Modifications to run e80cc/12bh7a/5687 for Crack+Speedball

[kscwuzhere]

Is your amp silent when using the 5687?  I substituted the above referenced LED with a different one with identical Vf (@20ma) but 2 orders magnitude lower luminous intensity, and although my voltages are right where they should be, I get a very faint hum when no signal is present. The hum is there with 3 different 5687 tubes, so I figure it could be the LED since I've seen mention of noisy LEDs before. The amp is dead silent when switched to use with 12AU7.

I get no hums whatsover, its black as can be.

[Maxhawk]

I've made another PCB to clean up my 5687 switch. It helps to clean up the implementation shown here because you no longer need multiple wires to certain connections. I haven't installed it yet because I don't have any more of the solid core wire that came with the kit, and I usually end up breaking one or more of them because the solid core doesn't like to be bent more than once. I'll install it once I have extra wire on hand.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FviOpCJjl.jpg&hash=b86f5a36f1686f351e4d05fc77980463f021084a)

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FB8I3Jywl.jpg&hash=e344eb5acba04d24b408ff331061262a30eb1058)

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FpUeLoVfl.jpg&hash=09ac318005f0add053dd6a88c06538518ca4c4f8)

[kscwuzhere]

Beautiful work my man! I know what I'm gonna do now.

[Tom-s]

Any updates? I wish i could make a PCB myself.
Everybody still in love with their 5687 or got something better?
Deciding on pin-out switch mods.

[Rhok]

I just tried out a 12BH7A and love it, however, voltage at T1/T5 are low, 50, and 53 - considering replacing the R1 resistors for lower resistance to bring the voltage up - one question (that may have been answered already, sorry if it was):

Is it unsafe to run it at low voltage? what is the danger if so?

[Paul Birkeland]

Is it unsafe to run it at low voltage? what is the danger if so?

It's not unsafe, but that voltage biases the 6080 in the Crack, and if this voltage is too low, the tube will not be properly biased, and you won't get optimal performance out of the amplifier.

[Rhok]

It's not unsafe, but that voltage biases the 6080 in the Crack, and if this voltage is too low, the tube will not be properly biased, and you won't get optimal performance out of the amplifier.

Understood, I'll wait until I get my new headphones to see if I still like the 12BH7A as much as I currently do before making any changes.

Currently running HD 650's, in the mail a HD 800 S is on the way.

You guys are fond of the HD 800's from what I've seen around, any interest in the new variant?

[Finkä]

Hello from Switzerland

First, i want to say thank you to the pioneers of this topic (especialy kscwuzhere,onelivewire, Snarii, and Maxhawk) and of course thank you to the Moderators in this Forum. With the information in this thread i was able to create (let create) two pc boards to handle the diffrent voltatges on t1 and t5 and to switch between stock and 5687/7119 tubes.

Here some pictures with a lousy smartphone cam:

(https://img5.picload.org/image/wicrorw/dsc_0139.jpg)
Hm... in this picture the blue light shines like a house with freaky christmas decoration. In reality its not that intense.
(https://picload.org/image/wicroog/dsc_0136.jpg)

As you can see (or not) i drilled a hole in the chassic plate to fix the small pc board. Spontaneous i was not able to get some nylon standoffs therefore i did it that way. I would not recommend this, because when you or someone else switch between the stock/5687 mod accidentally you could possibly break a tube. In my case the amp is far away from strangers hands and the switch is behind the input tube, so i got that goin for me

A note to the post #211 from maxhawk.  On the small pc board to switch between stock/5687 there is a solder joint named B+. On the big pc board and on the two small ones of the the speed ball uprgrade the B+ solder joints are connected to 2U. But in my understanding this solder joint should be connected with T1 (1U). It was a bit confusing for me

Best regards

[Tom-s]

Another 5687 switch board here.
Really like this this tube (Amperex 7119 PQ), lush, big soundstage with loads of details.
Worth it IMO.
All three (5687, 12bh7 and e80cc) are special sounding tubes in there own way.
Nice flavors or "sound seasoning" compared to the standard 12au7's.

[guildenstern]

I'm hoping one of you technically savvy forum members can help. On Head-Fi I bought a modded Crack from a BH forum member -- great build and very enjoyable sound. What I can't get from the builder is a clear explanation about which way the switches should be set for 12AU7 and which way for E80CC. Here are pictures of the resistor switch assembly he devised, taken by the builder of the amp. If you can use these pictures to deduce the proper switch positions for 12AU7 vs E80CC, I would appreciate it. Especially if you can explain in "for dummies" terms (as I readily confess I am). Thanks in advance.

6SN7,12AU7 =( T1 75V / T2 76V )-very happy with this 
E80CC=( 85/86V )
12BH7A=(55/57V )

Thank you Sir !!

[Doc B.]

Those switches are way too small. You should upgrade to something like this.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.hometrainingtools.com%2Fmedia%2Fcatalog%2Fproduct%2Fcache%2F1%2Fimage%2F9df78eab33525d08d6e5fb8d27136e95%2FE%2FL%2FEL-SWITCH2.jpg&hash=59cd93e1f4f7277a448a8fe87073756bfa22b9ff)

[guildenstern]

Those switches are way too small. You should upgrade to something like this.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.hometrainingtools.com%2Fmedia%2Fcatalog%2Fproduct%2Fcache%2F1%2Fimage%2F9df78eab33525d08d6e5fb8d27136e95%2FE%2FL%2FEL-SWITCH2.jpg&hash=59cd93e1f4f7277a448a8fe87073756bfa22b9ff)

I'm actually thinking of something a little more retro and heavy duty...

[Maxhawk]

I'm hoping one of you technically savvy forum members can help. On Head-Fi I bought a modded Crack from a BH forum member -- great build and very enjoyable sound. What I can't get from the builder is a clear explanation about which way the switches should be set for 12AU7 and which way for E80CC. Here are pictures of the resistor switch assembly he devised, taken by the builder of the amp. If you can use these pictures to deduce the proper switch positions for 12AU7 vs E80CC, I would appreciate it. Especially if you can explain in "for dummies" terms (as I readily confess I am). Thanks in advance.

In the speedball circuit there's a series resistor from B+ to the 2N2907 transistor that sets the current flowing through the tube. The stock 12AU7 uses a 238 ohm resistor while the E80CC requires 470 ohms. In the photo you can see that the switch is connecting a 470 ohm resistor in parallel with the resistor on the board (which looks to be 470 ohms).  When the switch is open it's set for an E80CC. When the switch is closed, it's set for a 12AU7.

I'm not familiar enough with rocker switches to tell you which position is which (I only know toggle switchs). You can take a DVM and measure the resistance on the switch between the middle and right terminal.  470 ohms = E80CC and 235 ohms = 12AU7.

[guildenstern]

In the speedball circuit there's a series resistor from B+ to the 2N2907 transistor that sets the current flowing through the tube. The stock 12AU7 uses a 238 ohm resistor while the E80CC requires 470 ohms. In the photo you can see that the switch is connecting a 470 ohm resistor in parallel with the resistor on the board (which looks to be 470 ohms).  When the switch is open it's set for an E80CC. When the switch is closed, it's set for a 12AU7.

I'm not familiar enough with rocker switches to tell you which position is which (I only know toggle switchs). You can take a DVM and measure the resistance on the switch between the middle and right terminal.  470 ohms = E80CC and 235 ohms = 12AU7.

Thanks very much, Maxhawk. I will dig out the VOM and give it a try. Thanks again.

[cddc]

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