Q: Voicing

[rmroza]

Well the Express(es) sound amazing and I haven't put a lot of time into them yet, but will tomorrow, but based on preliminary requests, what you guys recommend in changing to voice the amp to lower the high end?...or move the tone stack to more accurately lower the highy-end the in range the amp is exhibiting??

Maybe just being able to cut in appropriately in the tone stack would be the best remedy, but the amp is very bright, soo I think the bright switch is really radiculous to use, unless maybe you adjust the settings and Presence control to cut it.

Anyway, let me know your thoughts. After a little search I didn't find anything in querery that addressed this. Thanks in advance and again, wow, what an amazing amp and design!

Robb

[MikeSafreed]

Robb,

Before you make any changes to your amp, consider what's going on with your speaker(s). This amp will naturally get a little (or a lot) trebly. Maybe you need a "darker" speaker, something that will accentuate the mids and lows, and roll off the highs. You might want to talk to Jim at Scumback Speakers. You can go to his web site, fill out a simple questionaire about your gear, and he can make a pretty close speaker recommendation. One other thing you can do is to really use the tone controls on your guitar. This amp is super-responsive to what it gets from the guitar - a lot of us are used to turning up the tone controls all the way on our guitars, and then maybe using the volume pot to control comping versus soloing. But, this amp will sound good if you role the tone pots back, and you'll find a lot of great tones you didn't know were in your guitar. Give it a try before you start changing the components or circuit in the amp.

Mike

[MikeSafreed]

Robb,

One more thing I forgot to mention, although you brought it up in your post. REALLY play with the amp's tone and presence controls. Depending on the guitar you're using and the speaker(s), you might find a really nice tone without doing anything but twisting the amp tone knobs. There's nothing that says you have to have the tone controls set any particular way. They turn 300 degrees. Give them a turn and find the sweet spot.

Mike

[rmroza]

Hey Mike

Thanks for the quick feedback!

To give you guys some input, I'm pretty familiar with the marriage of the amp to the speakers and have literally 30 amps and different speakers at the house. I spent a LOT of time A-B'ing stuff over the last couple of years and what I've found as being the best in terms of "flat" response, great break up, not too aggressive, etc. is actually a Celestion G12H-30 70th Anniversary model! It's flat!

I know you mention Scumback and yes I can speak with them also, but I have spoken directly with Dr. Decibel at celestion over the years and about speaker selection and cabinet volumes, etc. Soo, I'm pretty familiar with it!

As I said, the above speaker was used during my initial demoing and it should be flat and not bright, so the amp is quite bright. I was using a 1972 LP Custom with a 57 Classic Plus in the bridge. The IS a brighter pickup, so must agree with you on pickup selection also. The neck seemed perfect with the original 72 PAF! I'll try much more playing and demoing and plug in my other LP with the Suhr Aldridge pickups that acually taper off the highs and is more compressed sounding.

Alas, even with all this, I'm just wondering how to change the voicing or tonestack to accomplish my original question and either get rid of some highs or be able to taper them off in the tonestack better. I don't want to recreate the wheel if someone has already done it. I'm basically looking for feedback on this specific "mod" if you will. I know other guitar players AND amp builders have commented about the highs!

Robb

[M Fowler]

Well I have always read good NOS tubes make a difference as well.

Looking at the Express treble cap C2 is 500pf that could lowered.

C3 and C4 are both .022uf you could change C4 to .047uf.

The only other changes would be lowering the 1M bass pot to 250kb.

[funkmeblue]

add a cut control like the komet

[Branson]

Changing the slope resistor (R4, I believe) to a smaller value will lower the register of the entire EQ. It will also substantially boost the mids. I went from 100k to 33k and it was WAY too dark. I finally settled with 80k and am quite happy.

[M Fowler]

There are a lot of different versions already tried.

[Zippy]

As I said, the above speaker was used during my initial demoing and it should be flat and not bright, so the amp is quite bright.

I'm basically looking for feedback on this specific "mod" if you will. I know other guitar players AND amp builders have commented about the highs!

Have you found the "lore" regarding using two long cables in series to add some capacitance and knock down the highs? See early posts from "geetarpicker".

I suspect you could similarly condition the front end with about 20-40pF across the input jack.

Edit: See geetarpicker's comments below: measured value of his cables ranges 600-3500pF.

[vibratoking]

Mark, thanks for those pdfs. I have not seen all of the schematics compiled into one like that. That's a great source of information.

[M Fowler]

There are more with EL84 output as well.

[geetarpicker]

I moved away from G12Hs years ago because they were too bright with my Express. I have old pulsonic cone G12Ms that are darker for sure. My Mogami gold 18' cords run about 600pf each and I run two in series. The 40' cord used on my CD was about 3500pf! That said these days that cord sounds too muddy for me. I've tried simulating the effect of longer cords with a small cap but it didn't work out, perhaps there is also some added inductance.... Remember if you want to try the bright switch keep the volume up to at least 1/2. There could be other issues. I've found that every clone I've ever played was brighter than my original, some only slightly but some by a totally extreme amount. Perhaps component choices are the culpret even when the circuit is the same. Hope that helps!

[Zippy]

Thanks for steppin' in, Glen. I appreciate you adding the capacitance value of your cords and your observations regarding trying to replicate the effect with a jack-mounted surrogate.

[vibratoking]

The 40' cord used on my CD was about 3500pf! That said these days that cord sounds too muddy for me.

Sure it's not your high frequency hearing heading south? Those damn things are loud and want to be played that way.

[Roe]

here's how I deal with the brightness:
- getting the right signal caps. I'm using the original type but would probably use mustards/sozos for a new build
- the right filtercaps. BC 450v is my favorite so far, esp. at the screens
- adding .1ish caps over filtercaps will change the top end a little, try it and see what you like
- finding right tubes and right speakser
- burning in circuit
- avoid harsh sounding resistors
- also I may add a 150pf snubber at v1a