The Amp Garage

Thanks Tubedude, I do try to remember that my HV coil is about a 3:1 ratio to the line coil and do expect some variation, its just going from a solid 466 +/- 3vdc all the way down to 440vdc or so, is such an unusually big dip, but, maybe the line voltage did do something crazy low at that time. And ...

Thanks for didit,

I see that there is a lot talked about, the Mullards power on flash, that it tends to happen when cold and not when the amp gets turned on and off in close time.

Very interesting.

thank you,

Phil D

I'm quite sure this PI tube is a NOS Mullard CV4024. I've only ever purchased 3 of them but this one and another showed unexpected early symptoms. Actually, this one I referring to here may be one that started whistling at some point. It still passed signal adequately but began high pitched whistle ...

Ok Xtian, thanks.

I will keep it in mind that that may not have been an issue. It was seeing my B+ 20-25 volts lower than usual that got my attention. Must see about that.

Thanks again,

Phil D.

Hello, I sure could use a little sanity check on this if you can. I was once again trying my rebuild which had been looking fine, except, when I hit the power switch this time, I witnessed a whiteish flash through the base of the Phase inverter socket that had a NOS 12AT7 in it. I have not seen this...

Hi Amp, Just wanted to mention that using a 5V4 helped my amp B+ come down 12 or 15 volts or so over a GZ34. This amp has a Plexi preamp but the power output section is nearly identical to a Deluxe reverb - a pair of JJ 6V6's with around 435vdc on the plates, 20mA or so bias current. Its working out...

Thank you Xtian, Where are you looking at the power consumption from? What part of the amp? I suspected that the output of the OT may not show a very high frequency oscillation but, that maybe a misnomer on my part. I always looking at power output with a 1Kh sine wave at the speaker, but I wouldn't...

Hello, I did a first sound check on my Blackvibe 6L6 rebuild (6L6WGB, reverb, no tremolo single channel). I seemed to be sounding fine through a Weber C12B, lots of Fender clarity and very loud. A couple of concerns if you have the bandwidth. I don't suspect that anything is wrong (besides an incomp...

Thank you Martin, That makes sense to me - having the inputted grid voltage bring negative bias voltage to "0" volts. I take it that you would get the greatest voltage swing at the plates without pushing the grid positive and causing things that are not necessary, well, at least for my application (...

Hello, First of all, I want to thank you all for sharing your valuable experience with me as I navigate through my amp builds and currently attempt to finalize this Fender 6L6WGB upgrade (now with reverb but without tremelo). I was curious if anyone puts any weight or value on say, input voltage (AC...

Thank you Rooster, And I will be keeping a Hawks ear on the 4.7uF that I placed in the preamp cathode bypassing. If I find anything down there is missing at all, I will pump those values right up. It will be interesting to see/hear/feel what those smaller values do to the sound. I know there are fol...

So I piggy backed a 68K ohm resistor in parallel with the 15K resistor and I was able to get the -52 or so volts DC at about the 1/3 rotation - which is fine. That plenty of room for required range of negative voltage I would imagine. So, that was nice! Thank you Martin. Now, to re-bias to say, 60% ...

Thank you Martin, Yes, it is a CRC filter, I believe with a 15K resistor. I will double check and also yes to wanting to get a more negative voltage from this. As a matter of fact, I will start by solder tacking some larger resistors onto the 15K until there is a better usable range to adjust within...

Hello folks, So finally, I'm looking at the scope traces (Input and dummy load output) and I believe I'm seeing good things However, I will need to tweak a thing or two and of course get to a real listening test. This was a Rob Robinette Blackvibe 6L6 that although came out very good, was just way t...

Absolutely Martin, thank you for sending this link.

It appears one or two who tried it out reported that it does just what is says it supposed to do, a clear direct signal with a tapped parallel line to effects that can be brought back.

Looks good, thank you.

Best,

Phil