Crack;Bottlehead OTL
May 2, 2021 at 4:50 PM Post #10,922 of 11,049

Tom-s

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Today I build a Crack. It's the one from last weeks pictures. I cheated the Hammerite dry times of 2-4 weeks by using the oven.

So this morning I started the journey and am now enjoying the new build Crack!
Leds lit. All checked out first time. And it's sounding great!

Here it sits next to my other Crack. This one looks better! :rolling_eyes:

IMG_E8783.JPG

What's done!
In no particular order.
Input wiring and all signal wires are silver plated solid core copper.
FAQ #3 was implemented for optimizing usable volume range.
The volume pot is a stepped ladder time with SMD resistors. For better balance and sound quality.

The 6SN7 is used as input tube.
The Speedball small board was replaced by a switch board. This allows to switch between 3.6mA; 7,2mA and 8,2mA.
The first option is for 6SN7's. The other 2 options are for; par example; 12BH7's; E88CC's. Depending on the condition of the tube (and sound preference).

The power supply uses Shottky SIC diodes as bridge rectifier. And a Hammond 158M choke as second resistor in the power supply.
A film cap still needs to be installed; space is there. This is for another time. I preferred to do the base build without for troubleshooting reasons.
Same goes for the diode ground mod by PB. During this fase; i prefer a solid wire connection to ground.

For output caps Mundorf film types were installed.

It's

Edit: Don't know why i stopped at It's. Anyhow; i'll enjoy this on the coming evenings; as is. Next weekend. Building a base and the rest of the upgrades.

IMG_8778.JPGIMG_8779.JPG
 
Last edited:
May 2, 2021 at 6:05 PM Post #10,923 of 11,049

Mightygrey

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Today I build a Crack. It's the one from last weeks pictures. I cheated the Hammerite dry times of 2-4 weeks by using the oven.

So this morning I started the journey and am now enjoying the new build Crack!
Leds lit. All checked out first time. And it's sounding great!

Here it sits next to my other Crack. This one looks better! :rolling_eyes:

IMG_E8783.JPG

What's done!
In no particular order.
Input wiring and all signal wires are silver plated solid core copper.
FAQ #3 was implemented for optimizing usable volume range.
The volume pot is a stepped ladder time with SMD resistors. For better balance and sound quality.

The 6SN7 is used as input tube.
The Speedball small board was replaced by a switch board. This allows to switch between 3.6mA; 7,2mA and 8,2mA.
The first option is for 6SN7's. The other 2 options are for; par example; 12BH7's; E88CC's. Depending on the condition of the tube (and sound preference).

The power supply uses Shottky SIC diodes as bridge rectifier. And a Hammond 158M choke as second resistor in the power supply.
A film cap still needs to be installed; space is there. This is for another time. I preferred to do the base build without for troubleshooting reasons.
Same goes for the diode ground mod by PB. During this fase; i prefer a solid wire connection to ground.

For output caps Mundorf film types were installed.

It's

Edit: Don't know why i stopped at It's. Anyhow; i'll enjoy this on the coming evenings; as is. Next weekend. Building a base and the rest of the upgrades.

IMG_8778.JPGIMG_8779.JPG
Very neat job. Nice work! Making me want to upgrade my caps...
 
May 3, 2021 at 1:29 AM Post #10,924 of 11,049

HTSkywalker

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Today I build a Crack. It's the one from last weeks pictures. I cheated the Hammerite dry times of 2-4 weeks by using the oven.

So this morning I started the journey and am now enjoying the new build Crack!
Leds lit. All checked out first time. And it's sounding great!

Here it sits next to my other Crack. This one looks better! :rolling_eyes:

IMG_E8783.JPG

What's done!
In no particular order.
Input wiring and all signal wires are silver plated solid core copper.
FAQ #3 was implemented for optimizing usable volume range.
The volume pot is a stepped ladder time with SMD resistors. For better balance and sound quality.

The 6SN7 is used as input tube.
The Speedball small board was replaced by a switch board. This allows to switch between 3.6mA; 7,2mA and 8,2mA.
The first option is for 6SN7's. The other 2 options are for; par example; 12BH7's; E88CC's. Depending on the condition of the tube (and sound preference).

The power supply uses Shottky SIC diodes as bridge rectifier. And a Hammond 158M choke as second resistor in the power supply.
A film cap still needs to be installed; space is there. This is for another time. I preferred to do the base build without for troubleshooting reasons.
Same goes for the diode ground mod by PB. During this fase; i prefer a solid wire connection to ground.

For output caps Mundorf film types were installed.

It's

Edit: Don't know why i stopped at It's. Anyhow; i'll enjoy this on the coming evenings; as is. Next weekend. Building a base and the rest of the upgrades.

IMG_8778.JPGIMG_8779.JPG
Indeed very neat and innovative job 👍
 
May 3, 2021 at 2:03 AM Post #10,925 of 11,049

HTSkywalker

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Today I build a Crack. It's the one from last weeks pictures. I cheated the Hammerite dry times of 2-4 weeks by using the oven.

So this morning I started the journey and am now enjoying the new build Crack!
Leds lit. All checked out first time. And it's sounding great!

