Hi there, very green here. But Ill dive right in.
I have a KT88 Tube amp, as seen in the photo below, I bought it second hand. The two smaller tubes in the front (12AX7) from what I understand only have one side of them used (ie one line per tube), though are capable of having two lines running through them. The reason for having a tube per line here is presumably for aesthetics? is this the only reason?
Well, its a little quite. I am wanting to build a pre-amp to bump up the gain before it goes through the current KT88 amp. My main question is, can I simple divert both channels through one of the two 12AX7, and re-purpose the other in this system as preamp tube. Im looking at building something like this which requires one 12AX7 Tube. This would save me having to buy a new power supply, and another tube, and socket and....
Im looking to redo the chassis for the KT88 Tube amp so I could make it a little larger, thought the preamp in the build above doesn't look to have a large footprint.
Are there any issues when integrating a preamp into an existing tube amp?
if this is fine, would it be best to use one for the purpose of pre-amp and the other as the pre-boost (which it currently does), or keep the lines separate so one side of of each 12AX7 is pre-amp, and the other continues to do the boosting that it already currently does before feeding into the KT88 tube?
Hope this make sense!
Thanks in advance.
Luke
I have a KT88 Tube amp, as seen in the photo below, I bought it second hand. The two smaller tubes in the front (12AX7) from what I understand only have one side of them used (ie one line per tube), though are capable of having two lines running through them. The reason for having a tube per line here is presumably for aesthetics? is this the only reason?
Well, its a little quite. I am wanting to build a pre-amp to bump up the gain before it goes through the current KT88 amp. My main question is, can I simple divert both channels through one of the two 12AX7, and re-purpose the other in this system as preamp tube. Im looking at building something like this which requires one 12AX7 Tube. This would save me having to buy a new power supply, and another tube, and socket and....
Im looking to redo the chassis for the KT88 Tube amp so I could make it a little larger, thought the preamp in the build above doesn't look to have a large footprint.
Are there any issues when integrating a preamp into an existing tube amp?
if this is fine, would it be best to use one for the purpose of pre-amp and the other as the pre-boost (which it currently does), or keep the lines separate so one side of of each 12AX7 is pre-amp, and the other continues to do the boosting that it already currently does before feeding into the KT88 tube?
Hope this make sense!
Thanks in advance.
Luke
The short answer is probably yes, with little modification, but the question you need to answer is would it help at all? You should be driving your amp with a preamp or a source that can put out line level signal, already. A 12AX7 driver will normally drive a single ended amp with enough swing to get all the power it can produce, unless your source of music signal is very low. To know if the mod you want to do will get you any benefit you need to know more about the operating points of the KT88 and if there is sufficient B+ power to use and bias point class A envelope available also, without driving your outputs into early cutoff. Much info about the amp needs to be known before you change someone else's design.
It would make more sense to leave the existing signal path as it is. Simply wire up the unused section of each 12AX7 as a simple gain stage, one for each channel, plus a volume pot which now feeds the original 12AX7 sections. Re-route the original input wires to the new gain stages and it's done. No?
(Heaters may be unconnected, currently, so don't forget those too)
(Heaters may be unconnected, currently, so don't forget those too)
A complete and accurate schematic of the amplifier, with voltage readings, and resistance values is worth 1,000 words;
and will save 10 to 30 Posts until any modifications are discussed and whether they are good to do.
The rest of the system, including the signal voltage levels that are fed to the amplifier input; and the loudspeaker sensitivity; will help answer if any modification will, or will not, be helpful.
An amplifier is not a device unto itself.
It is part of a system; systems can have positive synergy, or can have negative synergy.
and will save 10 to 30 Posts until any modifications are discussed and whether they are good to do.
The rest of the system, including the signal voltage levels that are fed to the amplifier input; and the loudspeaker sensitivity; will help answer if any modification will, or will not, be helpful.
An amplifier is not a device unto itself.
It is part of a system; systems can have positive synergy, or can have negative synergy.