I bought sockets exactly made for British Mazda tubes, made in China.
NEW MAZDA style P61 VR66 SP41 SP42 PEN25 OCTAL Ceramic Tube Sockets x10 MO8 BASE | eBay
NEW MAZDA style P61 VR66 SP41 SP42 PEN25 OCTAL Ceramic Tube Sockets x10 MO8 BASE | eBay
Here are some traced curves for a Raytheon VT-127
10 mA/div Vert. and 50 V/div Horiz.
a) Pentode 160V on grid 2, 0.8 V steps on grid 1
b) Triode 2 V steps on grid 1
Mu around 12
This Raytheon VT-127 looks just like a 1625 (807) tube except for the MO base and finer grid 1 wire pitch.
10 mA/div Vert. and 50 V/div Horiz.
a) Pentode 160V on grid 2, 0.8 V steps on grid 1
b) Triode 2 V steps on grid 1
Mu around 12
This Raytheon VT-127 looks just like a 1625 (807) tube except for the MO base and finer grid 1 wire pitch.
Attachments
Last edited:
Grid 2 too; I got red G2 when the amp oscillated without load. And definitely 200V is the maximum that I would supply for G2 of this tube. It is more like vertical video amplifier tube than horizontal sweep one. Like a predecessor for 6P15P, 12HL7, etc.
Wavebourn,
Was that oscillation on an amplifier that employed negative resistance?
I worked at a place that used negative resistance on 4 MHz crystal resolution filters for spectrum analyzers (resolution bandwidth filters).
Those were hard to tame.
Was that oscillation on an amplifier that employed negative resistance?
I worked at a place that used negative resistance on 4 MHz crystal resolution filters for spectrum analyzers (resolution bandwidth filters).
Those were hard to tame.
Yes, but not because of it. I just swapped by mistake leads from output transformers to negative feedbacks by voltage of wrong channels, and got a multi-vibrator instead of a stereo amp. 😀
Tunnel diodes? 😀
It depends on the value of negative resistance in respect to the impedance of the load. If enough, it flattens frequency response of the speaker servo-damping it; it too much, it oscillates.
I experimented today connecting 8 Ohm speakers to 16 Ohm outputs of a headphone amp through auto-transformer volume control, in last 2 positions speakers start oscillating. 😀
Wavebourn - Headphone amp drivibg 8 Ohm speakers | Facebook
The quartz crystals used as series resonators have an intrinsic series resistance.
To narrow the bandwidth, the terminating resistance must be decreased.
That increases the insertion loss of the filter; increases the noise floor of the analyzer because of the required amplification after the filter to make up for the loss.
Negative resistance drove the crystal, and made up for that loss.
Because of the large range of bandwidth settings (and termination resistances), there were some tapped transformers used to make it all work.
. . . Interesting, you used an auto-former on negative resistance amp.
To narrow the bandwidth, the terminating resistance must be decreased.
That increases the insertion loss of the filter; increases the noise floor of the analyzer because of the required amplification after the filter to make up for the loss.
Negative resistance drove the crystal, and made up for that loss.
Because of the large range of bandwidth settings (and termination resistances), there were some tapped transformers used to make it all work.
. . . Interesting, you used an auto-former on negative resistance amp.
Last edited:
Well; I used auto-former before in a parafeed 2 stage hybrid amp with 150V B+, with one tube stage directly driving P-type MOSFET. I postponed that project. It is very promising, but I did not figure out yet how to stabilize better it's working point.
Judging from anode curves I think that I was wrong assuming that the tube was used for sweep duties in monitors. Most likely, it is a video amplifier tube on steroids.
4P10S in triode mode?
Friends
I have several 4P10S tubes and they look like KT66 for me.
I tested it in triode mode years ago and the sound is very good.
I will test them again to see what power it can provide. Particularly I believe that it provides about 2W.
Aldovan
Friends
I have several 4P10S tubes and they look like KT66 for me.
I tested it in triode mode years ago and the sound is very good.
I will test them again to see what power it can provide. Particularly I believe that it provides about 2W.
Aldovan
Peter
Yes, but currently the train is no longer from the government, it is private and is more expensive.
It is good to know that you have been to Curitiba, a city with strong European colonization here in Brazil. Sorry for not responding in Portuguese, hahaha.
Yes, but currently the train is no longer from the government, it is private and is more expensive.
It is good to know that you have been to Curitiba, a city with strong European colonization here in Brazil. Sorry for not responding in Portuguese, hahaha.
Yes. 4P10S, VT127/CV1127, KT66 were customized successful Mazda Pen-46 design. KT66 was simplified for audio, the rest were improved for military usage in classified radars. I sold one prototype to a fellow audiophile in Australia, he loves the tubes.
Wavebourne Edelweiss-3 Prototype Power Amp review
I have the VT127, but strangely it was produced by American Raytheon with the mazda's famous octal socket.
I find it strange because the quality of Mazda valves is far superior to Raytheon.
I recently sold a pair of output transformers from my production to an audiophile in Australia who is very fond of different valves, like me. Perhaps we are talking about the same person.
Steel-Lab HIFI audio transformers
I find it strange because the quality of Mazda valves is far superior to Raytheon.
I recently sold a pair of output transformers from my production to an audiophile in Australia who is very fond of different valves, like me. Perhaps we are talking about the same person.
Steel-Lab HIFI audio transformers