[UntilThen]

I think you are right to go with the custom amplifier, of course you know the quality will be better. There are certain commercial designs that are poor IMO selling for over $10K USD, but since they use 300B, like moths to the flame the audiophiles are drawn. I don't doubt for a second that there are gains to be had using higher quality 300B tubes, but I think the person willing to spend 3-4K on their commercial 300B amplifier and another 4K on 300B tubes would be better served consolidating that money into a higher quality custom amplifier and one or two good pair of 300B. Of course there is the wait time to deal with, but quality takes time.

"Truer words have never been spoken".

... and I will have at most just one pair of good 300b. The days of spending on head-fi is over. I'm going fishing !

​

 

[triod750]

... and I will have at most just one pair of good 300b. The days of spending on head-fi is over.

Hmmm....

 

[Wes S]

For the cost of collecting extremely rare and valuable NOS tubes, the buyer could commission an entirely new amplifier, which would have much more drastic effects on listening experience than swapping tubes. There is an entire 300B thread right now where people are spending thousands of dollars on 300B tubes. Why not hold onto that money and commission a custom 300B amp as opposed to an off-the-shelf model? Just my opinion, but the money would be better spent that way. I think there is a misconception from tubehead audiophiles that the tube model makes the amp, but IME that is not the case, the totality of the circuit is more important and tubes are just another circuit element.

Take a 300B amplifier with a resistor loaded cathode biased input stage, cap coupled, and cathode biased output stage with an 60Hz AC filament supply and listen to it side-by-side with a CCS or inductor loaded fixed bias input stage, cap or transformer coupled, and a fixed bias output stage with a proper DC filament supply. There would absolutely be no comparison, the cheapest 300B tube in the latter circuit would slay the most TOTL 300B tube in the former.

Good stuff! Just out of curiosity, I would love to hear your thoughts on the Cayin HA300mk2 (off the shelf model) if you don't mind. The sound is insanely good, but now you have me wondering about custom options again. . . I was looking to go custom before the purchase of the Cayin, but decided not to go that route after hearing all the good stuff Zach (ZMF) had to say about the HA300mk2. I don't know anything about amp design, so I was not to sure about the custom route, and that was another reason I went with the Cayin. Honestly, I am in love with the sound and I am using some Elrog ER300B and RFT 6SN7 (welded plates with ceramic spacers) and can't imagine it getting any better, but again you have me wondering. . .did I make a bad purchase? If you or anyone in this thread thinks it can sound better than this for a similar amount of money with a custom option, I would really love to know, and thanks for your time!

I will say this from my own experience, the Cayin HA300mk2 with my upgraded NOS tubes included of which has cost me of total of around $4,800 all together, absolutely smokes my last amp the Pendant SE and it's not even close. So, I was thinking that was a pretty good deal for what I am hearing, but again I am really interested in how a custom 300B amp would compare.

 

[whirlwind]

You're absolutely right Joe, there does come a point where the ultra rare tubes just aren't worth it. Unless a happen across some insane deal, I will most likely pass on GEC KT88, and the metal base Mullards are out of the question. Lots of other tubes to try. Probably the highest up the rare tube ladder I want to go is a pair of Tung-Sol 6550, and likely some other Mullard EL34. If the amp / circuit is good, most any tubes will sound good in it. Right now I am listening to the Visseaux 6V6GT, they are relatively inexpensive and sound phenomenal. I've thought about grabbing some GEC KT63 / 6F6G too, which aren't too pricey.

I have not priced KT63's for awhile. I will vouch for them being nice sounding tubes though. I am listening to a pair now. Years ago I bought some for $70 a pair then it went to $100 but I still bought more because they sounded really good, and the bang for the buck was stellar compared to some other higher priced tubes. I am assuming @leftside will probably have every variation as he has a killer stash of tubes.

 

[Zachik]

you have me wondering. . .did I make a bad purchase?

No, you did not!
First, I auditioned the mk1 when it came out, with stock tubes, and it sounded wonderful. I bet the mk2 and with upgrade 300b tubes - sounds glorious.
Second, buying custom has its downsides too... I have one being finished as we speak, so I am not saying custom is the wrong way to go, but it is not perfect:
* Longer wait times. Much longer sometimes...
* In case of service needed (touch wood that does not happen) - well, best case it is more complicated, and worst case (e.g. Glenn amps) you're SOL.
* Unless it is a custom design that you can audition in advance, which usually it is NOT the case - it is a gamble that you'd like the sound. And you cannot return it if you do not.
* Custom amps are usually more expensive than commercial amps

Wes, and I know this advice usually falls on deaf ears in this hobby, since you love your amp so much - do not second guess your choice!

