Cayin HA-300MK2 (2022) TOTL Transformer coupled Direct Heated Triode Tube HeadAmp (Page 91)
Sep 18, 2023 at 12:12 AM Post #4,216 of 6,124
Be careful when placing your new caps too close to the 300B cathode resistors. For 300B to run at 6watt power, the cathode resistor will run hot in self-bias (not sure if HA-300 uses self-bias though). If this is the case, the new caps will die much faster than expected.

There is a reason why the coupling caps were quite a bit away from those cathode resistors in the original design as shown in you pictures.

I don’t know what voltage from power transformer secondary goes into B+, the filter cap with 500v can be an issue. If someone turns on the PSU without the amplifier box connected, 500v tolerance may not give too much margin.
 
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Sep 18, 2023 at 1:27 AM Post #4,217 of 6,124
Be careful when placing your new caps too close to the 300B cathode resistors. For 300B to run at 6watt power, the cathode resistor will run hot in self-bias (not sure if HA-300 uses self-bias though). If this is the case, the new caps will die much faster than expected.

There is a reason why the coupling caps were quite a bit away from those cathode resistors in the original design as shown in you pictures.

I don’t know what voltage from power transformer secondary goes into B+, the filter cap with 500v can be an issue. If someone turns on the PSU without the amplifier box connected, 500v tolerance may not give too much margin.
Thank you for mentioning that FFzz. I already forwarded your comment to my distributor. However, it seems that he moved the resistors to the side before placing capacitors into those spaces per below image.

Before :

S__27328548_0.jpg


After :

S__27328553_0.jpg
 
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Sep 18, 2023 at 1:30 AM Post #4,218 of 6,124
Thank you for mentioning that FFzz. I already forwarded your comment to my distributor. However, it seems that he moved the resistors to the side before placing capacitors into those spaces per below image.

Before :

S__27328548_0.jpg

After :

S__27328553_0.jpg
I would have put the caps on left as you look down on the bottom and on the right front.
 
Sep 18, 2023 at 2:01 AM Post #4,219 of 6,124
I would have put the caps on left as you look down on the bottom and on the right front.

I think you mean what llamaluv did on this link : https://www.head-fi.org/posts/16779526. You may see that his Duelund capacitors wires are longer that mine. The distributor owner explained me that the new Duelund capacitors wires length are shorter than old version. I think that's why he put them on those positions. You may compare from below picture and my previous post picture for the wire length.

duelund_caps.jpg

 
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Sep 18, 2023 at 4:28 AM Post #4,220 of 6,124
What kind of surface have folks tried with their amp? I mean wood, slate, granite, and have they found any differences. My table has an MDF shelf with a spike at each corner onto a metal frame and I was thinking about getting a piece of slate cut to size to replace it. Has anyone experimented???
 
Sep 18, 2023 at 6:59 AM Post #4,221 of 6,124
Thank you for mentioning that FFzz. I already forwarded your comment to my distributor. However, it seems that he moved the resistors to the side before placing capacitors into those spaces per below image.

Before :



After :

The resistors that are bolted to the chassis with built-in heatsink (the yellow ones with white markings on them) are the ones that may dissipate lot of heat (depending on the circuit design). That’s why these resistors were chosen in the first place…
 
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Sep 18, 2023 at 7:18 AM Post #4,222 of 6,124
I've been spending some time lately with yet ANOTHER 6sn7 substitute, the 6J5. Not much mention of these with the HA-300, but they seem popular in other 300b amp forums. So I HAD to take the plunge.

Primarily I've been listening to a quad of Brimar 6J5G/CV1067, having had them in for about 2 weeks straight. I'm not sure how old those tubes are, but I would guess old-ish based on the construction (oval plates and dimpled foil getters).

These sound really nice. They are a jack of all trades, master of none. They have really nice, textured, detailed bass, but it lacks the impact and quantity of the CV6/VR135. The treble is detailed and just slightly sweet, which is to my preference, but lacks ultimate extension. The staging approaches the 3d-ness of Melz 1578, but isn't quite as expansive.

Where they do shine is in the mid range. It's just a bit forward, detailed, a bit warm - just great presence overall. It's like there's a spotlight shining on the midrange instruments. In some ways this reminds me of Raytheon WWII-era VT-231, which have a similar quality. If you're familiar with those, you'll get a sense of the Brimars' tonality. Though the Brimars are much more technically proficient overall. These are great jazz/classical/folk tubes, anything on the more relaxing side, but with enough technicalities to do justice to faster/more complex genres.

BUT, being so close to the best of tubes in all categories, these are definitely near the top of my list. A tube I could live with, but of course I won't because I live that tube-rolling life.

I've also spent a bit of time with 1951 Sylvania round plate 6J5. These are just about DEAD silent, which is nice. I generally like the Sylvania house sound...but these depart a bit too much from that. Nicely even, maybe slightly on the bright side, clean sounding. But lacking in the midrange in comparison to other tubes, which is unfortunately most important to me. Maybe further burn-in will bring in the bass and mids. But so far, good but not my favourite.

