Low wattage Tremolo TMB reverb

[Bieworm]

Hey Josh... I would like to build a low wattage 3-5 watts tremolo TMB. Maybe ECL80 power tubes. Any ideas to pull this off?

[JMPGuitars]

Hey Josh... I would like to build a low wattage 3-5 watts tremolo TMB. Maybe ECL80 power tubes. Any ideas to pull this off?

Yeah, convert the power amp section and adjust the LTP to suit.

Thanks,
Josh

[Bieworm]

Jack, is the ECL80 a good way to go? Is the 125A a useable OT for that application? Any opinions? Jukeboxrevival sells these dirt cheap...
https://www.jukebox-revival.eu/catalogs ... t/?q=Ecl80

[JMPGuitars]

I don't really have an opinion of my own on the ECL80, I've never tried them. But from what I read of other opinions on the interwebs, it's not a great tube for guitar amps. Not great for getting good distortion, and there are stability issues people think an NFB helps with, which would obviously be a big no no for the TTMBR. I also get the impression it wouldn't give you the dirt you want either.

Thanks,
Josh

[Bieworm]

I don't really have an opinion of my own on the ECL80, I've never tried them. But from what I read of other opinions on the interwebs, it's not a great tube for guitar amps. Not great for getting good distortion, and there are stability issues people think an NFB helps with, which would obviously be a big no no for the TTMBR. I also get the impression it wouldn't give you the dirt you want either.

Thanks,
Josh

You're probably right. The moreI read about them, the less desireable they become.
VVR...that's the way to go me guesses

[JMPGuitars]

You're probably right. The moreI read about them, the less desireable they become.
VVR...that's the way to go me guesses

There's certainly other options out there. I've also toyed with the idea of doing an SE EL84 version, but that eliminates the PI, which obviously changes the sound of the amp a bit. I've also been curious about 6K6 or EL91, but I haven't bothered to look for or listen to any amps with them yet. Another option that might sound good, is to use two 12AU7s. Each one can be wired in parallel.

[Bieworm]

You're probably right. The moreI read about them, the less desireable they become.
VVR...that's the way to go me guesses

There's certainly other options out there. I've also toyed with the idea of doing an SE EL84 version, but that eliminates the PI, which obviously changes the sound of the amp a bit. I've also been curious about 6K6 or EL91, but I haven't bothered to look for or listen to any amps with them yet. Another option that might sound good, is to use two 12AU7s. Each one can be wired in parallel.

Now you mention it.. those 12AU7 tubes sound very good IMHO. It's just getting the PI to match the tremolo TMB. If I parallel them I need a 10k OT primary, right? That 125A has multiple taps.. so that's a good option..

[Bieworm]

Crap.. I should have not opted the VVR.. now he wants that. Best from both worlds...18 watt and less on tap. I Hope the VVR is gonna work out on the tremolo TMB reverb.. surely just scale down the PI and power amp to ensure tremolo to operate well?

[JMPGuitars]

Crap.. I should have not opted the VVR.. now he wants that. Best from both worlds...18 watt and less on tap. I Hope the VVR is gonna work out on the tremolo TMB reverb.. surely just scale down the PI and power amp to ensure tremolo to operate well?

I'm not a VVR guy, I can't offer any help with that. I'm sure somebody else can chime in. I would also be concerned with the trem. They should just get a standard TTMBR and use a good attenuator.

[Bieworm]

Crap.. I should have not opted the VVR.. now he wants that. Best from both worlds...18 watt and less on tap. I Hope the VVR is gonna work out on the tremolo TMB reverb.. surely just scale down the PI and power amp to ensure tremolo to operate well?

I'm not a VVR guy, I can't offer any help with that. I'm sure somebody else can chime in. I would also be concerned with the trem. They should just get a standard TTMBR and use a good attenuator.

I know...

[Daviedawg]

Yes you are right. The VVR will have to be PI and PA only as the tremolo will not work on lower voltage to its half of the preamp valve. Even small voltage changes can stop it starting up.

