[DecentLevi]

Very easy to hear differences. I guess it depends on what you are focusing on. Both myself and a number of other members here feel the Hexfred sound is a little on the dark and mellow side in terms of tone, but how much of this is due to the diodes and how much due to the change in voltage drop is hard to say. The clear and measurable difference is that there is no voltage drop, where as with a tube rectifier there would be anywhere between 20 and 60 volts of loss which changes the operating points of the other tubes in the amp. This is the primary reason why rolling rectifiers can change the character of an amp. It's inducing a change in behavior from the other tubes. The Hexfreds aren't noticeably more or less dynamic than a tube rectifier to my ears, though they have substantially better bass speed and control which you might choose to interpret as a more dynamic sound if you wanted to. I also found them to offer superior resolution and low level detail over tube rectifiers. Unless you specifically want your amp to have a brighter sound the Hexfreds are kind of a slam dunk if you ask me.

The other main audible difference comes from the amount of diode switching noise. This is where I feel the Hexfred really earns its keep and is the reason why I don't use tube rectifiers in my amp anymore. The Hexfred is a more refined and grain free sound that has less hardness and glare than any rectifier I ever owned or heard, and I believe that is mostly due to the fact that there is less switching and hash noise from these diodes compared to a tube diode.

The main downside is you lose the gentle and slow start up that tube rectifiers naturally have, but Glenn has ways of dealing with this so it's not really a problem.

As for a difference between having Hexfred in a removable socket adapter or having it built into the amp, I really doubt there would be any difference substantial enough to be able to hear it. It's the same diodes either way. If you want to preserve your ability to roll in different options then the adapters are the safe route, but if you are confident you would like the Hexfred sound you can eliminate one or two tube sockets from the amp and free up space for the chassis to be smaller or for other things to be up there depending on what you have in mind.

@Xcalibur255 interesting and helpful info. on Hexfreds. From your description sounds like I may go with Hexfreds too, especially the sound having better bass control and speed, and resolution... but doesn't that change depending on how good of rectifier tubes you're comparing it with?

For the next questions, excuse me for sounding like a noob but I'm coming from the simple 4-tube OTL Feliks Audio amp with drivers/powers of the same socket type.
- Does the Hexfred option even apply to a new GEL3N amp, or is it only for OTL amps?
- Can someone PLEASE post a photo of the Hexfred? For the life of me I can't decipher which photo on Google Images resembles one. (I have no idea what it looks like)
- Is there such a thing as Hexfred rolling, such as op-amp rolling? If so, what is the terminology of the removable component?
- Which is more recommended for low-z cans, either the Hexfred or tube rectifiers, and 1 or 2 tubes?

 

[UntilThen]

Found a picture of the plug in hexfred posted by @gibosi . https://www.head-fi.org/threads/2359glenn-studio.600110/page-1181#post-13957334

Not much to look at.

Also in the GEL3N, you can order it with tube rectifier and get one of this plug in hexfred from Glenn or you can order your GEL3N with build in hexfred i.e no option to roll tube rectifiers. There hasn't been a GEL3N with a build in hexfred yet but I know one is coming.

 

[rnros]

- Can someone PLEASE post a photo of the Hexfred? For the life of me I can't decipher which photo on Google Images resembles one. (I have no idea what it looks like)

Datasheet:
https://www.mouser.com/datasheet/2/427/vs-hfa25tb60-m3-1351200.pdf

There are different 'package' types, this one is TO-220. Other types for various build applications.
http://www.vishay.com/docs/49446/49446.pdf

 

[OctavianH]

Very easy to hear differences. I guess it depends on what you are focusing on. Both myself and a number of other members here feel the Hexfred sound is a little on the dark and mellow side in terms of tone, but how much of this is due to the diodes and how much due to the change in voltage drop is hard to say. The clear and measurable difference is that there is no voltage drop, where as with a tube rectifier there would be anywhere between 20 and 60 volts of loss which changes the operating points of the other tubes in the amp. This is the primary reason why rolling rectifiers can change the character of an amp. It's inducing a change in behavior from the other tubes. The Hexfreds aren't noticeably more or less dynamic than a tube rectifier to my ears, though they have substantially better bass speed and control which you might choose to interpret as a more dynamic sound if you wanted to. I also found them to offer superior resolution and low level detail over tube rectifiers. Unless you specifically want your amp to have a brighter sound the Hexfreds are kind of a slam dunk if you ask me.

The other main audible difference comes from the amount of diode switching noise. This is where I feel the Hexfred really earns its keep and is the reason why I don't use tube rectifiers in my amp anymore. The Hexfred is a more refined and grain free sound that has less hardness and glare than any rectifier I ever owned or heard, and I believe that is mostly due to the fact that there is less switching and hash noise from these diodes compared to a tube diode.

The main downside is you lose the gentle and slow start up that tube rectifiers naturally have, but Glenn has ways of dealing with this so it's not really a problem.

As for a difference between having Hexfred in a removable socket adapter or having it built into the amp, I really doubt there would be any difference substantial enough to be able to hear it. It's the same diodes either way. If you want to preserve your ability to roll in different options then the adapters are the safe route, but if you are confident you would like the Hexfred sound you can eliminate one or two tube sockets from the amp and free up space for the chassis to be smaller or for other things to be up there depending on what you have in mind.

