Yet another annoying mic and preamp idea solicitation

M

mmcfarlane

Guest
Can anyone recommend a particular transformer or similar device so I can feed the balanced out of the Summit into the inserts on my 01V96? I'd really prefer a plug-and-play solution but I can wire something up only if its required.
 

Boswell

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Apr 19, 2006
Location
UK
AudioGaff said:
Can anyone recommend a particular transformer or similar device so I can feed the balanced out of the Summit into the inserts on my 01V96?

Line level shifter from Ebtech and some cables.

http://www.ebtechaudio.com/products.html
Those won't work in this application because you need to retain the +4dBu level, not convert to -10dBV. At a pinch you could use two channels of LLS by jumpering two -10dBV jacks together and going in and out of the +4dBu jacks, but you may start noticing some signal quality degradation.

You should try to use single high-quality interstage transformers, or better, specific balun transformers. The impedances are not critical, but the turns ratios are. You need 1+1:2, i.e. a centre-tapped primary and the same total turns on the secondary. Impedances can be 600 Ohm to about 5KOhm.

Beware that the peak signal level is around +24dBu, so you need transformers that can handle those levels. You have to wire the transformer secondary to the ring and sleeve of a TRS jack to feed the 01V96 inserts, leaving the jack tip open circuit (it carries the 01V96 pre-amp output).
 

AudioGaff

Well-Known Member
Joined
Feb 23, 2001
Location
Silicon Valley
Boswell, if the 01V96 has unbalanced -10dBV inserts as I would expect, the LLS should work. I've used one for unbalanced inserts to a balanced device such as compressor and back. One channel of the LLS for insert send and one for return.
 
M

mmcfarlane

Guest
from page 286 of the manual:
http://www2.yamaha.co.jp/manual/pdf/pa/english/mixers/01V96V2E1.pdf
01V96 CH INSERT IN
0 db is .775 VRMS

Actual load impedance: 10k Ω

For us with nominal: 600 Ω Lines

Semsitivity: –12 dB
(195 mV)

Nominal imput level: –2 dB
(616 mV)

Max imput before clip: +18 dB
(6.16 V)

Phone jack (TRS)
(Unbalanced)

Output is the same, except impedances are switched. There is also a level block diagram on page 326, which if I am reading correctly, reinforces that the inserts at -2 dBu nominal and a max of +18 dBu.

So if
-7.8dBu is -10dBV
-2 dBu is -4.2 dBV
+4dBU is 1.78 dBV

It looks like the inserts are 'stuck in the middle' :)
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
AudioGaff said:
Boswell, if the 01V96 has unbalanced -10dBV inserts as I would expect, the LLS should work. I've used one for unbalanced inserts to a balanced device such as compressor and back. One channel of the LLS for insert send and one for return.
Yes, I would think that would work OK if you are careful about the levels, since the 01V96 has -2dBu inserts, as mmcfarlane points out. I have only used an LLS for a genuine +4dBu balanced to -10dBV unbalanced conversion for a minidisc recording. Before trying that for the first time, I measured the LLS using a TFA and found the expected 4:1 ratio in amplitude, but also some peakiness in the higher frequencies that could be smoothed out a little by resistive loading. What I didn't think of checking was distortion levels at high amplitudes, so I don't know what you get when you use levels above the nominal + headroom.
 
M

mmcfarlane

Guest
Boswell said:
... Before trying that for the first time, I measured the LLS using a TFA and found the expected 4:1 ratio in amplitude, but also some peakiness in the higher frequencies that could be smoothed out a little by resistive loading. What I didn't think of checking was distortion levels at high amplitudes, so I don't know what you get when you use levels above the nominal + headroom.

Well, it would be a pity to spend $100 for a device that introduces high-frequency spikes.

Maybe just using the line ins, which run through the 01V96 preamps wont be that bad.

I sent an email to Summitt to see what their recommendation is.

An Apogee Ensemble is looking better and better...
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
mmcfarlane said:
Well, it would be a pity to spend $100 for a device that introduces high-frequency spikes.

Maybe just using the line ins, which run through the 01V96 preamps wont be that bad.

No, don't get me wrong, these were not spikes. It's just that the frequency response curve was not perfectly flat. It's many years ago now, so I don't recall all of the details, but I do remember thinking that there was probably some self-resonance going on in the transformer. I tried various resistive loads, and that flattened things out, but also reduced the amplitude. I think that using the LLS into the insert returns should still give you a better sound than the 01V96 inputs at line level (20dB pad engaged). What do you want the dominant character of the sound to be: the Summit preamp or the 01V96 preamps?

My reading of the rather sparse 2BA-221 technical information on the Summit web site is that you can get at the unbalanced solid state preamp output at either the insert socket or at -10dBV on the rear panel Stack output (inverted polarity). From either of these outputs you would not need to go balanced to unbalanced. However, I guess you want the option of using the tube output stage, and that output is available in balanced form on the XLR or at -10dBV on a TRS jack.