And finally I just got in a quad of GEC L63, 1963 made in Hammersmith. I've only had a few days with these. They have almost no "personality" whatsoever, I don't hear any part of the frequency more or less than any other. Good extension on either end. Extended treble without being too hot. These are very immediate-sounding tubes, with the stage large and in your face. Impression of being on the stage, right in front of the band. Not much of a sense of space. Not necessarily a bad thing for me, but others may disagree. Also, very nice texture and tactility to the music, again emphasizing that right-there-with-the-band feeling. I can see these being a great rock tube, and to me there's not too many of these in the 6sn7 family. But these may change with more time.

Overall, 6J5s may be my favourite 6sn7 substitute, surpassing 6F8G. It's like the linearity of the 6F8G with a bit more life and realism. But I haven't heard every tube yet. I really wanted to like the CV6/VR135, but they're just too noisy in my MK1 for everyday use.

Sorry about the long post. Geez, I went on and on...
Excellent post! You have a really good way of describing how a tube sounds.
 
Sep 18, 2023 at 8:43 AM Post #4,223 of 6,124
What kind of surface have folks tried with their amp? I mean wood, slate, granite, and have they found any differences. My table has an MDF shelf with a spike at each corner onto a metal frame and I was thinking about getting a piece of slate cut to size to replace it. Has anyone experimented???

I was thinking about these things watching hifi racks. I looked to the same seller @RobertSM bought and I saw this rack which is cool because you can adjust any height when you want:

https://www.etsy.com/es/listing/780...ssoporte?ref=ap-listing&variation1=1355547698

But I am wondering how can it affect to HA-300 having it on the top and depending on wood as I guess the more thick and dense the woodis it will absorb more vibration and the previous shelves will absorb more vibrations as well than the top shelf., at the same time, the steel bar will be prone to transfer the vibrations to the shelves.
 
Sep 18, 2023 at 9:46 AM Post #4,224 of 6,124
The resistors that are bolted to the chassis with built-in heatsink (the yellow ones with white markings on them) are the ones that may dissipate lot of heat (depending on the circuit design). That’s why these resistors were chosen in the first place…
Understood, but like I mentioned before that the wire length does not give us many choices.
 
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Sep 18, 2023 at 9:59 AM Post #4,225 of 6,124
I was thinking about these things watching hifi racks. I looked to the same seller @RobertSM bought and I saw this rack which is cool because you can adjust any height when you want:

https://www.etsy.com/es/listing/780...ssoporte?ref=ap-listing&variation1=1355547698

But I am wondering how can it affect to HA-300 having it on the top and depending on wood as I guess the more thick and dense the woodis it will absorb more vibration and the previous shelves will absorb more vibrations as well than the top shelf., at the same time, the steel bar will be prone to transfer the vibrations to the shelves.
IMO vibrations only affect sound if your equipment is microfonic and you have vibrations in your environment, for example a tramline and traffic outside your window or speakers playing relatively loud. Otherwise it's aesthetics only.
 
Sep 18, 2023 at 10:44 AM Post #4,226 of 6,124
IMO vibrations only affect sound if your equipment is microfonic and you have vibrations in your environment, for example a tramline and traffic outside your window or speakers playing relatively loud. Otherwise it's aesthetics only.

Couldn't the microphonic sound appear in the HA-300 with strong vibrations or that happens only in bad construction/design/defective units? I have seen posts with people so paranoid with the hifi rack design for a tube amp or turntable. I didn't know for what amp they wanted the rack tho.
 
Sep 18, 2023 at 10:47 AM Post #4,227 of 6,124
Couldn't the microphonic sound appear in the HA-300 with strong vibrations or that happens only in bad construction/design/defective units? I have seen posts with people so paranoid with the hifi rack design for a tube amp or turntable. I didn't know for what amp they wanted the rack tho.
Turntables definitely react to vibrations, with tube amps it's usually a property of different tubes. Some tubes are more microfonic and some are completely silent.
 
Sep 18, 2023 at 12:20 PM Post #4,228 of 6,124
I was thinking about these things watching hifi racks. I looked to the same seller @RobertSM bought and I saw this rack which is cool because you can adjust any height when you want:

https://www.etsy.com/es/listing/780...ssoporte?ref=ap-listing&variation1=1355547698

But I am wondering how can it affect to HA-300 having it on the top and depending on wood as I guess the more thick and dense the woodis it will absorb more vibration and the previous shelves will absorb more vibrations as well than the top shelf., at the same time, the steel bar will be prone to transfer the vibrations to the shelves.
I was only able to completely disassemble and take everything out and clean and vacuum my old Head-Fi setup this weekend.

I think I'll finally get it all built and setup later today. So the verdict is still out. I'll let know know about the quality and drop a picture hopefully later today.
 
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Sep 18, 2023 at 3:56 PM Post #4,229 of 6,124
Trying a pair of these. Same date code. 12/53.

IMG_3388.jpeg
IMG_3389.jpeg
 
Sep 18, 2023 at 4:53 PM Post #4,230 of 6,124
Trying a pair of these. Same date code. 12/53.

Been there and done that, and they can't hold a candle next to any CV6.

However, if you want to stay with 6SN7 and avoid adapters, they are one of the best
 
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