JT_Marshmallow
Well-known member
This is a good write-up I found on Harmony Central. Keep in mind that the guy admits he "killed" his unit by using odd tubes, but its still worth a read:
Submitted 08/19/2007 at 06:59am by PAUL NIELSEN
Email: paulhnielsen at hotmail<dot>com
Which valves/ tubes work best I hear you ask. Just a quick addition to a previous review, after tube rolling using a variety of tubes. Most importantly, I was mixing 5751's to reduce overall gain in V1 and V3, and 12ax7/ ECC83 in V2 and V4. Initially I was very pleased with the result, as compared to using 12ax7's they had more focus, definition, linearity and less microphonics/noise given the 3 mica spacers and extra support rods with a military spec rating. They have 70% of the gain of a 12ax7, and 4 % more bandwidth. Every new production/ NOS 12ax7 tube, sucked in comparison. After blowing a plate resistor in V3 and hearing a friend who had similar problems in his Fender Reverb, I'm now not so convinced it was not such a good idea. Problem is that although substitutable, as indicated by many tube websites(even Stevie Ray Vaughn supposedly used these to get his sound), the surrounding circuit components may need to be modified to suit. Plate resistance, coupling capacitor rating, feedback/ grid and anode/cathode resistance influences the overall/ downstage gain. A website that explains this is www.pentodepress.com/tubes/plate-resistance.html ...............Something to think about!
As stated in previous review, this is my personal humble, opinion and experience that I'm sharing for those swapping tubes to achieve the holy grail (if there is such a thing). Be objective to anything/ everything I say. What works for me/ my sound, may not suit your style/ sound. After 12 months, hundreds of dollars on tubes, talking to Guitar Amp Technicians, and researching the net, I've concluded that Leo Fenders favourite valve, the RCA 7025 works for me, especially in V1 and V2 Clean channel. Interesting Groove Tubes website, lists the Mesa Studio Preamp should use 7025's in all 4 positions. 7025's are a low noise version of the 12ax7, same gain, plate transconductance. The 1980's made RCA 7025's I purchased, still had that horrible boxy, midrange glare common to many new production valves. Currently using 1950's NOS RCA Cleartop 7025's with a side getter. Excellent Fenderish clean sound. Still using Amperex NOS 12ax7 Bugle Boys made in 1962, in V3/V4 Distortion channel. Seem to have more focus than other 12ax7's, although still less than any of the 5751's I tried. Many people complained about the reverb in the Mesa, for good reason. Best Reverb valve I found to substitute for the 12at7 position, is a Sylvania GB-6201 NOS. These Gold pin tubes, are used as reverb drivers in many top end studio's which use valve only equipment. I can now turn the reverb knob to 10 to get a nice wet spring sound, without turning to mush. You may prefer modern outboard digital effects for this as reverbs have come a long way since 1960's technology!
Yep, I think I killed the Mesa tube rolling. It could have been the 5751's, it could have been me poking around with a Fluke DVM where I should'nt be. The 5751's were great while they lasted. Ultimately, Mesa Boogie engineered this circuit to run with 12ax7's, and modifying anything including cars, to get more horsepower is always at the expense of reliability. Stay stock standard or pay the price. A 10 cent plate resistor, and 1 hour of faultfinding and soldering, in my case. Valve technology and production methods were at their peak in 1960. Since then, cost cutting, using Chinese and Russian factories and labour have changed that wonderful valve sound we all love. Can you justify the cost of a rare, NOS, hard to come by, Valve? The Sylvania GB-6201 cost US$40. 4 slightly used RCA Cleartop 7025's cost me $45 on Ebay. Amperex Bboys, $70 each.
No, I haven't played 3000 live gigs, been paid $3000000, f***ed 3000 groupies in the last 20 years of my mostly non professional music career, as a previous reviewer states, so is my review noteworthy? If it helps at least 1 person, I think it is. I believe I know good sound from bad, especially guitar tone, no matter how times I played in my bedroom/ live. I'd rather you thought 50% of what comes out my mouth, could be ****. At least your being objective! It's an indoor STUDIO preamp, not a LIVE gigging preamp!
