Post by myles on Feb 10, 2007 18:09:41 GMT -7
Well ... as promised in some other thread in this SRZ-65 area of the forum, the results of the activity on Carl's two amps.
Above - our work area, or some of it.
Above - This is Carl's USA live rig in it's current incarnation. At times he uses two Marshall 4x12 cabs rather than the 2 THD 2x12 cabs.
This is his USA SRZ. We had tweeked this in the past but decided to take it a little farther.
The front end were three Svetlana 12AX7's. V1 was replaced by a hand selected 12AX7R2 (Sovtek LPS) longer plate. This tube has a different upper mid range response than the shorter plate Svetlana.
The SRZ-65 as with most Marshalls can tend to be an amp on the brighter side. One of the old Marshall tricks is to get all the tone controls and presence control as far open as possible. The more toward "10" the more signal gets passed on to the phase inverter and the output tubes. The slightly darker R2 in V1 let us bring the presence and treble a bit higher.
The output tubes were GT-E34LS #5's biased at about 55% based on plate voltage. These were replaced by GT-KT77S (The JJ KT77) in a #8 rating and biased at 65%ID.
I left enough room in the bias point to allow Carl to drop in a solid state rectifier if he desired without having to alter the bias. He has solid state rectifiers with his stuff as spares for emergencies if any of his GZ34 / 5AR4 rectifiers die on the road.
The solid state rectifiers limit some of the magic of the amp so the tube rectifier was retained.
I will leave it to Carl to give his take on the difference in this amp "before and after". He thought it was the best way a Strat could possibly sound before we changed things a bit. After the preamp tube change and the bias change he thought it was even better and did not want to change anything else. I suggested we go to the #8 KT77s and rebias as we could always backtrack. Let it be said that the KT77s stayed in the amp.
Above - the back side of Carl's USA rig. The 100 watt plexi Marshall only has it's power amp in use as the amp for the effects side of his rig.
Fender BF Twin reverb and Vox AC-30 are the clean side of the live rig.
Above - After we finished with SRZ-65 #1 it was on to SRZ-65 #2. This is the amp that will be shipped to Europe. The THD Flexi 50 in the photo has it's power section only utilized in the same way the Marshall 100 watter is used in the USA. It is the effects side of the rig. In this setup we had the SRZ using one side of the THD 4x12 (which can be split into two 2x12's) and the other side went to the THD post effects. Carl has a box something like the old H&K Red box that sends one part of the amp's output to the speaker cab and also has an adjustable line out that feeds the effects rack. The rack feeds the THD effects return, thus bypassing the front end of the Flexi-50 to turn it into something of a basic power amp.
We had a step up transformer as this amp is hard wired for Europe.
The amp had three Tung Sol 12AX7s. The were fine but in the end I opted for a 12AX7R2 (Sovtek 12AX7LPS) in V3 for phase inverter use.
The output tubes were GT-E34LS #6 ratings and the amp came biased right on the money to the spec that I had requested from the Doc within .25mA.
The output tubes were replaced though, by #8 GT-KT77S (again, the JJ KT77 tube). The bias was reset due to different tubes at a higher rating. By the way ... the bias setting on the #6 GT-E34LS if used for the #8 KT-77S was almost 10mA different (higher, and would have been at least 65mA per tube ... way too high).
Bias was set at 65% based on the amp's plate voltage which was a bit different than amp #1 but we were running at 230V input voltage with a step up transformer.
Both amps put out in excess of 65 watts and 45-50 clean watts is pretty easy. The wattage is deceptive though as the amps have a lot of harmonic content that makes them seem louder than their wattage would indicate.
Carl normally runs with his master full up but I showed him that if this is backed down to about 2:00 - 3:00 and you bring up the presence a bit (as this is part of the feedback loop in the output section) some wonderful things can happen without a loss of level or headroom when the gain is turned up a bit too.
