Unbalanced Ins to Thermionic Bustard--Level Loss

[forumuser761267]

hi guys, I recently got a thermionic fat bustard which I was told I could plug synths and drum machines straight into for tracking. when I do, though, I barely get any signal--the vu meters barely move. I have to crank the channel input and monitor both to max to hear much.

I'm assuming this has something to with unbalanced synth inputs going to "semi balanced" thermionic inputs. which is strange because I have a phoenix which does fine with synths. or maybe I'm wrong . the synths are cabled through a bantam patchbay which is half normalled to the ins on the bustard.

any ideas short of getting a large number of di boxes, which I don't particularly want to do?

[James Perrett]

Can you tell us EXACTLY how everything is wired? I'm wondering if there's a missing ground or whether your cables have the hot and cold swapped?

I must admit that I don't understand why they couldn't at least have provided impedance balanced outputs. In that way they could have catered for those who prefer balanced outputs as well as those who prefer unbalanced outputs.

[Arpangel]

Isn’t the Bustard unbalanced? I may have read that TC said it gives a better sound that way, someone correct me if I’m wrong.
I can’t see that there’d be any issues, did you buy it used?
Aren’t Thermionic in Essex somewhere? I’d give them a call, that’s the great thing about buying British.....

[Hugh Robjohns]

hi guys, I recently got a thermionic fat bustard which I was told I could plug synths and drum machines straight into for tracking. when I do, though, I barely get any signal--the vu meters barely move. I have to crank the channel input and monitor both to max to hear much.

As I recall, the FB is a passive line level mixer and has no gain, so if your synths have typical instrument level outputs, the main output from the FB will be around instrument level too -- and that's with all the level controls flat out. If the input channel controls and main output control are at 12-o'clock the output level will be 20dB lower still!

I'm assuming this has something to with unbalanced synth inputs going to "semi balanced" thermionic inputs.

They're not 'semi balanced' they are plain unbalanced inputs. Pin 2 accepts signal, and pins 1 and 3 should be grounded back to the synth. So if you have a polarity inversion in your cabling or patchbay, that would kill the signal, and the same is true if the ground is missing (possibly in an effort to cure ground loops).

any ideas short of getting a large number of di boxes, which I don't particularly want to do?

DI boxes won't help... In fact they'd make the problem worse!

There's no reason why the FB wouldn't work with synth sources, notwithstanding the absence of any gain in the standard signal path (so the output will always be at the same or lower level for individual sources). The attitude (distortion) control will add gain in extremis, along with a lot of grunge.

One possible factor is that the channel input impedance is relatively low for a line mixer, at around 8kOhms, and some (particularly vintage) synths might not be too happy with that. It could potentially result in a reduced output level from some synths.... But I doubt it would be a major problem in practice.

Assuming the FB is working and set up correctly, this will probably be a patchbay and/or cable wiring issue.

[Arpangel]

As I recall, the FB is a passive line level mixer and has no gain, so if your synths have typical instrument level outputs, the main output from the FB will be around instrument level too -- and that's with all the level controls flat out. If the input channel controls and main output control are at 12-o'clock the output level will be 20dB lower still!

Again, correct me if I’m wrong, but didn’t Thermionic address this issue at a customers request to reduce overall noise? They brought out the black MK11 that had a different design.

[ef37a]

As I recall, the FB is a passive line level mixer and has no gain, so if your synths have typical instrument level outputs, the main output from the FB will be around instrument level too -- and that's with all the level controls flat out. If the input channel controls and main output control are at 12-o'clock the output level will be 20dB lower still!

Again, correct me if I’m wrong, but didn’t Thermionic address this issue at a customers request to reduce overall noise? They brought out the black MK11 that had a different design.

Would you not think Arp' that this is a prime candidate for small mixer?

Dave.

[Arpangel]

As I recall, the FB is a passive line level mixer and has no gain, so if your synths have typical instrument level outputs, the main output from the FB will be around instrument level too -- and that's with all the level controls flat out. If the input channel controls and main output control are at 12-o'clock the output level will be 20dB lower still!

Again, correct me if I’m wrong, but didn’t Thermionic address this issue at a customers request to reduce overall noise? They brought out the black MK11 that had a different design.

Would you not think Arp' that this is a prime candidate for small mixer?

Dave.

Don’t worry Dave I have thought seriously about getting one of these, but it’s too limiting, I need more I/O and other stuff. It’s a lovely thing though.
However, I have heard that it hasn’t been worth it for some, the sonic rewards just aren’t worth it, no disrespect the TC, great company, but based purely on financial considerations you’ve got to be able to buy this and not really care about value for money.

[ef37a]

As I recall, the FB is a passive line level mixer and has no gain, so if your synths have typical instrument level outputs, the main output from the FB will be around instrument level too -- and that's with all the level controls flat out. If the input channel controls and main output control are at 12-o'clock the output level will be 20dB lower still!

Again, correct me if I’m wrong, but didn’t Thermionic address this issue at a customers request to reduce overall noise? They brought out the black MK11 that had a different design.

