Bottlehead Sex Kit Resistance and Voltage Check

[William Cheng]

Hi,

I have posted my question in the email, but I think I will post it here just to gather some advise before I conclude that one of the tube may be faulty.

I have wired up the kit and while checking the individual resistance, I encountered the following two problems.

1. Terminal 30,31,32, H2,H4,H5,H7 : fluctuating between 100 to 200 ohm.  Is this resistance value read normal since the manual indicates that it should wander in the tens or hundreds of Kohm.
All other terminals resistance checked are ok.
(Glow test was done successfully at the early stage with both tubes glow).

2. I tried measuring the resistance with the tubes insert and I got the the following reading.
- Terminal 2 : 2.8Kohm
- Terminal 16 : 200Kohm.
(Both values increase volume knob turns)

I tried power up the unit to check the Vdc and I got the following reading.
- Terminal 2 : 3.9Vdc
-Terminal 16 : 96Vdc


I suspect that one of the tube may be faulty, as both resistance and voltage reading at terminal 2 is out. I have swapped the the tubes and I got the opposite reading.

Cheers
 

[Paul Birkeland]

1. Terminal 30,31,32, H2,H4,H5,H7 : fluctuating between 100 to 200 ohm.
 Is this resistance value read normal since the manual indicates that it should wander in the tens or hundreds of Kohm.
All other terminals resistance checked are ok.

It looks like your meter is able to see through the diodes and capacitor and is measuring the resistors we use to reference these parts of the circuit to ground.  There's nothing wrong with these readings, and passing the initial glow test tells us that this part of the circuit is functional.

2. I tried measuring the resistance with the tubes insert and I got the the following reading.
- Terminal 2 : 2.8Kohm
- Terminal 16 : 200Kohm.
(Both values increase volume knob turns)

These values shouldn't change as the knob turns.  I would not power up the SEX until these issues are resolved, though the value at terminal 16 isn't unreasonable.

I tried power up the unit to check the Vdc and I got the following reading.
- Terminal 2 : 3.9Vdc
-Terminal 16 : 96Vdc

That just confirms the resistance issue.

I suspect that one of the tube may be faulty, as both resistance and voltage reading at terminal 2 is out. I have swapped the the tubes and I got the opposite reading.

Did the problematic voltage move to terminal 16?

[William Cheng]

These values shouldn't change as the knob turns.  I would not power up the SEX until these issues are resolved, though the value at terminal 16 isn't unreasonable.

Sorry. Only Pin 2 reading increases from 2.8kohm to 70kohm with volume knob turns.


Did the problematic voltage move to terminal 16?
[/quote]
Yes

[Paul Birkeland]

And terminal 16 shows the same problematic resistance with the volume knob turning?

If so, I would contact replacementparts(at)bottlehead(dot)com regarding a replacement tube.  Please do paste a link to this support thread and be sure to provide your name, shipping address, and order number if possible.

-PB

[William Cheng]

Hi PB,

So do I still need to ship back the faulty tube? I was told on the email that I need to do that in order to get a replacement.

Cheers

[William Cheng]

Hi,

I have recieved the replacement tube (GE) and everything is good now. Resistance measured at pin 2 & 16 is at hundreds of kohm now and does not change with volume knob turns. Connect it to my diy BIB speakers and also HD650 to listen before installing the C4S.

After installing the C4S, voltage measured at terminal OA : 126Vdc & OB : 146Vdc seems higher than the one indicated in the manual. Do note that i have two different brand tubes installed (GE & RCA).

Regards

[Paul Birkeland]

You have neglected to complete one of the steps when installing the C4S board.  Please review the instructions on page 15 of  the C4S installation manual.

-PB

[William Cheng]

Hi,

Wow...Thank you for the quick replied. I have clipped the 150K resistors and re-measured terminal 2 @ 68Vdc & terminal 16 @ 89Vdc now.

Its getting late here now. I will connect it to the spk & headphone tomorrow and report back on the sound.

Cheers

[William Cheng]

Hello,

As mentioned on my previous post, I will share my impression on the sound connecting to my headphone (HD6XX) and maybe little bit on my diyed speaker (a pair of Fostex FF165K mounted on BIB corner horn).

It took me a while as I was waiting for another well reviewed headphone amplifier (a Massdrop Cavalli Tube Hybrid) to arrive for reference. Do note that I am new to headphone and tube, I do not have any experience with the "TOTL" setup. I try not to go into discussion of the different type component or circuit topology, but just a general end product sound comparison. I hope this will encourage or help other newbies like me into making their decision on which headphone amplifier to get for their headphone.

My headphone setup
Source : Raspberry Pi 3 & Allo Digione
Amplifier : Bottlehead S.E.X 3.0 w C4S (8ohm) & Massdrop Cavalli Tube Hybrid (Stock EH tube)
Headphone : HD6XX

The impression I got listening from the BH amp after a few days is its ability to drive the HD6XX effortlessly with lots of dynamic & punch. The sound/headstage is especially good with live recording rock music ripped from CD. So when I received the MCTH amp, I hooked it up to the same setup and listened to it for a few days. First impression it has a much smaller sound/headstage, but a clearer high frequency. There is this emphasis on the high hat & cymbal which I somehow find it unpleasant and distracting listening to. On vocal it has this artificial 'sss' sound that make it sound 'digital' to me.

Played the same few familiar tunes and swapped the amps a few times has me concluded that the BH amp has a more expansive sound. It may not have the cleaner high frequency of the MCTH amp, but the huge and realistic sound/headstage the BH amp produce has really make up for it. It is especially enjoyable listening to it on loud and dynamic pieces.

Its late here and I will continue the second part (connecting to speaker) on my next post.

Wil