 

[Xcalibur255]

Part of the reason I am interested in trying something from the KT88 / 6550 family is simply to see how they perform in the amp and take some real-world measurements. All for the sake of science of course I can't bring myself to buy a new production KT88 though, probably what I will eventually do is try one of the variants that is only available new production, KT90, KT120, or KT150. Assuming they are drop in replacements for KT88 and will bias similarly, the amp should be able to use any of them, it has the heater current available to do so. But I will check the datasheets just in case. The KT150 would look hilariously huge in this amp though lol probably would go for the KT90 or KT120.

I researched the crap out of the KT150 before committing to it for my amp. There is a fairly solid consensus that the 150 is a substantially better tube overall than the 120. The engineers at New Sensor had triode strapping applications in mind when designing it and it gives nice results when used in a SET application.

On a side note, I recommend you give the Sophia EL34ST (the blue glass ones) a try too. I was honestly kind of cynical about these when I bought them and figured they would be overpriced for what they were. It seems like the goal of most new production tubes that are entering the market now are to be "boutique" so they can be incredibly expensive. These are absolutely worth what Sophia is charging though, I am quite in love with how they sound. The tone is divine and they reach deep into the music with excellent layering.

 

[L0rdGwyn]

Good stuff! Just out of curiosity, I would love to hear your thoughts on the Cayin HA300mk2 (off the shelf model) if you don't mind. The sound is insanely good, but now you have me wondering about custom options again. . . I was looking to go custom before the purchase of the Cayin, but decided not to go that route after hearing all the good stuff Zach (ZMF) had to say about the HA300mk2. I don't know anything about amp design, so I was not to sure about the custom route, and that was another reason I went with the Cayin. Honestly, I am in love with the sound and I am using some Elrog ER300B and RFT 6SN7 (welded plates with ceramic spacers) and can't imagine it getting any better, but again you have me wondering. . .did I make a bad purchase? If you or anyone in this thread thinks it can sound better than this for a similar amount of money with a custom option, I would really love to know, and thanks for your time!

I will say this from my own experience, the Cayin HA300mk2 with my upgraded NOS tubes included of which has cost me of total of around $4,800 all together, absolutely smokes my last amp the Pendant SE and it's not even close. So, I was thinking that was a pretty good deal for what I am hearing, but again I am really interested in how a custom 300B amp would compare.

Hey Wes, I'm sorry I didn't mean to make you doubt your purchase! The Cayin HA-300MK2 is one of the most reasonably priced 300B amps out there, and it has Zach's endorsement, so I'm sure it is a great sounding amplifier. I can't comment on the specifics of the circuit (I see no photos or specific information online), but for the price, to me it looks like you are getting quite a lot with a well-made chassis, separate tube rectified power supply unit, and other features. And the fact that you went straight for the Elrog tubes, which have a great reputation, ultimately is saving you money long term. I have seen some Head-Fiers collecting 300B tubes, which is an expensive endeavor unto itself, which is what motivated my comment primarily. There are also other 300B amplifiers out there that I would say offer less than the Cayin for drastically more money (there is one in particular I find especially egregious...). So I think you've made a good choice going for the Cayin as it isn't overpriced like some other 300B designs out there and you'll save long term going right for the best tubes.

And @Zachik 's points are all totally valid, there are drawbacks to the custom route. The advantage is you then have access to more exotic circuit elements / topologies, but it is still a gamble, that is absolutely true. The Telemachus seems to be the go-to custom 300B right now from Ultrasonic Studios, so maybe that is something you could investigate in the future, seems he will be making quite a few of them given the demand, maybe an audition could become available or a Head-Fier could compare it to the Cayin some day.

Sorry maybe I shouldn't be so loose lipped, I honestly did not have the Cayin in mind when making these comments, ultimately all that matters is that you are happy with your amplifier

 

[L0rdGwyn]

I have not priced KT63's for awhile. I will vouch for them being nice sounding tubes though. I am listening to a pair now. Years ago I bought some for $70 a pair then it went to $100 but I still bought more because they sounded really good, and the bang for the buck was stellar compared to some other higher priced tubes. I am assuming @leftside will probably have every variation as he has a killer stash of tubes.

Awesome, maybe I'll grab a pair. $100 for a NOS pair of GEC tubes seems like a steal these days, they always have a crazy markup!

 

[L0rdGwyn]

I researched the crap out of the KT150 before committing to it for my amp. There is a fairly solid consensus that the 150 is a substantially better tube overall than the 120. The engineers at New Sensor had triode strapping applications in mind when designing it and it gives nice results when used in a SET application.

