Search found 93 matches

by Wolfgang
Mon Jul 08, 2019 3:40 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

While I was getting ready for putting everything into the amp housing I realized that there is a mistake in the schematics of the output power supply. The two 20ohm/20W resistors between the two caps have to be in series (40ohm) and NOT parallel as the schematics show. It must have happened when I c...
by Wolfgang
Sun Jul 07, 2019 12:57 am
Forum: Everyones Projects
Topic: Remember These?
Replies: 658
Views: 29836

Re: Remember These?

The biggest advantage of tubes like the 5687 for the InvOTL is that the heaters need a less powerful transformer. Considering the output impedance the 6AS7 is relatively close to the 5687: 3,4ohm for ten 5687 and 5,6 ohm for 10 6AS7. If one measures the CDF for a single driver speaker one will end u...
by Wolfgang
Sat Jul 06, 2019 7:36 pm
Forum: Everyones Projects
Topic: Remember These?
Replies: 658
Views: 29836

Re: Remember These?

I’ll never build an inverted OTL as I simply don’t have the knowledge to execute a design or build the power sequencing circuitry. To build the amp itself is as easy or difficult as building any other tube amp. If you don't want to build the circuitry you can simply use an on/off switch for the hea...
by Wolfgang
Fri Jul 05, 2019 3:12 am
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

But why would they shut-down in the case of a power outage? Because Rel 5 turns off and the output of IA 1/2/3 goes to 0. The caps will lose their charging according to the time settings with resistor/no resistor and the SSRs will turn off. I use the DIP16 version, same as the gates you are using T...
by Wolfgang
Thu Jul 04, 2019 7:25 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

Though its behavior with a short term power out may be indeterminate unlike a controller with a brown out detector and known reset state. The secondaries which control the timer part are buffered with 30kuF which keeps the SSRs functional at power outage until they have shut down in the preset sequ...
by Wolfgang
Wed Jul 03, 2019 4:44 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

I forgot to attach this shot of the amp modules that I will put into the housing as soon as it's done. Like this I don't need to drill too many holes that can be seen from outside. This is kind of important in this case as I try to make the box look like intarsien wood finish as I feel that this amp...
by Wolfgang
Wed Jul 03, 2019 3:33 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

Time to move on to the next step. I am almost there that I can put both channels in the amp housing I was building (wood) and I was thinking about how to solve practically the remaining issues with this amp. 1. How to deal with 40V DC at the output after turning the amp on until everything has evene...
by Wolfgang
Tue Jul 02, 2019 3:29 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

How I see it now after this little discussion: Andrew's original way would show the different noise floors without a reference. It's not possible to say anything about the absolute numbers as it only shows a ratio. But it would tell us how much this ratio is. Nick's way would show us in addition als...
by Wolfgang
Mon Jul 01, 2019 11:14 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

This whole topic seems to be a problem for many picoscope users (and in general). I could find in many different blogs questions referring to the measured noise and the absolute noise (subtracting the noise of the measuring device) over and over and no real answers. Most important for me at this ear...
by Wolfgang
Mon Jul 01, 2019 6:04 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

I was considering a uTracer which Thomas had mentioned. But after reading more about the details and how it works I got the impression that for tracing inv. tube operation one would not only need to rewire a lot and use an additional low voltage psu but it would be impossible (for me at least) to pr...
by Wolfgang
Sun Jun 30, 2019 2:17 am
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

The noise would be better with a log frequency scale and some reference signal. You need a siignal to measure the noise against. Nick, I tried to figure out if we mean the same with “noise floor” because for me it simply means sum of all noise without any signal. Noise compared to a signal would me...
by Wolfgang
Sat Jun 29, 2019 4:17 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

My decision to use the 6AS7 was based on several things. First I wanted a cheap and easily available output tube. Secondly, I was a little irritated why S.B. would use a tube with MU=15 as he comments at p.2 that “An upper practical limit is achieved with devices with a normal MU of about 15.” The 5...
by Wolfgang
Fri Jun 28, 2019 8:02 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

Ray, this is what S.Bench calls "fringing". At both ends the tube looses its linear characteristics . fringing.jpg This shows the "plate characteristics" of the 6AS7. no fringing.jpg S. Bench explains it in his article. If we start using grids as anodes they have to be of a certain strength/sturdine...
by Wolfgang
Fri Jun 28, 2019 3:30 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

What would the panel say about subbing Russian 6N6Ps - claimed to be equivalent based on a quick bit of research (apart from the different pin layout) and much easier to find at a good price. In this case it's a little more complicated, Ray. "Equivalent" refers to regular use. You need to find tube...
by Wolfgang
Fri Jun 28, 2019 3:00 pm
Forum: Everyones Projects
Topic: Inverted OTL with 6SN7/6AS7
Replies: 59
Views: 2159

Re: Inverted OTL with 6SN7/6AS7

Not sure what the frequency response is showing, whats all the noise I used the spectrum analyzer with a sweep signal 10Hz-50kHz/10ms/10Hz intervals and flat top/peak hold.What you see on the bottom of the curve are the measurements/probes in very short time intervals and without "flat top" so it l...