What OT for a Pair of KT88's?

[fusionbear]

As the title states. Where can i get a transformer that is 100 watts but has the right primary impedance for a pair of KT88's. This is for my clean amp project. I think it needs 3300-3500 Ohms on the primary?

[Hellhammer]

I think you need more like a 4500-5000 Ohm primary.
http://www.tubezone.net/pdf/kt88new.pdf

Hammond 1650R?
http://www.tubesandmore.com/scripts/fox ... m=P-T1650R

[ToneMerc]

As the title states. Where can i get a transformer that is 100 watts but has the right primary impedance for a pair of KT88's. This is for my clean amp project. I think it needs 3300-3500 Ohms on the primary?

At what plate voltage?

[Hellhammer]

At what plate voltage?

He'd need about 600 for 100W if I'm reading the datasheet right.

[Alexo]

Not sure where you're getting 3K5, but to each their own.

I've used the Hammond 1650R for this setup and it worked great. Puh-lenty of headroom with that OT if you're building a clean amp.

You could also use a Hamm 1750U if you double up the load (3K4/100W).

FWIW, if I had it to do again, I might use a slightly lower plate voltage and run a quad of '88's to get 100W. JMHO.

[Hellhammer]

FWIW, if I had it to do again, I might use a slightly lower plate voltage and run a quad of '88's to get 100W. JMHO.

Interesting, may I ask why? They are quite expensive bottles, and I'm cheap!

[Alexo]

FWIW, if I had it to do again, I might use a slightly lower plate voltage and run a quad of '88's to get 100W. JMHO.

Interesting, may I ask why? They are quite expensive bottles, and I'm cheap!

Sure! Truth be told, I had a heck of a time actually getting 100W out of them. I think the closest I got in the real world was around 75 or 80, following everything the datasheets tell you to do and then some (560+ on the plates, 400 or so on the screens, 5K load, 465ma PT).

Just seems like the tubes had other plans, as they are want to do, 50watts+ is easy for a pair of them, better to play to their strengths.

But I hear you on the money!!

[David Root]

Edcor makes an 11 lb 3K5 OT rated 70W at 20 Hz to 20 KHz bandwidth, I got 100W out of a pair of 8417s at 520Vp thru it no problem. It would do 150W at 40-10KHz. $92.

[Hellhammer]

[I think the closest I got in the real world was around 75 or 80, following everything the datasheets tell you to do and then some (560+ on the plates, 400 or so on the screens, 5K load, 465ma PT).

I built an amp with the same specs except for higher screen voltage. I don't have the means to measure P out but I have a gut feeling it won't put out 100W clean. But I'm having other issues with it so hard to tell. That reminds me it still sits there collecting dust. That's a lot of money in iron, tubes and mustards. I should finish the amp some day! After the 1W SE amp I'm doing now maybe.

[Alexo]

[I think the closest I got in the real world was around 75 or 80, following everything the datasheets tell you to do and then some (560+ on the plates, 400 or so on the screens, 5K load, 465ma PT).

I built an amp with the same specs except for higher screen voltage. I don't have the means to measure P out but I have a gut feeling it won't put out 100W clean. But I'm having other issues with it so hard to tell. That reminds me it still sits there collecting dust. That's a lot of money in iron, tubes and mustards. I should finish the amp some day! After the 1W SE amp I'm doing now maybe.

Right on. Well even at less than 100W, it is still LOUD. It's never come up short on power, and it's a gigging bass amp, so I guess that's saying something. The owner has since retired his 300W SS head, because it can't compete. :l

Easy to get hung up on the numbers, but no one really cares!

[Phil_S]

Have you thought about using KT120's? For a few dollars more, you'll probably be able to get 100-120W no problem from a pair. The tube appears to have good reviews.

[jon]

What kind of driver circuit/PI are you planning on using. That can make all the difference in how easily you get to your desired output.

[fusionbear]

As the title states. Where can i get a transformer that is 100 watts but has the right primary impedance for a pair of KT88's. This is for my clean amp project. I think it needs 3300-3500 Ohms on the primary?

At what plate voltage?

I'll be running at about +490 using standard Marshall 100 watt PT

Also, I don't need the full 100 watts out of them. If I get 60 "clean" watts out of them, I'm happy. I want the amp to still feel "bouncy". The KT88's have a nice bouncy feeling to them when run at these lower voltages.

[fusionbear]

Edcor makes an 11 lb 3K5 OT rated 70W at 20 Hz to 20 KHz bandwidth, I got 100W out of a pair of 8417s at 520Vp thru it no problem. It would do 150W at 40-10KHz. $92.

This sounds right up my alley. Any pt# I should look for?

[fusionbear]

I think you need more like a 4500-5000 Ohm primary.
http://www.tubezone.net/pdf/kt88new.pdf

Hammond 1650R?
http://www.tubesandmore.com/scripts/fox ... m=P-T1650R

This also looks promising. Thanks!