Donate to This Project

Your donations help us continue to add new and exciting features. Please consider making a donation

DONATE NOW
HarmonicaSpace is a subsidiary of Brady Mills Graphics

Which Impedance Matching Transformer?

Back to the Gear Room

MrAck
Dec 31, 2009 10:49 AM GMT

I recently tried to compete with some guitar players who promised our little gig would not be a loud one. Well, it started that way and we began to have too much fun jamming some rock/blues, and up went to volume. I attached a Y-cable to another small amp as was able to just keep up. I would usually use someon else's mic or my Shure 533SA to mic my best amp, but had to give up the 533 to a vocalist who was missing a mic. I really like changing mic's while I am playing and missed using the 533, so I purchased an Audix i5 microphone (low impedance) to mic my smaller amps into the PA and to have as a backup vocal microphone. Incase I want to play through the Audix i5 plugged dircetly into an amp, I am may purchase an impedance matching transformer but I haven't tryed any out.

Are there significant differences between an Audix T50k and a Shure A95UF impedance matching transformer?

I assume most PA's will accept a high impedance mic input. If not, is there ever a need to reverse the transformer to plug a high impedance mic into the transformer and then into a low impedance input?

Any other thoughts on alternate solutions? I don't know much about PA/sound boards, so please forgive me if these sound like rookie questions.

I apprciate any advice and hope this may help other newbies.



Share |



Comments (18)

Login or Register to Post Comments

Order by Date

Jan 01, 2010 1:28 AM GMT
Chris C Replied:

I'm sorry something does not sound right in your question. You asked...


I assume most PA's will accept a high impedance mic input. If not, is there ever a need to reverse the transformer to plug a high impedance mic into the transformer and then into a low impedance input?


Well most PA's actually are looking for a Low Z(impedence) Balanced Microphone input via an XLR plug. I which case Audix i5 (being low Z as well) will plug straight into the PA with a balanced XLR-XLR lead(standard microphone lead). Perhaps I have not understood the question correctly. As for the diffence between the Audix and Shure impedence matching Transformers sorry don't know. I use a cheap passive DI from Jaycar that works great.



Jan 01, 2010 8:57 PM GMT
John P Replied:

The Audix transformer will sound VERY clean. The Shure will be a little thicker in the midrange, which I happen to like. I use a Peavey rat tail transformer. They are a little hard to find, but Greenfly Music Supply carries them. Be sure to order Female XLR, since they make one with a male XLR connector, too.

Most PA boards will accept 1/4" inputs or XLR inputs. The 1/4" input generally bypasses the board's mic preamps.

You would use a transformer on a high z mic to convert to low z (XLR) signal for very long cable runs to avoid signal degradation. BUT you should be okay for runs up to a max of about 30 feet w/o having to use a direct box or a transformer to convert to low z. Most literature says 15 or 20 feet, but, actually, you're probably ok up to a max of about 30 feet. Rolls makes a little inexpensive passive DI called the "Matchbox" that works well and is easy to carry around if you need one.

btw, there's nothing wrong with plugging direct into the board and getting you


Jan 01, 2010 9:02 PM GMT
John P Replied:

The last paragraph of my post got cut off. What i was was saying is, if you know how to set the levels and tone controls on the board properly, there's nothing wrong with plugging directly into the board and getting your tone with breath and mic handling technique. If you've got to mic the amp anyway, consider whether using an amp may be more aggravation than it's worth. After all, the PA is the biggest amp in the room. Just a thought...



Jan 02, 2010 6:28 AM GMT
Boris Plotnikov Replied:

I've tried Audix transformer and cheap soundking transformer. Both works bood. Only issue about audix is that I twice resolder wire from transformer block to jack. No issues about soundking. The sounds absolutely similar, I think I'll find any differences with blind test.



Jan 02, 2010 3:37 PM GMT
BlowsMeAwy Greg Replied:

There's very little difference between IMT's. There is nothing wrong with plugging a hi-Z mic into a low-Z output by using the IMT "backwards" - they are not directional. There is also nothing wrong with plugging a high-Z mic into the 1/4" input of a PA if it has one, as long as you can keep your cable length under 20' or so. (Low impedance cables can be run for 100 feet or more with no appreciable loss.)

John - you're right there's nothing wrong with plugging into a PA directly, it is the biggest amp in the room. And everyone should learn how to get a nice warm tone this way. But if you're suggesting that is equivalent to a classic tube amp sound, I have to disagree strongly. They're not even close - that is, IF you use your tube amp to produce the low frequency harmonics and distortion many of us feel is part and parcel of the true "chicago blues" sound.

BlowsMeAway Productions
Bluestate
Bluestate on CDBaby
Bluestate on iTunes



Jan 02, 2010 5:04 PM GMT
Barbeque Bob M Replied:

If you're used to using a Fender tube amp, the tone controls on those amps are passive, meaning that when the tone controls are turned all the way up, it is the flat, preshaped sound from the factory, and PA's use active tone controls, where either side of 1/2 way actually boosts and cuts for real, and so the tone control setting from many amps have to be different on a PA as well as most solid state amps, and certain tube amps like Marshall's since the late 60's or Fender tan Concerts/Vibroverbs/2-10 Supers.