So ..... That is it for now. If you have questions on tone or playability either put them here for Carl or stick them in the Ask Carl Verheyen area of the ask the experts thread.
Happy playing!
Above - our work area, or some of it.
Above - This is Carl's USA live rig in it's current incarnation. At times he uses two Marshall 4x12 cabs rather than the 2 THD 2x12 cabs.
This is his USA SRZ. We had tweeked this in the past but decided to take it a little farther.
The front end were three Svetlana 12AX7's. V1 was replaced by a hand selected 12AX7R2 (Sovtek LPS) longer plate. This tube has a different upper mid range response than the shorter plate Svetlana.
The SRZ-65 as with most Marshalls can tend to be an amp on the brighter side. One of the old Marshall tricks is to get all the tone controls and presence control as far open as possible. The more toward "10" the more signal gets passed on to the phase inverter and the output tubes. The slightly darker R2 in V1 let us bring the presence and treble a bit higher.
The output tubes were GT-E34LS #5's biased at about 55% based on plate voltage. These were replaced by GT-KT77S (The JJ KT77) in a #8 rating and biased at 65%ID.
I left enough room in the bias point to allow Carl to drop in a solid state rectifier if he desired without having to alter the bias. He has solid state rectifiers with his stuff as spares for emergencies if any of his GZ34 / 5AR4 rectifiers die on the road.
The solid state rectifiers limit some of the magic of the amp so the tube rectifier was retained.
I will leave it to Carl to give his take on the difference in this amp "before and after". He thought it was the best way a Strat could possibly sound before we changed things a bit. After the preamp tube change and the bias change he thought it was even better and did not want to change anything else. I suggested we go to the #8 KT77s and rebias as we could always backtrack. Let it be said that the KT77s stayed in the amp.
Above - the back side of Carl's USA rig. The 100 watt plexi Marshall only has it's power amp in use as the amp for the effects side of his rig.
Fender BF Twin reverb and Vox AC-30 are the clean side of the live rig.
Above - After we finished with SRZ-65 #1 it was on to SRZ-65 #2. This is the amp that will be shipped to Europe. The THD Flexi 50 in the photo has it's power section only utilized in the same way the Marshall 100 watter is used in the USA. It is the effects side of the rig. In this setup we had the SRZ using one side of the THD 4x12 (which can be split into two 2x12's) and the other side went to the THD post effects. Carl has a box something like the old H&K Red box that sends one part of the amp's output to the speaker cab and also has an adjustable line out that feeds the effects rack. The rack feeds the THD effects return, thus bypassing the front end of the Flexi-50 to turn it into something of a basic power amp.
We had a step up transformer as this amp is hard wired for Europe.
The amp had three Tung Sol 12AX7s. The were fine but in the end I opted for a 12AX7R2 (Sovtek 12AX7LPS) in V3 for phase inverter use.
The output tubes were GT-E34LS #6 ratings and the amp came biased right on the money to the spec that I had requested from the Doc within .25mA.
The output tubes were replaced though, by #8 GT-KT77S (again, the JJ KT77 tube). The bias was reset due to different tubes at a higher rating. By the way ... the bias setting on the #6 GT-E34LS if used for the #8 KT-77S was almost 10mA different (higher, and would have been at least 65mA per tube ... way too high).
Bias was set at 65% based on the amp's plate voltage which was a bit different than amp #1 but we were running at 230V input voltage with a step up transformer.
Both amps put out in excess of 65 watts and 45-50 clean watts is pretty easy. The wattage is deceptive though as the amps have a lot of harmonic content that makes them seem louder than their wattage would indicate.
Carl normally runs with his master full up but I showed him that if this is backed down to about 2:00 - 3:00 and you bring up the presence a bit (as this is part of the feedback loop in the output section) some wonderful things can happen without a loss of level or headroom when the gain is turned up a bit too.
So ..... That is it for now. If you have questions on tone or playability either put them here for Carl or stick them in the Ask Carl Verheyen area of the ask the experts thread.
Happy playing!