Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Toxophilite on November 19, 2015, 03:47:03 am
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Is there a good , relatively simple tube tremelo that isn't a bias vary, opti-bug, or harmonic vibrato.(though these are all great) One that could be used in a preamp for recording in an apartment?
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There are plenty out there. Gotta look at the bargain bin, lesser known amps. I've built this one...
http://el34world.com/charts/Schematics/files/marshall/marshall_18watt_schem.pdf (http://el34world.com/charts/Schematics/files/marshall/marshall_18watt_schem.pdf)
Here's another one...
http://el34world.com/charts/Schematics/files/supro/supro_1624t_scematic_263.pdf (http://el34world.com/charts/Schematics/files/supro/supro_1624t_scematic_263.pdf)
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I really like this tremolo as it is inserted to the cathode of V1. Of course it is bias vary, but not on the power tube and yes it does insert prior to anything else. I like it because it is so easy to add and can be very strong if you desire. In video is poor quality, but it will give you an idea. I added this to the normal channel of a Super Reverb I have and prefer the normal channel. I did put reverb on this as well so the tremolo is prior to reverb which makes it have an echo "feel". Very usable IMO.
The only issue I have had is getting it tweaked where it is not too strong. He starts the tremolo after 1 minute.
! No longer available (http://www.youtube.com/watch?v=DFsO4_UGWHI#)
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Is there a good , relatively simple tube tremelo that isn't a bias vary ...
Trick question, as Ed pointed out a lot of the preamp-based trems are bias-vary, just altering the bias of a preamp tube instead of the output tubes.
I'm surprised no one simply pointed to the VibroChamp (http://el34world.com/charts/Schematics/files/fender/Fender_VIBRO_CHAMP_AA764.pdf).
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I used the trem from a Gibson skylark subtle trem, nothing over the top, fwiw
http://el34world.com/charts/Schematics/files/gibson/Gibson_GA-5T_67_Skylark.pdf (http://el34world.com/charts/Schematics/files/gibson/Gibson_GA-5T_67_Skylark.pdf)
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There appear to be several possible insertion points for tremolo:
First preamp triode
Last preamp triode before PI or poweramp
Power tube
Seems like I've seen at least one circuit where the second grid of a Long-tailed phase inverter was used as the insertion point in an amp without negative feedback. Can't remember where though.
I've only played amps with power tube bias-vary tremolo. Have used a tremolo pedal before the amp though. Inserting tremolo earlier in the signal path means preamp distortion or compression varies with the tremolo, right? Must be a matter of taste, but any opinions on which insertion point you all like better?
Just curious,
Chip
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Seems like I've seen at least one circuit where the second grid of a Long-tailed phase inverter was used as the insertion point in an amp without negative feedback. Can't remember where though.
The Fender Tremolux (http://el34world.com/charts/Schematics/files/fender/Fender_TREMOLUX_5E9A.pdf) varied the bias at the shared cathode connection of a paraphase inverter.
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Inserting tremolo earlier in the signal path means preamp distortion or compression varies with the tremolo, right?
Must be a matter of taste, but any opinions on which insertion point you all like better?
Good question. :think1:
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To me insertion points vary per amp. For instance if I have only a simple tone control I will insert at the first tube, but if a higher power amp I prefer to insert at the power tubes as I am usually using these type of amps for performing and will use tremolo in a loop. This is because I will need to cover more tones.
If I am making a low watter I will usually insert early, but if it has reverb it takes a lot of tweaking to get them to get along. Normally I have to remove a lot of the higher frequencies from the verb so it does sound like the reverb does not continues during the low peaks. If not it kind of makes a ping pong sound.
I do have exceptions as I tried inserting the first tube in a 5E3 and monkeyed with the PI values but the asymmetrical distortion did not sound very good thumping. It ended up at the PI as HBP mentioned.
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The whole reason for Fender's Tremolux tremolo (and later variants moved to vary output tube bias) was to cancel pumping noise when the trem is activated. But there can still be pumping noise, and it's hard to get big enough swings to trem 6L6's effectively in later amps.
You're best just trying for yourself in a suitable experimental amp.
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This would be a stand alone preamp, that's why I couldn't consider output tube bias vary or even something that interacts with the PI.
Some cool suggestions, just checking them out is interesting!
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There's a number of the smaller Gibson 15w to 20w PP/2x6V6's amps that have preamp bias vari.
Most have an octal/8 pin pre tube but a few use a 12AX7 for the LFO (low frequency oscillator).