And, of course, it is very relevant to the OP topic for GU50 tubes that work optimally (according to Wavebourn) with 800V plate voltage and 270V on the screen into 10k primary impedance PP transformers.
Thank you guys for the interest.
I've got a very detailed reply from Tomasz of http://www.toroidy.pl/ for one pair of 6550.
Unfortunately it is not possible to have more than 100W, even reducing the bandwidth.
The specs are:
1) Supply voltage – 600V on screens, separate supply of 300V for screens.
2) Nominal anode current – 200mA
3) Nominal power – 100W max
4) Input impedance Raa - 4,2k anode to anode (or 3,3k – same price)
5) Output impedance - 4 Ohm / 8 Ohm
6) Circuit type - PP
7) Ultralinear taps – (25% for 4,2k) or (43% for 3,3k) – same price
Audio Grade version – 113,10 EUR
Supreme version (epoxy fille in the stainless steel box) – 165,40 EUR
Here’s a discount list:
10 – 20 pcs – 5%
20 – 50 pcs – 10%
more then 50 pcs – 15%
I've got a very detailed reply from Tomasz of http://www.toroidy.pl/ for one pair of 6550.
Unfortunately it is not possible to have more than 100W, even reducing the bandwidth.
The specs are:
1) Supply voltage – 600V on screens, separate supply of 300V for screens.
2) Nominal anode current – 200mA
3) Nominal power – 100W max
4) Input impedance Raa - 4,2k anode to anode (or 3,3k – same price)
5) Output impedance - 4 Ohm / 8 Ohm
6) Circuit type - PP
7) Ultralinear taps – (25% for 4,2k) or (43% for 3,3k) – same price
Audio Grade version – 113,10 EUR
Supreme version (epoxy fille in the stainless steel box) – 165,40 EUR
Here’s a discount list:
10 – 20 pcs – 5%
20 – 50 pcs – 10%
more then 50 pcs – 15%
@zintolo
The component values are taken directly from Marc's EL34 Baby Huey or his Tena amplifier schematics so I can't reply to the reasons for the choices.
It's possible, maybe likely, I won't be able to get it to work at all🙂
The component values are taken directly from Marc's EL34 Baby Huey or his Tena amplifier schematics so I can't reply to the reasons for the choices.
It's possible, maybe likely, I won't be able to get it to work at all🙂
I copy here some hints written by Wavebourn about the GU50s.
It will come handy when we will work on that version:
This link, even if for another tube, should be useful in future:
Posted new P-P power amp design
It will come handy when we will work on that version:
This link, even if for another tube, should be useful in future:
Posted new P-P power amp design
Why putting four tubes on one transformer ? Give each two tubes there own transformer and connect the outputs parallel or serial.
Like this, with some additional mod's 🙂
Mona
Attachments
Hammond makes a 1900 ohm 120w transformer for parallel 6550/kt88. I know many people do not like Hammond transformers. This particular one does offers excellent value and good performance. I believe JN Stills used it in a parallel 6550 amp article in Audio Express Magazine a few years back and he got excellent distortion figures and power output.
I think it is model 1650T.
I think it is model 1650T.
My experience with Toroidy is that the quality, performance and value are hard to beat. You could always use 1 pr of KT120 or 150 and likely get close to 100wpc. It is much simpler and cleaner to use one pair of tubes if possible. Perhaps looking at a design that can use these super KT88/6550 tubes is an alternative for maximum flexibility in a high power BH amplifier.
What about swapping the MOSFET's drain connection to +600V instead of the plate? This would reduce current density in the primary to some extend.
Best regards!
But then you would “loose” the potential few watts of power contributed by the screen current, i.e. similar to a separate voltage regulated screen supply. Mona’s suggested circuit may even have triode characteristics since the screen and plate are connected.
Even with max positive excursion of the anode the screen stays under 600V, so yes can be done.
But in real UL the screen current is part of the transformer current, with the mosfet on the Vb it isn't the case any more.
Is that good ? or not ?
Mona
Thanks Mona, but I don't like the idea of paralleling OTs. I will keep this thread on the 100 Watt area, then maybe when different options will be clear here, I will open another thread for a 200 W bass power amp.
Yes it is thanks. It only lacks the tertiary winding compared to what we are checking here at the moment.
Thanks for the feedback. Yes, I've always heard good reviews of their trafos, and prices are ver good.
Thanks Mona, do you think it could be detrimental to have such an high impedance for g2, based on these curves? Posted new P-P power amp design
Edit:
What about a current limiter with a small cap on the Rsens, instead of screen resistors? We will get a very low resistance until screen current goes up and resistance goes up as well, but a bit delayed by the cap across the Rsens.
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I'm looking for possible other phave inverters if more swing will be needed:
Posted new P-P power amp design
Transistor phase splitter (Yaqin MC-84L)
Choosing the right triode as a Phase Inverter
Designing Long-Tail Pairs - The Load Line Approach
Posted new P-P power amp design
Transistor phase splitter (Yaqin MC-84L)
Choosing the right triode as a Phase Inverter
Designing Long-Tail Pairs - The Load Line Approach
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