Here it sits next to my other Crack. This one looks better! :rolling_eyes:

IMG_E8783.JPG

What's done!
In no particular order.
Input wiring and all signal wires are silver plated solid core copper.
FAQ #3 was implemented for optimizing usable volume range.
The volume pot is a stepped ladder time with SMD resistors. For better balance and sound quality.

The 6SN7 is used as input tube.
The Speedball small board was replaced by a switch board. This allows to switch between 3.6mA; 7,2mA and 8,2mA.
The first option is for 6SN7's. The other 2 options are for; par example; 12BH7's; E88CC's. Depending on the condition of the tube (and sound preference).

The power supply uses Shottky SIC diodes as bridge rectifier. And a Hammond 158M choke as second resistor in the power supply.
A film cap still needs to be installed; space is there. This is for another time. I preferred to do the base build without for troubleshooting reasons.
Same goes for the diode ground mod by PB. During this fase; i prefer a solid wire connection to ground.

For output caps Mundorf film types were installed.

It's

Edit: Don't know why i stopped at It's. Anyhow; i'll enjoy this on the coming evenings; as is. Next weekend. Building a base and the rest of the upgrades.

IMG_8778.JPGIMG_8779.JPG
What cans are you using with the BHC
 
May 5, 2021 at 1:18 PM Post #10,926 of 11,049

skhan007

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Question about line level between the DAC and BHC:

I'm running my DAC (RME ADI-2) at -5dBu into the BHC. At this level, I find the BHC volume at about 9 or 10 O'Clock, which I think is pretty low on the dial, but sufficient and comfortable volume for me and my ZMF cans (about 70 dB listening level).

Curious if the BHC needs to be up at Noon or higher to get the proper tube benefits (i.e. the qualities we tend to love about tubes being driven at sufficient levels). I can certainly use my ears and dial down the output of the DAC a bit and turn up the volume on the BHC, but mostly curious how other people run their signal into the BHC?
 
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May 5, 2021 at 1:23 PM Post #10,927 of 11,049

HTSkywalker

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Question about line level between the DAC and BHC:

I'm running my DAC (RME ADI-2) at -5dBu into the BHC. At this level, I find the BHC volume at about 9 or 10 O'Clock, which I think is pretty low on the dial, but sufficient and comfortable volume for me and my ZMF cans (about 70 dB listening level).

Curious if the BHC needs to be up at Noon or higher to get the proper tube benefits (i.e. the qualities we tend to love about tubes being driven at sufficient levels). I can certainly use my ears and dial down the output of the DAC a bit and turn up the volume on the BHC, but mostly curious how other people run their signal into the BHC?
Normally you crank the DAC volume all the way up into the BHC, the less volume used on a tube amp the less audible humming and hissing.
 
May 5, 2021 at 2:22 PM Post #10,928 of 11,049

Galapac

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Question about line level between the DAC and BHC:

I'm running my DAC (RME ADI-2) at -5dBu into the BHC. At this level, I find the BHC volume at about 9 or 10 O'Clock, which I think is pretty low on the dial, but sufficient and comfortable volume for me and my ZMF cans (about 70 dB listening level).

Curious if the BHC needs to be up at Noon or higher to get the proper tube benefits (i.e. the qualities we tend to love about tubes being driven at sufficient levels). I can certainly use my ears and dial down the output of the DAC a bit and turn up the volume on the BHC, but mostly curious how other people run their signal into the BHC?
I guess it depends on your use. For me I use a FiiO DAP so I run an RCA to USB-C line that reaches my chair. I set the tube amp anywhere from 10 to noon on the dial and then control the volume from my DAP to increase/decrease the volume from my chair. I get very minimal hum depending on the tubes, if it is a 6080 very minimal, a 5998 has a bit more due to the gain.
 
May 7, 2021 at 7:19 AM Post #10,931 of 11,049

xkonfuzed

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I have found that lower the input voltage into the Crack, the more I can avoid the initial channel imbalance from the potentiometer. Also it seems that with a 3V input form my Mojo I am rarely ever going past 11-12 on the knob on any of my headphones. When I run it at 2V I can get a lot more out of the amp.
 
May 10, 2021 at 12:20 PM Post #10,934 of 11,049

DeweyCH

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Upgraded my Crack - after having it built for a couple of months, I finally added the Speedball package and replaced the stock pot with a 20k DACT-style stepped attenuator.

Other than being an idiot and miswiring the attenuator the first time, it sounds really great! I re-did the braided wire from the inputs to the pot, too. All in all, a DEAD SILENT noise floor, whereas the old pot/lack of Speedball had some static popping up enough to be annoying in the right channel.

Now I just need a better knob, because this one I got from eBay is just absurd looking.

IMG_1281.JPEG


Philips ECC82/12AU7 in the front with a RCA 6AS7 in the back. Not my everyday tubes, but a couple that are nice but I won't be too sad if I f'ed up something in the wiring and they melted. But they didn't. So huzzah.
 
May 10, 2021 at 12:41 PM Post #10,935 of 11,049

xkonfuzed

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Looks nice! Do you like the sound with Speedball more, or without?

I'm running JAN 6AS7G as well. Really smooth tube. I'm looking at input tubes to replace my RCA cleartop, to me its a bit too forward and can end up sounding too shouty in mid-forward headphones. Do you like the Phillips ECC82?
 

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