The Ultimate Tone Forum

Full Version: ToT + Resonance
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
I'm now in the planning stages of building a new amp head from scratch.  Plenty of chassis room to work with.  This will be my first LPSP,  I am looking forward to that.  Plan now is the to build the power supply, PA and preamp from ToT but with eyelet cards. 

"thunderous smooth" described in TUT caught my attention - I do not like bright tones or hard distortion.  Would the Active resonance presence circuit, fig 6-34 of TUT, work well in the ToT PA?  I'd use both 12AX7 tubes in the EQ network shown.  Would it work following C1 of the PA, fig 6-2 of ToT, with an added coupling cap?  0.47u?  Would a a larger OPT be a little smoother than the 1608 in the circuit?  I have a single 6lb 6.6k OPT that I could use.  6V6, 5881, 6Pi3C-E and 6L6 all are to be tried.  I will add a triode/pentode switch.  I plan to use the bias supply as described in ToT . 


I want to lay out the circuit cards and build this up from scratch.   I mostly play rhythm, the other guitarist I play with has a bright setup and I try to keep things lower (tone wise) and slightly clean to over-driven.  P-90s are on the guitar.

Thanks for any input from anyone, anywhere here.
Hi Sinusoids

Note that an eyelet card layout for the LPSP is available in TUT5 The Standard. The PA for that project is different than the TOT (Tonnes of Tone) PA, the latter which is definitely warmer sounding.

When laying out an eyelet card or any other type of physical circuit construction, try to keep the signal path as straight as possible inasmuch as it should move from one end of the chassis to the other and not cross itself. You should try to follow the Galactic ground scheme shown in TUT3. For example, the 800 has the same tube complement as you intend to employ except for twice as many power tubes, but otherwise, you could use it as a general guide. The preamp would necessarily be different for your project but the overall look will be the same as the 800.

When considering how to assign the physical tube stages to the circuit, the assignment in TOT Fig.4-1 is best. It keeps the signal moving in one direction for the lead sound, which uses all four triodes. The clean sound moves in the same direction but skips two stages.

Note that the TOT PA is 10W, which is fine if you have a couple of large detuned cabinets. You are likely going to find more power is useful if you use other cabinet styles and/or small drivers.Keep in mind that it is better to have too much power than too little as Power Scaling can control loudness in ANY tube amp.

What is the power rating for your 6k6 OT?

As far as adding a presence-resonance circuit, if you are looking at the active circuit in TUT Fig.6-34, this simply goes between the output cap of the preamp and the input stage of the PA.
I planned to use the Standard switch circuit and card. I think the standard is laid out chassis side down. i could drill out the Standard eyelet card and then flip it over. My pre chassis will be separate and upside down - above the PS/PA. lots of room and access to the circuit cards. I read the other thread re wiring two chassis and took notes.

The ToT PA is warmer sounding of the two?

I have drawn out the PS/PA layout and also the power supply + 6VDC regulator card and the bias divider/pot card so far. Somewhere here (on the forum) you mentioned a fine point or update for one of the galactic ground drawings in one of the books. i cannot seem to find that again. I'd like to reread and make note of that post.

I hope I am correctly following your layouts - power in opposite direction of signal, transformer orientation, etc.

I bought a 2x12 pine cab on ePay. It is now loaded with one Eminence EM12 driver. I could post a picture for reference. It is slightly bigger than your 2x12 dimensions in SPKR and has a port across the bottom like the TL806. I can block/tune the port. I just did not want to build a cab. It was 10x the price of a sheet of ply though.

The 6k6 opt is an old hifi UL. Masking tape said Bogen. Could be, is Z mount and weighs 6.5 lbs. 40-50W? I could save it for another amp. But I have done that for a very long time.

The TUT 6-34 active resonance circuit should be followed by a coupling cap, correct? 10x the cap it follows, like a MV mod? I wrote two 12AX7 tubes and meant two 12AX7 triodes = 1 tube, the version on the right side of the fig.
Hi sinusoids

The TOT PA uses an 8k OT.  Your 6k6 OT is likely a bit "heavy" for the PT in TOT's EPS (Experimenter's Power Supply). You can still use your OT but there might be more supply sag when you drive the amp hard.

