Tweet
Differences between two Fender Deluxe Reverb Reissues: 1965 Blackface vs. 68 Custom Silverface
This thread may not strictly belong in the "Vintage Amps" area, as it discusses modern reissues. But I can't think of a better place to post this information, so here goes:
In another thread I was looking for compatibility information about faceplate hole size and spacing between the current Fender DRRI boards and various aftermarket chassis options. A side topic came up about putting the 68 Custom boards into a 65 DRRI chassis:
If you already have a complete amp then you won't need the complete set of boards, you could also effect the change by just doing a few component swaps.
This is the difference in parts between the BF 65 DRRI and the SF 68 Custom:
Summary of the changes:
1. Changing the "mid" cap in the tonestack from 47nF to 22nF will result in a bit of bass boost in the 68 Custom. This is because the smaller cap changes the cutoff frequency for the RC lowpass filter formed by the slope resistor and the mid cap, in addition to changing the CR high pass filter frequency formed by the mid cap and the 6k8 fixed mid resistor.
Here are two plots from TSC that show the effect of the cap change with the bass control max'd out:
2. Changing the Reverb Mixing Resistor from 1M to 470k results in stronger wet signal available for mixing with the dry signal.
3. Increasing the ratio of the NFB series resistor R10 to the cathode resistor will result reduction of the feedback factor (H). Less NFB results in earlier breakup for the power amp. (You might want to make this mod switchable.)
4. Reducing the value of the coupling caps will reduce the frequency response for bass signals in the output stage. This is the classic fix for "Fender farting." Decreasing the size of the coupling caps from 100nF to 22nF decreases the time constant of the AC coupling circuit, thereby allowing faster cap discharge and decreasing the "Crowhurst" variety of "blocking" distortion.
Have fun!
This thread may not strictly belong in the "Vintage Amps" area, as it discusses modern reissues. But I can't think of a better place to post this information, so here goes:
In another thread I was looking for compatibility information about faceplate hole size and spacing between the current Fender DRRI boards and various aftermarket chassis options. A side topic came up about putting the 68 Custom boards into a 65 DRRI chassis:
Originally posted by Steve A.
View Post
This is the difference in parts between the BF 65 DRRI and the SF 68 Custom:
Code:
Descriptor Part # 65 BF DRRI 68 Custom SF DRRI Tonestack C23 0.047 0.022 Reverb Mixer R30 1M 470k NFB Shunt R10 2k7 5k6 Coupling C10,C16 0.1 0.022
Summary of the changes:
1. Changing the "mid" cap in the tonestack from 47nF to 22nF will result in a bit of bass boost in the 68 Custom. This is because the smaller cap changes the cutoff frequency for the RC lowpass filter formed by the slope resistor and the mid cap, in addition to changing the CR high pass filter frequency formed by the mid cap and the 6k8 fixed mid resistor.
Here are two plots from TSC that show the effect of the cap change with the bass control max'd out:
2. Changing the Reverb Mixing Resistor from 1M to 470k results in stronger wet signal available for mixing with the dry signal.
3. Increasing the ratio of the NFB series resistor R10 to the cathode resistor will result reduction of the feedback factor (H). Less NFB results in earlier breakup for the power amp. (You might want to make this mod switchable.)
4. Reducing the value of the coupling caps will reduce the frequency response for bass signals in the output stage. This is the classic fix for "Fender farting." Decreasing the size of the coupling caps from 100nF to 22nF decreases the time constant of the AC coupling circuit, thereby allowing faster cap discharge and decreasing the "Crowhurst" variety of "blocking" distortion.
Have fun!