Thanks for all your Advice, I wouldn't have tried using GZ37 MULLARD'S if Dan Wright didn't ok this move I am still using the Mullard's in both the PS 36.5 and the PS 9.0 with great success, I will watch out for glowing red tubes, thanks again all of you fantastic Audiogon posters
Rectifier Tube Rolling in a Modwight LS 36.5DM
I was hoping to get advice, I have been rolling Rectifier tubes in my two box preamp I am blown away how different tubes change the sound ,I own two sets of Mullard GZ37/CV378 a set of GE 5U4GB both vintage early 1960's and a set of stock Sovtek 5AR4 also have a NOS set of 6H30 DR I am trying in the clean box , both the Mullard's and Dr tubes only have about five hours of run in time but the sound seems defused on the top end ok on the bass the GE Tubes are good in the mids but soft on the highs and bass so far the stock Sovtek seems to sound best ,Dan says try 5R4-GY Tubes, any one tell me about the Mullard's in this preamp I am getting frustrated, thanks
- ...
- 31 posts total
| Post removed |
Yes don't go all crazy with tube swapping but...well researched substitutions can make a world of difference. I have a Modwright PS 9.0 that came with Sovtek 5ar4 tube. That one blew after a week. I replace it with the same tube...6 months and another blow. I put one last Sovtek in it and worked but sounded like crap. Edgy grainy unlistenable. I'm new to tubes so I started asking Mr. GoogleI settled on NOS Tung Sol 5R4GY which sound so much better. This was not an expensive tube and I learned what rolling could do. Next I popped for more expensive NOS Phillips 5R4GYS and bang Jackpot! Now lets see how long this one lasts |
@goofy you are highly unlikely to exceed the current capacity of a 5Y3 rectifier with a preamp utilising 2 6H30 tubes and two shunt regs. OTOH the suggestion of substituting 12A*7/ECC81,82, 83’s/5751’s, 7025’s, 6DJ8/6922/ECC88’s is ludicrous as they are totally different types of tubes with MUCH higher gains and plate resistances and totally unsuited to your preamp (6DJ8 family are less bad but still unsuitable). God only knows how they would bias. Behause they draw far less current than the 6H30 they may also overload the shunt regulator in the pre which is supplied by a constant current source. 6CG7/6FQ7 have a similar gain, but their plate resistance is about 10 x that of the 6H30 and they run at about a third of the current so you would lose a lot of drive capability. The only sub I would suggest trying is the 6N6P, 60‘s Reflektor are very nice. |
- 31 posts total