What OT for 4- 6V6 Marshally build?

fusionbear · Post by **fusionbear** » Thu Jun 06, 2013 5:15 am

Hello guys, I recently built and amp for a client that had a Marshall 2204 preamp, but 4- 6V6 power section. It used a weber kit amp as a donor. I liked the way it sounded so much, I want to build one for myself, but I want to use top notch parts. The OT is what concerns me most. What impedance do you guys think would work best for a nice balance of Marshally Crunchiness and some edge of break up chime? 3.8K, 4K, 4.2K?

Thanks for you input.

Here are some pics.

[IMG:640:480]http://i169.photobucket.com/albums/u223/fusionbear/Low%20Watt%202204%20Build/IMG_1835_zps31e1c8a1.jpg[/img]

[IMG:640:480]http://i169.photobucket.com/albums/u223/fusionbear/Low%20Watt%202204%20Build/IMG_1836_zps4db892b6.jpg[/img]

Reeltarded · Post by **Reeltarded** » Thu Jun 06, 2013 9:32 am

Food for thought: magic Marshalls (100w) are often found to have 2k2-2k5 output primaries. I am going to use Bassman head spec OT in a 50w soon because I think that puts me right in the middle there.

As usual, you have outdone yourself with a beautiful amp build! Awesome!

ToneMerc · Post by **ToneMerc** » Thu Jun 06, 2013 10:25 am

Terribly easy choice here, a Marshall 50w Drake or clone.

784-139

TM

jon · Post by **jon** » Thu Jun 06, 2013 10:42 am

ToneMerc wrote:Terribly easy choice here, a Marshall 50w Drake or clone.

784-139

TM

+1

katopan · Post by **katopan** » Thu Jun 06, 2013 11:53 am

And that lines up with the fact a 6V6 18 watt sounds great with the stock 8K OT, so a quad would be half that or around 4K.

fusionbear · Post by **fusionbear** » Thu Jun 06, 2013 12:22 pm

Thanks gents!

A friend of mine has a amazing sounding 50 watt plexi clone. I will use the OT he got.

I will post as I get the parts and start building...

Thank you!

cbass · Post by **cbass** » Thu Jun 06, 2013 12:53 pm

Nice looking build I think around 4k would be a good hoice.What kinda voltages you runnin?

Firestorm · Post by **Firestorm** » Thu Jun 06, 2013 2:40 pm

Impedance aside, I remember when Moose was originally having Heyboer OTs made for Express amps, he specced M27 steel, which turned out to be cruncher than the later, more "proper" M19/26. You might call your intended vendor(s) and ask about the laminations.

Phil_S · Post by **Phil_S** » Thu Jun 06, 2013 4:33 pm

Anyone who can make such a tidy build shouldn't be permitted to ask questions. Kidding aside, they have a 36W model over at 18watt.com that uses 4x EL84,. Whatever they are using there, that should be the right OT. It is one thing to say it should be 4K (FWIW I agree that 4K is right if voltages are similar), and another regarding the other characteristics of the OT.

The schematic for the 36W shows the item as Heyboer HTS-7013-1 and plate voltage is spec'd at 322VDC.

tubeswell · Post by **tubeswell** » Thu Jun 06, 2013 5:35 pm

If your plate voltages are around 350, then 4k. And if they are over 400, then maybe 3k3.

fusionbear · Post by **fusionbear** » Thu Jun 06, 2013 6:02 pm

tubeswell wrote:If your plate voltages are around 350, then 4k. And if they are over 400, then maybe 3k3.

I am glad I asked. The plate voltage is about 420V, but I might spec a slightly lower voltage PT. I would like to keep the plate voltage no higher than 400.

Thoughts?

ToneMerc · Post by **ToneMerc** » Thu Jun 06, 2013 6:33 pm

fusionbear wrote:
tubeswell wrote:If your plate voltages are around 350, then 4k. And if they are over 400, then maybe 3k3.
I am glad I asked. The plate voltage is about 420V, but I might spec a slightly lower voltage PT. I would like to keep the plate voltage no higher than 400.

Thoughts?

My thoughts, you are on the road to making this far too complicated. In all honestly, I dont think you will notice much difference between a 3.8, 4 or a 4.2. I built three Dumble style amps with quad 6V6's, all had a Marshall style OT transformers, one at 3.4, the others 3.8K and voltages ranged from 388-412 volts. The least of my concerns was the difference between a 3.4 and 3.8 primary impedance

TM

tubeswell · Post by **tubeswell** » Thu Jun 06, 2013 6:34 pm

A princeton reverb (running at about 420) sounds good with a deluxe reverb OT (which is spec'd at 6k6 and slightly bigger than a stock 8k princeton OT) and with a 12" speaker. (Soundbyte attached of one I did like this). So I figure 1/2 of that is 3k3.

Having said that, I did a 5G9 a while back with 6k OT which was running at 380. (Soundbyte attached FWIW)

Remember that in Class AB, you can have the load line 'above' the max Wa curve. (Its a bendy load line) Also if you bias it cooler (fixed bias that is) you can happily run the load resistance lower (as the load line drops a bit). Use 2W or 3W Rg2. If you go with JJ6V6S they seem to handle it pretty well. That's my theory anyway and I'm just a hobbyist who does what I likes. YMMV

fusionbear · Post by **fusionbear** » Sun Jun 09, 2013 2:48 am

Here are a few clips of the amp in question:

http://www.youtube.com/watch?v=fPfHkcDb5aA

http://www.youtube.com/watch?v=Nsw6qL23JIo

http://www.youtube.com/watch?v=PRSr2Pe6YPw

I really like the way this amp came out...

cbass · Post by **cbass** » Sun Jun 09, 2013 2:55 am

sounds great

Tube Amp Archive

What OT for 4- 6V6 Marshally build?

What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?

Re: What OT for 4- 6V6 Marshally build?