Recent Posts

Crack / Left Channel Spontaneously Dead
« Last post by Voxelr on Yesterday at 09:46:23 PM »
Hello! I have had an issue with my Crack + Speedball and would super appreciate some help, if possible. My knowledge and experience with DIY electronics is beginner, at best, so bear with me.

I had bought the Crack + Speedball kits a few years back, and was able to put them together and enjoy a working kit for a couple years, but I turned the amp on one day to discover that the left channel had gone out. Up until then, everything worked perfectly fine.

I've finally gotten around to pulling it back out and trying to get it to work again and could use some pointers.

A couple things to note:
  • The two LED's on the Speedball's big board towards the bottom right (picture attached) no longer light up.
  • I tried running the voltage tests in the docs. Of note, terminals 9 and OA both seemed to measure ~1.4V. Everything else appeared to fall within expected values

Otherwise, I have been unable to observe anything else wrong. Any help here would be appreciated! Thank you
Crack / Re: Low noise + wrong voltages
« Last post by vermeil on Yesterday at 10:28:25 AM »
We went over the soldered spots again and the voltages have not changed
Eros Phono / Original Eros resistance check tolerances
« Last post by dhherring on Yesterday at 09:59:25 AM »
I assembled my orginal Eros phono about 10-12 years ago.  At the time, I'm sure all the resistance and voltage test checked out, because I did use it for several years before getting away from playing LPs.

A couple of months ago, for some reason I decided to blow the dust off my LP's get back to spinning vinyl.  At some point while listening to an album, I left the volume up on my amp while flipping sides and noticed a strange hum.

After checking all of the components in the signal chain, I determined that the hum was originating from the Eros.  It was not strong enough to be heard while playing an album, but it was there.

I had a few othter things to take care of on my stereo, and today, I finally got around to troubleshooting the Eros.

As per the manual, I started with a resistance check.  Off the bat, I noticed that terminals 2, 4, 9, 10, 12, and 14 where all reading 19% to 20% high.  Terminals 6 and 7 tested fine.

I says, OK and turn the amp around to test the other terminal strip.

Immiediantly, I noticed a bit of a lead sitting across T21 and T22.  That didn't look right, so I went back through the dox and could not see that was ever supposed to be there.  So, I clipped it, and the hum went away. 

Yahoo!  Probable ground loop, and I ceased my troubleshooting at this point.

Away, with all that out of the way, my question (and purpose of this post) is do I need to be concerned with those higher than spec resistance values on the front terminal strip?   I know from my tinkering around with tube based guitar amps,  20% variances from the spec'd values are no big deal.  Just didn't know if that would apply to the Eros (or other Bottlehead components)


BeePre / Re: Resistance Check on 52
« Last post by Paul Birkeland on Yesterday at 09:18:43 AM »
I can't think of a way for the potentiometers to cause an issue.  If the resistors all measure correctly and the terminals where the resistors are soldered to show the proper resistances, that would contradict the information initially presented.
BeePre / Re: Resistance Check on 52
« Last post by Emoreigns on Yesterday at 08:16:28 AM »
Paul, all resistors to the pins seem good too- Only thing I can think of is maybe I accidentally installed the potentiometers wrong… Could this explain the incorrect readings? I attached a photo of the potentiometers- Thanks Paul
General Discussion / Website maintenance Monday night
« Last post by Doc B. on May 25, 2024, 03:07:30 PM »
The Bottlehead website will be down for maintenance Monday evening, May 27th.
General Discussion / Re: Transformers vs OTL
« Last post by Paul Birkeland on May 25, 2024, 11:31:03 AM »
Is this for speaker amps or headphone amps? 

OTL speaker amps tend to be a bit of a sticky topic on a lot of tube DIY forums.  There are not a whole ton of tubes that are all that happy passing the kinds of currents you need to drive a loudspeaker, so you end up needing a ton of valves to get the job done.  It's also tricky to maintain control of the current each valve draws without compromising the performance of the amp, and most often you'll see a generous lump of global feedback wrapped around these circuits to lower distortion and provide adequate damping.  On the positive side of OTL amps, the parts cost is quite low and there aren't any complicated audio transformers to design and manufacture. 

On the other side, SET amps typically use far more linear valves compared to those in OTL amps, far simpler circuits, usually a simpler power supply, but they require output transformers that are suitably made for audio performance, which isn't easy.  With the output transformer, however, the same amp can be used on a wide variety of different speaker impedances by adjusting how the speaker connects to the secondary of the output transformer.  To do this with an OTL amp isn't practical in any manner that I can think of. 

If we are talking about headphone amps, typically OTL amps are a bang for the buck product that will synergize really well with higher impedance headphones that work well with an amplifier that isn't voltage limited.  A good transformer coupled amplifier will typically outperform any OTL amplifier, but again this comes at the cost of highly specialized custom transformers that just aren't that easy to obtain. 
General Discussion / Transformers vs OTL
« Last post by Jimidick on May 25, 2024, 10:32:41 AM »
I am new to the forum and have questions. I have looked at kits from Bottle head and Transcendent Sound. What will I hear as the difference between using transformers and OTL? Other pros and cons? Thanks for your input.
Crack / Re: Low noise + wrong voltages
« Last post by Paul Birkeland on May 24, 2024, 10:36:04 AM »
One side of that board is not well soldered.
Crack / Re: Low noise + wrong voltages
« Last post by vermeil on May 24, 2024, 04:12:10 AM »
By the front C4S board, do you mean the small green one?

Would this be correct?