Express w 4gains

[surfsup]

I will be using it...

[M Fowler]

Did you build this amp yet?

I am curious because this circuit is so much fun to play.

I will be starting on a 100w version into a blank Ken Watt
s chassis; 100w Heyboer PT (Fender); and 100w Magnet Components OT/choke (Marshall).

I'll use Lopo large box Marshall head cab.

Mark

[surfsup]

I went to france for a couple weeks just got back. All my stuff was at my office this afternoon, so i plan to go thru it all tomorrow and get further. I need to decide if i will do a switchable parallel p-p output , i think it wont fit and the lead dress might bite me in the arse

[M Fowler]

I wouldn't put so many other circuits into this tight spaced chassis. If you were running the large 100w Marshall style you could put anything you want in it.

Going simple has it's advantages some times

Mark

[amplifiednation]

i've done an express with parallel triodes in the 1st stage. use 47kΩ for Ra and 750/820Ω for Rk.

This keeps same gain as standard express input, but drops output impedance closer to 20k. Change tone stack values to 47k slope, 500k treb/bass, .001/.047/.047 caps, 10k mid pot, and the tone stack will have the same response as standard Express.

Keep in mind that miller capacitance doubles so there might be some high-end rollof when using volume control on certain guitars which isn't the case with a standard express input (no grid stopper, tone stack loading down the 1st stage, reducing AC gain/miller capacitance).

the sound is a little hairier and "bigger" with parallel inputs, but clean to mean is worse.

I just paralleled my express v1 and there is much less response on the tone stack. Thanks for your suggestions on caps and pots. Maybe I will continue to mod it. The amp sounds awesome though. It has some serious girth.

Would just changing the pot values help with tone stack response without changing the cap values?

Is there a way to put the paralled triode on a switch? Like a push pull pot?

[Tone Lover]

I have put it on a pot before just the input of the extra triod I was suprised it didnt pop when switched in.
Bill

[amplifiednation]

If you don't mind me asking, what part of the circuit get switched to turn on and off that triode?

[surfsup]

With a high gain amp like this i'm thinking these extra leads will cause leaddress issues?

[M Fowler]

As high gain as this DBM#39 amp is, the Laney TI-100 has an additional stage post tone stack then into the PI. I want to build that next, it uses high gain/low gain input circuit. It is in TUT 3 book.

Mark

[surfsup]

Are the tut books worth the $ for the hobbyist ya think?

[M Fowler]

I only have two TUT books total and just received TUT 3 which I like because it starts off with Champ builds and expands to high gain options for the champ.

Then it goes into 5F6, JCM800, Laney's, Bass amps, etc. Lot of useful info in it. If you are more into grafts, tests, and other data measurement stuff. The Merlin Blencowe books are good.

Mark

[pamaz67]

i own all 6 tut ( got the first 5 issues 2nd hand ) and are definitely a good investment for the serious builder.
Bear in mind BTW, that these books are a reflection of the author's thoughts and sometimes are IMHO questionable.
In any case a sort of Bible for a lot of things.

[M Fowler]

If your looking for some fun builds Tino Zottola's books are great to own.

Mark

[surfsup]

Someone told me there is a method to calculate the bias circuit in tut4 so that's why i asked. I am not sure if 110 bucks is worth learning one method for one cicuit i'm intersted in. Maybe for xmas?