Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Dec Sat 16, 2017 5:55 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 54 posts ]  Go to page Previous  1, 2, 3
Author Message
 Post subject: Re: 10DE7 tube
PostPosted: Nov Fri 17, 2017 12:54 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 17981
Location: Warner Robins, GA
If it's your typical single ended output transformer it is a sure bet it will roll off the bass somewhat.


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Fri 17, 2017 4:55 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12248
Tube Radio wrote:
If it's your typical single ended output transformer it is a sure bet it will roll off the bass somewhat.
No doubt, both my transformers are for/from general consumer electronics, bass & treble controls are expected to mostly compensate for roll off at either end of spectrum...

In my OPT xfomer stash I have the one for PP bass channel from the 6AQ5 amp I mentioned earlier in this thread... Would be interesting to see it's frequency response, but I'd have to set something up for testing it and ones I'm now using... That amp has never impressed me at all, not done much with it, not even sure if it's operationable... With a good OPT(one now modulating Tx), the SE 6BQ5 amp would annihilate it...

No doubt the PP amp & plate modulation is a workable combo, been running continually since Tuesday, off a minute or two here and there to make circuit changes or adjustments... Since I "balanced" frequency response has a very pleasing sound... I'm actually more surprised my trash picked B&K P/S has stood the test but it's only powering amp, all the other Tx circuitry is on board ... Got to make some additional notes on voltages and settings, maybe even draw a schematic(the 6DE7 amp schematic is maybe ¾ finished)... About time to tear it down...


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Fri 17, 2017 6:49 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 17981
Location: Warner Robins, GA
All the bass controls and compensation in the world won't compensate for low frequencies the transformer cannot pass.


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Fri 17, 2017 7:40 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12248
Tube Radio wrote:
All the bass controls and compensation in the world won't compensate for low frequencies the transformer cannot pass.

AFAIK there are no brick wall/sharp cutoff transformers, just that they become less efficient at whatever(usually lower) freq... No doubt at some point they can be so inefficient it could be said they aren't passing past a certain range...


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Fri 17, 2017 8:18 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 17981
Location: Warner Robins, GA
What happens in my experience is below a certain frequency the transformer causes the waveform to start looking less and less like a sinewave which causes the output level to drop.

I often suggest testing any amp with an output transformer where the bass is lacking by connecting a resistor of tghe expected output impedance in place of the load then connecting a scope across it and feeding a sinewave starting at 100Hz such that the amp is just under the point of distortion look for the frequency where the sinewave starts to look different than a proper sinewave.

That is the frequency at which the transformer can no longer properly pass a sinewave.

You'd be amazed at how bad some transformers make a sinewave look below 50Hz.


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Fri 17, 2017 10:50 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12248
I'll have to try the transformer test...

Today turned out to be 7BD, 7BK & 7CM day... Meaning?? I've connected pins 2 & 7 so I could try tubes with the aforementioned basing, had everything in it from a 6AH6 to 9001... The 6AH6, 6AK6, 6CB6 etc perform similarly to the audio tubes... The 9001 not so good but I didn't try to make improvement... The 6AH6 is a long obsolete TV video amp that's been so since early 1950s(kicked to curb by 12BY7)... For some reason, I've always wanted to use one in something that actually worked...


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Fri 17, 2017 11:07 pm 
Member

Joined: Apr Thu 14, 2016 8:25 pm
Posts: 282
Location: pensacola fl
Remember for good low freq response bigger is better meaning more core and inductance. Those small opts saturate to soon as far as drive goes. they may pass 50HZ undistorted at -10DBM and distort it at 0DBM.


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Sat 18, 2017 1:42 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12248
Isn't size of xformer relative to size of output tubes???

The 6DE7 aren't very big, I could see issues if I were driving it with much larger a pair of 6V6G...

See?? The xformer is as big as tubes, ought to be OK... :wink: :lol:

Image


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Sat 18, 2017 5:14 am 
Member

Joined: Apr Thu 14, 2016 8:25 pm
Posts: 282
Location: pensacola fl
Hi 35z5. No the size with in reason is not a problem. I would not use a 100 watt transformer but a typical 6V6 or 6BQ5 se output transformer usually came from amps or radios with a decent low end. The 50C5 or 50L6 type generally do not have a very good low end due to not enough inductance and they have small cores so they saturate more easily even though they are gapped. I even built a transmitter for my high school back in the late 60's using a pair of vertical output transformers from the same model tv set that had the same transformer and coupled the yoke hot wires with an electrolytic B+ taps went to respective hi and lo B+ and it had a killer bass. Used the tv vertical output tube as modulator. It was a 6W6 as I recall but not 100% sure may have been a 6V6 or 6K6.