Still happy to be the proud owner of a Mesa Studio Preamp/ PRS/ 60 Watt Stereo Valve Poweramp/ Tone Tubby Alnico Speakers/ Cab. If anybody would like to email and recommend some of the latest High End, Digital Stereo Effects that worked well with their Mesa, contact me at [email protected]
Submitted 08/19/2007 at 06:59am by PAUL NIELSEN
Email: paulhnielsen at hotmail<dot>com
Which valves/ tubes work best I hear you ask. Just a quick addition to a previous review, after tube rolling using a variety of tubes. Most importantly, I was mixing 5751's to reduce overall gain in V1 and V3, and 12ax7/ ECC83 in V2 and V4. Initially I was very pleased with the result, as compared to using 12ax7's they had more focus, definition, linearity and less microphonics/noise given the 3 mica spacers and extra support rods with a military spec rating. They have 70% of the gain of a 12ax7, and 4 % more bandwidth. Every new production/ NOS 12ax7 tube, sucked in comparison. After blowing a plate resistor in V3 and hearing a friend who had similar problems in his Fender Reverb, I'm now not so convinced it was not such a good idea. Problem is that although substitutable, as indicated by many tube websites(even Stevie Ray Vaughn supposedly used these to get his sound), the surrounding circuit components may need to be modified to suit. Plate resistance, coupling capacitor rating, feedback/ grid and anode/cathode resistance influences the overall/ downstage gain. A website that explains this is www.pentodepress.com/tubes/plate-resistance.html ...............Something to think about!
As stated in previous review, this is my personal humble, opinion and experience that I'm sharing for those swapping tubes to achieve the holy grail (if there is such a thing). Be objective to anything/ everything I say. What works for me/ my sound, may not suit your style/ sound. After 12 months, hundreds of dollars on tubes, talking to Guitar Amp Technicians, and researching the net, I've concluded that Leo Fenders favourite valve, the RCA 7025 works for me, especially in V1 and V2 Clean channel. Interesting Groove Tubes website, lists the Mesa Studio Preamp should use 7025's in all 4 positions. 7025's are a low noise version of the 12ax7, same gain, plate transconductance. The 1980's made RCA 7025's I purchased, still had that horrible boxy, midrange glare common to many new production valves. Currently using 1950's NOS RCA Cleartop 7025's with a side getter. Excellent Fenderish clean sound. Still using Amperex NOS 12ax7 Bugle Boys made in 1962, in V3/V4 Distortion channel. Seem to have more focus than other 12ax7's, although still less than any of the 5751's I tried. Many people complained about the reverb in the Mesa, for good reason. Best Reverb valve I found to substitute for the 12at7 position, is a Sylvania GB-6201 NOS. These Gold pin tubes, are used as reverb drivers in many top end studio's which use valve only equipment. I can now turn the reverb knob to 10 to get a nice wet spring sound, without turning to mush. You may prefer modern outboard digital effects for this as reverbs have come a long way since 1960's technology!
Yep, I think I killed the Mesa tube rolling. It could have been the 5751's, it could have been me poking around with a Fluke DVM where I should'nt be. The 5751's were great while they lasted. Ultimately, Mesa Boogie engineered this circuit to run with 12ax7's, and modifying anything including cars, to get more horsepower is always at the expense of reliability. Stay stock standard or pay the price. A 10 cent plate resistor, and 1 hour of faultfinding and soldering, in my case. Valve technology and production methods were at their peak in 1960. Since then, cost cutting, using Chinese and Russian factories and labour have changed that wonderful valve sound we all love. Can you justify the cost of a rare, NOS, hard to come by, Valve? The Sylvania GB-6201 cost US$40. 4 slightly used RCA Cleartop 7025's cost me $45 on Ebay. Amperex Bboys, $70 each.
No, I haven't played 3000 live gigs, been paid $3000000, f***ed 3000 groupies in the last 20 years of my mostly non professional music career, as a previous reviewer states, so is my review noteworthy? If it helps at least 1 person, I think it is. I believe I know good sound from bad, especially guitar tone, no matter how times I played in my bedroom/ live. I'd rather you thought 50% of what comes out my mouth, could be ****. At least your being objective! It's an indoor STUDIO preamp, not a LIVE gigging preamp!
Still happy to be the proud owner of a Mesa Studio Preamp/ PRS/ 60 Watt Stereo Valve Poweramp/ Tone Tubby Alnico Speakers/ Cab. If anybody would like to email and recommend some of the latest High End, Digital Stereo Effects that worked well with their Mesa, contact me at [email protected]
