Bottlehead Forum
Bottlehead Kits => S.E.X. Kit => Topic started by: Darkblade48 on July 03, 2020, 01:17:18 PM
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Just as a quick forward - if there is a better place to put this, please let me know! I'll be keeping/limiting my updates to this thread only
I was just very excited to show my progress on the S.E.X kit so far - it is no where near complete yet as I just finished the tube heater glow test. Nevertheless, a very exciting moment for me (nothing exploded yet, hurray!), and I thought I'd share it with everyone.
As an aside, is it normal for the tubes to be fairly difficult to get into/out of their sockets?
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Yes it’s normal. Looks good!
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From the looks of it, it is coming out really well. Just a quick question, did you powder coat the chassis plate and the transformer caps?
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From the looks of it, it is coming out really well. Just a quick question, did you powder coat the chassis plate and the transformer caps?
Nope, the topside of the chassis plate was painted with several coats of semi-gloss black and then clear coated (also semi gloss).
The transformer caps and choke bell ends were sanded down to remove any extra protective lacquer, and then again clear coated with several coats of semi-gloss clear coat.
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did you powder coat the chassis plate and the transformer caps?
You definitely do not want to powder coat the chokes.
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So this is a long overdue update (yes, one could say I took my sweet time, slowly enjoying and savouring the build process!).
I finished gluing, prepping and staining the alder wood (ended up using a wood pre-conditioner, as recommended, followed by a dark walnut stain). It came out relatively well, considering it was my first time doing any kind of woodworking. Afterwards, several polyurethane clear coats (thinned down with some mineral spirits, also as recommended by some helpful folks online) and polishing, and the case was done.
I also finished up the electronic side of things, while waiting for the case to dry. It all came together earlier this week, and I am very excited to report that there were no mishaps along the way (all resistance checks and voltage checks went well, without any hitch). All that soldering practice came in handy ;) I swapped out the stock potentiometer for a Blue Alps (RK27) that I ordered from Mouser, and thankfully, there were no mishaps there either.
An interesting point that I noted was that the amp was not 'black' (as in, the noise floor seemed high - there was some static/hissing, even with no music playing). Points that I noted were:
- With nothing plugged into the RCA inputs, there was no noise in the headphones, even if I turned the volume knob all the way up
- With a Topping D50 DAC plugged into the RCA input (which was plugged into my computer via USB), there is no noise to around the 10 o'clock position of my pot (no music playing). Then, there is some hissing beyond this point (though, it is worth noting that listening at a volume past 11 o'clock is already intolerable)
- With a portable DAP (digital audio player; Cayin N3) plugged into the RCA input (via 3.5 mm line out), noise is not heard until around the 3 o'clock position
This leads me to conclude that there is nothing wrong with the amp itself, but that most likely, the noise is coming from the DAC (or a likelier culprit, my computer). I haven't installed the C4S upgrade yet, as I'm still listening to the stock S.E.X, but will experiment with it in a month's time or so, to see if the noise floor can be improved upon.
Finally, a question regarding amp usage: when I power on/off the amp, is it OK to leave my headphones plugged in? I have been taught that I should turn on the amp, then plug in my headphones. When turning off the amp, I should unplug the headphones before turning off the amp. However, I'm lazy, so was wondering if I could just leave my headphones plugged in all the time...There is some confusion for me here, as I know there are some amps that also require a resistive load across the jack when turning on, but I am not sure what is the case for the S.E.X
Sorry for the long post/comments/question! As always, I look forward to everyone's replies
Summary of photos:
1) Staining completed
2) A decent shot of the amp
3) The amp in its new home. Excuse the mess of cables (perhaps they might be causing my noise!)
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This leads me to conclude that there is nothing wrong with the amp itself, but that most likely, the noise is coming from the DAC (or a likelier culprit, my computer). I haven't installed the C4S upgrade yet, as I'm still listening to the stock S.E.X, but will experiment with it in a month's time or so, to see if the noise floor can be improved upon.
https://forum.bottlehead.com/index.php?topic=11676.0 (https://forum.bottlehead.com/index.php?topic=11676.0)
You could try this mod, it may keep some of that grunge out.
