Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Homebelly on November 11, 2011, 08:00:16 pm

Title: Steve Luckey dual preamp plexi..
Post by: Homebelly on November 11, 2011, 08:00:16 pm

Hi..
I'm new to the board so as a quick introduction to my amp building back ground.
I have built a Dumble clone and a JTM45 from the ground up.
Now i'm looking to build a slightly more flexible Plexi and i came across Steve Luckey's schem/layout.
So,,
I'm wondering if any one has made one?
I know some one on here called plexi50 has, and so i am hoping he/she might pop up and give some feed back.
The first question i have is, how radicle is the jump from the plexi voice to the JCM800 voice, and would it be useful
to add a volume control after the JCM800 gain pot?

My ultimate idea is to build some thing along these lines, but maybe use a dumble style cascaded OD along side the two plexi channels.
I'm still working on that idea.. I love the sound of a big fat clean JTM45/100 superlead and would love to build a hybrid based on that amps
voice.

Cheers for any help..

Title: Re: Steve Luckey dual preamp plexi..
Post by: shortfuse on November 11, 2011, 08:46:42 pm

I think Tubegeek has built it twice.
I would like to give that one a shot someday.  I think there are 2 versions of that amp.

Title: Re: Steve Luckey dual preamp plexi..
Post by: Tone Junkie on November 12, 2011, 02:31:09 am

Im getting ready to build one similer I thought his idea was very good I was going to build it with two tonestacks , one for each side with a tube effects loop , I really like the fact he made the bright and normal channel to run into each other without having to make a 4 holer and running the cord from one to the other, then with the added versatility of the jcm 800 circuit you just cant go wrong there.
 I would imagine it to be very versitile.(LOL) its late Im not spelling to good, time to go to bed  :think1:

Thanks Bill

Title: Re: Steve Luckey dual preamp plexi..
Post by: TubeGeek on November 15, 2011, 11:08:15 pm

Yep, I built a couple of amps based on Steve's idea/layout.  I think I asked if it was possible and next thing I know Steve has this drawn up :notworthy:

One of the amps I built was stolen from the owner's touring van, never was found.  The other one I built has since been changed to another circuit altogether.  The owner changed his mind.

I am going to build one for myself very soon.  I am beginning a big project of building a 5f6-a bassman along with the jtm-45 side by side while analyzing both of them along the way.  I've got the book by Kuehnel to guide me  http://www.ampbooks.com/home/books/bassman/. (http://www.ampbooks.com/home/books/bassman/.)  Should be a fun project. 

I've got everything I need...now I need to begin assembling.

Title: Re: Steve Luckey dual preamp plexi..
Post by: Homebelly on November 16, 2011, 03:05:34 am

Mr Geek..

Did you think it could benefit from a volume control on the JCM channel, or was the change over from one to the other not to much of a volume jump?
I'm going to use a foot switch to change channels..

Title: Re: Steve Luckey dual preamp plexi..
Post by: TubeGeek on November 16, 2011, 09:34:15 am

I don't recall it being a big problem

Title: Re: Steve Luckey dual preamp plexi..
Post by: sluckey on November 16, 2011, 10:21:11 am

There's already a volume control in the JCM channel. I suppose you could put another volume control after V2B for even more control.

Title: Re: Steve Luckey dual preamp plexi..
Post by: Homebelly on November 16, 2011, 01:19:10 pm

Of course there is.. :BangHead:
I think get it now..
The JCM channel pot is controlling the gain of V2-a/b
and V1 a/b works as normal.
Then the master volume controls the out put of the whole amp.

So, i am imagining you could set up volume 1 and 2 to around 3 or 4 on the pots to get a cleanish tone, then jack
the pot on the JCM channel to get an overdrive.

I guess i'm wondering if there is much of a volume jump switching between the two preamps if the amp is set up to work how i have described?
I'm looking to be able to do this using a foot switch and use the JCM channel as a lead/OD channel.   

Title: Re: Steve Luckey dual preamp plexi..
Post by: TubeGeek on November 16, 2011, 07:07:24 pm

I think it will work for you and if it doesn't work like you want, you can tweak it until it does what you want. 

Title: Re: Steve Luckey dual preamp plexi..
Post by: DummyLoad on November 17, 2011, 01:50:44 am

Quote from: sluckey on November 16, 2011, 10:21:11 am

There's already a volume control in the JCM channel. I suppose you could put another volume control after V2B for even more control.

did you ever build one?

thanks,

--DL

Title: Re: Steve Luckey dual preamp plexi..
Post by: sluckey on November 17, 2011, 07:28:58 am

No, other stuff just kept getting in the way. I do plan to modify my 'Stuffed Vox' (http://home.comcast.net/~seluckey/amps/vox/vox.htm) (which is a Plexi preamp) to include the 2204 preamp also. It would be a simple mod. Someday...

Title: Re: Steve Luckey dual preamp plexi..
Post by: DummyLoad on November 18, 2011, 03:17:06 am

i'd like to take it for a spin around the block on the breadboard. would you be OK with that?



--DL

Title: Re: Steve Luckey dual preamp plexi..
Post by: sluckey on November 18, 2011, 05:33:46 am

Absolutely. I look forward to it. I'm sure you'll find some improvements also.

Title: Re: Steve Luckey dual preamp plexi..
Post by: plexi50 on November 19, 2011, 10:33:36 am

I think it a fine amp. I actually enjoy just starring at the PDF layout