ... (or musicality in general) as the more important factors over technicality on a high-end audio system. I have a base line in technicality, and that is not a very low baseline, I just don't let technicality have the final say of my headphone preference. In my experience, once these attributes reach certain level, improvement in technicality will only fulfill my hardware ego, it won't enhance my musical enjoyment. Similarly, if you take the technicality of Susvara, HE6, K1000 and HD540 aside and look at their musicality factors, that probably also explained your expereince.

On the other hand, I'll won't look down on modern headphones simply becuase I had good experience with old headphones. It is more than a sound signature issue IMHO. Modern high quality headphones that place musicality over technicality in their priority is my cup of tea. They can offer refinement and technicality without scarifying musicality, and let me embrace the best of both sides. Meze is one example, Kennerton is another example.

 

[project86]

Absolutely! The Meze Empyrean, Meze Elite, and Kennerton Thekk are all examples of that - and consequently make for some of my favorite/most often used headphones.

As you mentioned, there's gotta be a technical baseline that must be met, or else the experience is too far off from reality. Could still be a fun guilty-pleasure type sound, but that's about it. Some headphones straddle that line closer than others but the Elite, Empyrean, and Thekk all clear it fairly easily.

 

[rmsanger]

Can't wait for a review of the Mk2 to be posted.. I think I heard from someone in another thread (similar product) a post where they implied they will be getting one for review to compare with that said similar product.

https://www.head-fi.org/threads/feliks-audio-envy.960600/post-16866722

 

[Andykong]

1. The irresistible 300B Direct Heated Triode

A lot of tube enthusiasts consider the Directed Heated Triode (DHT) as the holy grail of vacuum tube for audio application. DHT refers to Triode tubes that use the cathode as the filament and will heat up the cathode directly during operation. These can be considered as the minimal approach to amplification and have a huge following, especially among Japanese and Chinese audiophile communities. There is a long list of vacuum tubes belongs to this family, but for modern audio application, the more commonly used DHT are 45, 2A3, 300B, 845 and 211, and 300B is probably the most well-known and sought after DHT in audiophile community. In fact, if you happen to have audiophile friends who were into tube amplifier seriously, there is a large chance that you heard the good old saying: once you tried 300B it’s hard to go back. Howard Stone claim that “No tube — and possibly no component — in the world of tube audio has attracted so much attention over the years than the 300B triode” in The 300B Tube Lives Again! This is a bold claim, but the statement was endorsed by audiophiles since 2014.

The 300B offers an attractive tonal characteristic that is very close to the dream of audiophiles. It has a prominent full-body midrange, harmonically rich with unforced details that bring out the best of acoustic instrument, and the holographic presence that how the singer (or the band) appeared to be directly there in front of you. Technically, 300B offers very high linearity during amplification. This probably accounts for the natural presentation and excellent low-level details that re-created the presence that bring us closer to our music.

If 300B is that good, why it wasn’t mass produced and dominated the audio market? There are two major problems with 300B in audio applications. One of the weaknesses of 300B is the directly heated cathode makes it very sensitive to hum and interference. The microphonic effect is very prominent if you touch/knock at the tube or the chassis of the amplifier. This can be a minor problem to speaker based setup because when the amplifier are placed in a Hi-Fi rack 3 meters away from you, its unlikely that you’ll touch the amplifier, and the hum noise will only cause minimum disturb when the speaker is 2 meter away from you. But when we use 300B as headphone amplifier, the chassis is normally placed at arm-reach distance and the drivers of your headphone is probably 2 inches away from your ear, the microphonic effect will be very annoying, especially when you are using a high sensitive headphone such as Focal Stella or AKG K812. That explained why 300B based headphone amplifier is a challenge to design and costly to build.

On the other hand, the 300B is a relatively small powered output tube. Typically it can deliver 7-8 watt only without over driven. There are newer variants of 300B that offers slightly higher output, but they need to draw higher filament currents than the original 300B, as defined by Western Electronic back in 1938. The low output power has limited the 300B to pair with very sensitive speakers or to use in fairly small listening area. Fortunately, their lost is our gain. When we used the 300B in Personal Audio applications, the relatively small output for speakers is strong enough to drive very demanding headphones already. That makes 300B a wonderful choice for high-end headphone amplifier.

