Crack;Bottlehead OTL
Feb 1, 2021 at 3:03 PM Post #10,621 of 10,868

HiFiHawaii808

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The regulated PSU definitely made the biggest change out of all the upgrades (aside from the speedball). Early impressions are that the sound is just flat-out cleaner and more resolving, and the bass is more defined and punchier.
Can I achieve something similar just by purchasing a different amp? That seems a lot of work and the aesthetic of it really does leave quite a bit to be desired.
 
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Feb 1, 2021 at 3:08 PM Post #10,622 of 10,868

InstantSilence

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The impedance of the Rad0 is only 29 ohms, so this amp is a bad pairing. This amp is more suited for high impedance headphones like Sennheiser and ZMF (200-300 ohm or above headphones).
When looking for an amp how do I match inpedence and all that ohms ect.
I never quite understood electricity.
Dumb it down for me as simple as possible. How do I match things up and read on paper and assume the pairing is OK or bad?
 
Feb 1, 2021 at 3:41 PM Post #10,624 of 10,868

carlman14

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Can I achieve something similar just by purchasing a different amp? That seems a lot of work and the aesthetic of it really does leave quite a bit to be desired.

It was a lot of work. The main purpose of doing this was for the fun of tinkering and learning about amp design. The crack is all about tinkering... some just take it further than others.

And personally, I love the aesthetic of adding the rectifier tube. It looks super unique as far as cracks go. It's not ugly... It has character lol.

You could accomplish something similar by just buying a crackatwoa instead of a crack. It has a lot of the common upgrades people do to the crack included already.

Sometimes it’s about the journey :).

Exactly!
 
Feb 1, 2021 at 4:01 PM Post #10,625 of 10,868

carlman14

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When looking for an amp how do I match inpedence and all that ohms ect.
I never quite understood electricity.
Dumb it down for me as simple as possible. How do I match things up and read on paper and assume the pairing is OK or bad?

As far as I understand it, planar magnetic headphones need a lot of current to be driven properly, whereas high impedance dynamic headphones need more voltage. OTL designs like the bottlehead crack output sufficient voltage into high impedance headphones, but not nearly enough current for lower impedance panars.

For planars, look for either a solid state amp, or a OTC (output transformer coupled) tube amp with a relatively low output impedance (8 and 32 ohm outputs are common in OTC tube amps). Most planars will do well with either.
 
Feb 1, 2021 at 4:55 PM Post #10,626 of 10,868

cddc

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Alright everyone, I have the next big modification to my franken-crack ready. Meet the tube-rectified bottlehead crack! I completely re-implemented the power supply with an oversized power transformer capable of supporting a tube rectifier. The high-voltage winding is maida-regulated for a consistent, stable, low-ripple B+ voltage no matter what rectifier is plugged in. Any 5V rectifier is supported. I've tried 5U4G, 5U4GB, 5AR4, and 596 rectifiers with great success.

One neat thing here is that if I wanted to go back to SS rectification, I can! I have a SS plug-in rectifier that fits in the octal socket. This was tons of fun, and I learned a lot about power supply design in the process!

Under the hood you can see the maida regulator for the HV winding, as well as the massive heatsink attached to it. I managed to fit this while keeping all the previous upgrades in place, including the onboard DAC.

I also replaced the input wiring with shielded cable, as there were now AC lines closer to the input wiring. With the shielded wire in place, the amp is completely silent with no hum whatsoever from the new PT. It's silent using both the RCA inputs as well as using the onboard DAC.

Overall I am very pleased with how this turned out. The differences in sound are noticeable, and my BHC has never sounded this good! Aesthetically, it came out better than I expected too. I managed to fit the new transformer in such a way that it covered the massive hole in the top plate from the original transformer.

IMG_20210131_161638.jpg
IMG_20210131_163839.jpg
IMG_20210201_081612.jpg
IMG_20210201_081624.jpg


Wow...this Franken'd Crack is awesome, you are the man!

While I do prefer tubes to SS in the signal path, I've been trying to avoid tube rectification when considering amps (it's not in the signal path anyway). I heard SS rectification is superior to tube rectification, as there are voltage drop and voltage instability (up and down) with tube rectification.

So how is the tube rectification going? How does it compare to the SS rectification in your opinion, which one do you prefer? :)
 
Feb 1, 2021 at 5:03 PM Post #10,627 of 10,868

cddc

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When looking for an amp how do I match inpedence and all that ohms ect.
I never quite understood electricity.
Dumb it down for me as simple as possible. How do I match things up and read on paper and assume the pairing is OK or bad?

You should consider Mainline from Bottlehead, it works with both low-impedance headphones (like planars, Grado's,...) and high impedance headphones. Crack works best for high impedance headphones.
 
Feb 1, 2021 at 5:22 PM Post #10,628 of 10,868

DenverW

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You should consider Mainline from Bottlehead, it works with both low-impedance headphones (like planars, Grado's,...) and high impedance headphones. Crack works best for high impedance headphones.

I have a mainline, and I often don’t love it with some planars I’ve tried, for example the he-500. I’m in the process of getting a Bottlehead sex amp, and I’ll see how that pairs.
 
Feb 1, 2021 at 5:24 PM Post #10,629 of 10,868

MattTCG

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I have a mainline, and I often don’t love it with some planars I’ve tried, for example the he-500. I’m in the process of getting a Bottlehead sex amp, and I’ll see how that pairs.

The SEX amp pairs well with planars. I believe that you will enjoy that combo. Best of luck!
 
Feb 1, 2021 at 6:10 PM Post #10,630 of 10,868

carlman14

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Wow...this Franken'd Crack is awesome, you are the man!

