Hi everyone,
I am looking to build a guitar amp as a wedding gift for a mate. I've pretty much settled on the Fender 5F2-A Princeton circuit using 5Y3GT (Or 6X4), 6V6 and 12AX7.
What voltage configuration of transformer should I be looking at getting? The schematic has 320V marked as the rectified output (perhaps I've misread the schema?). I have found a toroidal on Ali that has reasonable shipping: Vacuum tube amplifiers Ring transformer 50W output 220V 0 220V 0 6.5V 0 6.5V-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
I think that the voltage on this may be too low? Or would I use the 0-440v configuration for this?
I'd love to get Hammond transformers but they aren't readily available here and shipping is extortionate to Oz. I'd also love to hear suggestions for AU or Asia-Pacific sources.
Thanks in advance!!
*edit*: I just want to add that I am on a tight budget for this build (aiming at $200AUD tops) so I am after the most cost effective solution with respect to transformers.
I am looking to build a guitar amp as a wedding gift for a mate. I've pretty much settled on the Fender 5F2-A Princeton circuit using 5Y3GT (Or 6X4), 6V6 and 12AX7.
What voltage configuration of transformer should I be looking at getting? The schematic has 320V marked as the rectified output (perhaps I've misread the schema?). I have found a toroidal on Ali that has reasonable shipping: Vacuum tube amplifiers Ring transformer 50W output 220V 0 220V 0 6.5V 0 6.5V-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
I think that the voltage on this may be too low? Or would I use the 0-440v configuration for this?
I'd love to get Hammond transformers but they aren't readily available here and shipping is extortionate to Oz. I'd also love to hear suggestions for AU or Asia-Pacific sources.
Thanks in advance!!
*edit*: I just want to add that I am on a tight budget for this build (aiming at $200AUD tops) so I am after the most cost effective solution with respect to transformers.
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It could work with 6V6 datasheet design values, not quite as how Leo pushed things. It would work if you went solid state rectifiers giving you around 300V. Since one tube in Class A the current doesn't change much you are not really concerned with rectifier sag. It also saves you the cost of the 5Y3 and the socket. But as a drop in transformer for the Champ/Princeton it is short, in voltage.
220VAC (and silicon diodes) makes 300V DC which is very near how Fender flogged the 6V6 those days. 200 bucks is too small, IMHO. So go ahead with what is readily available. I have seen far worse wedding gifts. (OTOH the Foley Fork turned out more useful than we imagined.)
Haha I had to look that one up on Google.. An interesting device! As for solid state rectification, would a simple bridge rectifier and filter arrangement suffice? What are your thoughts on this 5Y3 plug in rectifier: Yellow Jackets YJR
Wondered if that would give 300V also as it is SS - might leave the option open for conversion to a 'proper' transformer and rectifier tube should the recipient want to do that, at minimal effort.
Thanks, Printer2, for the link. There are plenty of cool mods there for me to look into after I get this built! I'm gonna do away with the rectifier stage and use a dual diode full wave rectifier setup (the PT is centre tapped). Another requirement of this build is that is has an output for headphones. Will I need a seperate OT for this (the OT I selected is into 8 ohms) or can this be done via a resistor?
Cheers
Cheers
I looked for a schematic with a headphone out, Traynor on their 15W amp disconnects the speaker and puts a 100 ohm 5W resistor across the transformer. Then they put a 680R 1/2 watt in series with each headphone side.
Firezog also try 10k with 5k pot
I've seen this circuit crop up a few times on various forums. I wonder if that would work? I've seen some with an 8 ohm dummy load (and this would match the transformer setup).
I've seen this circuit crop up a few times on various forums. I wonder if that would work? I've seen some with an 8 ohm dummy load (and this would match the transformer setup).
There are no currents specified for that PT, that's a bit tricky. 50W ought to be enough though. Since it'll be a low powered amp, i wouldn't worry too much about the actual voltage. It'll put out a fraction less power, that's all.
There is no 5V winding, so you can't use the original rectifier. Dropping one of the 6,3V windings with a resistor to 5V is an option, but it's doubtful that the transformer has the insulation to withstand the HT. You can consider using an EZ80 or EZ81 rectifier. 6,3V and no HT on the heater.
There is no 5V winding, so you can't use the original rectifier. Dropping one of the 6,3V windings with a resistor to 5V is an option, but it's doubtful that the transformer has the insulation to withstand the HT. You can consider using an EZ80 or EZ81 rectifier. 6,3V and no HT on the heater.
Hi Parafeed
I've decided to use solid state rectification for this build, mainly to keep within the budget I've set myself. But also thinking I can wire this as parallel 0-220v to get the extra current, then dual diode full wave rectify to yield (as others have said) around 300v.
The data I found for the original PT (66079) suggested about 45W maximum draw including SOL. So I'm happy with the 50W (although less happy about the non-existant amperage values), especially if I parallel the windings of the secondary in case this xfmr is 25W per winding...
I've decided to use solid state rectification for this build, mainly to keep within the budget I've set myself. But also thinking I can wire this as parallel 0-220v to get the extra current, then dual diode full wave rectify to yield (as others have said) around 300v.
The data I found for the original PT (66079) suggested about 45W maximum draw including SOL. So I'm happy with the 50W (although less happy about the non-existant amperage values), especially if I parallel the windings of the secondary in case this xfmr is 25W per winding...
Just realised I wrote something a bit dumb... if I parallel the secondary, I can't full wave rectify with 2 diodes as the transformer will no longer be centre tapped as such...
You end up with full wave rectification with two diodes and a center tap. You know, going SS diode gives you two 6V windings free. Could use that for a +/- supply and go nuts with opamps. Ir you can add another 12V to the HV supply
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I was going to feed the heaters of the 6V6 and 12AX7 with those windings. Although it is tempting to go nuts with some opamps! 😀
One winding, I was messing with the concept of all Mosfets for the last day and while I was thinking HV my mind blanked out the heaters.
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