Valve rectifier

[sgmypod]

Can I add a valve rectifier to my amp(See pdf)

[Twinfan]

Not without a lot of faffing about.  I wouldn't bother mate!

[dave_mc]

probably not worth the bother in a 5-watter, from what i hear it doesn't make much difference in those low powered amps anyway (could be wrong, though).

as dave says, it's probably not going to be too easy a switch. going from valve to SS rectifier is the easy way to do it, i think (again, could be wrong). :)

[tomjackson]

I think Valve rectifiers need a separate AC supply so you would need the transformer to have the apropriate tap on it.
For example a 5F2 Princeton requires a 5VAC supply for the rectifier as well as 6.3 for the other valves heaters.

Even if the above is rubbish I don't think it would make a difference in a 5W amp as it's not powerfull enough to create the sag.

[sgmypod]

Yeah was problem...didn't think it had a tap for the rectifier...so just trying different valves at mo el34, NOS6v6...try kt66 later

[tomjackson]

Do you have any clips, still fancy trying one of those out....

[jpfamps]

You don't  need a 5V tap to install a valve rec. The EZ series use 6.3 VAC on their filaments, and will deliver enough current for your amp. The proviso here is that the filament supply can deliver the extra current required to heat the rectifier filament.

Is it worth trying in your amp?

Conventional wisdom is that:

1) class A amps draw constant current so wouldn't experience any sag when driven hard.

True for push pull class A amps, and over the whole conduction angle for single ended amps; however, instantaneous current in a single amp does vary, in which case a valve rectifier will cause the B+ to be dragged down on positive signal excursions and vice versa. This will cause the signal to be distorted assymetrically (ie even order distortion).

2) All single-ended amps are class A.

Might be the case with your, but many go into class B (or even class C) loading when driven hard, and thus in fact will have considerable variations

Personally I wouldn't bother trying to add a valve rec to your amp. The sag effects of a valve rec can be achieved simply be putting a resistor in the B+ after the rectifier. Try 100-400 Ohms to start with. This mod is cheap and easily reversible. Obvioiusly use a power resistor here. A 5W cement box would be adequate.

[sgmypod]

Thanks am just enjoying messing with amp...always looking for new ways to adjust

[sgmypod]

You don't  need a 5V tap to install a valve rec. The EZ series use 6.3 VAC on their filaments, and will deliver enough current for your amp. The proviso here is that the filament supply can deliver the extra current required to heat the rectifier filament.

Is it worth trying in your amp?

Conventional wisdom is that:

1) class A amps draw constant current so wouldn't experience any sag when driven hard.

True for push pull class A amps, and over the whole conduction angle for single ended amps; however, instantaneous current in a single amp does vary, in which case a valve rectifier will cause the B+ to be dragged down on positive signal excursions and vice versa. This will cause the signal to be distorted assymetrically (ie even order distortion).

2) All single-ended amps are class A.

Might be the case with your, but many go into class B (or even class C) loading when driven hard, and thus in fact will have considerable variations

Personally I wouldn't bother trying to add a valve rec to your amp. The sag effects of a valve rec can be achieved simply be putting a resistor in the B+ after the rectifier. Try 100-400 Ohms to start with. This mod is cheap and easily reversible. Obvioiusly use a power resistor here. A 5W cement box would be adequate.

Also can this easy mod be done one bigger amps

[Roobubba]

jpfamps' quality posting to post-count ratio puts us all to shame!

[sgmypod]

man knows his stuff

[dave_mc]

jpfamps' quality posting to post-count ratio puts us all to shame!

yeah, definitely :oops: :lol:

[JamesHealey]

if the power transformer has the secondaries for 5v heaters then sure you can run a tube recto but you gotta also think about power level of the amp and the HT filters and screen filtering, depends on the amp really but the conversion is possible on some amps.

[jpfamps]

You don't  need a 5V tap to install a valve rec. The EZ series use 6.3 VAC on their filaments, and will deliver enough current for your amp. The proviso here is that the filament supply can deliver the extra current required to heat the rectifier filament.

Is it worth trying in your amp?

Conventional wisdom is that:

1) class A amps draw constant current so wouldn't experience any sag when driven hard.

True for push pull class A amps, and over the whole conduction angle for single ended amps; however, instantaneous current in a single amp does vary, in which case a valve rectifier will cause the B+ to be dragged down on positive signal excursions and vice versa. This will cause the signal to be distorted assymetrically (ie even order distortion).

2) All single-ended amps are class A.

Might be the case with your, but many go into class B (or even class C) loading when driven hard, and thus in fact will have considerable variations

Personally I wouldn't bother trying to add a valve rec to your amp. The sag effects of a valve rec can be achieved simply be putting a resistor in the B+ after the rectifier. Try 100-400 Ohms to start with. This mod is cheap and easily reversible. Obvioiusly use a power resistor here. A 5W cement box would be adequate.

Also can this easy mod be done one bigger amps

Yes you can put a power resistor after the rectifier in any amp to give valve rectifier-like sag. Just make sure that the resistor is rated appropriately. For larger amps I like to use aluminium clad wirewound resistors, such as the Arcol HS25 or HS50. These are bolted to the chassis and have solder tags which makes wiring easy.

Try 47 to 330 ohms, although for most amps 100 ohms seems to work well.

[sgmypod]

cool may mod my kelly