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Splitting SRPP over 2 tubes and raising heater
Splitting SRPP over 2 tubes and raising heater
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Old 19th May 2018, 02:48 AM   #31
popilin is offline popilin  Argentina
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Quote:
Originally Posted by 6A3sUMMER View Post
Some amplifier designers choose to exceed the ratings (either intentionally, or because they do not know any better).
I think that Italian designers have done a magnificent work on the Smart 845.

Quote:
Originally Posted by 6A3sUMMER View Post
By the way, squealing/squeaking is not the only performance or failure mode when cathode filament leaks. There is loss of gain, distortion, etc.
Squealing is the most usual complaint against SRPP, at least here on the forum.
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Old 19th May 2018, 04:30 AM   #32
TonyTecson is offline TonyTecson  Philippines
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Splitting SRPP over 2 tubes and raising heater
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Squealing is the most usual complaint against SRPP, at least here on the forum.
i never encountered this, that is because i never used this SRPP, instead i used a broskie type circuit, the top triode used a CCS....i got very good results doing this on my 5894 SET amp....
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Old 19th May 2018, 04:35 AM   #33
TonyTecson is offline TonyTecson  Philippines
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Splitting SRPP over 2 tubes and raising heater
Quote:
Originally Posted by 6A3sUMMER View Post
You can check the results of floating the filaments. <snip>
in many of the amps i have seen, the filaments of the output tubes are not lifted with dc, a center tapped 6.3 volts supply is often enough connected to ground, and the reason for this is that hum and noise are not generated much at the output stage more than in the input and intermediate stages, wherein hum and noise are amplified by the succeeding stage(s), in the output tubes, the succeeding stage is the output transformer...

btw, in case of the output tubes being cathode resistor biased, the voltage developed there are also used to lift the filaments of early stages, in some case, even used to power the filaments, in this case the early tube filaments doubled up as cathode resistor biasing, i saw this on a Fisher receiver with 6bq5 output tubes...powering 12ax7 filaments with dc voltage..
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Old 19th May 2018, 05:07 AM   #34
popilin is offline popilin  Argentina
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Originally Posted by TonyTecson View Post
filaments can also be floated, not referenced to ground...
You should never do this, regardless of the topology used, a floating filament in the presence of an electric field can reach a voltage which violates the manufacturer specs by far.

I think that this kind of errors is responsible of the bad reputation of SRPP.
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Old 19th May 2018, 05:33 AM   #35
TonyTecson is offline TonyTecson  Philippines
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Splitting SRPP over 2 tubes and raising heater
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Originally Posted by popilin View Post
You should never do this, regardless of the topology used, a floating filament in the presence of an electric field can reach a voltage which violates the manufacturer specs by far.

I think that this kind of errors is responsible of the bad reputation of SRPP.

how many tube amps have you built?

i have done this on many occasions, no detrimental results, but you are not me, so do not do this yourself....

you only need to know when to do this or not....

for the record i have never done an SRPP and no plans of doing it ever,
Broskie is adequate for me thank you.....

so i am not responsible for the bad reputation of SRPP that you claim....
i had nothing to do with it...my tube amp builds do not hum, do not hiss, do not buzz and is enjoyable to listen to...
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Old 19th May 2018, 08:41 AM   #36
kodabmx is offline kodabmx  Canada
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I've only built one SRPP and I think it was in spec. (300V B+, 6SN7) but I didn't like it compared to grounded cathode. I'd rather use the whole 300V on each stage with 6SN7 I almost always use DC for heaters (SMPS) and never an issue so far (Soviet tubes). I routinely exceed Vhk by 50V without issue. Not that there won't be one in the future, but so far, so good. I'm also used to sudden catastrophic failures (like arc over in cheap tubes), not gradual failures creeping in over time.

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Old 19th May 2018, 10:10 PM   #37
TonyTecson is offline TonyTecson  Philippines
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Splitting SRPP over 2 tubes and raising heater
Quote:
Originally Posted by kodabmx View Post
I've only built one SRPP and I think it was in spec. (300V B+, 6SN7) but I didn't like it compared to grounded cathode. I'd rather use the whole 300V on each stage with 6SN7 I almost always use DC for heaters (SMPS) and never an issue so far (Soviet tubes). I routinely exceed Vhk by 50V without issue. Not that there won't be one in the future, but so far, so good. I'm also used to sudden catastrophic failures (like arc over in cheap tubes), not gradual failures creeping in over time.
good learning....nothing beats actual experience.....if i am right, my understanding is that the srpp by its nature removed much of the 2nd harmonics...unlike the common cathode amp...

i have done broskie ccda and the aikido....and guess what?
folks who listened to both swears that the ccda sounded better....
they say the aikido was "too honest" for their taste...
very much like a very good solid state amp....
so now i only do ccda's...
my latest, the 6BC4 common cathode line amp is yet another thing....
very enjoyable and very tube like sounding....
and very easy to build and low cost, what is not to like?
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Old 19th May 2018, 11:22 PM   #38
popilin is offline popilin  Argentina
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Originally Posted by TonyTecson View Post
good learning....nothing beats actual experience.....if i am right, my understanding is that the srpp by its nature removed much of the 2nd harmonics...unlike the common cathode amp...
That's right for a theoretical, optimized SRPP, for the real world optimized SRPP things are a bit different, see measurements here

Survey: Aikido distortion

Survey: Aikido distortion
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Old 20th May 2018, 12:52 AM   #39
kevinkr is offline kevinkr  United States
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Splitting SRPP over 2 tubes and raising heater
Since this is a violin amp I've moved it over to Instruments & Amps forum. Hopefully most of the participants will follow it here.


Interesting project.
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Old 20th May 2018, 01:43 PM   #40
Printer2 is offline Printer2  Canada
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Originally Posted by kevinkr View Post
Since this is a violin amp I've moved it over to Instruments & Amps forum. Hopefully most of the participants will follow it here.


Interesting project.



Violin? Send It Back! Send It Back!






Just kidding.
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