Hoffman's 6v6 Plexi build

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mehfuzhoss
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Hoffman's 6v6 Plexi build

Post by mehfuzhoss »

Hello,

I am ordering parts for a 6v6 plexi build, with 3 preamp tubes. I will use SS rectifier. Do I need sag resistor, if yes, where it will be best to put in. Also, I am planning to use a Hammond 125E OT. Please advise if there is a better option OT wise.
125E.PNG
also which secondary lugs should be wired for best output with 8 ohm V30 speaker.

Thanks
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crgfrench
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Re: Hoffman's 6v6 Plexi build

Post by crgfrench »

Heyboer is better than Hammond
https://el34world.com/projects/Plexi6V6.htm

Get it from GDS or Mojo
Last edited by crgfrench on Sat 02/13/21 1:42 am, edited 1 time in total.
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Re: Hoffman's 6v6 Plexi build

Post by crgfrench »

no sag resistor, just the choke
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Re: Hoffman's 6v6 Plexi build

Post by BlueBoozer »

With a couple of 6V6’s in a push pull config, I’d look for a Classictone Deluxe Reverb OT first. That will give you great output at about 22W. Depending on how you configure the gain stages in your pre-amp this OT will give you the best tone IMO.

I’ve tried Heyboer on two amp builds and Hammond on 1 SE build. I’ve not been able to tell if one has more punch or range than the other. I’ve not tried a CT version of the Hammond yet. It’s on my build list tho. Hammond is definitely the least expensive option.

These are personal opinions and should be taken as such. It’s extremely objective as to the tone you’re looking for. The best answer is to try one and if it just doesn’t have “that” sound, try another.

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Re: Hoffman's 6v6 Plexi build

Post by TriodeLuvr »

Specifications for the 125E look good at 8 ohms. You want to use the 8.2K setting (2&5) for a pair of 6V6. I assume frequency response would fall between the 5.6K and 11.6K curves in the Hammond graph below. If so, it's down only about 1dB at the lowest note on a six string (at 15W output). Low frequency THD and phase shift also appear to be well-controlled. Can't comment on the tone personally, but I wouldn't hesitate to use one of these in a build. Bear in mind it won't perform as well at higher output levels.

Jack
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Re: Hoffman's 6v6 Plexi build

Post by mehfuzhoss »

thank you for input. I heard that under sized OT sounds a little pushed/compressed, so lets see how it sounds. and I do not plan to use the amp at full volume.
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Re: Hoffman's 6v6 Plexi build

Post by TriodeLuvr »

Oops, here's the Hammond graph I was referring to:

Image
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Re: Hoffman's 6v6 Plexi build

Post by mehfuzhoss »

Is hammond 1760H would give slightly more fuller output than 125E ?

please advise
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Re: Hoffman's 6v6 Plexi build

Post by mehfuzhoss »

1760H is a 20 watt and 125E is a 15 watt. I use a 8 ohm V30 celestion / closed cabinet.
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Re: Hoffman's 6v6 Plexi build

Post by mehfuzhoss »

Hello'

I finished the build with 1760 OT. Amp is poweing on okay.
now i want to bias the amp for proper tube life/good tone.

Plz advise me with steps to set the bias

Thank you.
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Re: Hoffman's 6v6 Plexi build

Post by JMPGuitars »

mehfuzhoss wrote:
Sat 03/06/21 2:20 am
Hello'

I finished the build with 1760 OT. Amp is poweing on okay.
now i want to bias the amp for proper tube life/good tone.

Plz advise me with steps to set the bias

Thank you.
The first step is to test all your voltages. Then you can put your voltages into a calculator (or do the math yourself). For example: https://robrobinette.com/Tube_Bias_Calculator.htm
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Re: Hoffman's 6v6 Plexi build

Post by mehfuzhoss »

Hello,

I set bias at 22.5ma. sounds decent. B+ is quite high at 462. Amp feels a little stiff and sterile st MV 2/3. with pedals at front sounds amazing and i like it.

any suggestion to make the amp feel a little softer/fatter/spongier!

Any suggestions are welcome.

i have a lite ii that feels spongier than ss 6v6

Thanks
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Re: Hoffman's 6v6 Plexi build

Post by Bieworm »

An EL84 pushed into OD is hard to beat imho
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Re: Hoffman's 6v6 Plexi build

Post by mehfuzhoss »

Hello,

I want to lower amp's b+ voltage. I have two 1n5408 diodes and planning to use them in series on filter cap that has 40/20/20/20 uf poles. which pole would be best to solder them into? and how much voltage can I expect to cut down with these diodes? currently, b+ is 462V

advise or recommendation is appreciated.

Thank you.
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Re: Hoffman's 6v6 Plexi build

Post by JMPGuitars »

mehfuzhoss wrote:
Thu 03/11/21 9:18 pm
Hello,

I want to lower amp's b+ voltage. I have two 1n5408 diodes and planning to use them in series on filter cap that has 40/20/20/20 uf poles. which pole would be best to solder them into? and how much voltage can I expect to cut down with these diodes? currently, b+ is 462V

advise or recommendation is appreciated.

Thank you.
You need Zener diodes. Read the thread in my signature.

Thanks,
Josh
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