Recent Posts

41

Kaiju Stereo 300B amp / Re: Painting Suggestions Concerns for PC-5's

« Last post by Emoreigns on November 20, 2024, 06:02:52 AM »

Is it necessary to paint the PC-5's to prevent rust like the transformer bell/ caps?

I'm right at the point of installing these in my Kaiju build right now, and figure it will be easier to paint them before they are attached haha-

I'm not sure if it is proper protocol to reply to an old thread like this for a similar topic, or if it is correct just to start a new thread!

Thanks for the help everyone!

42

Technical topics / Re: Fixed attenuator for balance control?

« Last post by Paul Joppa on November 20, 2024, 04:04:55 AM »

The problem with that kind of attenuator is that the impedances are important but never provided by the maker. (I think that's because the explanation it thought to be too complicated for the average customer.)

I have some 12dB Harrison Labs units with 10K input impedance, which is pretty low for Eros. One person, somewhere on the Web, has measured a Rothwell - I think it was a 10dB unit - at 100K which is good for Eros, but it's output impedance would be around 30K, which means it would likely change the attenuation of the switched controls.

Technically, you are better off rolling your own.

43

Technical topics / Re: Fixed attenuator for balance control?

« Last post by hmbscott on November 19, 2024, 08:30:33 PM »

It contains a very simple circuit called an LPad, that consists of two resistors. One connects signal to ground (R2) and the other connects inline in the signal path (R1).

The trick is to figure out what two resistor values to use, which is complicated by the fact that the LPad R values depend to a degree on the impedances of both the source and driven components (driven impedance typically is the most important).

It's possible to buy the RCA shell and add your own R1 & R2 resistors wired as described to make your own LPad attenuator with the attenuation you want.

Assuming the impedance your driving is 50kOhm. A pair of resistors that will preserve that 50KOhm impedance while introducing approximately 1.5dB of attenuation is R1 = 23.2kOhm and R2 = 124kOhm. I believe both values should be available as 1% tolerance resistors. If anyone would care to double check my numbers, I'd appreciate it. However, I think if you build one using close to those values, it should be about the right attenuation.

44

Technical topics / Fixed attenuator for balance control?

« Last post by phatfish on November 19, 2024, 06:29:56 PM »

I have a bit weaker hearing in my left ear and was happy to add a balance control to my crack.
https://forum.bottlehead.com/index.php?topic=15470.0

Well, I've got the upgrade bug and I'm planning on a mainline.  I'm looking for the best way to attenuate the right channel a fixed 1 - 1.5db between my EROS2 and future mainline.  I'd prefer not to add a balance pot to the mix with the assumption that'll defeat the benefits of the stepped attenuators.  My thought was that I could add a bit of fixed attenuation via an RCA adaptor.  Something like this:
https://www.parts-express.com/RCA-Line-Level-Attenuator-1-dB-266-230?quantity=1

I haven't been able to find something like this in stock anywhere (only much larger values).  I assume it's just a resistor in there and is something I could create myself, but I have no idea what value I would need.  Any advice on the best way to accomplish this?  I'm also curious the ideal place in the audio stream for something like this: Turntable > Phono Preamp > Amp > Headphones?

Thanks for reading.

45

Moreplay / Re: Moreplay add ons - were there still any upgrades planned?

« Last post by cpditter on November 19, 2024, 11:53:59 AM »

I too was too slow to order as we were on vacation and thought, "Well I'll just order when we get home"...oh well, hopefully will get in on the next run!

Thanks for the explanation on why the small first run.

Thanks,
Chuck

46

Eros Phono / Re: Clogged tube adapter

« Last post by Paul Birkeland on November 19, 2024, 03:27:07 AM »

Yes, that is really an unusual problem.  I've probably handled over 1000 of these little 9 pin sockets over the years, and I can't ever remember running into that!

47

Crack / Re: Right channel hiss

« Last post by Paul Birkeland on November 19, 2024, 03:26:29 AM »

Trying different tubes may be a helpful datapoint for something like this.  How long have you run the amp with the tubes you have now?  Sometimes you'll need to let the tube set you have run for a few days straight to allow the tubes to get nice and hot and issues like this will clear on their own. 

It's also worth noting that you can poke around the circuit with a wooden chopstick to see if there's a spot you can poke that produces or changes this noise, and that can help direct your resoldering efforts.

48

Crack / Right channel hiss

« Last post by Pharane0 on November 19, 2024, 01:34:01 AM »

Hello,

I finished building my crack + speedball this summer. But since the build, there is a noticeable slight hiss / static / white noise coming from the right ear of my headphones. This hiss happens even without the input RCAs plugged in. It also happens even if the volume pot is all the way to 0 or OFF. I tried my HD6XX and then HD800S with the same result. I tried plugging the amp in a different socket and then in a different room in the house with the same result.

To give you a bit more info on the hiss, here is what happens chronologically when I start the amp :
1. First instant, a "surge" of hiss in the LEFT channel
2. Quickly this LEFT hiss disappear and becomes inaudible
3. Then a surge of hiss in the RIGHT channel (as if it transferred from left to right, but i'm not sure if that's thing in electronics or not)
4. The right hiss kinda progressively becomes quieter but is still audible and that"s the issue


The amp passed the voltage tests present in the manuals. I think, if i remember correctly, that this hiss was present even before the speedball upgrade. I though the speedball would reduce it to zero but I was wrong. Today I re flowed all the solder joints with a bit more solder. I also checked continuity with a ohm-meter. This unfortunately didn't solve the issue. I "cleaned" the tubes pins by inserting them repetitively, didn't solve it either.

Now I don't really know what else I could check, so if you have experience with a similar problem, can I ask for your help please ? I'm thinking about ordering a set of tubes to see if the problem comes from the tube but if you have any idea before I order them please feel free to tell me. Thank you !

49

Eros Phono / Re: Clogged tube adapter

« Last post by maarten on November 19, 2024, 12:41:55 AM »

In the end used a small philips screwdriver and drilled through the glass -- it is indeed a glass substance. I was working at night and wanted to avoid sound

Thanks - was mostly sharing so that people who run into the same know how to find this -- I bent one of the lamp legs before I figured out what was happening - but no harm done they're all glowing brightly now.

50

S.E.X. Kit / Re: Sub out - like Stereomour?

« Last post by dpwoos on November 18, 2024, 08:32:31 AM »

That's good news - thanks! In fact, I think I will add the sub outs to both of the S.E.X. amps while I am at it. On the Stereomour we used two 2-lug terminal strips and shielded 2-conductor - pretty neat and performs perfectly.