On a side note, I recommend you give the Sophia EL34ST (the blue glass ones) a try too. I was honestly kind of cynical about these when I bought them and figured they would be overpriced for what they were. It seems like the goal of most new production tubes that are entering the market now are to be "boutique" so they can be incredibly expensive. These are absolutely worth what Sophia is charging though, I am quite in love with how they sound. The tone is divine and they reach deep into the music with excellent layering.

Thanks, duly noted. I am thinking I will most likely try the KT90 actually. None of these tubes are going to be biased anywhere close to their max specs, so seems like the lowest power model is the most sane one to try. That is the second time the Sophias have been recommended to me, so they certainly seem to have garnered a good reputation!

 

[Deleeh]

Good stuff! Just out of curiosity, I would love to hear your thoughts on the Cayin HA300mk2 (off the shelf model) if you don't mind. The sound is insanely good, but now you have me wondering about custom options again. . . I was looking to go custom before the purchase of the Cayin, but decided not to go that route after hearing all the good stuff Zach (ZMF) had to say about the HA300mk2. I don't know anything about amp design, so I was not to sure about the custom route, and that was another reason I went with the Cayin. Honestly, I am in love with the sound and I am using some Elrog ER300B and RFT 6SN7 (welded plates with ceramic spacers) and can't imagine it getting any better, but again you have me wondering. . .did I make a bad purchase? If you or anyone in this thread thinks it can sound better than this for a similar amount of money with a custom option, I would really love to know, and thanks for your time!

I will say this from my own experience, the Cayin HA300mk2 with my upgraded NOS tubes included of which has cost me of total of around $4,800 all together, absolutely smokes my last amp the Pendant SE and it's not even close. So, I was thinking that was a pretty good deal for what I am hearing, but again I am really interested in how a custom 300B amp would compare.

Don't misunderstand.
Just because Zach says the Cayin is good doesn't mean anything.
If Zach said something like that, I would read between the lines.
Which means that the Cayhin amplifier goes very well with the Zmf headphones.
That's all he's saying, Zach would never say it would be as good with other headphones.
Would also be counterproductive for him pessimistically.
With the Cayin amp you have, I would say you have a good one, most of the bugs from the Mk1 series have been fixed or even improved.
So no need to panic.
The Mk 1 has been slightly discredited because it was a lot of money for what it offers.
Similar to the Mcintosh mha 200 it sounds good but with the unity gain pot Mcintosh drove the amp to the wall and upset many.

Homemade amps don't necessarily sound better than the over-the-counter ones and vice versa.
It tends to depend more on the skills of the builder and the know how he has and how it was implemented.
Choice of components, type of concept, etc....
These are far more important aspects that determine how good an amplifier will be.
The result can be better, worse or the same.
But with people like Lord gwyn it is hard to say because there are only a handful of people who can enjoy his good work.
It has to be said that his parts selection, which I have roughly skimmed, is very good.
And he approaches it very differently than industrial manufacturers who go for the low cost principle.
He can afford to do that and his results speak for themselves in all areas.
Therefore, one can safely assume that a built amplifier in his range where 2500$ costs also annoys the large manufacturers who cost 5000$. The size order of the amount of money is now freely invented.
It's just to show that something like this is possible but not a must.

The best way to compare it is to have Lord gwyn's amplifier one day and compare it with your Cayhin and judge for yourself.
That would be the best and most sensible thing to do.
I wouldn't let anything else worry me now.

I also admire Lord's work and am fascinated by it and a little envious that I can't do it myself, because I would like to be able to do it.

 

[L0rdGwyn]

Homemade amps don't necessarily sound better than the over-the-counter ones and vice versa.
It tends to depend more on the skills of the builder and the know how he has and how it was implemented.
Choice of components, type of concept, etc....
These are far more important aspects that determine how good an amplifier will be.
The result can be better, worse or the same.
But with people like Lord gwyn it is hard to say because there are only a handful of people who can enjoy his good work.
It has to be said that his parts selection, which I have roughly skimmed, is very good.
And he approaches it very differently than industrial manufacturers who go for the low cost principle.
He can afford to do that and his results speak for themselves in all areas.
Therefore, one can safely assume that a built amplifier in his range where 2500$ costs also annoys the large manufacturers who cost 5000$. The size order of the amount of money is now freely invented.
It's just to show that something like this is possible but not a must.

The best way to compare it is to have Lord gwyn's amplifier one day and compare it with your Cayhin and judge for yourself.
That would be the best and most sensible thing to do.
I wouldn't let anything else worry me now.

I also admire Lord's work and am fascinated by it and a little envious that I can't do it myself, because I would like to be able to do it.

