audio-talk

Nick, I'll try tapping the valves next time to find the culprit. The second part to my question is slightly unrelated. My system shares the living room with my family and TV etc so if I know I am going to have the opportunity to listen to it, I switch the system on beforehand, and starting the CD tu...

It has a GZ34. I wasn't in the room while the amp was warming up so don't know symptoms as it started. Once I turned the volume up it went but not immediately and not shure when and how quickly because of the music playing. I'd never experienced this before and the time for the amp to sound OK seeme...

Last night I switched my system on to warm-up for say 30 minutes, (all switched on, CD/DAC playing and volume control on the Rocky amp turned down). I returned to the room and before the amp was turned up, I could hear a constant 'whistling' noise from the amp itself, (not audible through the speake...

The current 4.7uF Rapid electrolytic is only 10V rated as per the MJ text. Total grid bias across the MJ circuit measures 4V. It just seems that functionally the cap might be doing something similar to a cathode resistor bypass cap, regarded by many as influencing amp sonics. I was thinking more lik...

On the schematic that I posted on the 18th incorporating MJ's Beta-follower, might it be worthwhile looking at 'boutique' alternatives to the 4.7uF cap or is this unlikely to yied any audible differences (I initially used bog standard Rapid electrolytics)?

Yes I didn't suggest that the filter F-3dB frequency is audible in itself, but I was more interested whether: 1. maximising the grid resistor in my case to 470k from the current 220k will give an audible difference and/or lead to a useful increase in gain (I could use a little bit more gain when not...

I've been reading up about coupling circuits and have a few questions about the values I've nicked from previous designer's amp. Currently my EL34 set up is a grid R of 220k and ac-coupling cap of 0.68uF. If I understand correctly this gives an f-3dB of just over 1Hz (also suggestedt by MJ as a good...

Why does the anode have 4 connections? I presume you just wire to the 'easiest' pin in terms of layout, or is there some other more subtle or alternative reason for the 4-pin connections? What is the type of plug needed for the top cathode connection, (I've searched slease-bay for "1/4" sw...

the most frequently used is the 6DS22 - a great rectifier I tried unsucessfully to find a datasheet for the 6DS22. Is this or other diodes directly ar indirectly heated? Can they handle greater current and/or capacitor sizes? Do they require 'limiting' resistors as advised for the GZ34? Anyone got ...

Hopefully with schematic this time but had to import it into PowerPoint.

Well no photo just yet because the family are in Wales with the camera. Anyhow having listened to the amp for some time with the 6SN7 SRPP input running at about 7.4mA, it was time to try something else and this was in the form of MJ's Beta-follower (page 126), supposedly a SRPP variant with the low...

Guys, I've been following a number of your builds and many of you seem to be employing pairs of diodes rather than a single rectifier valve. Why is this? Is it because of cost, performance, voltage/current ratings or is it down to particular applications? Are there any down sides such as fast voltag...

I can remember reading this when considering a standby/warm-up for my amp before I was advised it wasn't required in my design.

http://www.freewebs.com/valvewizard1/standby.html

Steve,

I am going to try and attend.

Mike.

Well I live and learn. Resited the DC heater TX at the rear with other AC ironwork and the dominant hum from the left channel is now gone. There is now only a very slight hum and it is the same on both channels so I'll leave it there. Won some Sylvania JAN VT-231s on slease bay tonight so can't wait...