Ampeg PF-20T to (power) amp

[Wasnex]

I like this one, dBm is not so standard for audio these days: dB dBu dBFS dBV to volts audio conversion digital - calculator volt to dBu and dBV dB mW SPL dB decibels 0 dBFS - convert dB volt normal decibels relatioship relation explanation analog audio absolute level true rms convertor converter decibel to dbfs converter calculation online attenuation loss gain ratio reference audio engineering sound recording dBFS dBVU 0 dB audio logarithm level converter peak to peak p-p impedance voltage pro consumer audio digital analog recording level - sengpielaudio Sengpiel Berlin

And the manual specs that P-P figure as max, so yeah, overload. Looks like nominal line level in any case.

That's the calculator I usually reference as well...couldn't find it for some reason; thanks. I figured @Downunderwonder might still relate to +4dBm like me .

From what I have read, the XLR input works with a dynamic mic, but the overload level suggests it is flexible enough to handle line level fine.

 

[Downunderwonder]

Now I got it. Peak to Peak. Cheers.

 

[Zbysek]

That's the calculator I usually reference as well...couldn't find it for some reason; thanks. I figured @Downunderwonder might still relate to +4dBm like me .

From what I have read, the XLR input works with a dynamic mic, but the overload level suggests it is flexible enough to handle line level fine.

The manufacturer states "max. voltage 10 Vpp" (impedance 33 kOhm) for the FX return. The same for the XLR input is 25 Vpp (impedance 100 kOhm). Do I understand correctly that the higher max. voltage means that the XLR would sustain higher overload in comparison to FX return? Thank you.

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[Zbysek]

Ok so I tried it with my PF-50t and Little Mark 250 going back into my PF-115HE cab... it worked fine, not noisy, but I didn't care for the complexity so don't think it's a setup I'd use myself. Note this is the transformer balanced line out with PF-50t gain and volume at around 50%.

Ps not noticing any colouring of the tone or overloading of the LM input even with the PF-50t master dimed.

Is the level of transformer balanced line affected by setting of the Ampeg's master (volume) knob?

 

[Zbysek]

It's a feature that many people would never use, although at NAMM the last two years a whole lot of people commented on how much they liked it in my amps. Typically those were the guys who wanted to play along to tracks when doing solo bass demos. Seems like very few people use EFX loops for EFX these days.

I have this feature on my EBS Microbass II preamp. I have discovered it's usefullnes just recently. I am using it as a dry/wet blend knob for my effects...

 

[Zbysek]

The PFT20T manual describes the Preamp Out and Transformer Bal Out with the exact same words: "This signal may be used to feed an external power amplifier, mixing console, interface or house PA system."

Correct. My assumption is that the Transformer Bal Out will provide more saturated/overdriven sound.

Choose whichever output gives you the function and sound you want. If necessary you might be able to split the Transformer Bal Out and send it to your Little Mark and FOH. But you will need an isolation transformer or some other device to protect the Little Mark against phantom power coming from the mixer. Also you need to be mindful of how any control changes you make impact FOH sound. This varies with signal path.

Depending upon how you eventually connect everything, you may be able to route the Transformer Bal Out from the PF20T to the Little Mark, and then use the Little Mark's DI to get the signal to FOH. This may work well or be too noisy. The manuals don't provide enough detail for me to say sure, so time for you to experiment .

I don't plan to split the signal as it seems to be an unnecessary complication.

I plan to send the Transformer Bal Out to FOH and feed the LM III from the Preamp Out. The reason being that I like less overdriven sound for on-stage monitoring purposes.

I might also send the FOH second line from Little Mark's DI.

But I will experiment with the other possibilities as well.

 

[Deleted member 165050]

Is the level of transformer balanced line affected by setting of the Ampeg's master (volume) knob?

It is, but not as much as you'd expect - like many tube amps most of the action is in the first half of the master volume, beyond that you are adding more overdrive than level. It didn't overload the LM input at all, although I didn't dime the input level.

 

[Zbysek]

It is, but not as much as you'd expect - like many tube amps most of the action is in the first half of the master volume, beyond that you are adding more overdrive than level. It didn't overload the LM input at all, although I didn't dime the input level.

THX

 

[Passinwind]

I have this feature on my EBS Microbass II preamp. I have discovered it's usefullnes just recently. I am using it as a dry/wet blend knob for my effects...

Yep, that's one of my main uses as well. In one of my DIY preamp builds I also used an EFX send pot, and a bypassable FET "sweetener", with separate master for the sweetener. Sort of like a built in Tube Screamer circuit that can go various places in the chain. That works pretty well for warming up digital time domain effects, or for a mild clean/dirty thing with a blend control.

