Marshall Silver Jubilee capacitors

[Joe L]

Dai may be right, the cheap ceramics may give the "tone" people "like" in this amp. As a rule, in all-tube amps, I replace all signal path ceramics with film, with old low value polystyrene caps being my first choice for the pF range. Ceramics have there place, as do tantalums (in voltage regulators!) but I have never regretted replacing them in most tube audio circuits.

Yellow mustard ceramics are Vishay or AVX or maybe Kemet...

And I totally agree with Dia. Like you Ted, I always upgrade the caps on a repro if I think it will sound better but this is a special case where I'm looking for a specific sound. I'm using a 4212 (2205 schematic) donor chassis for this which uses the same exact transformers so if I can work out the component differences, I should have a near match.

As an aside, I swapped some emails with Steve Snider of Monotone who built the Jubilee clones for Alex Lifeson. They are calling them "Lerxst" which is Alex's nickname. Steve confirmed my suspicions that since he built the two amps in a week, he used in stock parts. That includes their Dijon film caps and JCM800 Heyboer transformers. Alex loved them and is using them on tour. So, if you want to build your own Lerxst Jubilee clone, you have the recipe.

[Pedro Vecino]

Dai may be right, the cheap ceramics may give the "tone" people "like" in this amp. As a rule, in all-tube amps, I replace all signal path ceramics with film, with old low value polystyrene caps being my first choice for the pF range. Ceramics have there place, as do tantalums (in voltage regulators!) but I have never regretted replacing them in most tube audio circuits.
Yellow mustard ceramics are Vishay or AVX or maybe Kemet...

I've been using polystyrene for more than fifteen years in modifications, but excessive use can have negative effects on certain characters. They bring in filters a fluid and soft character,
uniform and musical, ideal for solo sounds in most cases, but when speak of Marshall.., these need some "ceramic contribution", associated to "curdle" overdrives to achieve the tactile sensation associated with them.
The use of each model I always establish in relation to the design and the choice in each tube function.

I recognize the mustard color caps as cheap multilayer types. I can't believe they are using those as coupling caps.

They are not used as coupling caps. Are typically 100 volts and work always isolated from the high voltage.
The proposed solution if you are using plastic capacitors in these functions gives the character and tactile sensation associated with the original Jubilee. I have worked with several Jubilee and also with the Ceriatone version, so I know the effect you mention. Ceriatone Jubilee sounds great but lacks certain character in that respect.
Tube models also has an effect. In the original Jubilee 12AX7 tubes were the Chinese (not exactly identical to the current model but the most similar).

[dai h.]

if the ultimate destination is a subjective one, (and presuming the part is safe,etc.), then I don't know if there is necessarily a right or wrong type of cap. In this case since there is a fixed existing goal, then maybe the ceramics are helpful. The way the temperature compensating ones sound to me is more clarity and definition, and the non-temp. compensating having a bit more "blur" or fuzz. Maybe the temp. compensating would be good for something like a clean Joe Pass, etc. type sound, where you play another note in a chord for added harmonic complexity instead of hitting the strings harder or in a certain way with the picking hand (semi-muting or whatever) as you might with a more distortion-based sound.

Also, perhaps the amount of difference shouldn't be overemphasized, since (as I understand) things like biasing, topology (single-ended vs. differential), feedback, plus other distortion reducing techniques seem to make more difference percentage wise (in the amount of distortion). Moreover, the particular spot in the circuit is supposed to make a difference in the audibility(or potential) of differing types of caps (bright caps, tone circuits, coupling caps reduced to lessen low freq response (the bigger the C the less voltage drop across the cap esp. at the lower freqs. = less distortion), so different types being not necessarily audible in every circuit location and value.

Also, if you look at say old Marshalls, they used (for the smaller value and sometimes even the 22nF coupling--presumably they ran out of the usual films on hand (so they used x2 10n ceramics paralleled)) mica, temperature compensating ceramics (temp. coefficient "N750"), and non-temp. compensating ceramics in various combinations (probably just whatever they bought when they purchased parts--as I understand out of the Radio Spares catalog at first but since this was relatively expensive, thereafter whatever they could get cheaper). Kind of hard to say that a certain type is "best" with the variance in the actual amps.

Additionally, the "worse" the spec. (for non-temp. compensating ceramics) the worse the tolerance can be (and more change with application of DC and AC(bias, signal voltage)) so maybe you need to confirm the value to make sure that you are comparing like for like in terms of the value. The voltage rating for non-temp ceramics apparently affects performance (can try choosing a higher voltage rating for less change under bias), plus they can be microphonic. In a way, the non-temp. compensating are more interesting than the "boring"(ly) linear NP0/C0G, etc. types.

[washingtomsb]

Hello guys
Sorry if my english seem confusing , I'm from Brazil and I'm using a translator
Joe, you did some more mod since the last post? could approach the sound of the original jubilee with these mods I'm trying to build one, wanted it to be the most possible near the marshall sound