Anderton '64 reissue JTM145 - any info?

[roberto]

It depends. Do you have 5V DC? Peak-peak? Rms?

[Littlewyan]

Sorry, 10V peak to peak.

Edit: This is a voltage reading I got from ltspice btw so its not an actual measurement from the real amp.

[roberto]

So you already know the answer.

[Littlewyan]

Ok so say I know that 10V Peak to Peak is coming off my 16ohm secondary.

10Vpp * .707 / 2 = 3.5Vrms

3.5Vrms / 18R = .19A

3.5Vrms / 346R (330R + 16ohm speaker) = .01A

You said to square the RMS Current flowing through the speaker and to multiply by the impedance, but I don't see how this would take the current used by the 18R resistor into account?

[Littlewyan]

I used your values Roberto and they work fine. Didn't realize how loud the amp actually was until I got my brother to play my guitar whilst I stood outside my bedroom door. Whoops!

Anyway here they are as promised, audio clips! Sorry for the sloppy playing but I was trying to play guitar whilst tapping the screen on my iPhone so it didn't lock and I'm just making excuses . Enjoy.

[Matec]

1W? Really?

Sounds Great!

I have no words to describe.

I can only say, this is unbelievable!

Congratulations on your development.

Matec

[Littlewyan]

Thanks Matec

As my B+ is around 330V I'm looking at trying an ECC99 which would handle the voltage better. I've also noticed there is some fizz, which in some cases is nice, but could be because I left out the conjunctive filter. The ECC99 may not have this fizz. I may also increase the first HT Resistor to 10K to lower the voltage a bit going to the pre amp valves as they are running quite hot at the moment.

[Matec]

At the beginning of my tests, I also used a 12BH7 in power.
The sound grew louder, but some features were different.
It is a more clean and more fat sound, yet it is a good option.

330V is even a high value. With 240V, my 12AU7 is already hot.

Cheers

Matec

[Littlewyan]

The ECC99 is no longer an option, heater current is 800mA compared to the 12AU7's 300-400mA and my PT wont be able to take that. Looks like the 12AU7 is staying, might try that conjunctive filter though and increasing the first HT dropping resistor. Save the ECC99 for the next build

[jazbo8]

Thanks for sharing the clips, I actually liked "8" - the full-on clips seemed a bit buzzy as you said, I can't help but think that's due to the higher than spec B+, if you have a variac, try to dial it down to see if the tone improves or you can put in a Zener dropper.

[Littlewyan]

Unfortunately I don't, however I do have a light limiter which might drop the voltage, but only if I use a low wattage bulb (100w currently in there). Just a shame that my PT wont take the ECC99. I'll try the conjunctive filter and perhaps a 10K dropping resistor so the pre amp is running at a cooler voltage. Altho I suspect it is the 12AU7 causing the fizz as its the output stage that distorts first in this amp and you can hear a slight fizz with the volume on 5.

[jazzkramer]

Congratulations Littlewyan! Sounds good! Only that little buzz to solve
Thanks for the audio samples

jazzkramer

[Matec]

Hey Littlewyan.

In the schematic you posted, does not appear the filter RC, between the plates of V3.
Perhaps his presence diminish these noises, which are appearing.

Cheers.

Matec

[Littlewyan]

Yer the conjunctive filter, going to try it tomorrow if I get time.

[Littlewyan]

Ok I added the conjunctive filter and what a difference! I always suspected there was some buzz but I hadn't played any other amp for a while so thought it may have been me. Anyway there is still some buzz but no where near as much as before. I've also increased the first dropping resistor to 10K to run the other valves a bit cooler. Here is a clip I made with the volume on full at first and then with everything on full when I start to attempt van halen .