The Immortal Amplifier

[R.G.]

It is too bad really as forums are a better source for the information because it is all saved and is searchable, but the facebook groups just scroll down and it's gone.

I agree. FB is pretty much worthless for the kinds of things discussed here.

Yep, completely agree.

I suspect that it's actually a little worse than that. I wound up moderating a "technical" forum on fb. I was appalled at the sheer volume of snotty replies to beginner questions, so I took sane answers, researched the deeper ones, and wrote up a FAQ for the forum. The people with genuine questions loved it, the snotty ones wound up getting more and more silent, so the technical quality went way up as the volume of chaff went down. Good, yes?

But the sheer volume of traffic also went way down. I may have accidentally mortally wounded the group by improving the signal to noise ratio.

It struck me that fb is all about sheer volume of chatting, snarking, and so on - low-content gabbing. They're all about "engagement". It's almost like it's worthless for technical stuff by design. Technical answers are (or should be) either factually correct or not, so they don't spawn endless strings of gabbing. FB's business is, after all, eyeballs and clicks to gather user data, no particular other purpose. FB is built on endless back and forth, not anything specific. Specificity may be counter to their purpose.

[jabguit]

It struck me that fb is all about sheer volume of chatting, snarking, and so on - low-content gabbing. They're all about "engagement". It's almost like it's worthless for technical stuff by design. Technical answers are (or should be) either factually correct or not, so they don't spawn endless strings of gabbing. FB's business is, after all, eyeballs and clicks to gather user data, no particular other purpose. FB is built on endless back and forth, not anything specific. Specificity may be counter to their purpose.

Absolute truth....

[nuke]

And just to digress another 2-degrees, LinkedIn is a total sewer of useless nonsense and impossible to use. If someone does manage to post something or a link you want to read, it scrolls away and disappears, or you let your phone go dark for a second and it is never to be found again. Just endless emails trying to get you to visit the site.

Same deal. Volume of clicks, not useful resource.

[solderhead]

Greg, in addition to the people you've mentioned, I miss Steve Ahola. It's sad that his site, blueguitar.org, became lost when he was gone and unable to renew the domain name registration, and somebody snatched it. Tboy was able to host an archived version of blue guitar at MEF, but now they're both gone.

It's a problem when someone has to host a web site in their garage or in their basement. BTDT. That's the way that we had to do things back in the days of the open frontier, but times have changed and remove hosting is cheap today. I hosted an open source linux distribution on an old PC in my basement, complete with worldwide remote mirrors, for a couple of years and it was a major pain, until I was able to transfer the site to a university hosted virtual server that had full IT support for the project. For what it costs to do remote hosting today, I wouldn't consider building my own LAMP server all over again.

the problem with having a site that's totally dependent on one person is that you've got high diversification risk.

[mhuss]

A single point of failure.

[martin manning]

A quick search on this topic (on-line forums vs. other SM) shows there has been lots of discussion around popularity of discussion forums vs. the mainstream social media sites for years. The consensus seems to be that there is a need for technical discussion forums for both entertainment and professional development. Redit wants to be the Amazon of forums, but it has its own drawbacks (too big and too diverse). Let's hope TAG can be an immortal amp forum, and stay alive one way or another.

[soundmasterg]

Greg, in addition to the people you've mentioned, I miss Steve Ahola. It's sad that his site, blueguitar.org, became lost when he was gone and unable to renew the domain name registration, and somebody snatched it. Tboy was able to host an archived version of blue guitar at MEF, but now they're both gone.

It's a problem when someone has to host a web site in their garage or in their basement. BTDT. That's the way that we had to do things back in the days of the open frontier, but times have changed and remove hosting is cheap today. I hosted an open source linux distribution on an old PC in my basement, complete with worldwide remote mirrors, for a couple of years and it was a major pain, until I was able to transfer the site to a university hosted virtual server that had full IT support for the project. For what it costs to do remote hosting today, I wouldn't consider building my own LAMP server all over again.

the problem with having a site that's totally dependent on one person is that you've got high diversification risk.

Yeah Steve Aloha was a fantastic resource. There were some others too, including one guy when I was first getting started that was a HUGE help to me. He left the forums soon after to do other things, which was unfortunate for everyone else. The days in the late 90's/early 2000's were great as there were all kinds of great resources around like Randall Aiken, Andy Marshall, Mike Soldano, all on the MEF, and there were a bunch of really detailed guys at AX84 too. Not sure what is going on at MEF but I hope it comes back.

Greg

[Colossal]

I am putting an amp together right now with RG's MOV protection method for the OT; one each between the plate and centertap leads for a cathode biased push-pull pair of EL34s.

Neat! I would appreciate your opinion on any tone changes this might cause, if you can take the time to listen with and without. MOVs have few nF of capacitance, and it is possible that this could change high frequency response a bit. I've tried it, and tested for response, but never seen any real effect; but I can see that some circuits might be sensitive to it.

Last time this got discussed, someone mentioned TVSS devices, which are more of a zener and less of a variable resistance device like a MOV. TVSS will clamp like a zener in both directions at its breakover voltage and have lower capacitance, so less of a chance to affect high frequency response. They have lower power ratings, but this isn't really a high power application, so they might work OK.

R.G.

FWIW, and some closure, I just finished a 2xEL34 garter cathode biased amp and used two MOVs between the plates. Although I did not perform a with and without test of the MOVs, the amp has a lot of punch, chime, and clarity (Vox OT) so even if the MOVs are affecting the high frequency response it would seem unnoticed. The parts used were Eaton 625VAC/825VDC, 1.65kV, 230J, 280pF (Mouser 504-MOVHE14V625Y).

[R.G.]

Thanks for remembering and trying it out!

[trobbins]

I just finished a 2xEL34 garter cathode biased amp and used two MOVs between the plates.... The parts used were Eaton 625VAC/825VDC, 1.65kV, 230J, 280pF (Mouser 504-MOVHE14V625Y).

Was that with one MOV from each anode to B+ ?

The datasheet indicates a max capacitance of 200pF ? The 1mA Vdc is at least 900V, which should be a good margin for you.

[Colossal]

I just finished a 2xEL34 garter cathode biased amp and used two MOVs between the plates.... The parts used were Eaton 625VAC/825VDC, 1.65kV, 230J, 280pF (Mouser 504-MOVHE14V625Y).

Was that with one MOV from each anode to B+ ?

The datasheet indicates a max capacitance of 200pF ? The 1mA Vdc is at least 900V, which should be a good margin for you.

Yes, one MOV from anode to B+.

[shane]

Hi Colossal.
I'd really be interested to hear more about that cathode Garter biased El34 amp! Don't know much about garter biasing.

[pompeiisneaks]

I built Sluckey's Marshal dual project with all film caps and loved it.

~Phil

[Colossal]

Hi Colossal.
I'd really be interested to hear more about that cathode Garter biased El34 amp! Don't know much about garter biasing.

Shane,

My apologies; I did not see your post until now. I finished the amp probably a month ago or more now and have been playing it with my stereo rig which is largely a pedal platform. The amp is a bit of a mashup. A Dumble 102 preamp, Dumble PI, and into a cathode biased pair of EL34s. Vox AC30 power and output transformers. The PT is wound for 117V and with modern voltages (mine especially), runs too hot for EL84s without having to greatly reduce the screen voltages but it was a perfect fit for this project. I also added variable negative feedback which turns out to be a useful feature on this amp. I ended up removing the protection MOVs. Have a google on garter bias. It is a clever method which keeps the power tubes in close match. The EL34s are pulling 75mA each and dissipating 24.2W apiece.

We can continue this discussion but don't want to derail R.G.'s thread.