OT and bass response for AC15

[MysteryFever]

Hey Folks,

Getting around to scratch building an AC15, not quite verbatim to any classic circuit;
my aim is to improve bass response. I'm thinkin about ordering this set: http://westlabs.com/Trannys.HTML#15watt

Is there someone willing to recommend me a better option (if there is one) based on what
I'm trying to accomplish? There's an awful lot of transformers out there...

[M Fowler]

That is a very high quality transformer set and would make a great sounding amp.

Sure there are other transformers available but you picked a good set.
With other transformers you could get a standup version if space inside the chassis is a concern.

Mark

[Weathered]

With regard to bass response, what kind of "more bass" are you looking for? There are a few ways you could do it, depending on what you want. If you want tighter low end, but more of it, you're likely looking power amp, and probably going to have to tighten up power amp to keep it from getting overly loose with the extra low end. If you're going to be overdriving the preamp, you'll want to keep the low end in control between stages by using the stock (or possibly even smaller than stock) coupling caps between stages. If you're going to be shooting to run the amp a bit cleaner, you can get away with larger coupling caps.

Are you going to be building the EF86 based AC15, or 12AX7 based preamp?

[MysteryFever]

I'll be going with the 12AX7 based top-boost style circuit but I'll be likely to try using smaller cathode bypass caps as part of my effort to achieve tight bass response. I want to keep the bass end of things clean and controlled without cutting it off, even when driving the amp. With the preamp you can tweak around without expensive or exhaustive repercussions, but I want to make sure that I've got a good OT that won't distort unpleasantly or flub out when fed a healthy dose of bass frequencies.

[rp]

The TDS tranies are first rate. I've have used two set, the PTs run really cool, always a good sign. But a heads up, these are Matchless tranies, the 15W OT is 4K as for some reason Matchless liked it that way, the AC15 is likey 6K-8K (IIRC it's 6K). Also that choke is itsy bitsy, it's correct for the Lightning/Spitfire but might be too small for the Vox, compare the schematics to be sure where it's placed. An AC15 with that OT would likely sound fine too, might change the tone a bit, maybe for the better, who knows. BTW their 30W is also 4K which is correct for the AC30.

[Crumpletone]

I've built loads of AC15 based units for customers, never had a bad comment and the trannies i've used have been the Hammond 1750Y which has a 6K3 primary and Danbury electronics OT's which are built in the UK and have a 6K2 primary. both sound brilliant and 6K2 was the original Vox/Dick Denney spec.
Choke wise i use the Hammond 158M, 100ma, 10H and 2620hms, works fine.
To tighten up the bass response i would agree that upping the filtering is an option but not the preamp node capacitors as it would adversly affect the core tone of the amp, try playing with the tonestack values, you can have a look at the Duncan tone stack calculator, should give you some good ideas.