Grateful Dead Music Forum

I have a Carvin DCM1000L power amp which I feed my preamped Princeton standard into. I have noticed that the inboard speaker loses volume when I am running the preamp tap thru the Carvin. Is this normal---or something I should be concerned about? I am not sure whether the wiring of the preamp tap is optimal at all...it is a modified Princeton (in other respects also).

So, you are using both the preamped signal through the carvin, and the normal signal through the fender's power section at the same time, correct?

I really struggle with concepts like this, because I'm fairly certain that signal does not work like a hose, i.e. if you split it off it becomes less strong, so I'm wondering if this has something to do with input impedance of the carvin loading down the signal in the fender.

I should really open a damn book and learn...

Hey now! That's something I hadn't considered. Good guess. Yes I am speaking about when I use both the tap and the Fender's power section. I haven't figured out the best way to run it safely yet; I am concerned about having a proper load on the output tranny and someone suggested pulling the output tubes could stress components so I haven't done that yet.
I suppose the best thing to do would be to do a power shunt deal like Garcia'a amp had per Wald.

I am really happy with the tone so far though. Really happy.

I just added a mid pot to my princeton, and I can't recommend it highly enough. Before, the mids were just too scooped, and if I went to add in bass it became to bass-y.

I've done several mods to the princeton, as it really is my test bed for development, and you seem like you are having fun with the princeton, so perhaps you may be interested in what can be done to these (or not, see if I care )

The first thing I did was the ol' .022, .022 caps in the preamp section. When one looks at the frequency plot for the standard Garcia knob settings, it really does seem to explain that low E tone (~80 Hz)

This is the .022/.022 preamp


While this is the stock preamp


The next things I did were an attempt to overcome the limitations of the output transformer. I therefore strapped another 20uF across the first stage filter capacitor, and then I performed the "Stokes Mod" (https://sites.google.com/site/yourtubea ... r-headroom). This was a nice set of modifications, and it allowed for more bass with less flub.

Then I swapped the baffle out for a 12" cutout and dropped in an E120. This was like night and day, since I had been using a really cheap Weber speaker.

The combined modifications have resulted in a nice little amp; I've even listed my twin on craigslist because of my happiness!

Hey great...much obliged for sharing your experience/knowledge. I will definitely look into the midpot thing etc.
I have a K110 in it currently which is okay especially when I use an external cab. I put a 12" JBL in my SF Princeton but I think the fiberboard cabinet really limits the tone on that amp. I didn't like the ceramic Weber "JBL" style speakers much, nor a reconed E120 I had from them--the loss of sensitivity compared to an original JBL was drastic. I haven't tried their alnico or neo "JBL" style models. But they seem to do the Jensen/CTS thing well though.

I am pretty happy with this amp for the Fender thing, and now with a power amp I can use it for bigger applications. It just gets better driving the JBL's harder w/ the extra power. Tweaking the tone is very attractive idea too. That's one of the greatest things about these simple circuit handwired vintage amps.
2 x .22 very nice.