600 Ohm inputs

[abbey road d enfer]

How about the "Gates" approach of making a 600 ohm input act like a bridging input putting by putting a 10K resistor in series on each input leg?

It attenuates the signal by about 25dB. Draw your own conclusion.

 

[SmokeyJoe]

I believe you may have inverted graphs. The one with lower level and bass cut should be the oe with the secondary loaded with 600 ohms.

I’m not sure - the reason I had an issue to begin with was due to bass roll off with the original 10k resistor.

 

[abbey road d enfer]

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?

 

[SmokeyJoe]

Well, it does not make much sense.
What is the impedance of your signal source?

10 ohm output resistors on your suggestion.

 

[abbey road d enfer]

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?

 

[SmokeyJoe]

That's what I thought. Can you confirm the DCR of the whole primary is about 60r and the secondary about 20r?

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.

 

[SmokeyJoe]

That's what I thought. Can you confirm the DCR of the whole primary is about 60r and the secondary about 20r?

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.

 

[abbey road d enfer]

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.

 

[SmokeyJoe]

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?

 

[abbey road d enfer]

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.

 

[Walter66]

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.

 

[abbey road d enfer]

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]

Good to see abbey is still around giving reality checks.

 

[MidnightArrakis]

Learned alot of awesome stuff on this DIY SITE and I have experienced your argumentative nature on every post I've made. Your input leaves a sour taste in my mouth and makes me sad for others. No comment about me calling you out on being a commercial equipment designer with commercial interest in selling sub par equipment to customers who don't know better and praying on people's lack of knowledge instead of enlightening them.

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!!!

/

 

[gyraf]

I made measurements with the EQ switched in (with all controls set to 12 o' clock) and bypassed.

Note that pultec filter circuit is neutral with all pots CCW, not centered (!)

 

[Brian Roth]

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!!!

/

?????? What are you replying to? I'm confused. BTW arrakis I appreciate your comments.

 

[abbey road d enfer]

?????? What are you replying to? I'm confused. BTW arrakis I appreciate your comments.

He is referring to post #133.

 

[SmokeyJoe]

Looks to me like you're the only one to use an output xfmr (and a very special at that) as input.

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.

Note that pultec filter circuit is neutral with all pots CCW, not centered (!)

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?

 

[gyraf]

for low-freq response, make sure you drive with low enough impedance, and that you have enough primary inductance in your iron

 

[JohnRoberts]

Learned alot of awesome stuff on this DIY SITE and I have experienced your argumentative nature on every post I've made. Your input leaves a sour taste in my mouth and makes me sad for others. No comment about me calling you out on being a commercial equipment designer with commercial interest in selling sub par equipment to customers who don't know better and praying on people's lack of knowledge instead of enlightening them.

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

 

[SmokeyJoe]

enough primary inductance in your iron

Are you referring to the input transformer? I used an LL5402 as specified in the schematic.