It attenuates the signal by about 25dB. Draw your own conclusion.
600 Ohm inputs
- Thread starter Brian Roth
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I’m not sure - the reason I had an issue to begin with was due to bass roll off with the original 10k resistor.
Well, it does not make much sense.
What is the impedance of your signal source?
10 ohm output resistors on your suggestion.
That's what I thought. Can you confirm the DCR of the whole primary is about 60r and the secondary about 20r?
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According the the spec sheet the primary should be 60r and the secondary should be 14r. I’ll measure the exact values on my unit tomorrow.
I’ve measured the transformer in situ as it’s a bit of a pain to remove. Primary and secondary are measuring as ~15R each which makes sense as they are wired in parallel and series respectively, on the pcb.
That correlates with the spec sheet of 60R and 14R.
So the primaries are in parallels. Well, you didn't mention that. It results in quite a low nominal inductance, which explains the bass roll-off.
Ok that’s interesting, I’m not sure why the circuit would be designed like that but I seem to be the only person who’s built it having this issue.
Any suggestions for a solution here, or is this question better asked in the G-Pultec help thread?
Looks to me like you're the only one to use an output xfmr (and a very special at that) as input.
Some known people are doing so. The only difference often is: input trans have a higher shielding. Otherwise no problem.
This particular transformer has a very low inductance (about 0.5H), which makes it unsuitable for the task. It can work only with teh aid of an active circuit.
user 37518
Well-known member
Good to see abbey is still around giving reality checks.
MidnightArrakis
Well-known member
I would take it easy with your hammering on "Abbey Road" or he will threaten you with your being banned from this GroupDIY website, as he has done with me a couple of times due to some of my older comments!!! You need to learn to "Play Nice With Others" on this site, despite how you may feel about someone's background, experience and/or knowledge of whatever it is that is being discussed within a particular thread.
To me.....your comments come across as being "overly-righteous" and a bit "arrogant"!!! CALM DOWN!!!
/
Note that pultec filter circuit is neutral with all pots CCW, not centered (!)
Brian Roth
Well-known member
?????? What are you replying to? I'm confused. BTW arrakis I appreciate your comments.
He is referring to post #133.
Very much appreciate your help so far. Odd transformer choice noted, although I don’t think I’m the only one - please note that I’ve built this Gyraf Pultec circuit which specifies an LL5402 and has been successfully built by a lot of people, presumably without the same issues as me.
Thanks for mentioning, I was deliberately applying some amount of EQ to see how it responded under ‘normal use’. Perhaps some measurements at full CCW would have been useful too.
Gyraf, now that you’re here, any thoughts on why I’m having bass roll off issues? Is it likely my source is not able to drive it properly?
for low-freq response, make sure you drive with low enough impedance, and that you have enough primary inductance in your iron
Abbey is the kinder-gentler moderator here, not argumentative in my experience.... If he finds issues with your posts perhaps you need to reconsider what you wrote.
Abbey has a lot of design experience and AFAIK is not actively promoting commercial products here....
JR
Are you referring to the input transformer? I used an LL5402 as specified in the schematic.