Finally, a question regarding amp usage: when I power on/off the amp, is it OK to leave my headphones plugged in?
Yes. The SEX amp does not need a load on the speaker terminals and it won't do any harm to your headphones if they are plugged in during powerup. Your confusion is well founded, there's a lot of misinformation out there!
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Lovely build, congrats.
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Nice! The polished steel against the black top plate really works. Enjoy.
Karl
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Looks great, congrats!
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Thank you everyone for their kind words so far!
https://forum.bottlehead.com/index.php?topic=11676.0 (https://forum.bottlehead.com/index.php?topic=11676.0)
You could try this mod, it may keep some of that grunge out.
Excellent, thank you for the quick reply! I just want to confirm that I want to replace the drain wire (i.e. remove the drain wire completely) between ground of the IEC outlet and the chassis ground tab (circled in red in the attached photo) with two diodes as specified in the linked thread (one diode going one way, and another the other way). For the picture, you can ignore the (lack of) wires, as it was taken before the S.E.X was completed
I saw from the other thread that you recommended a STTH2R06; however, checking my box of jellybean components, I have the following:
1N4148
1N4007
1N5819
1N5399
1N5408
1N5822
FR107
FR207
I am supposing that the average forward rectified current rating of the diode should be at least 2A, and non-Schottky, which eliminates the 1N4148 (150 mA), 1N4007 (1 A), 1N5819 (1 A, Schottky), 1N5399 (1.5 A), 1N5822 (3A, but Schottky), and FR107 (1 A)
Of the two remaining choices, I have the 1N5408 (general purpose, rated for 3 A average forward rectified current, 1000 V) and a FR207 (fast recovery, 2A, 1000 V).
Would either of these be a suitable replacement for the STTH2R06?
Edit: It appears that the 1N5408 should work, as mentioned in the other thread! My apologies for not looking more carefully
Edit 2: It appears that I should be looking at peak forward surge current instead, and not the average forward current. If this is the case, would the above non-Schottky diodes work? The 1N5408 has thick leads, so if possible, I'd love to replace them with something smaller like a pair of 1N4007.
Yes. The SEX amp does not need a load on the speaker terminals and it won't do any harm to your headphones if they are plugged in during powerup. Your confusion is well founded, there's a lot of misinformation out there!
This is good to know! I was a bit concerned because upon powering on, I can hear a bit of hum as soon as the switch is flipped. I was wondering if this might cause damage.
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The 1N4007 has adequate surge current rating to pop a circuit breaker, so you may use it.
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The 1N4007 has adequate surge current rating to pop a circuit breaker, so you may use it.
As always, thank you for the speedy response, Paul!
So what I should be looking at is the peak forward surge current (IFSM) of the diode, rather than the average forward current?
If this is the case, then something like a 1N4148, with peak forward surge current of 2A would not work, as it will not pop a circuit breaker (and I assume, it will end up "sacrificing" itself instead?)
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Yes, IFSM is what you want to keep an eye on. A 1N4007 has a 30A rating, which is more than enough to do the job. You don't want the diode popping before the breaker does. The 1N4148 would just explode under a catastrophic fault.
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Thank you for the quick lesson, Paul. As always, you've been very helpful!
I'll install the double diodes tomorrow night, and see if there's any improvement.
Thank you again.
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Sorry for the incessant questions, but I just want to be sure of what I'm doing.
I should be cutting and removing the drain wire that goes from IEC ground to chassis ground (circled in red)
I am guessing the wire that connects the A-side choke to chassis ground (blue) can stay where it is, and does not need to be hooked up directly to the IEC ground?
I also assume that the other wires are fine where they are?
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Yes, just replace the wire in red with the antiphase diodes. You may find it easier to clip that wire in the middle and then bend each end into a loop, then attach the diodes to those.
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As always, I have to say thank you for all the help and speedy responses, Paul!
The pair of diodes worked wonderfully. Absolutely black background now. Now to enjoy some more music!
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I'm glad that took care of it for you. As always, we are here if anything else comes up.