Among the choices, Cayin adopts a matched pair of Gold Lion Genelex PX300B as output tube for HA-300MK2. For stock output tube, Cayin has to be realistic and put reliability, availability and cost performance as top priority. Since the 1950's, only the very best Marconi-Osram Valve Company audio tubes have been labeled GEC (Genalex) Gold Lion. A tube had to endure and pass the toughest testing the industry offered before it can carry that label. In keeping with the tradition of Genalex to provide the highest quality tubes, they have released the Genalex Gold Lion PX300B low-noise audio triode that offers very decent frequency extension with a natural, sensible and realistic sound signature. This tube is considered to be an excellent upgrade tube by many 300B users and has been called the best “Common Man” 300B Tubes.

 

[Andykong]

2. SETA, a Purist’s One-way Ticket

Single-ended Triode Amplifier (SETA) is a vacuum tube-based design that uses a single-triode tube per channel to produce output without splitting the musical signal's plus/minus parts in each channel. In contrast, a push/pull amplifier, which uses a pair (or more) of tubes, splits the plus/minus of the music signal, then it has to put them back together to form the complete musical wave in each channel. Many argue that, once you split the signal's plus/minus, you never quite put it back together again with the exact purity that it contained beforehand. This is technically referred to as a crossover distortion, which ironically doesn't have anything to do with actual speaker crossovers. Also, almost all reference-level SET amplifiers run in pure Class A, not AB, to further avoid this type of distortion. The perceived high sonic quality is mainly attributed to the simplicity and minimalist approach of the circuits involved, as well as the triode vacuum tubes that are typically used. One SET aficionado describes it as "a Zen simplicity to reproduce the complexity of music. Less is more."
(extracted from Terry London, Home Theater Review)

If you prefer a video version, you can also check out HERE.

This article also explain the special charm of SET amplifier by comparing it to different types of amplification.

Cayin recognized the beauty of SETA and has devoted a lot of resource to develop dozens of SETAs in our history. In fact, you can find SIX sets of SETAs (A-300BMK2, CS-300A, CS-805A, CS-845A, A-845 Pro 25th Anniversary and M-845i) using 300B as output tube or driver tube in our current speaker amplifier line up, on top of the HA-300 and HA-300MK2 in this thread. We can safely claim that Cayin knows SETA and we are one of the authoritative behind the SETA movement.

Is SETA a perfect amplifier? Definitely no. Although SETAs are more dynamic than their low power would suggest, but they are still very low power after all. Their constraints are clear as day and they are appreciated by a niche group of audiophiles who are willing to limit their choice of speaker to very efficient design, typically horn loaded or “crossoverless” single-driver speakers. However, this low-power constraint becomes non-existed for headphone applications. While high power amplifiers like CS-150A or Soul 170i are well-received when compare to CS-805A or A-845 Pro, SETA such as HA-300/HA-300MK2 will sound better than push-pull design in both tone and detail even with the most demanding headphones, which make personal audio the most ideal platform for SETA followers.

HA-300 and HA-300MK2 employs the same 2-stage single-ended amplification with 6SN7 as driver tube. It will boost the input signal to the appropriate level so that the 300B output tube will perform its second stage amplification at a very linear condition. In simple terms, driver tube amplifies singal voltage while output tubes amplify current. The driver tubes are primarily for gain and signal processing while the output tubes take care of the heavy lifting to drive the headphone. This explained why users experienced significant change in tonal characteristic when they roll the drive tubes.

If you look into the tube combination of our SETAs mentioned earlier on, you’ll probably will notice that Cayin always use 6SN7 as driver tube when we use 300B as output tube. Chris Marten called this combination “legendary in audiophile circles” in his HA-300 review (HiFi+ July 2018, issue 161, page 69-72). For the HA-300MK2 implementation, Cayin uses a matched pair of Tung-Sol 6SN7GTB as driver tube for almost the same reason as Genalex Gold Lion PX300B. This is a super linear, low noise high performance, highly reliable and natural sounding driver tube for SET amplification.