Many thanks for your detailed answer. One last question, if we add the transformer type to this equation, is there any advantage or disadvantage in combining the rectifier socket with a Lundahl transformer? What I read and found out, thanks to @L0rdGwyn was that the Lundahl transformer version with octal rectifier socket has also 2 x Hexfreds inside and the rectifier is basicly wired to the positive polarity.

 

[Khragon]

Guys... I like to share that I've sold my Glenn 300B amp (https://www.head-fi.org/threads/sold-glenn-300b-amp.911550/#post-15117835)

And.. I'm happy to report that the buyer is @zach915m of ZMF Headphones. I'm a fan of ZMF headphones, having own every of Zach custom designed model from Eikon/Atticus up to the Auteur (both stock and black wood).
I know the amp pair really well with Zach headphones, and excited that Zach may take this amp on tour, giving everyone a chance to experience Glenn's amp, both OTL and 300B!

Look for Zach table at the next meet to hear both of Glenn's master creations.

 

[DecentLevi]

Found a picture of the plug in hexfred posted by @gibosi . https://www.head-fi.org/threads/2359glenn-studio.600110/page-1181#post-13957334

Not much to look at.

Also in the GEL3N, you can order it with tube rectifier and get one of this plug in hexfred from Glenn or you can order your GEL3N with build in hexfred i.e no option to roll tube rectifiers. There hasn't been a GEL3N with a build in hexfred yet but I know one is coming.

Thanks much guys, that actually clears it up so fast. So the Hexfred is a brand of diode, which can run in the place of a rectifier either internally in place of or can be externally interchanged with rectifiers with adapter. I suppose that would also give us the option to swap with other diodes too right?

That being said, I think I will go with a GEL3N amp with tube rectifier and a plug in external Hexfred option... that along with multitudes of great EL and other tube rolling will leave me more than happy! @2359glenn - unless you think there's any merit to my concept for the switchable 6AS7G or 6336 add-on let me know, otherwise I'll happily go ahead with the above. Please let me know soon by PM to secure my place in line, thanks!!

 

[UntilThen]

Does a tube rectifier really make an amp sound better or does a solid state rectifier really make an amp sound better? Well it depends on what you're looking for.

This article is written in an easily digestible manner. Although it referenced guitar amps, it should also apply to headphone tube amps.

https://reverb.com/au/news/does-a-tube-rectifier-really-make-an-amp-sound-better

 

[UntilThen]

Guys... I like to share that I've sold my Glenn 300B amp (https://www.head-fi.org/threads/sold-glenn-300b-amp.911550/#post-15117835)

And.. I'm happy to report that the buyer is @zach915m of ZMF Headphones. I'm a fan of ZMF headphones, having own every of Zach custom designed model from Eikon/Atticus up to the Auteur (both stock and black wood).
I know the amp pair really well with Zach headphones, and excited that Zach may take this amp on tour, giving everyone a chance to experience Glenn's amp, both OTL and 300B!

Look for Zach table at the next meet to hear both of Glenn's master creations.

Wow what can I say... Congrats Zach !!!!

You're probably the first person to own all 3 Glenn's amps - OTL, GEL3N and now the 300b amp. I would expect a detail comparison of all 3 further down the track. .. with the ZMF headphones of course.

I too have owned the Eikon and Atticus. A big mistake of mine to have sold them but I have a Verite Pheasantwood arriving on Tuesday !

 

[UntilThen]

Thanks much guys, that actually clears it up so fast. So the Hexfred is a brand of diode, which can run in the place of a rectifier either internally in place of or can be externally interchanged with rectifiers with adapter. I suppose that would also give us the option to swap with other diodes too right?

That being said, I think I will go with a GEL3N amp with tube rectifier and a plug in external Hexfred option...

Good decision on going with tube rectifier and a plug in hexfred. As for swapping other diodes.... well life shouldn't be that complicated.

 

[UntilThen]

Bought another pair of GEC 6080 so I can run quad GEC 6080 in the GOTL... for the Verite. This one from a local seller, so it's cheap for a less than 30 hours tubes.

 

[OctavianH]

Is it possible to use 3 x 6SN7 as drivers via 6SN7 -> C3g adapters? Has anyone made such an adapter? Maybe @Deyan ?
Or only a pair of 6SN7 via the C3g sockets? I am not sure if I really want this, just asking for the sake of "unlimited rolling options".

 

[Deyan]

Is it possible to use 3 x 6SN7 as drivers via 6SN7 -> C3g adapters? Has anyone made such an adapter? Maybe @Deyan ?
Or only a pair of 6SN7 via the C3g sockets? I am not sure if I really want this, just asking for the sake of "unlimited rolling options".

In which amp?? As far as I know the GOTL already uses the 6SN7 as a driver.

 

[OctavianH]

In which amp?? As far as I know the GOTL already uses the 6SN7 as a driver.

In the GOTL. Yes, you have in the maxed version as drivers 1 x 6SN7 + 2 x C3g and 6 x output sockets. But I was thinking to use all 3 driver sockets for 6SN7.

 

[UntilThen]

No you can't use dual 6sn7 in the c3g slots. Those slots are meant for pentodes in strapped triodes mode. You 6sn7 is a dual triode tube and it goes in the 6sn7 slot. Contrary to others experience, I don't find it beneficial to use 3 tubes as drivers. The GOTL was not designed for that. It's an accidental discovery.

For instance, why would I dilute the qualities of a ECC33 mixing it up with a pair of pentode as strapped triodes.

 

[Deyan]

Maybe a single 6SN7 with both triodes in parallel to C3g. But I can't really say. @2359glenn can tell us for sure.