creitone express

[HiGain]

Daer Higain, so do you suggest to make these tweaks on a normal wreck clone? I'm very satisfied with my clone, but I'm tinking to change all pre values according to a komet. I'll not have the same sound... voltages are very different so behaviour of the amp is different.
Did you try something similar? What do you suggest to do with an Express clone in order to keep the gai and quality of sound but try to have more clean and more response to picks attack?

Of course, as a DIYer, I can relate to the desire to tinker and modify But, in the end, the express seemed to be so perfectly tuned by KF. I prefer non-invasive mods in the express, where the stock circuit is unchanged. For instance, I do like a 47pF or 82pF ceramic cap in place of the 100pF mica cap on the bright switch. Gives a less aggressive less gainy sound for strat/tele guitars.

On your point about the Komet. I would not change the express values based on your observations about voltage, as well as differences in OT, etc. However, the other modification I did was to make a switch for the R-C combo ahead of the third stage. It toggles between the stock .002/150k, and .0047 into a 220k/330k voltage divider. The second setting is inspired by the Komet, and produces a deeper bass sound without getting muddy, especially with the 500pF bright switch engaged. Of all my efforts to increase bass, this was the mod that did it without altering the cutting clarity of the stock sound.

For less gain and a little more perceived bass, you could try a .0056/56k combo ahead of the third stage. I did this for a while, but ultimately changed to the switch outlined above.

Were is the best source for the PEC potentiometers in the US?

Digikey has them. Do a search here and you should find the part number.

Jake

[castor]

Yes, i agree with you. I started with ceriatone kit (but nothing mounted) because is very difficult to find in Italy some parts... specially Mallory caps..
after that I replaced all ceriatone 40 and 20 micro caps (ceriatone are 47 and 22 if I remember them correctly) with ATOM Sprague ones. I also put ELNA 22 micro 25V.
After Changing the power caps all amps started to sound more balanced and with more bass.
Changing bright switch caps is one of the less invasive tweak you can do... and I agree with you that this amp is very good balanced as it is.
I was thinking of some mods that can keep the same quality of sound but can allow to clean up better (keeping the same distorsion)

[Fischerman]

higain,
Did you try a cathode follower at the end of the preamp? I've read that when doing this some folks go to a 3K3 unbypassed cathode R instead of the 10K unbypassed cathode R and then change the 150K to that 220K/330K divider. But some say they use a 220K series resistor between the CF and the PI. I assume that these are Komet values but I've never verified that (I don't know where a Komet schemo might be found). Not that it matters...that's pretty standard stuff.

Anyway, glad to hear reports from someone that did a bunch of mods but ended up back at the stock circuit (pretty much). I went through that with non-MV Marshalls...ended up right back at (or very near) the stock circuit.

castor,
I'm building a Ceriatone kit right now and I measured all of the filter caps that came with the kit. The 47uF caps measure closer to 40uF-42uF, the 33uF measured 30uF and all of the 22uF measured a bit high...23uF to 25uF. I'm going to deviate from the layout a bit and use both 47uF caps for the plates (which when added only measure 82uF) and just use the 33uF (measures 30uF) for the screens, then put the others in 'descending' order (25uF for the PI).

[castor]

Yes, probably it can be... in fact caps have large tolerances, so a 47 micro can be close to 42-40 micro.
But everytime you change caps (only the brand, not the value) you will have a different feel in the amp, and not only caps in the signal flow, but even supply caps.
my amp changed strongly his sound, so now I use the bright switch on (on 100 pico) and have the same brightness as before with the switch off.
--> sound fantastic with lespaul-type-guitars, but too bright with strato-type-ones.
I also replaced the 0.0022 micro, but only because mine had problem and when I tryed to remove it it opened in 2 parts easily. I had not the possibility to find a mallory's one in italy so I used a hi-fi italian cap..
Anyone added a slow-fast switch? Do you think it's interesting to have one mounted or at the end you have the best without it? I'd like to collect some tweaks, so when I'll re-open the amp (in 2-3 weeks) I'll test directly some of them.

[tjauernig]

I've done several of the Express kits. Both using completely Niks parts, and my own sources. I've come up with a series of "tweaks" that allow me to get as clean or dirty as I want, at just about any volume level. The KF design was very basic, and that's why it sounds good. There are a ton of non-invasive mods that can be done.

[sliberty]

T - care to share your mods?

[gearhead]

T, I would be interested too!


BTW, are you TCJE of WI? If so, I got one of your GKs and LOVE it!

[mac0611]

How easy/worthwhile would it be to tweak an express for more clean headroom?

sure you could, but why? The energy expended to build an express is to get that awesome powertube distortion and singing lead voice, that cleans up with just your guitar volume. I posted pics of a bassman I modified with the bass channel being an express preamp, and the normal channel blackface super reverb. The express side starts to churn at about 9:00 as usual, but the super reverb side stays clean all the way up to almost full. This would be the best way to go without compromising what the express is all about. I plug in a kendrick ABC box to both imputs for switching between the two. I had to tweak the hell out of the power supply to get it right, but it was worth it. Also, the bassman and non tweed circuits use the 12AT7 for the PI, and that had to go to get the express side to work right. I ended up using a 100K resistor for the normal input to make the blackface side sound right. gotta go, my kids are "wrecking" the house!

[rfgordon]

Just today I took an amp back to its Wreck roots, but tweaked. Yeppers, there's nothing like a TW. There are some tweaks, but it's a Wreck again. There was no point to the anger-management attempts!