CindyJarvis

Thank you oscarear for bringing up a great point!! There are a number of threads/posts that are about politics which from my understanding are against the Terms of Use. A couple times I wanted to join the discussion but felt it best to stay out of it. Like I said the rules seem confusing to me because they aren't enforced all the time. -Cindy

Yes I got a warning point issued to me. I just feel like I was sticking up for myself from his attacks. https://community.klipsch.com/index.php?/topic/162090-my-bespoke-st70-amp-build/page-2 Post #38 -Cindy

Well I am figuring out and learning the warning points here. I guess we can't see if they have been issued to others. It looks like if you say something that gets you a warning point that comment still stays in the thread? Learning that a lot of you are friends in "real life" makes sense now. This is indeed a unique forum. The main issue is this NOSValves character, it appears I am not the only one that is having issues with him so I don't feel so bad. -Cindy

NOSValves, maybe you should design your amps around more robust tubes if you know they only last two years of service. -Cindy

So I take it this is a known thing around here? We can chalk favoritism up to human nature? -Cindy

I see your point, maybe he was given a warning and maybe he wasn't. I did issue a report, thanks. -Cindy

It seems the Terms of Service and Rules are not enforced equally on this website by moderators. A grim observation in the short period of time I have been a member. What gives? -Cindy

Under "Terms of Use / Rules" "You agree, through your use of this service, that you will not use this bulletin board to post any material which is knowingly false and/or defamatory, inaccurate, abusive, vulgar, hateful, harassing, obscene, profane, sexually oriented, racist, threatening, invasive of a person's privacy, or otherwise violative of any law." Post #23 NOSValves called me a "smartass" and was not issued anywarning points. He has also called others names like "delusional" in other threads. I on the other hand get a warning point for saying "Your remarks are a good indication of your intellect". The moderators are clearly discriminating against me for whatever reason and I don't appreciate it. -Cindy

Consider this a formal complaint about NOSValves avatar. I find it and him extremely offensive. Forum rules states no profanity. Your remarks are a good indication of your intellect. -Cindy

Since nobody helped me to find the answer I dug through some text books and I believe I found what I was looking for. If anyone else is interested here is what I learned. Let's go with the 50% full power that we require for 20kHz. For the 40 watt amp we will use the figure 17v peak for 17.7 watts RMS, close enough to half for me. So for this amplifier we are looking for a slew rate of 2.13 V/us I assume the scope is set for 10us/div in the last photo showing 20kHz squarewaves in post #2. I also assume the vert divisions are 5V/div. So we want to see no more than a 1/10 a horizontal division (1us) in at least 42% a vertical division (2.13v). We can also deduce the -3db rolloff by looking at the rise time from 10% to 90% of the pulse. I count about 3us which would put the -3db point at around 116kHz. This would be a lot easier if the "experts" here would share there information and explain what we are looking at instead of putting down my lack of knowledge in a field I am not an expert in. I am sure all of us could learn form it. -Cindy

SS gear can actually be a greater burden to restore, early SS gear with germanium transistors comes to mind. -Cindy

Pots, switches, capacitors, and carbon comp resistors are the biggest offenders in old gear. I have seen just as many bad transistors as bad tubes, tubes are much easier to replace IMHO. Some people even build "tube rollers dreams" amps so replacing tubes is actually a positive feature. As mentioned by Maynard if one isnt into "rolling" tubes a well designed amp using high quality tubes can function properly for a very long time, a lot longer than most audiopholes keep their gear for. -Cindy

It would be neat if someone with the capability can do some before and after room eq sweeps. I like how they mention P.W. Klipsch in this article. http://www.audiophysic.de/aufstellung/index_e.htmlGoodnight -Cindy

Sorry to disappoint, this is a case of mistaken identity. I am just used to some men not accepting me in the field. I have found xxjpmxx in some recent threads and I am currently doing some catching up. -Cindy

Why are you calling me a sloth and xxxjpmxx? Inside joke?

Excuse me Mr Cranky pants. There seem to be plenty of knowledgeable tube amp designers willing to help answer questions. If you have nothing positive to add to the conversation why participate?

Yes I am new to tube ampliers. This is why I ask you gurus questions I think the higher frequencies need not not be tested at full output, its not needed. Maybe 50% full output. Since there is no RMS with square waves I would like to see 20v peak to peak. -Cindy

Very nice looking amp!!! I am a bit perplexed to why one would test an amp capable of 35-40watts at only 3 watts. I would think a high power amp should perform well up to it's rated limit. -Cindy

I propose measuring DCR from the output transformers centertap to each plate tap. Then while the amp is on with no signal measure voltage drop across said points. I=V/R Balance accordingly. -Cindy

Looks so cute! I am certain it us using a smps. It is an interesting subject to me at this time. I am currently recycling a laptop power supply good for 20vdc at 3.3A. I plan to run two 12au7 with the heaters in series. The switching noise 66.6kHz is evident on a scope, roughly 100mV so some additional filtering will be still necessary. It is above our hearing but still.. -Cindy

2.4gHz will travel through materials like walls better than 5gHz. -Cindy

The amplifiers domestically assembled are still loaded with parts from around the world including China. Who is kidding themselves that it is an American product just because they were the last in the chain of production? -Cindy

From a musicians POV some of those SS amps that sound like SET amps probably have high second order harmonic distortion and or low damping factor. I am starting to learn that the folks that like SE amps like the second harmonic distortion. Too many variables to make accurate broad statements maybe. -Cindy

"We" was the group of engineers I worked with. I was in charge of quality control and testing of the boards. -Cindy

Thanks guys for the informative responses, it now makes complete sense. Maynard, I see you have good 120Hz rectifier ripple smoothing! I was talking more about AC line noise. I was asking because i noticed you have a small cap from line to neautral but not line to ground and neautral to ground. We also use low pass filters in series with line and neautral. My thinking is that tube circuits arent as sensitive to noise as with most modern digital circuits. Advantage tubes so to say. I also just noticed a small cap to ground at signal input, is this for RF possibly being picked up? -Cindy