the 1954 Limiter!!

[Stevie342000]

OOPS!!! I got a phone call while I was typing my previous response and I forgot to attach my updated schematic!!! Please find it here. THANKS!!!

/

Opps me too, I think I was on my 1st cup of coffee for the day when I asked the Question but I now see where the Bal 1 & Bal 2 connect to, I knew it had to be a reference level and from what I recall it is the same in the revised schematic. If you scroll a few messages/pages back I asked the same question as to what the revisions were Dave M answered that. OK

 

[opacheco]

MidnightArrakis,​

Excellent!

opacheco

 

[Stevie342000]

It's late and I am being simple again possibly the question is where the X goes to around SW2 & SW3. My thinking is VT7 but I am checking my thinking....?

 

[scott2000]

X goes to around SW2 & SW3

In the original, the limit section (sw2) of the switch is normal operation (x doesn't go anywhere...off?) I'll try to upload the original so it's clear. Thought it was in the thread somewhere. Looks like the new schematic may be based on Dave's version and just normal operation as well. Not sure about sw3 but x looks like it's just some timing modification turned off. Would have to read Dave's journey to see what he did.

 

[Stevie342000]

Thanks it probably is in the thread somewhere I am making sure I understand all the revisions before I build the original ....I may modify it later...If my memory serves it says in the original article that the limiter is low on gain and that gain plus a volume control is taken care of in later stages....Was the alternative to the A18 ever discussed? I would be surprised if it was not as freely available....I remember the discussion about the input and output transformers. I am getting myself ready to build this and want to know that I got it all before I do...It is simple enough to build...I have built stuff before and that worked first time right of the bat....with no issues.....

 

[scott2000]

Was the alternative to the A18 ever discussed? I would be surprised if it was not as freely available...

The original used A12 and A27 iirc. Not exactly sure what you are asking as it relates to the original build if that's what you're after? I think Dave subbed the A27 with an A18 but used as an interstage to the 6sn7 output stage he added . Curious what the output of this thing really is stock.

 

[Stevie342000]

Well stock is what I want to find out as I can add gain...thinking of Sub Preamplifier or the Dave One bottle which gives options without transformers plus it has variable gain...I wanted to know what the modern equivalent of the A18 was as that is the bolted on gain stage in the Modified version....with either option I may run into impedance mismatch issues......when adding a gain stage?

 

[MidnightArrakis]

Well stock is what I want to find out as I can add gain...thinking of Sub Preamplifier or the Dave One bottle which gives options without transformers plus it has variable gain...I wanted to know what the modern equivalent of the A18 was as that is the bolted on gain stage in the Modified version....with either option I may run into impedance mismatch issues......when adding a gain stage?

WOW!!! About 16-months after my posting of my CAD-schematic, this thread re-awakens!!! WOW!!!

In any case.....keep me updated with any changes, modifications, additions, deletions, etc., and I will gladly update my version of this schematic to reflect how things need to be. In addition, if anyone would like to add-in any additional information on specific resistor wattage ratings, specific capacitor types, types of switches, connectors, etc.,.....I will also include that information into a set of -- NOTES: -- into my schematic in order to make it more complete. Sound good???

Keep at it, you guys!!!

/

 

[Stevie342000]

I just want to be build it as stock to the original I do not see any issues with the original design as I have re-read the thread from start to finish. The only issue is that the original design has low gain which is outlined in the earlier posts. It then go reawakened years later and the modifications were added in essentially the output stage of the Federal mixer a few tweaks had to be made to make it work along the way.

As I am not operating the Limiter in a Studio environment...I am not sure I need the extra gain but any discoveries I make along the way more than happy to keep the post alive.

There are many ways to skin a cat....I am double checking my thinking....the only issue I might run into is the low output impedance running into a high impedance input....are there are any issues?

I never remember if that is an issue or not that's all....

