The Amp Garage

You want to look at this: http://www.audiomastery.com/interview1.php
An interview with Bob Ohlsson, who was at Motown from 1964 onwards.

Guitar amp PT heater windings tend to be a somewhat smaller fraction of the total PT load than the HT, so a fault current load on the heater may not draw sufficient current to blow a primary fuse. :idea: .... and this amp the AC heater wiring only serves the EL84s and the pilot light, the 12AX7 fil...

Many of the later 60s Geloso PA heads (in particular the G1/10xx series) suddenly have an 10A fuse in the filament wiring. Like in the 1020: Screen Shot 2019-09-15 at 21.30.59.png If you look at earlier version of this amp (it's a 15W pushpull EL84 amp) like the Geloso 3215 or 215AN, this fuse is ab...

what could he be measuring from the empty chassis from one side to another? the "scrapping the whole build" after remeasuring at the end part had me confused though... he's not BS'ing... Of course Dumble is BS'ing -- now you heard first hand what a BS-er Dumble is Why? Myths create dollars, especia...

pompeiisneaks wrote: ↑Tue Oct 09, 2018 8:40 pm Man to me that newer amp he had made for him sounds better than 008, but that's just me.

I was thinking exactly the same thing. It's not just you!

One thing that is nice about the jumbled mess the [Dumble] file[s] section is in, it prevents the paint by number guys that don't know a thing about working with high voltages from killing themselves.This also forces people to search for the information and not expect it on silver platter.:wink: is...

I am curious, where does the 120k resistor in reference to #124 come from? me too. All the layouts and schematics I have show a 220k. I was actually wondering the same as well You're right it should be 220k. Edit my post :lol: This is from the 124 schematic linked earlier in this thread: there is a...

By the way, is there a consensus that the high plate overdrive (ie #102) is nicer than the low pate overdrive (ie #124). Also on the #124 it must have been a 500K trimmer to have it set at 346K, correct? This was the original question, but looking at the 124 schematic, it hints at a 500k trimpot Sc...

Modman: are we going on this all over again? I remember you had some diffuculties on a thread understanding the concepts of low pass and high pass filters. If a 350k of 500k trimmer doesn't make any difference: WHY is the a resistors in front of it? What does it do? The best way is to solder the ci...

The trimmer (346k) is a voltage divider, it was set at 100k to ground which leaves 246k+220k(in front of the trimmer) resistor=466k. So basically a 466k/100k divider. It matters for this reason; the 466k is a low pass filter, the 100k defines how much signal is going to the grid of the od stage. So...

Also on the #124 it must have been a 500K trimmer to have it set at 346K, correct? The trimmer pot isn't set to 346K it measured 346K. It s probably a 350k trimmer but they're hard to find. If you do a search you'll find a way of adding a resistor across a 500k to get it in the ball park figure. I ...

hello everyone I have a geloso g1 1040 50w that after few mods (preamp stage for guitar use and changed the exaust electrolitics) for functional test i would complete modifying. the trasformers specs are PT: 6v-6v 4A, 332v-332v 270mA, 39,2v-39,2v 150mA OT: 4000ohm - 50-60w choke: 3H I already have ...

I forgot to post the update, finally got this thing running, after shocking myself with 110V!
Tremolo is to die for...

A remarkable find in this area of the world. Most suprising was to find that the amp had been completely overhauled electronically and fitted with European power cord. That leads me to think the original transformer might have had a 240V primary connection. Better fire it up slowly without tubes and...