suggestions for optimizing loud & clean (50w)

[Pete]

I have been giging with my 50W (2 6L6) build for a couple years and find that it is often lacking in clean headroom especially at higher band dynamics.

I would appreciate any comments and suggestions for techniques addressing optimizing the circuits for clean headroom. i.e. the loudest and cleanest in non OD mode.

Specs are: Magic Parts Bassman replacement iron w/choke, EH tubes (6L6 & 12AX7), circuit is 99% the #0124 (non HRM), 1X12 combo cab.

Speakers I have experimented with include old EVM12L, Emi Tonker, Celestion Classic Lead 80, Heritage G12-65 all with similar disappointing results in the area of clean volume.

I have a '67 Super Reverb and '69 Bassman head for reference and would describe my experience with my ODS clone as not quite up to par by comparison.

I guess I'm looking for a sanity check and to see if I'm missing something or just expecting too much. Are other's 50 watt clone amps as loud or louder than 50w Fenders?
Thanks

[Chris333]

I have a non-HRM (pretty close to the ODS-101 schematic) with an OT that's a replacement 80W Twin style, running two KT-66s into a JBL K-130 or an EV SRO (both are 15"). It stays pretty clean. Also have a '66 Tremolux, which isn't 50W, probably more like 35, but anyway, my clone is definitely louder/cleaner. I have an EVM 12L, and it's pretty clean, but it sounds hostile compared to the JBL or the SRO. I suppose your combo cab won't fit a 15, but if you like clean, you might wanna try one.

Anyway, I would think a 100W OT would help, and if your PT can handle the heater current, maybe try a pair of 6550s. I had one of those '70s Marshalls with a pair of those, and without a dirtbox in front of it, it was so loud, clean and clangy it would make your skin hurt. Still, the highs and lows would start to round off with the volume above 5, even though it wouldn't really get any louder. Maybe you just need a 100 watt amp...

[heisthl]

Ditto on the D130 - they are so efficient that a 50 watt build I just did(delta in the files section) is waaaay louder than the twin w/ev-12ls that the guy is replacing. I'm talking 2 or 3 times louder....most of it I attribute to the D130 but you may want to look at my schematic to see how it differs from yours in the clean area.

[Tonegeek]

You have probably done this, but-
1) Check you plate voltages. When I upped V1A on mine just 10 volts (to 200v), it cleaned it up a noticeable amount.
2) You can reduce neg feedback which will give a cleaner/louder sound (tone will change too though - just try it and see)
3) Make sure bias is correct for tube you are using. You may be losing some power if the tubes are over biased.
4) If no choke, put it back in to clean it up. More filtering will clean it up too.
5 ) Check the mains voltage at the clubs you play.
6 ) I second the 6550's suggestion. My 50W JCM 800 w/6550's was easily as loud as my 100W Twin

[Pete]

Thanks for the comments

I have played D130s with my '69 Bandmaster Reverb (purchased new) many years ago. My memory today has little detail of the undoubtedly great clean guitar tone I had. A very good suggestion. Possibly more for clean only and a compromise for the OD sound, and less desirable for portability.

Another suggestion I like is the use of bigger & better OT. I would like to investigate more and learn more about that.

heisthl, I'll check out your schematic of the delta, thanks. At first glance I noticed no neg FB, is that really best for clean headroom?

You have probably done this, but-
1) Check you plate voltages. When I upped V1A on mine just 10 volts (to 200v), it cleaned it up a noticeable amount.
2) You can reduce neg feedback which will give a cleaner/louder sound (tone will change too though - just try it and see)
3) Make sure bias is correct for tube you are using. You may be losing some power if the tubes are over biased.
4) If no choke, put it back in to clean it up. More filtering will clean it up too.
5 ) Check the mains voltage at the clubs you play.
6 ) I second the 6550's suggestion. My 50W JCM 800 w/6550's was easily as loud as my 100W Twin

I'm getting about 195v on V1 plates, I will try bumping it up some.
Plate voltage on outputs is 468V - biased 32-33 ma

I played with neg feedback (global) once long ago. It seemed to me that more FB cleaned it up some but you lose volume, so you turn it up and then it just breaks up easier. I may need to experiment a bit more to see if I can optimize this.
My amps have chokes and 220µf/350v stacked filtering @ first stage

I will make note of line voltage at venues.

I'm also considering a fresh build with 6550s just to compare things, don't have the tubes on hand right now but may have some suitable iron lying around.
thanks, Pete