Recent Posts

1

Kaiju Stereo 300B amp / Re: driver testing

« Last post by joralieu on Today at 04:43:50 PM »

CS4 jumpers look good to me and don't see any obvious miswires or broken wires, checked them for continuity. Any clues where else I could look?  It is probably something simple , just not finding it.

2

Crack / Re: Volume mod combined left and right channels (and sounds weird)

« Last post by loadexfa on Today at 03:26:00 PM »

From looking more into this, it appears I need a second 33K resistor: https://forum.bottlehead.com/index.php?topic=6982.0

I think the FAQ should clearly state that two 33k resistors are needed, I did not get that from this sentence: "Attach and solder one 33K resistor between each outer pair of lugs on each level of the volume pot and the ground lugs on the pot."

I attached one 33K resistor to all of the lugs indicated. I assume that is the reason for my issue?

3

Crack / Volume mod combined left and right channels (and sounds weird)

« Last post by loadexfa on Today at 03:01:13 PM »

I think I followed the FAQ correctly and installed the two 75k resistors and one 33k. After installing them (and passing all resistance and voltage checks), the volume pot has more room as expected. But the music sounded off, especially the staging. When I removed one RCA input, I still heard the same music from both left and right channels in my headphones. I took a pic of my mod and the bags for the resistors to confirm I used the correct ones.

4

Mainline / IERC Tube Shields without Bases

« Last post by Art Andrews on Today at 01:42:56 PM »

I recently purchased an unfinished Mainline kit from a friend. It has most components but does not have the 9-pin shields/shield bases (it does have the 9-pin connectors) for the two large tubes. In researching these, several people mentioned IERC tube shields, and even Doc B. mentioned them.

Since I don't have the shields with the kit, are the IERCs a good alternative?

I see sets on eBay, but there are no bases, and my searches have turned up no bases.

I saw a post (here: https://forum.bottlehead.com/index.php?topic=10405) in which Doc B. says, "If a shield isn't grounded, it's not shielding."

Does that mean IERC shields, as I am finding them, without bases, shouldn't be used?

5

Crack / Re: Turntable-like static in left channel only (not volume dependent)

« Last post by big_n8_dawg on Today at 01:19:18 PM »

Ah, I see that you've tried different tubes, never mind on the pin cleaning then.  Please do not attempt to clean or mess with the tube sockets, as that tends to make new problems that aren't otherwise there. 

Just to rule things out, I would also add this mod:
https://forum.bottlehead.com/index.php?topic=11676.0
It's not all that likely to resolve your issues, but it could help.  Also be sure that all your hardware is nice and tight.

Thanks Paul, I have ordered a 10-pack of your recommended diodes from that thread and I will give that a shot.
I will also recheck all the hardware connections and put a little more torque on all of them.

Have you measured voltages when the amp is making noise? One possible source of that kind of noise is a resistor that is either not well.soldered or internally damaged. If that is the case it could make voltages shift around when it is misbehaving as it heats up.

Thanks Doc, I have not measured voltages while actively listening to the noise. (I have only measured with no headphones connected.)
I will recheck the voltages while listening, and look for any fluctuations in conjunction with the noise.
Heating up does seem to be a factor, as it is usually quiet initially, only to manifest after 30 seconds to a minute, so I will make sure it is warm for the checks.


Thank you both for your replies.

Unfortunately, the soonest I might be able to work on the amp again would be this weekend, but I will report back when I have an update.

Also, I can't believe that I didn't think about this before, but would it be of any benefit if I were able to capture an audio recording of the noise?

Thanks Again,
Nate G

6

Mainline / Re: Voltage check issue / page 52 / 6.3vDC reading [resolved]

« Last post by N72826 on Today at 11:41:42 AM »

How do the pads look for the 1085 regulator?  How do the 124 and 499 ohm resistors measure now?

Not home at the moment but I will send a photo later. I can see that being an issue because the 1085 had already been soldered and the leads had been clipped. So when I went to solder it again on the regulator board, the leads just barely made it to the pad. And what readings should I expect when testing the 124 and 499 ohm resistors?

7

Mainline / Re: Voltage check issue / page 52 / 6.3vDC reading [resolved]

« Last post by Paul Birkeland on Today at 11:35:07 AM »

How do the pads look for the 1085 regulator?  How do the 124 and 499 ohm resistors measure now?

8

Stereomour II / Re: Stereomour II mods

« Last post by hmbscott on Today at 11:08:02 AM »

I installed the shunt regulator board a couple days ago, and the DC filament board today. The shunt regulator impacted high frequency performance the most obviously, introduced a touch of sparkle and high end clarity. To me, sonically similar to adding a Speedball to a Crack. Sounds even more awesome!

The DC board completely silenced a pretty loud heater hum, which prior to, could be heard from 10 feet away, so very nice!

Like a dunce, I was bending the lead of the very last 0.13 ohm 3W resistor needed to complete the DC filament install, and suddenly the lead snapped off, WTF ?!?! Because, as I discovered, I was "bending" it with my side cutters, doh. F it! Decided to voltage test the amp anyway even though it was missing that one resistor. After staring at the circuit for a couple minutes I realized the added resistors increase the voltage feeding the heater, being paralleled with the existing 0.15 ohm resistors, dropping the resistance to about 0.07 ohms. So, testing without one should be safe.

Turns out in my case my heater voltages are already running a bit hot, the socket with both of the new 0.13's installed was running too high (2.71 VDC), vs almost too high on the socket where I'd only installed one of them (2.62 VDC). I ended up removing all of the new 0.13 ohm resistors to get the correct target 2.5 VDC on both sockets. So accidentally cutting off that lead was the accidentally right thing to do. Hah.

And with that, my stripped-down pimped-out Stereomour II is officially finished. The Stereomour/Moreplay is an absolutely delicious sonic combination, thanks to the awesome crew at Bottlehead for creating them! And thanks to all who have offered encouragement and advice. Much appreciated!

9

Mainline / Re: Voltage check issue / page 52 / 6.3vDC reading [resolved]

« Last post by N72826 on Today at 08:31:21 AM »

Nevermind I guess. I replaced the regulator and now 6.3vDC is reading ~11.2v and 275vDC is reading ~375v

I'm lost.

10

Mainline / Re: Voltage check issue / page 52 / 6.3vDC reading [resolved]

« Last post by N72826 on Today at 06:55:08 AM »

Ah fuck. I found the culprit in another thread of someone having the same issue where you determined the issue was in an incorrect regulator, not the resistors.
https://forum.bottlehead.com/index.php?topic=13786.msg125850#msg125850
I mounted the LM1085 on one of the c4s boards. At least I resolved the question, now the hard part is going to be exchanging the MJE5731A and LM1085. I saw in that thread you suggested "The blue spring loaded solder vacuum pump will do this job pretty well." so I will have a go at that instead of solder wick because as I said in my previous reply, solder wick wasn't really doing jack on those massive heatsink pegs.

Edit: Just remembered I don't need to remove the heatsink, I just unscrew the regulator and desolder it.