Finding the Right OT - Quad of EL84

[Weathered]

I'm looking to start acquiring parts for a new build, and all I have left to figure out where to source it from is my OT. The amp is going to be running a quad of EL84, but fixed bias rather than cathode biased, which is going to up the wattage output just a bit.

PT is going to be a TW PT, since I can use the 260-0-260 taps to get the right B+ (going to be SS recto rather than tube, so I think going with an AC30 290-0-290 would push the B+ too high for EL84s).

I've been thinking about just going with an AC30 OT, but want to be sure I'm not going to overwork it. So far, I know that I need a 4K primary, and it needs to be able to handle the output of a quad of EL84.

Any ideas apart from going to a custom build from Edcor/Heyboer/etc? Could the AC30 iron handle the higher wattage coming from fixed bias and a bit higher plate voltage?

Edit: Did some searching, and it sounds like the Dynaco 470 clone might be the way to roll. Thinking I may just order the Heyboer 'wreck set from RJ and roll with that - I see no reason not to.

[oldhousescott]

Unless you plan on going ultra-linear, the Dynaco is overkill. The TW OT is also perhaps not the best choice at 6k6 primary impedance. You could actually get by with the Fender HRD or Bassman OT at Triode Electronics. The Allen TO35MT or TO40MT would also work.

[dartanion]

The Heyboer TW OT has both 5.2k and 6.6k primaries. The Pacifics are single primaries at 4.3K, 5.2k, and 6.6k. Overkill? Maybe. Depends on what you want tonally. Also consider the various Marshall 36W OTs as options. Basically a double 18W setup, so based on Radio Spares. As well, there are a few different Heyboer made AC30 OTs with different lams (M6, M19, and M50).

Lots of options.

[M Fowler]

I have a Traynor 18w amp on my bench with 310-0-310 secondary SS recto with fixed bias.

The Pacific PT with 280-0-280 might work nicely I use the 300-0-300 for my builds but I use 5AR4 recto though.

I would use the A-470-S Dynaco 4k3 primary.

Mark

[Weathered]

The Heyboer TW OT has both 5.2k and 6.6k primaries. The Pacifics are single primaries at 4.3K, 5.2k, and 6.6k. Overkill? Maybe. Depends on what you want tonally. Also consider the various Marshall 36W OTs as options. Basically a double 18W setup, so based on Radio Spares. As well, there are a few different Heyboer made AC30 OTs with different lams (M6, M19, and M50).

Lots of options.

I saw that RJ has an Edcor that has a dual 4K3 and 5K2 primary - thinking that may be my best option. I want a pretty crisp sounding power amp, so headroom in the OT isn't really a bad thing - I don't really want the amp to compress until I hit 7-8 on the volume knob, unlike my old AC30 that started to compress around 3-4.

[Cliff Schecht]

The Heyboer TW OT has both 5.2k and 6.6k primaries. The Pacifics are single primaries at 4.3K, 5.2k, and 6.6k. Overkill? Maybe. Depends on what you want tonally. Also consider the various Marshall 36W OTs as options. Basically a double 18W setup, so based on Radio Spares. As well, there are a few different Heyboer made AC30 OTs with different lams (M6, M19, and M50).

Lots of options.

What is M50? I thought the progression was (thinnest lams to fattest) M2, M3, M4, M5, M6, M19 (at least in with what we use for audio purposes). Never heard of M50...

[dartanion]

The Heyboer TW OT has both 5.2k and 6.6k primaries. The Pacifics are single primaries at 4.3K, 5.2k, and 6.6k. Overkill? Maybe. Depends on what you want tonally. Also consider the various Marshall 36W OTs as options. Basically a double 18W setup, so based on Radio Spares. As well, there are a few different Heyboer made AC30 OTs with different lams (M6, M19, and M50).

Lots of options.

What is M50? I thought the progression was (thinnest lams to fattest) M2, M3, M4, M5, M6, M19 (at least in with what we use for audio purposes). Never heard of M50...

Check out this link to Edcors site:

http://www.edcorusa.com/Topic.aspx?TopicID=21

It's a nice discussion about lamination alloys.

[rp]

I've used the 15W set, and a few PTs, I thought they were first rate w/ great sound.

http://www.transformerdesignandsupply.com/

http://www.westlabs.com/Trannys.HTML#5watt

[Roe]

the classictone ac30 ot works well

[212Mavguy]

This is admittedly way out of left field, but why not see if you can get one from Mesa Engineering? (Mesa Boogie) The one for the now discontinued Maverick should work, since the Maverick is a 4-el84 amp. They also currently produce a 4-el84 amp, the Lone Star Special. Both of those amps sound godly.

[Weathered]

I've used the 15W set, and a few PTs, I thought they were first rate w/ great sound.

http://www.transformerdesignandsupply.com/

http://www.westlabs.com/Trannys.HTML#5watt

I looked at the West Labs stuff and loved it, but for the price.....

I may still purchase some transformers from West Labs at some point, but that would more than likely be for a DC30/AC30 clone.

the classictone ac30 ot works well

That's the way I'm leaning right now - the TW35 PT (with dual HT taps) and the AC30 OT. Otherwise, there is a Bandmaster etc. OT that is designed for ~40 watts and has a 4K2 primary, which would be pretty close as well. Also happens to be a bit cheaper than the AC30 OT.

[M Fowler]

Most brands are cheaper then the AC30 OT and in my opinion the AC30 OT is wimpy compared to the Dynclone A-470-S or Heyboer 5k2 for the four EL84 amp.

Or call Alden at Heyboer get a custom OT which from my experience the cost is lower. Even at dealer pricing the AC30 is high.