PT for a quad of KT 88's

txbluesboy · Post by **txbluesboy** » Sat Jan 12, 2019 4:55 pm

I have built a Stereo amp using 4- KT 88's and 3 - 12AU7's that I need a proper power transformer for. I want to end up with 450 - 500 volts with solid state rectification. I figure I need at least 650 ma of plate current capacity and about 8 amps of 6.3 volt heater current. Any suggestions on a source for such a critter?

martin manning · Post by **martin manning** » Sat Jan 12, 2019 5:13 pm

Check listings at Edcor: https://www.edcorusa.com/xpwrseries-1#/ ... geNumber=6

txbluesboy · Post by **txbluesboy** » Sat Jan 12, 2019 5:45 pm

Thanks Martin, I don't see anything there that looks stout enough.

Phil_S · Post by **Phil_S** » Sat Jan 12, 2019 7:30 pm

If you are willing and patient, you might find what you are looking for on eBay. Example:
https://www.ebay.com/itm/Pair-of-Older- ... rk:35:pf:0
https://www.ebay.com/itm/TRANSFORMER-PO ... 1209!US!-1
https://www.ebay.com/itm/classic-tube-a ... 1209!US!-1
You might choose to make some compromises to power the amp. I'm guessing you need about 250mA on the primary? You might consider a separate 6.3V transformer to get what you need to power the quad of KT88's.
I think the transformer you are seeking will weigh in around 10 pounds!

didit · Post by **didit** » Sat Jan 12, 2019 8:56 pm

Hello -

Hammond builds beasts in this class. Have a careful look through biggest of their 300 series.

Best .. Ian

gldtp99 · Post by **gldtp99** » Sat Jan 12, 2019 10:08 pm

Call up Heyboer and give them the specs you want for your PT (they may ask a few questions):

https://www.heyboertransformers.com/tubeamps.shtml

I had them wind up some PT's with similar specs for a few 6L6GC x 6 Hi Gain projects.

Very happy with the custom PT's they provided.

They were also less expensive than I thought they would be because it eliminates the markup of any middleman vendor.

Heyboer makes transformers of many different types, not just audio transformers, so it's just another order to them----- as long as it's not a transformer that's available "off the shelf" from one of their major tube guitar amp customers such as Mojotone.

txbluesboy · Post by **txbluesboy** » Sat Jan 12, 2019 11:16 pm

Thanks guys! I'll look into these options.

jelle · Post by **jelle** » Thu Feb 07, 2019 2:40 pm

Classictone has a big project transformer that works great too.

txbluesboy · Post by **txbluesboy** » Fri Feb 08, 2019 2:56 pm

Jelle, I see the 100 watt PT Classistone has but nothing larger. Is there a part number I'm missing?
I currently have the amp up and running with a 100 watt Fender PT, however, It gets REALLY hot when using
KT 88's. I am having to us KT 66's presently.

M Fowler · Post by **M Fowler** » Fri Feb 08, 2019 4:18 pm

Terry,

The Hammond 378CX is what I have been using for four KT88 bass amps, suggested by Jelle.

I use the Hammond 1650TA OT

Mark

378CX.pdf

1650TA.pdf

Stevem · Post by **Stevem** » Fri Feb 08, 2019 5:06 pm

If you have the chassis room and want top notch performance you can have PT do the V+ and one for the heater power.

txbluesboy · Post by **txbluesboy** » Fri Feb 08, 2019 10:31 pm

After looking closer at the Classictone project PT, I see it has 10 amps of filament power. This is probably where most of my heating problems are coming from on the Fender PT with only about a 6 amp capacity. There are a lot of possibilities for selection of higher B+ voltages as well. This looks like the best option so far. Thanks Jelle!

The Amp Garage

PT for a quad of KT 88's

PT for a quad of KT 88's

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Re: PT for a quad of KT 88's

Re: PT for a quad of KT 88's

Re: PT for a quad of KT 88's

Re: PT for a quad of KT 88's

Re: PT for a quad of KT 88's

Re: PT for a quad of KT 88's

Re: PT for a quad of KT 88's

Re: PT for a quad of KT 88's

Re: PT for a quad of KT 88's

Re: PT for a quad of KT 88's