ivan H
Ambassador of Tubes & Grooves
Hi people, it's been quite a while since I've been here (apologies guys). After taking several months off travelling 'round on the old Bonneville, I've since been flat out catching up on requests for builds. This Princeton Reverb build is for quite a high calibre picker (he also has a 5F1 Champ & JMP50 that I did).
Though I'd have preferred to use a SOLandFA chassis (SOLandFA.com : Custom Made Service) & a Guitar Cabinets Direct cabinet, he went with Weber for these to save on shipping costs, as the speaker used is also from Weber. Here's a gutshot.
The chassis' power transformer cutout is sized for the Weber (Chinese) PT, so is too large for the "correct" 125P1B type transformer, which thus needed to be rotated 90 degrees & the chassis drilled to suit. With the PT fitted & wired in, & the OT fitted with just the secondary wired in, I hooked a set of 8 ohm headphones to & powered up the PT so as to listen for any hum,,, all good. Transformers were sourced from SourSound (great sounding OT & PT gives schematic correct voltages). I prefer using bifurcated turret boards over eyelet board & turreted them up myself. All wiring is with waxed cotton "pushback" wire (22AWG solid core) & all is above the board. The yellow lead seen above the components carries the signal from the pre-amp to the concertina phase inverter, & was done like this so it could be positioned so as to not pick up interference from the oscillator circuitry.
Valves are all NOS/NIB. The rectifier is a JAN Philips ECG 5U4GB.
The output valves are JAN Philips ECG black plate 6V6GT's.
V4 (oscillator/concertina phase inverter) is a Sylvania 12AX7A.
V3 (reverb recovery/3rd pre-amp gain stage) is a Sylvania 7025.
V2 (reverb driver) is a (diamond bottom) Telefunken 12AT7.
V1 (1st & 2nd pre-amp gain stages) is a very strong (both mA & gm) Sylvania 7025.
The speaker is a Weber 10F150T (8 ohm, 25 watt, lightly doped).
I added a bias supply trimmer but it's currently running the stock bias supply values. Should he wants the output valves biased warmer, I'll sub in a slightly lower value AC bias dropper resistor & dial the bias to his liking. I also put a 560k grid stopper on the concertina phase inverter, to prevent nasty overdrive artefacts. Notice there is a resistor tacked across the standby switch. This is from my forming/conditioning the filters (before fitting the valves). Apologies for taking the gutshot pic before cleaning out the chassis/turret board etc.
So, he picked it up 3 days ago. Rang me the next morning saying that another guitarist had commented that it sounds better than his original old blackface Princeton Reverb. He gigged it last night & this morning another picker came to see me saying that he had got to play a set through it & it sound awesome.
Ol' mate is recording with it today, then on the weekend it'll come back to have a few things dialled in to his liking;-
1) Reverb dialled down/made more usable by changing out the linear reverb pot for an audio taper one & maybe changing the (V2) reverb driver's 1 meg grid leak for a voltage divider so that the driver doesn't hit the spring tank so hard.
2) Tremolo slowed down so as to achieve that nice "swampy" tremolo (why on earth did Leo call tremolo vibrato & vibrato tremolo???).
Cheers
Though I'd have preferred to use a SOLandFA chassis (SOLandFA.com : Custom Made Service) & a Guitar Cabinets Direct cabinet, he went with Weber for these to save on shipping costs, as the speaker used is also from Weber. Here's a gutshot.
The chassis' power transformer cutout is sized for the Weber (Chinese) PT, so is too large for the "correct" 125P1B type transformer, which thus needed to be rotated 90 degrees & the chassis drilled to suit. With the PT fitted & wired in, & the OT fitted with just the secondary wired in, I hooked a set of 8 ohm headphones to & powered up the PT so as to listen for any hum,,, all good. Transformers were sourced from SourSound (great sounding OT & PT gives schematic correct voltages). I prefer using bifurcated turret boards over eyelet board & turreted them up myself. All wiring is with waxed cotton "pushback" wire (22AWG solid core) & all is above the board. The yellow lead seen above the components carries the signal from the pre-amp to the concertina phase inverter, & was done like this so it could be positioned so as to not pick up interference from the oscillator circuitry.
Valves are all NOS/NIB. The rectifier is a JAN Philips ECG 5U4GB.
The output valves are JAN Philips ECG black plate 6V6GT's.
V4 (oscillator/concertina phase inverter) is a Sylvania 12AX7A.
V3 (reverb recovery/3rd pre-amp gain stage) is a Sylvania 7025.
V2 (reverb driver) is a (diamond bottom) Telefunken 12AT7.
V1 (1st & 2nd pre-amp gain stages) is a very strong (both mA & gm) Sylvania 7025.
The speaker is a Weber 10F150T (8 ohm, 25 watt, lightly doped).
I added a bias supply trimmer but it's currently running the stock bias supply values. Should he wants the output valves biased warmer, I'll sub in a slightly lower value AC bias dropper resistor & dial the bias to his liking. I also put a 560k grid stopper on the concertina phase inverter, to prevent nasty overdrive artefacts. Notice there is a resistor tacked across the standby switch. This is from my forming/conditioning the filters (before fitting the valves). Apologies for taking the gutshot pic before cleaning out the chassis/turret board etc.
So, he picked it up 3 days ago. Rang me the next morning saying that another guitarist had commented that it sounds better than his original old blackface Princeton Reverb. He gigged it last night & this morning another picker came to see me saying that he had got to play a set through it & it sound awesome.
Ol' mate is recording with it today, then on the weekend it'll come back to have a few things dialled in to his liking;-
1) Reverb dialled down/made more usable by changing out the linear reverb pot for an audio taper one & maybe changing the (V2) reverb driver's 1 meg grid leak for a voltage divider so that the driver doesn't hit the spring tank so hard.
2) Tremolo slowed down so as to achieve that nice "swampy" tremolo (why on earth did Leo call tremolo vibrato & vibrato tremolo???).
Cheers
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