Tube Amp Archive

Hey guys, well its a DSL401.. but I copied the Dumble 102 schematic on here (for V1 and V2)... V3 Ive used as a different clean channel on a switch. So what I did this morning was just get get rid of all the dropping resistors and connect up all the string with a copper wire to see where Im at with ...

I completely overlooked this but have been using Tunsgram El84 tubes... only I bought two pairs of these separately. So each pair is matched, but both pairs may well spec differently. Could these mismatched output tubes cause a considerable output hum (50Hz UK)... (regardless of pre PI master volum...

Hi guys, Just wanted to ask any advice with regard to the B+ line and troubleshooting a triode with much lower plate voltage than it should read. Its very annoying but I have checked the plate resistor and connections, the cathode resistors, the grounds, swapping tubes... but this one triode positi...

Hi guys, Just wanted to ask any advice with regard to the B+ line and troubleshooting a triode with much lower plate voltage than it should read. Its very annoying but I have checked the plate resistor and connections, the cathode resistors, the grounds, swapping tubes... but this one triode positio...

Hey guys! I'm just back regarding the hum on the output.. as its been a mystery to me.. but now have thought of this, was hoping anyone here could tell me what they think?? Basically the hum on the output, which is quite loud when I move the master volume pot to before the PI. I completely overlooke...

Guys!
Thanks so much. So its equal between the two, great. So.. just curious... why does the datasheet label one wire xxV and the other 0V? Is it a 'theoretical' thing in terms of the application being DC?

There is 300v BETWEEN the two red wires. Doesn't matter which is called what. Oh shit! Sluckey thanks man, do you mean whichever I hookup to my B+ and the other to the ground node... all will be well? Would this apply to the 230V blue and the 0V brown in the primaries too?? I could just swop them? ...

Hey Martin, I bought the TT transformer in the end, and am just trying to install it... I was hoping I could get your advice on this.. Basically on the datasheet attached.. the secondaries are in 3 pairs and each pair is the same colour so for example - red - 300V B+ red - 0V ... Just finding this c...

Ah right! Very interesting.. a problem I came across when removing the post PI master volume, and moving it pre PI.... was that the hum became quite loud... and yes independent of master volume, just one static volume buzz. So I did what Sluckey said and isolated the problem by not adding a master v...

The PT's in the data sheets you linked will not work in your amp. The winding that supports the bipolar supply for the op amps and the negative bias supply for the EL84's needs to be around 12VAC. You could measure that to find out exactly what it is. Have you replaced all of the electrolytics in t...

Well the feedback resistor has a great effect, because if you lower it (keeping everything else constant) you'll increase the gain difference between the frequencies that are full fed-back and the frequencies grounded, so not fed-back. Then it's just a ratio, so different combination of values give...

Hi people, I just have a quick question regarding global NFB loops and the presence pot, as seen on many amps. Basically I was thinking that in regard to the feedback resistor and the presence pot.. If one was to reduce the feecback by increasing the resistor... would one have to change the value of...

Hello Folks :) I was hoping I may be able to get some advice and help with regard to selecting a power transformer for an old amp of mine I've fully upgraded.. it sounds really nice now but since Ive invested in the upgrades and time, I feel I may as well go the whole hog and replace the power trans...

Phil! Thanks!!! This is awesome I think I undertsnad better,,, so it gives the built up charge somewhere to go when switching.. I think ill try it on my amps switch on every tube input first, thats 2 more 4.7m resistors, n see if that gets it.. really appreciate the info.

Oh I see! Great thanks, so depending on the pot some of the signal stays in the circuit.. well to me that says that the cap type will certainly be somewhat audible. Excellent drawing really helped me understand!! Have any of you guys auditioned PIO caps, like the k40 Y type??. Any thoughts? I think ...