Would you not think Arp' that this is a prime candidate for small mixer?

Dave.

Don’t worry Dave I have thought seriously about getting one of these, but it’s too limiting, I need more I/O and other stuff. It’s a lovely thing though.
However, I have heard that it hasn’t been worth it for some, the sonic rewards just aren’t worth it, no disrespect the TC, great company, but based purely on financial considerations you’ve got to be able to buy this and not really care about value for money.

No no matey, I mean forumuser should get a small mixer to gather his synths etc together and drive the Bustd harder.

[Arpangel]

As I recall, the FB is a passive line level mixer and has no gain, so if your synths have typical instrument level outputs, the main output from the FB will be around instrument level too -- and that's with all the level controls flat out. If the input channel controls and main output control are at 12-o'clock the output level will be 20dB lower still!

Again, correct me if I’m wrong, but didn’t Thermionic address this issue at a customers request to reduce overall noise? They brought out the black MK11 that had a different design.

Would you not think Arp' that this is a prime candidate for small mixer?

Dave.

Don’t worry Dave I have thought seriously about getting one of these, but it’s too limiting, I need more I/O and other stuff. It’s a lovely thing though.
However, I have heard that it hasn’t been worth it for some, the sonic rewards just aren’t worth it, no disrespect the TC, great company, but based purely on financial considerations you’ve got to be able to buy this and not really care about value for money.

No no matey, I mean forumuser should get a small mixer to gather his synths etc together and drive the Bustd harder.

Is that worth it? You’ll end up paying nearly four grand for a glorified distortion box, the FB is a beautiful unit, looks great, but I’d want it for subtle coloration, oops, is this to do with me or the OP?

[Hugh Robjohns]

...didn’t Thermionic address this issue at a customers request to reduce overall noise? They brought out the black MK11 that had a different design.

The Mk2 added a monitoring section. I don't know if they changed much else.. I didn't think so and the specs and controls all appear the same -- but I didn't review the Mk2.

At the end of the day, though, it's fundamentally a passive line mixer with an integrated make up amplifier, which is a very different way of working compared to a typical modern mixer with individual channel gains.

Regardless, if the mixer is as it should be, and the OP is aware of the lack of individual channel gain, I feel the problem is far more likely to be related to wiring problems.

[Arpangel]

...didn’t Thermionic address this issue at a customers request to reduce overall noise? They brought out the black MK11 that had a different design.

The Mk2 added a monitoring section. I don't know if they changed much else.. I didn't think so and the specs and controls all appear the same -- but I didn't review the Mk2.

At the end of the day, though, it's fundamentally a passive line mixer with an integrated make up amplifier, which is a very different way of working compared to a typical modern mixer with individual channel gains.

Regardless, if the mixer is as it should be, and the OP is aware of the lack of individual channel gain, I feel the problem is far more likely to be related to wiring problems.

Hugh, I did speak to Vic Keary at Thermionic as I got close to buying one of these, and I’m sure he told me that the noise performance was improved on the MK11owing to a customers request, which lead to the new model.
I can’t remember exactly, I may have got confused with something else.

[ef37a]

From the spec' https://www.thermionicculture.com/image ... spec51.pdf

It has no clean gain but does have +11dB in "Attitude" mode.

I have to wonder why it has an input impedance of only 10k and not even that at some settings. Have they not heard of Cathode Followers?

Dave.

[Hugh Robjohns]

Hugh, I did speak to Vic Keary at Thermionic as I got close to buying one of these, and I’m sure he told me that the noise performance was improved on the MK11 owing to a customers request, which lead to the new model.

Vic is continually tweaking his designs to 'improve' them... often without announcing the fact, often simply because the original valve types were unavailable at the time of a new batch production, and sometimes because a customer had an issue, or special requirement, or good idea...

But the biggest difference and feature introduced in the Mk2 was the added monitor controller section. If the make-up amp's noise performance got improved along the way, that's great too, of course,... but it wasn't desperately poor in the first place (although we are talking about a passive mixer with valve gain stage here...).

[Hugh Robjohns]

From the spec' It has no clean gain but does have +11dB in "Attitude" mode.

Yes, as I said earlier:

The attitude (distortion) control will add gain in extremis, along with a lot of grunge.

I have to wonder why it has an input impedance of only 10k and not even that at some settings. Have they not heard of Cathode Followers?

I suspect the concept is based on vintage consoles intended for 600 Ohm interfacing and updated slightly... Sources feed the passive mixer's pots directly. Adding active cathode followers for each of the 14 input channels would have added considerably to the cost and size of the beast! I wondered why they didn't use higher value pots, but maybe there's a noise penalty.

[ef37a]

Cost? Could always use small signal, high voltage FET followers?

I jest I JEST!

Dave.

[Arpangel]

Cost? Could always use small signal, high voltage FET followers?

I jest I JEST!

Dave.

Dave, if you can make something better I suggest you do it, I’m looking for a good idea/company to invest in. But the boutique valve mixer market somehow didn’t immediately spring to mind as a sound business proposition.

[Hugh Robjohns]

I jest I JEST!