While I do prefer tubes to SS in the signal path, I've been trying to avoid tube rectification when considering amps (it's not in the signal path anyway). I heard SS rectification is superior to tube rectification, as there are voltage drop and voltage instability (up and down) with tube rectification.

So how is the tube rectification going? How does it compare to the SS rectification in your opinion, which one do you prefer?

Thanks! Voltage drop, instability, and heat are definitely disadvantages of tube rectifiers. I mitigated the voltage drop and instability by using a regulated power supply. So no matter what rectifier is plugged in, I get the same output voltage. No need to worry about voltage drop.

Realistically, there's no benefit big enough to use tube rectification over SS. The only thing I can think of is that some tubes have a slow start up (like the 5AR4), which gives the input/output tubes time to warm up before being hit with B+ voltage. This is better for tube health and will lengthen the life of the tubes in the signal path. Also, I'm not sure if this is the particular SS plug-in rectifier I'm using... but I get a lower noise floor with tube rectifiers than SS. Sound-wise, to me rectifiers make almost no difference in sound. If there's any differences between tube and SS, they're either very minute or I'm just imagining them. The improvements I described earlier are likely the result of the revamped power supply rather than the actual rectifier used.

But like I said... using a tube instead of SS was 100% for fun/looks and not for sound improvements :)
 
Feb 1, 2021 at 9:26 PM Post #10,631 of 10,868

cddc

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Thanks! Voltage drop, instability, and heat are definitely disadvantages of tube rectifiers. I mitigated the voltage drop and instability by using a regulated power supply. So no matter what rectifier is plugged in, I get the same output voltage. No need to worry about voltage drop.

Realistically, there's no benefit big enough to use tube rectification over SS. The only thing I can think of is that some tubes have a slow start up (like the 5AR4), which gives the input/output tubes time to warm up before being hit with B+ voltage. This is better for tube health and will lengthen the life of the tubes in the signal path. Also, I'm not sure if this is the particular SS plug-in rectifier I'm using... but I get a lower noise floor with tube rectifiers than SS. Sound-wise, to me rectifiers make almost no difference in sound. If there's any differences between tube and SS, they're either very minute or I'm just imagining them. The improvements I described earlier are likely the result of the revamped power supply rather than the actual rectifier used.

But like I said... using a tube instead of SS was 100% for fun/looks and not for sound improvements :)

Fantastic, thanks a lot for letting us know the difference between tube rectification and SS rectification on Crack! No one has done that before!

You are correct, the slow start-up with tube rectification does help improve the working conditions for tubes and lengthen their lives. With SS rectification B+ hits tubes almost right away after amp is turned on, while tube rectifiers need some time to boil electrons off the cathodes.

I guess the maida regulator that you implemented plays a pivot role in getting a solid power supply for your Franken Crack, so that it minimizes the impact from different rectifier tubes or SS. The gigantic heatsink on the regulator also looks awesome btw, really love it! So you ditched the CRCRC filter in Crack PSU all at once, or you added the maida regulator after the CRCRC filter in case you still use the SS rectification?
 
Feb 1, 2021 at 10:16 PM Post #10,632 of 10,868

carlman14

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Fantastic, thanks a lot for letting us know the difference between tube rectification and SS rectification on Crack! No one has done that before!

You are correct, the slow start-up with tube rectification does help improve the working conditions for tubes and lengthen their lives. With SS rectification B+ hits tubes almost right away after amp is turned on, while tube rectifiers need some time to boil electrons off the cathodes.

I guess the maida regulator that you implemented plays a pivot role in getting a solid power supply for your Franken Crack, so that it minimizes the impact from different rectifier tubes or SS. The gigantic heatsink on the regulator also looks awesome btw, really love it! So you ditched the CRCRC filter in Crack PSU all at once, or you added the maida regulator after the CRCRC filter in case you still use the SS rectification?

So I went home and re-listened to tube vs SS rectifiers, and I half-take back what I said earlier. Take this with a grain of salt... but It sounds like the SS rectifier could have slightly faster, leaner bass, whereas the tube rectifier has a little bit fuller bass. The tube seemed to have a tiny bit more treble extension too. These differences are so minuscule that there's a chance I'm imagining it. So basically, what I said holds true. You're not missing anything with either type of rectifier.

To answer your question, I completely tore out the CRCRC (CLCRC in my case) in favor of the regulator. The order of PSU components now is PT -> rectifier -> 33uF input cap -> regulator -> output voltage. The regulator has insane DC filtering on it's own (about 20uV of ripple), which is way better than I would have gotten with the CLCRC filter. I am able to still use SS rectification because I have a plug-in SS rectifier that plugs into the octal socket where a tube rectifier would go. I attached a pic of the SS rectifier I'm using.

SS_rectifier.jpg
 
Feb 2, 2021 at 1:36 AM Post #10,634 of 10,868

evonimos

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I think, if one chooses to go with tube rectification then it's kind of 'counterproductive' to also apply an IC-based regulator in its path.
It sort of defeats the purpose of choosing to forgo with the sand based rectification in the first place. Especially when you place an IC down the line.

That's just me but hey, it is all about fun and that's why we do stuff.
 
Feb 2, 2021 at 12:40 PM Post #10,635 of 10,868

carlman14

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I think, if one chooses to go with tube rectification then it's kind of 'counterproductive' to also apply an IC-based regulator in its path.
It sort of defeats the purpose of choosing to forgo with the sand based rectification in the first place. Especially when you place an IC down the line.

That's just me but hey, it is all about fun and that's why we do stuff.

That's a great point. I was actually wondering about this myself when I was building this. I already had these parts on-hand, so I ran with it! I think I found a way to fit a couple chokes under the hood to try out a more traditional tube rectifier setup. And because this is the frankiest franken-crack, I think I just might try it!
 

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