Post by myles on Dec 5, 2006 16:02:07 GMT -7
Yesterday I ran some checkups on the SRZ-65. The amp had been gone for a week or two and whenever they come back from shipping I check things out.
I ran some output tests at 400Hz and 1kHz as typical with an 8 ohm load. A variac set at 117VAC was implemented.
This is what I found:
Using a Sovtek 5AR4/GZ34 rectifier the amp developed about 62 watts. You see the voltage output rise but then it falls back a bit as the rectifier cannot keep up with things. This is why we like tube rectifiers by the way.
The Sovtek is a reliable rectifier generally but current production falls quite short of the 225mA current output that is standard spec. Just like most things today, current production is not close to old standards in many cases.
Next I tried a JJ GZ34. With this rectifier in place my max wattage output was 66-67 watts. These rectifiers are stronger than the Sovtek but still below spec in most cases. If they meet spec they generally will not exceed spec by much.
Last was a used (that was an NOS) British GZ34 with GE branding but "made in Britian" on the tube. These are Mullards and were rebranded in many cases. Sometimes these are less pricy than a Mullard branded tube and can be a nice value.
Output with the GT was 72 watts initially but after than amp was warmed up a bit (ten minutes) this increased to 76 watts.
The Mullards as a general rule exceed 225mA by quite a bit. 240-250mA is not at all uncommon. A Sovtek hitting over 170mA is generally a find on the good side of their average as a side note.
The voltage drop of these rectifiers is much the same as their current output. The Mullard exceeds spec by a wide margin and the JJ just makes spec until it is pushed. The Sovtek had a voltage drop more excessive than spec states.
On a side note, in a Vox AC-30 or Matchless DC-30 one of the biggest improvements that can be made is making sure a good NOS rectifier is utilized. Anybody for the most part will find the amp louder, tighter, more dynamic and more fun to play.
There is also a reliability factor increase by many times with any of the NOS rectifiers. I don't care if they are Mullard, Amperex, RCA, GE, Phillips, Sylvania or whatever. The are much more reliable than any current production tube rectifier. Their life is decades so they are actually a better deal at times that one might initially figure.
I did not test any Chinese rectifier due to general reliability issues and lower specs than the Sovtek.
Keep in mind that if you want to really go for output and tighten up the SRZ-65 (but loose a lot of the touch dynamics and fun) you can always remove the tube rectifier and replace it with a solid state plug in unit. Be sure to rebias if you do this. What you will end up with might be great for power chord players that want a very tight and in your face feel.
I ran some output tests at 400Hz and 1kHz as typical with an 8 ohm load. A variac set at 117VAC was implemented.
This is what I found:
Using a Sovtek 5AR4/GZ34 rectifier the amp developed about 62 watts. You see the voltage output rise but then it falls back a bit as the rectifier cannot keep up with things. This is why we like tube rectifiers by the way.
The Sovtek is a reliable rectifier generally but current production falls quite short of the 225mA current output that is standard spec. Just like most things today, current production is not close to old standards in many cases.
Next I tried a JJ GZ34. With this rectifier in place my max wattage output was 66-67 watts. These rectifiers are stronger than the Sovtek but still below spec in most cases. If they meet spec they generally will not exceed spec by much.
Last was a used (that was an NOS) British GZ34 with GE branding but "made in Britian" on the tube. These are Mullards and were rebranded in many cases. Sometimes these are less pricy than a Mullard branded tube and can be a nice value.
Output with the GT was 72 watts initially but after than amp was warmed up a bit (ten minutes) this increased to 76 watts.
The Mullards as a general rule exceed 225mA by quite a bit. 240-250mA is not at all uncommon. A Sovtek hitting over 170mA is generally a find on the good side of their average as a side note.
The voltage drop of these rectifiers is much the same as their current output. The Mullard exceeds spec by a wide margin and the JJ just makes spec until it is pushed. The Sovtek had a voltage drop more excessive than spec states.
On a side note, in a Vox AC-30 or Matchless DC-30 one of the biggest improvements that can be made is making sure a good NOS rectifier is utilized. Anybody for the most part will find the amp louder, tighter, more dynamic and more fun to play.
There is also a reliability factor increase by many times with any of the NOS rectifiers. I don't care if they are Mullard, Amperex, RCA, GE, Phillips, Sylvania or whatever. The are much more reliable than any current production tube rectifier. Their life is decades so they are actually a better deal at times that one might initially figure.
I did not test any Chinese rectifier due to general reliability issues and lower specs than the Sovtek.
Keep in mind that if you want to really go for output and tighten up the SRZ-65 (but loose a lot of the touch dynamics and fun) you can always remove the tube rectifier and replace it with a solid state plug in unit. Be sure to rebias if you do this. What you will end up with might be great for power chord players that want a very tight and in your face feel.