jane,
The number is just what I thought the 6v6 can handle. I'm an old newbie, and this is my first design. Please kindly help and don't hit too hard. Ah.....kidding.
The reason for making this amp, I was once listening to a system with a pair of A7 and a power amp with a 6dj8, 6v6 and a pair GU50. Sound gorgeous.
I thought since the A7 doesn't need that many power and the GU50 should be in triode mode. The drive is from the first tube 6dj8, I therefore thought the 6v6 might be work in CF.
Please comment
Albert
Wavebourn,
Since I want to use whatever I have in hand. I don't want to buy another OPT for more current. The OPT that I have are 3.5K and V/I = 400v/60mA = 6.666K. I therefore have to go PSE and it's good that I have more power too.
I know I can go auto bias for pure class A, but don't know how to balance the 2 tubes. If I go fixed bias then I push the amp into A2. Your suggestion ??
I'm going to give up the 6v6 and go for the single front end. I have some Mullard CV5311/6j4, 6e5p and 6au6. The CV5311 is mu 52, can it be a good candidate - sound wise, or pentode the best.
Albert
Since I want to use whatever I have in hand. I don't want to buy another OPT for more current. The OPT that I have are 3.5K and V/I = 400v/60mA = 6.666K. I therefore have to go PSE and it's good that I have more power too.
I know I can go auto bias for pure class A, but don't know how to balance the 2 tubes. If I go fixed bias then I push the amp into A2. Your suggestion ??
I'm going to give up the 6v6 and go for the single front end. I have some Mullard CV5311/6j4, 6e5p and 6au6. The CV5311 is mu 52, can it be a good candidate - sound wise, or pentode the best.
Albert
Why?
Find plate curves for GU-50 in triode, post them here, and we will help you with load line related things.
Hello
I just received my power transformer.
Nice PC, close to 6Kg. Hard to believe on the plate only 250mA.
I decided I will build the Sergeev schematic. I'll build that amplifier.
All do he use 420V I have to go a bit higher voltage, my power transformer will give 450V under load even if I use power choke.
I think if I go with lower bias (must go lower because my power transformer do not let me to bias each tube 90mA). May be 65mA/tube.
Someone sell a nice Hammond choke 500mA 1000V on the forum, if I can get one that will be enough for both channel.
From the schematic I'll remove the choke and I will use it somewhere where I pot the green arrow, or between the PS caps. So I can use one choke for both chanel.
I hope that not a problem.
I have 8 tubes 4 sockets, the driver tubes etc.
If I get the power choke after I need only the OP trannies, I can start test her.
Greetings Gabor
I just received my power transformer.
Nice PC, close to 6Kg. Hard to believe on the plate only 250mA.
I decided I will build the Sergeev schematic. I'll build that amplifier.
All do he use 420V I have to go a bit higher voltage, my power transformer will give 450V under load even if I use power choke.
I think if I go with lower bias (must go lower because my power transformer do not let me to bias each tube 90mA). May be 65mA/tube.
Someone sell a nice Hammond choke 500mA 1000V on the forum, if I can get one that will be enough for both channel.
From the schematic I'll remove the choke and I will use it somewhere where I pot the green arrow, or between the PS caps. So I can use one choke for both chanel.
I hope that not a problem.
I have 8 tubes 4 sockets, the driver tubes etc.
If I get the power choke after I need only the OP trannies, I can start test her.
Greetings Gabor
Attachments
Hello Wavebourn
If I go 450V plate voltage the 360V Zener still OK?
I did purchased the choke already.
May be I use the choke only??
Thanks any way.
Greetings Gabor
Hello Wavebourn
If I go 450V plate voltage the 360V Zener still OK?
I did purchased the choke already.
May be I use the choke only??
Thanks any way.
Greetings Gabor
You will get something like 358 Volt after stabilizer with 360V Zener.
Of course, if you remove it and use choke you will have higher voltage. But do yo need it for 6Э5П?
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Hello
These choke made by Hammond 193Q 500mA 1000V, $66 with shipping. I'll used between the PS caps.
On the 6E5P I will use the stabilizer in case that help.
What I don't know the choke will be enough for the GU50. Al do I run them almost half of the orig anode bias 60-65mA instead 90mA.
Still I don't want to over load the tubes even if it for a few second.
If the choke not enough I have to use some UZF there to.
Because I can't bias the power tubes 90mA I want to use that extra voltage on the GU50 anode.
Here is the UZF someone advised to me but I have to check all the parts if there are up to the higher voltage so I can use it on the GU50 tubes.
I'll try my best not to lose to much voltage on the power tubes.
