muddy new build

[afm_380]

I just finished an interesting build .. it went pretty well (with alot of research off this forum ... thanks)

I've taken a basic 5e3 circuit and added a few twists ... to simplify the twists, first I decided to make it a single input channel (I know ... it's already NOT a 5e3 without the interactive tone and volume ... ;o). I put a volume control (gain) between the first two phases, added a complete fender tone stack (initially I drove the tone stack off the cathode of the 2nd phase, but there wasn't nearly enough gain to drive this circuit above low practice volume), which feeds a longtail phase inverter. So it's a single channel, two preamp phase, LTPI, cathode biased used to be 5e3 (that has been wired to accept el34's). Oh and it has some pretty heavy power supply filtering powered by a diode bridge rectifier.

It's far from sterile ... but it sound best with the treble full on and the mid and bass controls at zero. The tone stack works, but it'd be nice to get some of the 'mud out'.

Here's what I built ... any and all comments are definitely appreciated.

Thanks in advance

[txstrat]

I'd try to change the Bass pot to 250K, the mid pot to 10K to get the mud out.
I might also help to change the bias resistor bypass cap to 25uF.
...and welcome to the forum.

[loudthud]

Smaller coupling caps will reduce bass and get the mud out. Change C2, C7, C10 and C11 to .02uF or .047uF. Try changing them one at a time and in different combinations until you find what you like. Is C9 really .047uF? That will kill all treble. Should be 47pF.

[afm_380]

OOOOPPPPPPSSSSSSSSSS .... AWESOME catch.
yes C9 is really an .047uf. That was the part of the circuit that I couldn't find much info on in my research. The old bassman schematic was difficult to read the value. Looking closer at other similar schematics I can make out the 47 mmf. I knew it had to be something simple that I had overlooked. I had a spare 250pF to throw in ... That definitely brightened it's voice. A little more fine tuning and build will be a success. Thanks

[Chris / CMW amps]

I just finished an interesting build .. it went pretty well (with alot of research off this forum ... thanks)

I've taken a basic 5e3 circuit and added a few twists ... to simplify the twists, first I decided to make it a single input channel (I know ... it's already NOT a 5e3 without the interactive tone and volume ... ;o). I put a volume control (gain) between the first two phases, added a complete fender tone stack (initially I drove the tone stack off the cathode of the 2nd phase, but there wasn't nearly enough gain to drive this circuit above low practice volume), which feeds a longtail phase inverter. So it's a single channel, two preamp phase, LTPI, cathode biased used to be 5e3 (that has been wired to accept el34's). Oh and it has some pretty heavy power supply filtering powered by a diode bridge rectifier.

It's far from sterile ... but it sound best with the treble full on and the mid and bass controls at zero. The tone stack works, but it'd be nice to get some of the 'mud out'.

Here's what I built ... any and all comments are definitely appreciated.

Thanks in advance

1st coupling-cap lower (let's say 0,022)
input-cap-PI lower (0,022 or smaller)
seperate B+ node for V1
C10 and C11 lower, 0,022 or 0,047
C12 lower, let's say 22uF/>63V
maybe enlarge R8 for slightly more scooping (100k or so)

[MWJB]

100uf filter caps at preamp & screen nodes? Sub the preamp cap for 20uf, 50uf tops for the screen supply.

[MWJB]

Your schem says "Deluxe PT", what PT did you actualy use?

[afm_380]

Thanks for the suggestion guys ... This is an AWSOME forum.

I've dropped the screen filter cap to 47uf, dropped the cathode bias cap (c12) down to 22uf, and replaced c9 with two 100pf ceramics in series (that was the only thing I could find locally). It's close enough to take out to play this weekend. My new supply of coupling caps should arrive Monday ... ;o)

The PT and OT are from Triode Electronics ... here's the links.
Upgraded Tweed Deluxe Power Transformer 120/240V
Deluxe Ultra Output Transformer TF110-4816/UL 6600CT 4/8/16 ohm (Paper Bobbin)

Thanks Again

[MWJB]

Your PT is not up to running 2xEL34, if you continue to run these tubes it will most likely burn up.

[MWJB]

Which PT secondary taps did you use for the bridge rectifier? Why not just use a full wave (non-bridge) ss rectifier?

[afm_380]

Thank you for the warning about running the El34's. I primarily built this to use 6V6/6L6's, and it ran flawlessly Friday nite and all day Saturday and Sunday with a pair of T/S 6L6-STR's. It held it's own sharing the jam stage with some REALLY nice amps ... it was the one that everybody kept plugging into ... ;o) It was REALLY rewarding to be able to hear so many different players playing thru this little amp.
Thank you for the warning about running the El34's. I primarily built this to use 6V6/6L6's, and it ran flawlessly Friday nite and all day Saturday and Sunday with a pair of T/S 6L6-STR's. It held it's own sharing the jam stage with some REALLY nice amps ... it was the one that everybody kept plugging back into ... ;o) It was REALLY rewarding to be able to hear so many different players playing thru this little amp.

I used the HT taps (330-0-330) for the rectifier, and actually built it as a full wave with 4 MUR4100E's running the standby switch off the CT thru a 30v/10w zener diode to ground (to get my output voltages down so that I was running the preamps tubes so hard). Forgive me for not updating my schematic.

Thanks again for all of your help.

[pdf64]

Increasing the value of the bright cap C3 would add more sparkle to the amp, depending on where the volume control was usually set. 220pF would be a lot brighter, 470 even more so, so try that then work back to your current value if it's too much. Peter.

[MWJB]

Have you tried a cathode bypass cap at the input triode?

[afm_380]

I had cathode bypass caps in both halves of v1 in my initial build which were removed during troubleshooting before my error at C9 was discovered. Since that correction I have reinstalled these caps. My preference was to reinstall a 47uF v1a. I have a ton to learn about tuning the tone ... this has been a lot of fun. Thanks Again for ALL of your help.

[afm_380]

Here's the latest schematic (I believe it's an accurate representation of what I have currently built ... ;o) I will be swapping out coupling caps to experience what does what .... but it sounds GREAT the way it is right now.

Since I just can't leave well enough alone, the next modification will be to build a dc heater supply. I know just enough about this to be really dangerous ... As I understand it, I need to build a full wave bridge rectifier (four 1n4002's in a diamond) off the 6.3v tap of the PT, but this will give me close to 9vDC. So that will need to be regulated back down, and I need to remove the 100ohm resistors (r29, r30) to ground that make up the current artificial heater center tap. But this probably constitutes it's own thread.

I've said it too many times already ... but, It's genuine appreciation ... Thanks Again