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Sat 18, 2017 5:50 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12248
Vertical output transformer eh?? I have a universal version of one those setting on the bench... Plus a old tube caddy with several misc xformers in it... Sometime back I used the voltage tests to determine what tap(s) were closest match... Now, what'd I do with that note book??

BTW I also matched a power transformer from junk scope, found the 6.3v and 175v B+ windings were closest... But I don't remember to what amp I had it connected...


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Sat 18, 2017 7:24 pm 
Member

Joined: Apr Thu 14, 2016 8:25 pm
Posts: 282
Location: pensacola fl
Howdy. I am not a fan of using power transformers for carrying audio unless it is in a pinch. As a modulation transformer it must carry D.C. which can saturate the core causing problems. The vertical output transformers are plate to yoke many are auto transformers. This allows them to carry the D.C. The inductance is high enough for 60 HZ and they can carry high frequencies fairly well. if you have the Auto transformer type use the B+ and plate as usual and couple the yoke leads through an electrolytic as the yoke side is lower impedance winding. I take it the B+ on your final is in the 50V area the plate and screen current should be quite low around near 5MA so heating should be no problem. Remember to polarize that coupling electrolytic with + to the modulator tube transformer as it will be carrying full B+ voltage. We don't want you to get hurt.


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Sat 18, 2017 10:41 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12248
Well today I ran the quick & dirty acid test, in other words I compared the plate modulated xmitt with my favorite 9KC6 version... First shot out the gate the 9KC6 was a clear winner as there was some distortion in the plate modulated unit... I then realized I didn't retune antenna after moving plate mod unit 20KC in freq(needed a bit more separation between two)... I mentioned this thing was finicky, the suppressor modulated xmitt would have cared less if antenna was a little mistuned... On second go round it's a bit of a tossup, audio is roughly equal with the 9KC6 xmitt having a edge on the bottom end... BUT the plate mod unit has a bit better response on the upper end... Signal is fed to both through the EQ that I used to increase bottom end on the plate mod unit, those settings haven't been changed...

Sooo which would I rather listen to?? I dunno, listening to a variety of songs, some are better on 9KC6 others better on the plate mod unit...

What am I going to do?? If anything, look at increasing upper end in the 9KC6 unit...


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Sun 19, 2017 6:44 pm 
Member

Joined: Apr Thu 14, 2016 8:25 pm
Posts: 282
Location: pensacola fl
Do not forget there are other ways to hi level modulate (plate modulate) a class c final amplifier. I am currently working on such a project and trying to keep its cost down for those who may like to make one. The way I am modulating it it can produce 100% modulation in both directions and even a little more positive modulation. The problem with asymmetrical modulation is that the source material has to be that way to begin with or processor that can produce it is needed. To keep it under control the processor is a must as few recordings possess the same amount of asymmetry. I will keep you posted as I progress with it. It is already in breadboard form and operating and needs to be fine tuned as to part values etc.


Top
 Profile  
 
 Post subject: Re: 10DE7 tube
PostPosted: Nov Mon 20, 2017 2:26 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12248
If I build another transmitter it'll be a screen modulated version using the mid/late 30s shouldered(G) types... I had a working prototype on cake pan that had more holes than metal...

As it is I have more than one for each day of week & that's after giving a couple away... Except for running changes on the 9KC6 and cathode follower/plate mod unit, I haven't built anything in around five years... That's excepting the 6DE7 amp I built a couple years ago and modification to the AA6 to add PP audio...

Those are...

1) 6C4/6888 - shown in the three different Tx thread(currently on air with 6AB4 in place of 6C4)
2) 6AV6/6C4/6SN7/6GY6 - has osc & audio cathode followers(now plate modulated 6AQ5, for a little while anyway)
3) 6BK7/6GY6 - also in the three Tx thread
4) 9KC6 using a pair 6GK5(or similar) TV RF amp tubes as audio & VFO. This one is the usual daily runner
5) 6BA11 single tube version, no documentation, accidentally deleted the schematic
6) 12AE6/12EG6 version that runs on 30v B+ (It's actually in pieces)
7) really rough 12AV6/12CS6, I mean ugly - Don't remember why I have this one, gave the prototype away
8 ) LM386 version
9) Knight Broadcaster... Other than interesting to look at, it's basically worthless
10) Ramsey AM-25
11) A plate modulated, 11 toober, homebrew that was used at a drive in theater, has 7868 RF out modulated by pair of 5881(not exactly pt 15 compliant)
Also has 5R4 rectifier, gas voltage regulators and audio limiter circuitry - Another interesting display piece

Probably a couple more


Top
 Profile  
 
Post New Topic Post Reply  [ 54 posts ]  Go to page Previous  1, 2, 3

All times are UTC [ DST ]


Who is online

Users browsing this forum: Joezenithman and 13 guests



Search for:
Jump to:  


















Privacy Policy :: Powered by phpBB