60W mono's design help

[bigjppop]

I'm looking for a good design for a couple of 60+ watt monoblocks and I'm wondering if there's anything "off the shelf" that you guys can recommend as a good starting point.

I'm hoping to run a quad of the Russian 6P3S-E tubes per channel and I'd love to do it in triode if possible. Now, I'll be upfront and say that I've never heard anything but triode so I'm open to ideas for something different. I'm planning on using Edcor iron but if the budget works out maybe I'd go for something like Electraprint or O'Netics. I'm hoping to keep the total cost under 1000 USD for the pair (not including the chassis or tubes).

I'm not skilled enough to do a total ground up design/build but I can follow directions well enough to not kill myself or my project.

Thanks in advance for any help you can offer.

[Eli Duttman]

The 6П3С-Е is a member of the 6L6 clan and 6L6s are rated for a positive g1 current regime. So, PPP triode wired combined with Tubelab's PowerDrive (1 FET for each "final") should get you 60 W. easily enough out of Class "AB2". Mullard style circuitry, as was done recently by several members with KT88s, will serve you well.

As for O/P "iron", Edcor's model CXPP100-MS-3.3K seems suitable.

[bigjppop]

Tubelab's Simple SE was my first project and I really enjoyed it. I've read a lot about the powerdrive setup and I think I just need to bite the bullet and do it. I just wish there were some boards for the powerdrive...

[chrish]

Powerdrive is pretty easy to implement, just a FET and a resistor. The tricky part will be building the +/- supply to feed it and getting the grounding right for all of the components and power supplies. If you are going to have a negative supply for the FEt source followers, adding constant current sources for a diff amp driver will work. I am working on a 30 watt 6L6 amp now using Tubelab's driver schematic. 6L6GC AB2 Amp

[bigjppop]

Chrish:

I've been following your project for quite a while now and its pretty much exactly what I want to do, I just want to get 60 watts per side out of it. How much of an effort do you think it would be to take the design your using and just bump it up with 4 output tubes per side instead of two?

I've read through that thread a couple of times and the technical details are a little beyond me but I can buckle down and study that project if its something that can be adapted to what I'm looking for.

Thanks for the comments so far.

[chrish]

First off, I have to state that my knowledge is limited. The more technically savvy might like to correct me if I am wrong...

The driver stage designed by Tubelab is a 'universal driver'. It has drive capability greater than a 6L6 requires. The powerdive circuit (MOSFET follower) provides the drive current, so I imagine you would just have a powerdrive circuit for each tube. You would also require a bias control for each MOSFET/tube. This is not too bad, as it allows you to cater for mismatched tubes.

You would have to make sure that your power supply is capable of handling the 200-250mA of current required, and your +/- supplies will have to be a little beefier than what I have. VR tubes are not required for these supplies, I just wanted to use them for giggles. You may find it easier to use a SS regulated supply here too.

My limitation is that I have a 30 watt output transformer. With parallel tubes, you will be able to experiment with ultralinear and pentode of your output transformers are up to it.

[bigjppop]

Thanks for the input. I'm thinking I'll go with something from Edcor in the 100W range for OPTs which should allow for some experimenting. I need to check with O'Netics and Electraprint as well to get some quotes on what they would charge. Depending on how "Universal" I can make this thing, maybe I can even experiment with some other tubes (EL34's, KT88's, etc).

As for power supply, any good recs on designs to look at for that? I'm still a long way off from building, I need to do some serious study first, but I'd like to study some good designs that might work in the application I'm pursuing.

All the help is much appreciated!