 

[emrr]

> the output reaches -20dbm. I might have to build a line amp

Indeed. The max clean output near 20dB GR is around 0.5V in 600 ohms. You don't get "real line level" from a couple low-current tubes. You either go big, or lots, or add an output stage.

That max output is -3.8dBm. This isn't low gain, it's low output. Plenty of condenser mics put out more than that.

 

[Stevie342000]

That max output is -3.8dBm. This isn't low gain, it's low output. Plenty of condenser mics put out more than that.

I probably meant Low output so it is line level about 500mV which should be fine for what I need....

It is not professional line output level at +4dB.

No impedance or loading issues operating Low impedance into a high impedance environment?

 

[scott2000]

No impedance or loading issues operating Low impedance into a high impedance environment?

You may have to tell us what worked best for you in your final scenario.
Here's a thread that may be helpful
https://groupdiy.com/threads/using-600-ohm-vintage-gear-in-conjunction-with-modern-stuff.2845/page-2and a rabbit hole
http://www.sengpielaudio.com/calculator-bridging.htm

 

[Stevie342000]

You may have to tell us what worked best for you in your final scenario.
Here's a thread that may be helpful
https://groupdiy.com/threads/using-600-ohm-vintage-gear-in-conjunction-with-modern-stuff.2845/page-2and a rabbit hole
http://www.sengpielaudio.com/calculator-bridging.htm

I have a number of options for boosting the signal level but then given I am working into line inputs that need about 500mV as input I should not have issues. However that is my domestic set up in the Living Room I may run into issues in the Man Cave system as that will be a mixed impedance scenario mostly still HiZ.

If the 1954 Limiter is in my Living room system then the two room systems will be linked by a Western Electric WE141A which should drive long run and give me the gain I may need.

It's a work in progress still in the early stages right now...still doing all the research and checking out the options...if I need to add gain....

 

[Walrus]

WOW!!! About 16-months after my posting of my CAD-schematic, this thread re-awakens!!! WOW!!!

In any case.....keep me updated with any changes, modifications, additions, deletions, etc., and I will gladly update my version of this schematic to reflect how things need to be. In addition, if anyone would like to add-in any additional information on specific resistor wattage ratings, specific capacitor types, types of switches, connectors, etc.,.....I will also include that information into a set of -- NOTES: -- into my schematic in order to make it more complete. Sound good???

Keep at it, you guys!!!

/

Am I wrong in thinking your redrawn schematic has the output 6SN7 round the wrong way?

 

[scott2000]

Am I wrong in thinking your redrawn schematic has the output 6SN7 round the wrong way?

looks more like heaters are just in wrong spot and plate and cathodes are drawn wrong...so yeah...

eesh....6sk7 look confusing....

 

[emrr]

No impedance or loading issues operating Low impedance into a high impedance environment?

Usually not, you’ll have to see what eq effects occur. Safe medium is putting a 1k2-2k resistor across the output.

 

[xazrules]

sorry to resurrect an old thread, the 6sk7 portion of the circuit is pretty similar to the ba6a but i see that the resistors everywhere are way higher, is there some differences in the bias point? is it made to send the tubes early in deep gr? the ba6a seems biased hotter at idle. i thought to make the tubes not crap out at high gain reduction were to biased very hot at idle.

 

[thomasdf]

sorry to resurrect an old thread, the 6sk7 portion of the circuit is pretty similar to the ba6a but i see that the resistors everywhere are way higher, is there some differences in the bias point? is it made to send the tubes early in deep gr? the ba6a seems biased hotter at idle. i thought to make the tubes not crap out at high gain reduction were to biased very hot at idle.

i am also interested in an answer to that question

 

[MidnightArrakis]

Am I wrong in thinking your redrawn schematic has the output 6SN7 round the wrong way?

[Am I wrong in thinking your redrawn schematic has the output 6SN7 round the wrong way?] -- Is THIS better???



/

 

[scott2000]

Not sure what's going on with G1..but I'm dizzy now...