In the supply, R2 would be better as a choke, or as 10R-10W, or make it 1k-5W and use C1 for Va and C2 for Vs

The TOT PA has no input cap, so the output cap of the res-pres circuit does not have to be large - 22nF is sufficient.

I expect that your pine cabinet is 12" deep or less. I've never seen one deeper. That will reduce some of the bass output compared to having 16" depth regardless of whether the baffle area is larger than shown in SPKR.
Thanks for all this info. I will re read all of this a few times and review the 800 and standard plans to incorporate everything I can.

Likely best to use the 8k OPT as you designed and see how that sounds with the cab (it is 12in deep). That way I have a baseline and known good starting point for comparison if I really want to try the big OPT or other changes later on.
Seems like really cool project! I might suggest adding one of the SUS kits to it. You said that your preferred smooth tones and the SUS really go a long way to adding some pleasant compression and bloom to the amp. I've used a few of them and was really pleased with the results.
Thanks for calling my attn to this kit - I had to look it up to what you were referring to and had not looked at the extensive kit catalog in way too long. One of the QRKs could be used to switch channels as well. Transistors in eyelet cards gets tight. Maybe a 7912 to supply the QRK. I had planned to use a vector card for the switching stuff.
What amps did you add these to? I decided to build ToT due to the LPSP because I didn't want to commit to the Standard amp build having never heard the this preamp. Kept putting it off. and off.
Hi sinusoids

ERK (Electronic Relay Kit) is the usual means to channel switch the LPSP. (LP-PRE in kit form). ERK needs negative voltage, so if there is a fixed bias supply to tap then you do not need anything extra.

ERK uses jfets for the switching, and these are located on the pots or the card as is convenient.

Build the amp first and then lay in the switching as another layer, as it were. Testing prior to switching requires turning controls up and down to hear the two channels independently.

LPSP is voiced as a Fender clean channel and hot-rodded Marshall lead channel. The latter particularly can be voiced as hot or mild as you want simply by changing Rs or Cs, any of which can be made switchable themselves (as presets typically).

When you look at a project like The Standard, you can decide to build only a portion of it and/or change any part of it. For example, you could build it without the effects loop, or without the reverb, or without both reverb and effects loop, or just as a preamp. You could replace the push-pull PA with a single-ended amp. The relevant point to you being that in this instance where the TOT project and the TUT5 projects use the same preamp circuit, you have two examples of how to build it.

Another important point when considering a project is to look at a lot of other projects that do not seem related, as there might be a good idea to lift and incorporate into yours. For example, the Body control in the TUT3 SVT project can be applied to any push-pull amp.
I built this with one goal being easy mod and plenty of room for changes, that may not happen soon.  It seems to sound great.  LPSP layout is from the Standard amp and the supplies and PA circuits are straight from ToT, except all filaments are 6VAC, biased at ~50VDC.  This is my first LPSP. Easy to dial in a good tone is true.  May try some of the TUT options - lower lead plate resistors, thick switch, etc.  Looks kluged but works great for me.[attachment=33][attachment=33][attachment=34][attachment=35]
Does Idss matter if the application is your channel switch? The 2SK30As available are binned and marked for Idss. GR (3-6 mA) seems most common. Looks like the pedal builders use these too. Thanks.
Hi

Jfet Idss is not important for switching unless the signal currents can be significant, i.e. all the circuit impedances are very low, none of which is the case in a tube amp.

Rds-on is the key figure of merit for jfets as audio mutes. In the late 1980s I used the 2SK30s because the pedal guys used them, but later I realised it is actually far from the ideal audio switch. It has a very low Vgs so goes from looking like an infinite resistance down to its lowest resistance with very little gate voltage, which is ideal when the supply voltage is effectively half of a 9V battery. Rds for the 2SK30 is about 400R, which is okay in a tube amp where series resistances are in kilohms or tens of kilohms.

The best jfets for switching are the National Semiconductor series from J105 to J112. These have a lower Vds rating than the 2SK30 but there on-resistance is <100R for the high-end of the series and as low as a few ohms at the other end.
Hi Sinusoids

The mechanical arrangement of your amp is clever in that the two chassis have their open side out for easy modification and repair.

The only questionable facet is the heat of the power tubes between the chassis may cause accelerated aging of the preamp components. Maybe a fan should be added if there is not one already. This can be a 12Vdc fan operated from 8Vdc generated from the 6V heater.