2Rok JM Sig with CF driver

[M Fowler]

2Rok JM Sig with CF driver:

Need to finish taking voltage readings and burn in for awhile.

Next time I will use top mounting PT and move filter cap board over to allow more board space plus increase the length of the tone board too.

Mark

[M Fowler]

The extra cap stack, I tried to put the caps on the right end but no room you can see I drilled side holes there.

Ended up going high rise (two tier) on this ghetto amp.

[beasleybodyshop]

Looks great Mark! Can you hear a tonal difference with the CF versus the other JM sig you built?

[mhartman]

Very nice Mark. I'm glad that you finally got that CF going. Post some clips!

Mike

[M Fowler]

Thanks for the help on the bias Mike.

Dustin the CF seems to stay cleaner at high volume. Haven't had too much comparison testing yet.

[talbany]

Mark
Your amp is now running in AB2 (Sourcing grid current) so it will be noticeably cleaner in the output section, with extended bandwidth (cleaner highs and deeper bass response) will be obvious..You will also have more power available and more natural compression since you have essentially eliminated the effects grid clamping!!..

To be honest I didn't care much for an overdrive type amp to sound that good running in AB2..The added power is always nice but the extended bandwidth made the OD sound a bit muddy or to bassy and the extended top end gave it a kind of strident almost sterile crunch..OD amps to me always sounded best when you get a bit of output tube distortion to smooth and flatten things out on the way to the speaker..This is just my opinion of coarse and yours might be different and perhaps you can tweak the OD section to compensate,but I ended up removing mine from my ODS style amp..I just couldn't get used to it??...The clean channel however should kick some ass though and you should dig that tone...Let me know if you agree with me!!

Your speaker is on the way!!

Build looks good!!

Tony

[Aaron]

Nice build Mark.

What issues are there with the bias? Is it the fixed resistor? In my build I put in another bias pot because changing CF valves changed the bias so much.

Cheers,
Aaron

[dreric]

Beautiful work, as usual.

I haven't studied the schematic on the JM does it normally have the CF?

[M Fowler]

Beautiful work, as usual.

I haven't studied the schematic on the JM does it normally have the CF?

Thank you no it normally does not have the CF and I really enjoy the one I built without it. I'm blaming Talbany for the CF driver on this one or thanking him

[M Fowler]

Nice build Mark.

What issues are there with the bias? Is it the fixed resistor? In my build I put in another bias pot because changing CF valves changed the bias so much.

Cheers,
Aaron

Aaron, Mike helped me to understand that I needed more voltage for the bias circuit then what the Twin PT bias tap provides so I tapped off the HT and followed his layout but added a bias pot.

[M Fowler]

Mark
Your amp is now running in AB2 (Sourcing grid current) so it will be noticeably cleaner in the output section, with extended bandwidth (cleaner highs and deeper bass response) will be obvious..You will also have more power available and more natural compression since you have essentially eliminated the effects grid clamping!!..

To be honest I didn't care much for an overdrive type amp to sound that good running in AB2..The added power is always nice but the extended bandwidth made the OD sound a bit muddy or to bassy and the extended top end gave it a kind of strident almost sterile crunch..OD amps to me always sounded best when you get a bit of output tube distortion to smooth and flatten things out on the way to the speaker..This is just my opinion of coarse and yours might be different and perhaps you can tweak the OD section to compensate,but I ended up removing mine from my ODS style amp..I just couldn't get used to it??...The clean channel however should kick some ass though and you should dig that tone...Let me know if you agree with me!!

Your speaker is on the way!!

Build looks good!!

Tony

Tony I will get back to you in email with my voltages and see what you think. I don't move very fast anymore so not sure when, but thank you Tony. I needed one more English Vin 30 for my 4x12 for a complete set.

[Colossal]

That came out great Mark. Looks really sharp.

[M Fowler]

Thanks Dave the next amp project a Marshall, I need to get with you for relay switching design Your the master.

[M Fowler]

talbany,

Tony what I like about the JM Signature Reverb there is no OD loop it is basically a SSS without the step filters. The first version I built is very hard to break up which I love about the amp. This second version with CF driver should have even less breakup at high volume.

Mark

[talbany]

talbany,

Tony what I like about the JM Signature Reverb there is no OD loop it is basically a SSS without the step filters. The first version I built is very hard to break up which I love about the amp. This second version with CF driver should have even less breakup at high volume.

Mark

Mark
Oh!..Sorry I thought the JM Sig verb was an OD style amp (How many sig series does he have now ).. Ignore my last post about OD then and enjoy the amp, and post some clips if you can!

All The Best!

Tony