I wondered to myself whether this was from an output transformer that could be connected balanced or unbalanced. Bingo! Here is a clue on their FAQ page: When using the XLR +4dB tube output, use a balanced cable. If you need to use it unbalanced, float the low instead of tying pin 3 to ground. So, no need for LLSs, you can wire the XLR output to be unbalanced. You will need a 2:1 resistive divider to get the levels about right for the 01V96 insert return, or else run the preamp at 6dB less gain than you otherwise would. Maybe you could even use just pin 1 and pin 3 for half the output. See what the response is from Summit.
 
M

mmcfarlane

Guest
Here's my (second) response from Summitt.

Hi Mark, I hadn't looked at the block diagram, but when I did it looks like channels 13-14 are made for a line level input. It goes straight to the buffers as far as I can see here.

Otherwise you can use the insert on any channels, that bypasses the mic pre but it is unbalanced so make sure you plug the 2BA-221's into the same power supply as the mixer to avoid ground loops.

There are both +4 dB (on XLR) and -10 dB (on TRS) tube outputs on the 2BA-221 so no problem getting a useable level, as long as you can bypass those Yamaha preamps you don't like! The stacking out and the insert are solid state.

You may be able to use the effect returns as well, with the -10 dB outputs. Again, use the same power supply as it's unbalanced

Actually I think he misread the block diagram, the inserts on 13-16 go through their own amp with adjustable gain. Anyway, I think I'll try one without a transformer or line balancer.

His response did raise one question though, he suggested using the same AC power source because I wasn't using the balanced outputs. This caused me some confusion because I thought balancing was for noise rejection picked up on the cable run and I thought ground loops would be the same whether balanced or unbalanced. Maybe they have a ground lift on the balanced outs and he gave a in complete answer, or maybe my understanding of ground loops is incomplete.
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
Looks like he missed the possibility of floating the XLR outs. Doing this would eliminate any ground loop effects at the same time as producing the unbalanced output that you need.

I would try a cable wired with an XLR socket on one end and a TRS jack plug on the other. Wire XLR pin 2 to TRS ring and XLR pin 1 to TRS sleeve. Leave both XLR pin 3 and TRS tip open circuit. Wire (clamp) the cable screen to the XLR shell. When used between the Summit XLR outputs and the 01V96 insert jack, this cable should give you a -2dBu single-ended unbalanced signal.
 
M

mmcfarlane

Guest
Thanks Boswell, that's how I'll do it. It'll be Early September before I return from vacation with my new gear but I'll report the results.

As a learning experience I'll try to compare what the 01V96 preamps do in comparison to using the inserts points. I think I can figure out a way to route the 01V96 pink noise generator without having a feedback loop to test both setups.
 

Boswell

Moderator
Joined
Apr 19, 2006
Location
UK
Have fun, but the sort of difference you are looking for aren't those that would show up on a pink noise test. Your ears are the best judge.
 
M

mmcfarlane

Guest
mmcfarlane said:
Thanks Boswell, that's how I'll do it. It'll be Early September before I return from vacation with my new gear but I'll report the results....

Thanks again to everyone for your help.

I ended up with 2 channels of the Summitt 2BA-221, a channel of Joe Meek for fun, a free Joe Meek mic, 2 Shure SM81C's and an AT4050. I'll be trying them out this weekend on acoustic guitar and vocals (solo act).
 
M

mmcfarlane

Guest
My first impressions on the Summit 2BA-221:

I wish it had a switch for the post-tube 1/4" TRS out to select +4/-10 levels. This would allow me to cable in 1/4" and easily select pre/post-tube by swapping jacks on the back. A minor nag, I'll probably never use the pre-tube output. I actually made a 1/4" cable first thinking I would test this but wasn't happy with the output levels so I changed to XLR.

(Remember, the 2BA-221 is going unbalanced to the insert points on a Yamaha 01V96R2 mixer and then via firewire into Cubase.)

The only thing I really tested so far is the "instrument in" using an active/passive Warwick 5 bass with customized electronics and pickups - my main axe. I gotta say the detail on the instrument-in is excelent, and quiet enough till I push the tube past 3 oclock. I wish I could get a little more growly tube distortion but alas I couldn't figure out how to with any mixture of solid state, tube, and on bass gain... I can't turn everything up all the way at the same time without overdriving the Yamaha inserts at -2.

I still prefer the sound of the DI on my Eden bass amp (with Eden's magical Enhance [EQ] turned to 2 o'clock) except the Eden is a lot noisier... Eden wants about $300 to upgrade the DI.

I can see using the Summit at least for Jazz recordings. I still have to test my electric upright and test using a few Radial DI's through the mic section.

This weekend I have a session planned with vocals and acoustic guitar to test out all the new toys.

So far so good, and thanks again for the recomendation.
 
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