Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Bieworm on February 21, 2023, 03:10:12 am
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Hi guys
I have an amp that runs on2x EL84 tubes in the power section. I have tweaked that to run on 6AQ5 and I really like them there.
I had to lower the B+ from 345V to 260V (zener diodes) to safely keep Va under 250DCV on the 6AQ5 tubes.
This has scaled the voltage of entire preamp down too, but now the tremolo is too weak for me (V1)
The tremolo tube shares the 1st preamp bottle and has a shared Rk and bypass cap.
Are there suggestions to address this? The least desireable fix would be to split the B+ after the rectifier and add separate filter caps to feed only V1 and V2... but I hope there are other tweaks in the tremolo circuit that I could try to make the intensity stronger...
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Show us the complet schematic. I'd like to see the power supply
On RCA Receiving tube manual
6AQ5 max plate voltage is 275 volts
6BQ5 ( EL84 ) is 300 volts
You wrote your EL84 where working at 345 volts , 45 volts more the the max
Why dont you drive 6AQ5 with higher voltage than 250 ?
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Show us the complet schematic. I'd like to see the power supply
On RCA Receiving tube manual
6AQ5 max plate voltage is 275 volts
6BQ5 ( EL84 ) is 300 volts
You wrote your EL84 where working at 345 volts , 45 volts more the the max
Why dont you drive 6AQ5 with higher voltage than 250 ?
Dang!! I read everywhere not to exceed 250V! That 275V would indeed solve the whole thing I guess... I'm using 9 pin 6P1P-EV =C= tubes.. would that matter?
I changed the schematic attachment in my first post for full build specs
You reckon it's a problem when I would run Va at +- 300V ? Since EL84 are ran at much higher voltages than the spec'd 300V.. maybe the 6P1P-EV will handle proportionately higher voltages too? That would definitely handle the tremolo problem
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I have a 6AQ5 amp that runs just fine on 320V.
http://sluckeyamps.com/smoky/smoky.pdf
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I worked on a Gibson/Epiphone EA50T a while back. It had nice trem. Looking back at the schematic, B+ was down in the 240 range. After removing some extra T-filter stuff, it was a fine sounding amp. Anything you can glean from it?
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WAG... You maybe could squeeze a bit more gain from the oscillator tube by increasing the 100K plate load to 220K or even 470K
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WAG... You maybe could squeeze a bit more gain from the oscillator tube by increasing the 100K plate load to 220K or even 470K
That’s an option I considered, but I will try raising the B+ to 280-300V first. With EL84’s and 335 Va the trem worked very good
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Well I set the plate voltage to 283V and biased the tubes at 80% dissipation. Trem works quite strong.. so I’m gonna settle for that and use the amp for a while.
Thanks for the input guys👍👍👍