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I use a Fuchs Verbrator with my OTS. I've had it for 3 years - fantastic piece of kit, great sounding reverb, very reliable.

The "high plate" with 150k slope features in many Dumble circuits, most commonly with the "Skyliner" tonestack which is included in the OTS. One of the most famous Dumble amps (Robben Fords) serial number 102 also has same mismatch.

I'm not trying to pick a fault in your observations, mearly pointing out that the Ceriatone OTS replicates the architrecture and component values that are found in actual Dumble amps. I'm all for modifying the circuit as the standard design will not suit all tastes, playing styles or guitars.

My OTS was built in 2009, it was built with a 220k slope, when I noticed this, I changed it to stock 150k value and preferred the resulting sound.....bottom line is that it is a great amp platform.

Your observation regarding impact on output impedance of V1a verses Anode (Plate) resistors is perfectly valid however there was no mistake in the use of 220K / 150K plate loads.

There are a few different variants of D - Style circuits and the 220k/150k version is more generically referred to as "High Plate" - 100k/100k is referred to as low plate. The values of the components used in the following tone stack within the Ceriatone OTS amps are based on actual examples of Dumble produced amps. Tweaking the amp to suit your personal tastes is not a bad option assuming that you have the necessary knowledge and experience with High Voltage electronics with respect to personal safety.

I had a set of Fralin Blues Specials complete with Base Plate on Bridge Pickup, to be honest they sounded much the same as the Lollars that I currently have fitted - the neck / middle and "in between" sound great - the bridge is very weedy and thin.

I'm relatively inexperienced with Strats - my other guitar is a Hot Rodded Telecaster (Fender Japan Ritchie Kotzen) this has a mini humbucker in the Bridge position and it absolutely sings - I can roll the tone back and get something that is close enough to the Matt Schofield tone - with a Strat, I can't get near.

My pickups are set quite low - about 1.5 - 2mm protruding from scratch plate - tilted as you described. I learnt the nasty tones that you can get if you raise them up too much. My bridge pickup is a lot closer to the strings to balance out the levels - I'll try dropping everything down a bit to see if that gets me any closer.

I also have a Fender Eric Johnson which has low output pickups - this is no better when it comes to getting the "Fat, singing OD Tone". The temptation is to drop a humbucker in and be done with it but you know how the hunt for tone goes....sometimes you just have to take the most difficult route!

Like many I have found that the stock OTS does not "like" Strats - it's strange because my immediate reaction is "Strats =  lower output from pickups = crank the gain" but this really doesn't help in my experience.  I have found that changing the Mid Cap improves things quite dramatically - a 0.01 in parallel with the stock 0.01 gives a total of 0.02 (Fender Bassman type value). This works well with a Strat but makes my Tele OD sound rather thin so I plan to make it switchable as others gave done.

Finally I tried a few OD pedals (stacked, into the clean channel of the OTS or set very low and pumped into the amps OD) - none have been particularly successful in getting a lead sound

Damn, I missed most of that...be great if it was made widely available "on demand" as it appeared to be quite high quality.

I like Matt Schofield a lot....but whenever I listen to him I always end up wondering how he gets that lead sound on the Bridge Pick up......I really struggle with Strat sounds on this pickup.......always sound thin and weedy in my hands, even with lollar specials, thick strings, tone control and volume wound back. Any suggestions?

Please don't take offence by this reply but...have you tried putting a linking cable between the FX Send & Return jacks when operating in Series Mode?

What you describe sounds like normal operation when there is a break in the serial FX Send / Return path.

I use one mainly for the Reverb.

I like it a lot. The only thing that it lacks is a "master volume"  that would allow you to wind up the master on the amp and control the overall amp sound level via the Veberator.

You can sort of do this if you put the Verbrator into Series mode which then puts the main signal path through the Fx Send / Return on the Verbrator and linking the Send / Return loop with a cable (assuming that you don't have any other Fx in the loop. The Fx Return gain then acts as a Master. Overall, I prefer the sound with the unit running in Parallel.

I've had mine for 2 years, no problems and a lovely sounding unit.

I've owned a Fuchs Verbrator for nearly 2 years now.

I like it a lot, great sounding reverb and no issues when driven hard at gigs.

I've not heard one but I'd guess that it has the potential to sound a lot brighter than the standard OTS especially when you wind up the presence control as the feedback loop here has a larger capacitor - allows more midrange / Highs to be impacted by use of presence. There has been a whole lot of speculation that the Robben Ford dumble upon which the FM amp has been based is practically unusable without the HF rolloff imparted by the dumblator and even the additional capacitance of cables linking FX send / return. My view is that whether the OTS or FM variant is for you depends upon the guitar(s) that you want to use it with. Personally my OTS is great with Telecasters and H/B equipped guitars but hopeless with Strats. The BM is better bet with Strat probably down to the tonestck which is closer to Blackface Fender. There again, so much of this is subjective. 

You could mod your OTS 50 to an FM 50 very easily, there are only a few component tweaks.

I'd say that he gets snowed under trying to field support calls from people who either can't get their kits to work or don't like the tone.

Am I just reading something different into the statement?

Nik says he will still sell Pack 1 which is a kit isn't it?

If you were going to build one of these amps yourself and you live in UK or US, Pack 1 is what most would buy to reduce shipping charges?

What's changed?

Determining any sonic improvement to an amp without hearing in person is so difficult - interpretation / playing style / personal taste etc.

In my view the stock OTS like it's Dumble cousin has a very 'full' bass that is more prone to mushiness than other designs especially in OD mode.

Things to consider.

1. Is there too much bass without OD engaged?

2. Can you 'dial out' the bass with the bass control

3. Are you using open or closed back cabinet

4. Is cabinet placed close to a wall / corner?

At least you have played the amp at gig levels - I thought my amp was bass heavy until I played a gig, then I found it to be just fine.

5.You can adjust the bass content in various ways but you need to remember that some changes act on just the OD sound whilst others are 'global' and will change the clean sound as well.

An easy one to implement is to change the 10k resistor that links the Bass control to ground. This effectively sets the minimum level of bass (when the control is set at zero). If you change this to 1K, you should find that you have a bit more control over the bass content at the lower end of the bass control range.

If that doesn't help then you need to think about coupling capacitors. These link the various stages on the amp together. Between each valve (tube) stage there is a coupling cap, if you reduce the value of these, you will lower the bass content. Changing the value between V1a and V1b or between V1b and V2 will reduce bass 'globally' I.e your clean and OD character will change. Lowering the capacitor value between V2a and V2b or V2b and V3 will impact on OD only. I'm afraid that component substitution by trial and error is the only way. If the existing capacitor has a value of .05 then try .02 (basically shoot for half the current value - depending on the original capacitor value, you may find that there is one half way between.

Finally, some have found that changing the power supply filter caps for higher value or 'high quality' brand such as F&T helps to tighten up the bass when the amp is played loud.

Unless your speaker is in a closed back cab, I'd be surprised if changing it will dramatically change the bass character.

The Jazz voicing changes the standard Fender style TMB tonestack into something that is known as the James Tone Stack (or close to it anyway).

The James Tones Stack has a completely different response  and probably the most noticeable difference is the amount of loss that is induced i.e. you loose more of your signal compared to the Rock setting. In theory, tonestacks with greater loss allow you more variation in tone with the TMB controls - can't vouch for that as I really haven't played with it that much in the Jazz setting.

I'd say that if you want a  nice OD tone using the Jazz setting, you will probably need to increase the internal OD trimmer to let more signal through to the OD stage.