Tube Amp Archive

I have decided to give a try to https://www.ebay.com/itm/DC-12V-to-150V-420V-DC-High-Voltage-Power-PSU-Board-f-Tube-amp-Preamp-Filament/112894482735?hash=item1a4909192f:g:8moAAOSwL9pauPNv PSU, for more flexibility in experimentation with voltages. I am a little bit concerned about EMI noise with usi...

It’s that 1.5K ohm cathode resistor as opposed to one of about 300 ohms that keeps the higher voltage its getting from burning up the tube. The question I have is which taps of that multiple tap 125E transformer is needed to be used? Something between 3.5-4 kOhms on primary side will be OK, or I am...

It’s that 1.5K ohm cathode resistor as opposed to one of about 300 ohms that keeps the higher voltage its getting from burning up the tube. The question I have is which taps of that multiple tap 125E transformer is needed to be used? Something between 3.5-4 kOhms on primary side will be OK, or I am...

Hi, I would like to build some SE amp, based on 6112 and 5902 tube. I have found one schematic on the net, it is exactly what I need, but voltages seems a way to high, according to tubes reference data. (for 5902 Max. plate voltage is 165Vdc, 110VDc recommended). Have anyone experiences and advice ?...

Hi, I have Belton sockets on my Express, in last time I often change preamp tubes, and try to find best combination. After few changes, tubes become something loser in socket (not so tight how when they are new, and without resistance when pull out). What you think, how many times can man put in and...

I will go with capacitors in preamp stage, as sugest Dana, to eliminate issues. Is anyone try 5751 on V1 position ? It is lower gain, but how affect the tone ?

Noticed one interesting thing that is not directly connected with VVR. When I was put some old cheep SOVTEK AX7 WA tubes, and haven't scratchiness on pots when using VVR so didn't need upgrade preamp section, but I was order few new Tung-Sol higher quality, tested tubes from tubedepot, and put it in...

Maybe I will take amp to friend who has osciloscope, and try messure frequency and amplitude of noises, hum, hiss and find source of problem. It would be cool to have some oscilogram of good working Express as reference. Sorry I am engineer, admittedly mechanical but.... :D I'm sure I was made some ...

It is my first express, I was build some other projects in past, low gain like 18 watt Marshall, Deluxe reverb...,and never have any issue with noise, but on my Express it is to much noise, and interference. Yesterday I was hear radio signal from amp ,so something is definitely wrong there. I am pla...

Thanks for advice. I know that high gain amps like TW have something increased hum, and hiss,expectet that but in my case it is way to much. Now i suspect on pot grounding. Because I didnt solder bus direct on pot, but use separate bus wire for grounding, and conect it in one point on chassis. Maybe...

Hi, I finaly build my Express, amp work, and sound what I expect, but have some issues. 1. Noise and/or hiss is to high even on idle, and increase with volume. It is not 60-cycle hum, but something higher freq., I was try decribed methods, but with no results. When pull out preamp and PI tubes, amp ...

Hi, one quick question. Can I use in place of R23, R24 (100k 3W) , 2W resistors ?
Because i cant currently find 3W in local store. Culd I expect problems ?

Thanks.

Hi, I will appreciate if somebody send me komet schematic. I am interested in cut and fast control. Someone try implementation of this control in Express ?

toskrlec@yahoo.com

Thanks.

Hi, I just implementing VVR in my express, but can’t decide between heat sink out of chassis, and cooling direct on chassis. What experience you have? I thing that heat sink have better thermal dissipation. Thermal condition is direct involved in reliability of electric components, so I think it is ...

Hi, I build my first Express, and read some instructions and sugestions from forum. Have question about wire from volume pot wiper. Some sugest to move it from chassis and pot ( i understand ground), and some to use coaxial shielded wire to reduce microphony. It confuse me little, which option is be...