Dd

[Bieworm]

I thought so.. but I have been looking up amp schematics with VVR. I stumbled upon the 18W TBM SIII VVR and took that with a bit of tweaking into Josh's Tramolo TMB Reverb.
This is what I came up with... worth a shot? No offence Josh, but manipulating your schematic was the easiest way for me to clarify what I'm thinking of. Not meaning to hijack your work...

18 watt tremolo TMB reverb VVR mod.png

[Bieworm]

Tube Town sells a VVR kit. They appear to put it on the power tube screens. Is that effective compared to the usual way it's done?
https://www.tube-town.net/cms/?DIY/Amp- ... Control-EN

[Bieworm]

I have another idea.. suppose I use the primarywindings.uk 20W PTX. It has a HT secondary with an extra tap. 190V and 275V. I could look into making that switchable.. 3 way: 0-190 / 0-275 and 190-275
Suppose I can do the switching simultaneously with the cathode resistor.. wouldn't that he something to look into further? Ampmaker advertises the TX for those applications...

[geoff 1965]

That VoCo on the screen voltage looks interesting,have’nt seen any feedback though from anyone who has used it.

[Bieworm]

That VoCo on the screen voltage looks interesting,have’nt seen any feedback though from anyone who has used it.

I guess we'll find out

[TriodeLuvr]

Jack, is the ECL80 a good way to go? Is the 125A a useable OT for that application? Any opinions? Jukeboxrevival sells these dirt cheap...
https://www.jukebox-revival.eu/catalogs ... t/?q=Ecl80

The ECL80 can't be used for a push-pull TMB-style amp from what I see in the data sheet. The pentode and triode have a shared cathode. There's no way to separate them to create a long tailed pair PI driving a push pull output. Actually, I suspect the shared cathode configuration is the reason they're inexpensive. You can build a push pull amp with these tubes, but it requires trickery and is unlikely to produce the tone you want.

The Hammond 125 series has a very limited low end response with some impedance combinations. The 125A looks OK if the 8 ohm output is used in conjunction with the 11.6K (or less) primary taps.

For the power level you're asking about, triodes are probably more useful. A tube like the 6BL7 (dual triode, octal base) or a pair of 12B4 (single triode, 9-pin miniature) would be excellent. Both types are characterized by low Rp, so they don't require the use of high-Z transformer taps.



Jack

[TriodeLuvr]

Just an afterthought, one more consideration regarding the 125A is its limit of 20 mA per side. I would move up to the 125C, which is rated 45 mA. Here in the States, there's very little difference in the price of any transformer in this series.

Jack

Note: The Hammond site is inconsistent regarding the maximum standing current of these two transformers. One page specifies them as I listed above, another states 25 mA and 60 mA respectively for the 125A and 125C.

[Bieworm]

thanks Jack... but I'm not going that route anymore. I've convinced the man the best way to go is the 18 watt. I'm going to do some testing with the different secondary taps to see if that is a better alternative for attenuating things. The only concern is the tremolo operation at lower voltages.. but since tremolo isn't that important to him it's no disaster if it don't wiggle at lower B+ settings.
OTOH I could look into the mosfet IRF840 system that the toneking has. That tremolo is pretty darn good too...
Lots to think about for now.. even been thinking about building him a superlite TMB with reverb for that matter

[JMPGuitars]

thanks Jack... but I'm not going that route anymore. I've convinced the man the best way to go is the 18 watt. I'm going to do some testing with the different secondary taps to see if that is a better alternative for attenuating things. The only concern is the tremolo operation at lower voltages.. but since tremolo isn't that important to him it's no disaster if it don't wiggle at lower B+ settings.
OTOH I could look into the mosfet IRF840 system that the toneking has. That tremolo is pretty darn good too...
Lots to think about for now.. even been thinking about building him a superlite TMB with reverb for that matter

Definitely go with the SLTMB if he doesn't care about tremolo. It's a great amp, and then you won't have your trem voltage concerns.