Jan 02, 2010 6:04 PM GMT
OrthodoxBlues Replied:

Bob --

I believe that you've explained the tone controls elsewhere here, but I still don't have it. Can you explain that in more detail? I'm trying to understand how to use the controls on my Fender amps, and how they differ from PAs. I hope I haven't derailed your thread, MrAck.



Jan 02, 2010 6:35 PM GMT
John P Replied:

Greg, You are unquestionably correct. One cannot get a classic tube amp sound through a PA. BUT, some of us don't strive for that particular type of classic distorted Chicago tone, which, btw, you achieve so wonderfully well when you play. BUT, it is generally possible to get a little more tonal texture playing through a PA than most players usually do.



Jan 03, 2010 1:40 PM GMT
John P Replied:

There are actually 2 different tone control formats on the older Fender amps. The amps that have Bass Treble and Midrange will not produce ANY sound if all the tone controls are turned all the way down to "0."

On the amps that have only Bass and Treble you CAN turn them all the way down to "0" and still get normal volume. The SuperbReverb Reissue has both configurations since one channel has 2 tone controls and one channel has 3 tone controls.

Maybe BBQ Bob can enlighten us about these.



Jan 03, 2010 4:19 PM GMT
BlowsMeAwy Greg Replied:

John - then you and I are in "violent agreement."

BlowsMeAway Productions
Bluestate
Bluestate on CDBaby
Bluestate on iTunes

Cheers

John PReplied:

Greg, You are unquestionably correct. One cannot get a classic tube amp sound through a PA. BUT, some of us don't strive for that particular type of classic distorted Chicago tone, which, btw, you achieve so wonderfully well when you play. BUT, it is generally possible to get a little more tonal texture playing through a PA than most players usually do



Jan 03, 2010 6:32 PM GMT
OrthodoxBlues Replied:

Thanks all, for the great information, both on the Fender amp controls, as well as the impedance transformers. I think that I now understand how the passive controls really constitute a way of cutting the treble (for example), while the active ones actually boost. I will check out my '83 Champ II, which has a treble knob that also pulls out for mids, and a bass knob. I think that it is active, because the mid knob can get into some significant overdrive.



Jan 04, 2010 3:42 PM GMT
Barbeque Bob M Replied:

John actually describes the way Fender black face tube amps work, and many of their tube amps still wotk that way. The tan series (1960-63/64) does have some that work that way, as well as some spillover from the way the tweed amps from the 50's work as well as far as the tone controls work. The only Fender tube amps that ever had active tone controls were the tan 4-10 Concerts, the Vibroverb (both the 2-10 and 1-15 versions) and most of the 2-10 Super amps. Many tube amp companies, including Marshall and Hiwatt adapted their amps to active tone controls.

On my real '59 Bassman, I turn the treble all the way down and it still has sound hapening, and this circuit works laregly the same for tube amps they made in this period. The amps they made with a single tone control can have the tone turned all the way down and still work, which is exactly the same thing that the Pro Junior does, and this is still a passive tone control.



Jan 04, 2010 9:13 PM GMT
John P Replied:

But, if I turn all 3 tone controls to "0" on my Super Reverb RI i get no sound. You can zero out 1 or 2 of them, but not all 3. Now, on the other channel than just has 2 tone controls, or on my Princeton Reverb RI which also has just 2 tone controls, you can turn both to zero and still get sound.



Jan 04, 2010 9:14 PM GMT
John P Replied:

But, if I turn all 3 tone controls to "0" on my Super Reverb RI i get no sound. You can zero out 1 or 2 of them and still get sound, but not all 3. Now, on the other channel that just has 2 tone controls, or on my Princeton Reverb RI which also has just 2 tone controls, you can turn both to zero and still get sound.



Jan 15, 2010 3:11 PM GMT
Andrew T Replied:

I'm looking into an alternative to the ol standard, Shure "Green Bullet" mic. What's a good "clean," low impedance mic I could look into for playing directly into the harp? I also wonder if anything beats the ol SM57 for amp mic-ing...



Jan 15, 2010 5:12 PM GMT
HTrain Replied:

After using nothing but the sm57 for amp micing, I tried the advice of a friend harp player - the Sennheiser 609. It is flat and rests against the face of the amp so it requires no stand. Clean pick up that gives you what the amp is producing. I'm sold on it for an amp mic.



Jan 24, 2010 7:28 PM GMT
Boris Plotnikov Replied:

Andrew

Yes, try SM57 with impedance transformer. Or even better ultimate 57 fro blowsmeaway. You can order SM57 with high impedance and no need for transformer.




© 2009 HarmonicaSpace

Advertise with Us | Terms and Conditions | Privacy Policy | Anti-Spam Policy | Report Abuse | Report Problem | Contact Us

Harmonica Space offers free social networking, harmonica forums and harmonica chat for harmonica players.
Join today and meet other harmonica players from all over the world!


Web Development and Web Design by Brady Mills Graphics