Thanks Wavebourn
Greetings Gabor
These choke made by Hammond 193Q 500mA 1000V, $66 with shipping. I'll used between the PS caps.
On the 6E5P I will use the stabilizer in case that help.
What I don't know the choke will be enough for the GU50. Al do I run them almost half of the orig anode bias 60-65mA instead 90mA.
Still I don't want to over load the tubes even if it for a few second.
If the choke not enough I have to use some UZF there to.
Because I can't bias the power tubes 90mA I want to use that extra voltage on the GU50 anode.
Here is the UZF someone advised to me but I have to check all the parts if there are up to the higher voltage so I can use it on the GU50 tubes.
I'll try my best not to lose to much voltage on the power tubes.
Thanks Wavebourn
Greetings Gabor
Attachments
Looks like my far-out ideas on PP amp design have been thought of before, in 2001 no less by John B!
My post here outlines partial feedback combined with noise cancellation, and what should I stumble across in my research but this gem:
http://www.tubecad.com/march2001/2001_03.pdf
This article additionally highlights an area of amp design that concerns me with common cathode power tubes - that of the amplifier controlling the voltage output of the tube, not the primary.
As JB mentions in the article noise injection cancels out the PSU noise by making the anode follow the noise too - but this doesn't just work with noise, any lack of perfection in the supply is compensated for.
I.e the feedback in the amp actually applies to the primary, instead of the usual (B+ - Vanode) that most amps concentrate on.
I.e. in most amps you will also be listening to the power supply, with this technique you will not be.
In my design I have an SRPP driver mixing with the anode feedback to create the partial feedback of output anode, which probably means it isn't really an SRPP at all by then, but I'm not sure what else to use. Perhaps a cascode instead, or a pentode. Thinking of the cascode perhaps, as I have more double triodes than pentodes!
Partial feedback also has the good effect of allowing a DC feedback path, so that there is no capacitor distorting the feedback signal, which I like.
My post here outlines partial feedback combined with noise cancellation, and what should I stumble across in my research but this gem:
http://www.tubecad.com/march2001/2001_03.pdf
This article additionally highlights an area of amp design that concerns me with common cathode power tubes - that of the amplifier controlling the voltage output of the tube, not the primary.
As JB mentions in the article noise injection cancels out the PSU noise by making the anode follow the noise too - but this doesn't just work with noise, any lack of perfection in the supply is compensated for.
I.e the feedback in the amp actually applies to the primary, instead of the usual (B+ - Vanode) that most amps concentrate on.
I.e. in most amps you will also be listening to the power supply, with this technique you will not be.
In my design I have an SRPP driver mixing with the anode feedback to create the partial feedback of output anode, which probably means it isn't really an SRPP at all by then, but I'm not sure what else to use. Perhaps a cascode instead, or a pentode. Thinking of the cascode perhaps, as I have more double triodes than pentodes!
Partial feedback also has the good effect of allowing a DC feedback path, so that there is no capacitor distorting the feedback signal, which I like.
This is what I've been following. I also do the math with that formula inside the chart.
Attachments
revintage,
Yes the opt is 3.5K and Imax is 150mA, the power transformer is only with 350V on secondary. The 60mA per tube is only after my calculation V 400/ I 60mA = 6.6k and 2 tubes will be 120mA at 3.5K.
Albert
Hey Globulator,
The Broskie idea is not the smartest even if wrapped in thousands of words and formulas. It is still far from good to drive a I/V stage with a triode-driver. A pentode/cascade/FET on the other hand is what can be looked upon as a current source and is what should be used here.
Remember you use a 4,7k series feedback element making things easier for the driver triode. So it might be looking into something like 7-10kohm. Although the one you use has a lousy low Ri CCS(made from a triode)on top. Didn´t it work to take the signal from the SRPP-output?
The Broskie idea is not the smartest even if wrapped in thousands of words and formulas. It is still far from good to drive a I/V stage with a triode-driver. A pentode/cascade/FET on the other hand is what can be looked upon as a current source and is what should be used here.
Remember you use a 4,7k series feedback element making things easier for the driver triode. So it might be looking into something like 7-10kohm. Although the one you use has a lousy low Ri CCS(made from a triode)on top. Didn´t it work to take the signal from the SRPP-output?
Given the GU-50 some more thought and virtual testing. GU-50 is mediocre for triode strapping at low voltage. Unlinear and low efficiency. So either use it as righthanded triode or Schade if you want triode characteristics. Still this tube should work better from Ua 600V and up. This has been shown by both Artosalo and Wavebourn.
If you want to go 3,5k/400V, find another tube.
If you want to go 3,5k/400V, find another tube.
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