I'm especially interested in this thread since I'm about to try my hand at a few tube amp builds. Should be fun after doing mostly onboard preamps for the last few years. Love the feature sets on the PF-20T and PF-50T.

 

[Zbysek]

Love the feature sets on the PF-20T and PF-50T.

Me too!

 

[Engle]

I'm also interested in this thread. I have a PF-50T that I could use as a preamp. I have a Soundstream DA-2 power amp that has balanced XLR inputs, so I think it should be a simple connection. I'm going to give it a try.

The other setup I will probably test is using the PF-50T with one cab and running the line out into the FX return of my PF350 to power the other cab. That FX return is unbalanced, so what's the simplest/best way to make that conversion? I have a passive DI on hand that I could use, but that's intended to work in the other direction with an instrument on the unbalanced side.

 

[Zbysek]

I have a Soundstream DA-2 power amp that has balanced XLR inputs, so I think it should be a simple connection. I'm going to give it a try.

The other setup I will probably test is using the PF-50T with one cab and running the line out into the FX return of my PF350 to power the other cab.

Please, let us know your experience after you try either way...

That FX return is unbalanced, so what's the simplest/best way to make that conversion? I have a passive DI on hand that I could use, but that's intended to work in the other direction with an instrument on the unbalanced side.

This issue has been discussed above. There are two lines of thoughts: 1. one needs "thingies" to make it work, 2. no "thingies" necessary...

 

[Wasnex]

The manufacturer states "max. voltage 10 Vpp" (impedance 33 kOhm) for the FX return. The same for the XLR input is 25 Vpp (impedance 100 kOhm). Do I understand correctly that the higher max. voltage means that the XLR would sustain higher overload in comparison to FX return? Thank you.

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That's how I interpret it. The Mark Bass manual does not really clarify what the expected signal level is though, so we are drawing some inferences that may or may not be correct. The XLR will safely handle a line level signal, but that doesn't mean it will sound great or work well being driven by the PF20T Transformer Bal Out.

 

[Wasnex]

Correct. My assumption is that the Transformer Bal Out will provide more saturated/overdriven sound.

I don't plan to split the signal as it seems to be an unnecessary complication.

I plan to send the Transformer Bal Out to FOH and feed the LM III from the Preamp Out. The reason being that I like less overdriven sound for on-stage monitoring purposes.

I might also send the FOH second line from Little Mark's DI.

But I will experiment with the other possibilities as well.

The problem with sending Preamp out to the LM and Transformer Bal Out to FOH is you will not know how distorted the sound is at FOH. The Transformer Bal Out signal will be at least as distorted as the signal at the Preamp Out, potentially much more so. Definitely run some experiments .

 

[JimmyM]

This issue has been discussed above. There are two lines of thoughts: 1. one needs "thingies" to make it work, 2. no "thingies" necessary...

In the end, that's probably the only practical difference.

 

[Engle]

Please, let us know your experience after you try either way...



This issue has been discussed above. There are two lines of thoughts: 1. one needs "thingies" to make it work, 2. no "thingies" necessary...

My initial thought was that I should find out what the input impedance of the PF350 EFX return is, but.... it's expecting line out from effects pedals, so it seems like itshould be fine.
I'm going to start without any "thingies" - just an XLR to 1/4" TS cord.
Will report back after experimentation

 

[Zbysek]

The problem with sending Preamp out to the LM and Transformer Bal Out to FOH is you will not know how distorted the sound is at FOH. The Transformer Bal Out signal will be at least as distorted as the signal at the Preamp Out, potentially much more so. Definitely run some experiments .

That' true. I will experiment. My goal is to always give FOH two signals: one clean and one overdriven. This will allow the FOH guy to blend them or even mute one if he finds the other one much better...

 

[Zbysek]

My initial thought was that I should find out what the input impedance of the PF350 EFX return is, but.... it's expecting line out from effects pedals, so it seems like itshould be fine.
I'm going to start without any "thingies" - just an XLR to 1/4" TS cord.
Will report back after experimentation

My understanding of the issue is that you need to convert ballanced signal to unballanced signal...some say

 

[Wisebass]

My understanding of the issue is that you need to convert ballanced signal to unballanced signal...some say

Balanced DI out (XLR) into poweramp input (1/4")



greetings

Wise

edit to add: lots of information about the signals, cables and thingies on only two pages!

 

[Engle]

Balanced DI out (XLR) into poweramp input (1/4")



greetings

Wise

edit to add: lots of information about the signals, cables and thingies on only two pages!

I just read through that thread paying close attention to what agedhorse had to say, and it still seems to come down to experimentation to see what works.