Hello to all a while back i repaired and recapped my HH scott 299D with the help of people from the board . Amp sounds fantastic but i am thinking about changing the preamp and output tubes to maybe NOS or good new production tubes. Right now i have Russian EH 7591s and Tungsol reissue 12ax7s and it sounds really good. There are a lot of variables about tubes so any info or suggestions would be great .
NOS 7591s are very scarce. Proper matching will be difficult and cost high. Stay with the current production EH stock.
You can experiment with the voicing by using the Sovtek 12AX7LPS in the phono section and "reissue" Mullards in the line section.
Install the series SS diode tweak on the 5AR4 socket and rest easy about using the comparatively inexpensive Sovtek tube. My preference is for UF4007s, instead of the 1N4007s shown in the graphic. It may not matter here, as the vacuum rectifier blocks SS diode noise, but UFnnnn parts generate much less switching noise than the corresponding 1Nnnnn stuff and quiet diodes are the ones to have on hand.
You can experiment with the voicing by using the Sovtek 12AX7LPS in the phono section and "reissue" Mullards in the line section.
Install the series SS diode tweak on the 5AR4 socket and rest easy about using the comparatively inexpensive Sovtek tube. My preference is for UF4007s, instead of the 1N4007s shown in the graphic. It may not matter here, as the vacuum rectifier blocks SS diode noise, but UFnnnn parts generate much less switching noise than the corresponding 1Nnnnn stuff and quiet diodes are the ones to have on hand.
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Thanks for the reply Eli and the info on the tubes . I will install the Diode tweak on the rectifier ( is this mod to prevent the rectifier from arcing ) right now i have a genalex gold lion GZ34 rectifier . But after some research i see that genalex and sovtek are both made by new sensor. Maybe i should at least try to find a NOS rectifier tube . What brand NOS would be worthy . But i will still do the diode mod .
Forget about NOS 5AR4s. Do you really want to pay over $100?
The Sovtek 5AR4 is prone to startup arcing, when used at the top of its documented range. The series SS diodes kill the arcing and do no harm, when a top notch tube is present. Win/win, which is something that does not come along frequently. Other than arcing, the Sovtek tube is quite satisfactory.
The Sovtek 5AR4 is prone to startup arcing, when used at the top of its documented range. The series SS diodes kill the arcing and do no harm, when a top notch tube is present. Win/win, which is something that does not come along frequently. Other than arcing, the Sovtek tube is quite satisfactory.
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