I agree with many of your points, the result will depend on the designer. I will try to stop speaking in generalities and being overly critical of commercial designs, it is really a small subset of these amplifiers that are frustrating as their prices are inflated to the point of being disingenuous, IMO, and I don't think the Cayin falls into that category. It's true that I design from a DIYers perspective with a much more liberal budget and without the supply chain and manufacturing complexities of large volume production, so it is a little unfair to be so critical.

I am hoping to bring this pentode amplifier to a wider audience in some way as I've said, there are definitely some outlying questions as to the practicality of commercial production, supply chain, cost of manufacture, etc. Those conversations will take place in the coming months and we will see what comes of it. If I am able to get the amplifier to CanJam SoCal, well then Head-Fiers themselves can compare it then and there. If no one likes it, then that will be that

 

[Xcalibur255]

Thanks, duly noted. I am thinking I will most likely try the KT90 actually. None of these tubes are going to be biased anywhere close to their max specs, so seems like the lowest power model is the most sane one to try. That is the second time the Sophias have been recommended to me, so they certainly seem to have garnered a good reputation!

I haven't tried a KT90 yet either. That would probably bias up about the same as a KT150 does in my amp in the EL34 bias setting. I did try a KT66, which sounds fine but is my least favorite of the power tubes I have on hand. They're very nicely made but the sound lacks the depth that the KT150 and EL34 offer.

 

[L0rdGwyn]

I haven't tried a KT90 yet either. That would probably bias up about the same as a KT150 does in my amp in the EL34 bias setting. I did try a KT66, which sounds fine but is my least favorite of the power tubes I have on hand. They're very nicely made but the sound lacks the depth that the KT150 and EL34 offer.

Yeah I bet KT90 would work well in your amplifier. Like the KT150, it is a KT88 type with a higher plate dissipation, 50W. So maybe you would use the KT150 setting unless they KT150 are biased pretty hot, obviously Mischa would know. Are they new production KT66? Like the KT88, prices for NOS are a bit crazy. I have found big differences in sound in my circuit with different 6L6 types, pretty drastic in fact. Best one I have is the Ken-Rad 6L6G.

 

[Wes S]

No, you did not!
First, I auditioned the mk1 when it came out, with stock tubes, and it sounded wonderful. I bet the mk2 and with upgrade 300b tubes - sounds glorious.
Second, buying custom has its downsides too... I have one being finished as we speak, so I am not saying custom is the wrong way to go, but it is not perfect:
* Longer wait times. Much longer sometimes...
* In case of service needed (touch wood that does not happen) - well, best case it is more complicated, and worst case (e.g. Glenn amps) you're SOL.
* Unless it is a custom design that you can audition in advance, which usually it is NOT the case - it is a gamble that you'd like the sound. And you cannot return it if you do not.
* Custom amps are usually more expensive than commercial amps

Wes, and I know this advice usually falls on deaf ears in this hobby, since you love your amp so much - do not second guess your choice!

Thanks for the info buddy! I really appreciate the detailed response.

 

[Wes S]

Hey Wes, I'm sorry I didn't mean to make you doubt your purchase! The Cayin HA-300MK2 is one of the most reasonably priced 300B amps out there, and it has Zach's endorsement, so I'm sure it is a great sounding amplifier. I can't comment on the specifics of the circuit (I see no photos or specific information online), but for the price, to me it looks like you are getting quite a lot with a well-made chassis, separate tube rectified power supply unit, and other features. And the fact that you went straight for the Elrog tubes, which have a great reputation, ultimately is saving you money long term. I have seen some Head-Fiers collecting 300B tubes, which is an expensive endeavor unto itself, which is what motivated my comment primarily. There are also other 300B amplifiers out there that I would say offer less than the Cayin for drastically more money (there is one in particular I find especially egregious...). So I think you've made a good choice going for the Cayin as it isn't overpriced like some other 300B designs out there and you'll save long term going right for the best tubes.

And @Zachik 's points are all totally valid, there are drawbacks to the custom route. The advantage is you then have access to more exotic circuit elements / topologies, but it is still a gamble, that is absolutely true. The Telemachus seems to be the go-to custom 300B right now from Ultrasonic Studios, so maybe that is something you could investigate in the future, seems he will be making quite a few of them given the demand, maybe an audition could become available or a Head-Fier could compare it to the Cayin some day.

Sorry maybe I shouldn't be so loose lipped, I honestly did not have the Cayin in mind when making these comments, ultimately all that matters is that you are happy with your amplifier

Thanks for the info man! I really appreciate all the info, and I am absolutely loving the amp. The Telemachus was the one custom I was considering, but I am just going to stick with what I have as I am happy, and I am at the max of my budget anyway.

Cheers bro!