Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mike123 on July 30, 2017, 04:48:56 pm

Title: Reverb Transformer & Tank Impedance Matching
Post by: mike123 on July 30, 2017, 04:48:56 pm
Hi all, I'm building a Princeton Reverb (AA1164 circuit).

The 022921 reverb transformer from Hoffman Amplifiers has an input Z of 14500 ohms input & an output Z of 4 ohms.
The Mojo 4AB3C1B tank from Hoffman has an input Z of 8 ohms.
 
Googling around it appears that the typical Fender 022921 reverb transformer has an input Z of about 25K ohms & an output Z of 8 ohms.
 
What will be the effect of this Z mismatch be on my reverb?

Cheers
Mike
Title: Re: Reverb Transformer & Tank Impedance Matching
Post by: 2deaf on July 30, 2017, 05:54:14 pm
What will be the effect of this Z mismatch be on my reverb?

There is no impedance mismatch.  25K : 8  is almost the same ratio as 14.5K : 4  and it turns out that this is how output transformers work.   
Title: Re: Reverb Transformer & Tank Impedance Matching
Post by: kagliostro on July 31, 2017, 12:36:43 pm
I think Mike mean which will be the effect of mismacth using the 14500/4 ohm transformer with a load of 8 ohm

14500 x 2 = 29000 ohm

so 29000 ohm primary instead of 25000 primary

I think he will reach only a bit lower strongness of the signal, but probably no other negative effects

Franco
Title: Re: Reverb Transformer & Tank Impedance Matching
Post by: 2deaf on July 31, 2017, 05:08:31 pm
I think Mike mean which will be the effect of mismacth using the 14500/4 ohm transformer with a load of 8 ohm
14500 x 2 = 29000 ohm
so 29000 ohm primary instead of 25000 primary
I think he will reach only a bit lower strongness of the signal, but probably no other negative effects

Probably it.
Title: Re: Reverb Transformer & Tank Impedance Matching
Post by: mike123 on August 06, 2017, 10:43:41 pm
Thanks all for the input. The amp build is now complete & the reverb sounds lush!
Title: Re: Reverb Transformer & Tank Impedance Matching
Post by: kagliostro on August 07, 2017, 11:27:26 am
Quote
The amp build is now complete & the reverb sounds lush!

Nice :smiley:


but ...... with wich configuration for the reverb transformer + tank ?


Franco
Title: Re: Reverb Transformer & Tank Impedance Matching
Post by: mike123 on August 09, 2017, 06:13:47 pm
With the "mismatched" tank.