K+H UE100 frequency response

I am working on a pair of UE100's to go in my mastering rig. They sound mighty good. I have run into a couple of things that puzzle me.

1. When in Linear(bypass) only the In/Out amplifier is in the signal path. When I feed program through the pair it sounds like there is a low end boost. When I feed tones though it it measures pretty flat. Any ideas on what might cause this? I don't think its my imagination.

2. When I switch to "In" I lose a dB across the audio band. This is with all the other amplifiers in Linea r(out). The only thing that has changed is that the signal is going through some cable.

The docs are on Jakob's site www.gyraf.dk

I dont know anything about those equalisers but I noticed a similar thing when testing my passive mastering eqs. They have a hard relay bypass that links in to out but when I put them 'in' with 0 cut/boost set there is what sounds to me like a slight HF boost and a level increase that I can hear but not measure with tones or noise. To get tones to sounded matched between bypass and 'in' I have to turn the makeup gain down about 1db. However I dont know if this is for the same reason as your low end boost.

Are you sure its not just the transformer sound? Have you recapped and replaced any other parts that may be worn out?


M@

[quote="Gold"1. When in Linear(bypass) only the In/Out amplifier is in the signal path. When I feed program through the pair it sounds like there is a low end boost. When I feed tones though it it measures pretty flat. Any ideas on what might cause this? I don't think its my imagination.

...[/quote]

maybe it´s distortion in the low frequency area wich gives the impression
of a boost?

steff

[quote author="Steffen"]

maybe it´s distortion in the low frequency area wich gives the impression
of a boost?

[/quote]

I was thinking along those lines too. I think I'll do some FFT type tests and see what happens.

These things were expensive so I doubt the transformers are as colored as what I'm hearing. The Neumann transfer console I use has at least 10 pieces of iron in the signal path and is far more neutral than this. I wasn't driving the units very hard when I was testing them.

It must be distortion - I measured mine, it's around 1,2 % distortion flat, EQ in or out... But every "vintage" is producing distortion...

Regards

It does seem like it has to be the transformers. I haven't done the fancy tests(surprise,surprise). Since all the amplifier stages have a cathode follower output I'm hoping the output impedence is low enough to skip the transformer. They will be installed in a 'closed' mastering console. So they don't have to interface with the outside world and/or be idiot proof.

On a side note I find the layout of the schematics very confusing. I'm certainly no genius but a block diagram would be very helpful. There is also no mention of the overall system layout of the induvidual amplifier sections(besides the cable labling). I assume there are some summing resistors somewhere but there isn't a drawing that shows it. I know they are not in series.

I should have the drawings for the new front panels I'm having made any day now. I'm just drooling to get these going and installed.

"On a side note I find the layout of the schematics very confusing. I'm certainly no genius but a block diagram would be very helpful. There is also no mention of the overall system layout of the induvidual amplifier sections(besides the cable labling). I assume there are some summing resistors somewhere but there isn't a drawing that shows it. I know they are not in series"

How do you think they are not in serie? Everything shows me a serial connection of all modules. Just follow the wires on the last page and you will see that the signal passes all modules (this is the block diagram).

Also, avoid to remove the transformers.... They have a turn ratio that is necessary to the gain structure. Without them the unit will be very noisy...

Regards

On one of the units I have, one of the mid bandpass amplifier sections is not working. When trying to figure out what was wrong I made cables to swap the attenuators between the two sections to isolate the problem. It passes signal with no cabling to one amplifier section and one attenuator. If the sections were in series I don't understand how it could pass signal.

The block diagram only shows where the cables plug into. It doesn't show what happens behind the female panel connectors. There is no way to determine the signal flow from this diagram.

Does anyone know what a "Stutenschatter" is? The symbol they use is a circle within a circle. It is not a symbol I've run across before.

Stutenschatter is stufenschalter and means "selector"...

I'm analysing the diagrams and I come back...

following the schematics, the scheme is an F - E - D - C- B- A path.

IE (in my very pooor english) : the signal goes first to the Hi Cut Filter, then Lo Cut, then Hi Mid section, Lo Mid section, Hi boost section and finally Lo Boost section.

Many wires are linking the modules, just because some of them are splitted in two blocks. All the audio links are via RCA connectors, both the signal chains and the links between parts of the blocks. But it appears to be a totally serial path.

There are probably some mistakes on the diagram (some inputs appear to be output and vice-versa). It happens sometimes, and even in very serious companies.


regards

Daniel

On one of the units I have, one of the mid bandpass amplifier sections is not working. When trying to figure out what was wrong I made cables to swap the attenuators between the two sections to isolate the problem. It passes signal with no cabling to one amplifier section and one attenuator. If the sections were in series I don't understand how it could pass signal.

Also, many of the cables are linking the electronic parts of some blocks to frequency selectors, as you can see it on "Baustein C or D". So, some removals have no effect on the signal path, just on the EQ effect.

"2. When I switch to "In" I lose a dB across the audio band. This is with all the other amplifiers in Linea r(out). The only thing that has changed is that the signal is going through some cable. "

Not true...

One of the sections has a different bypass system (all the others have really -indeed- a hardwire bypass), it is section B - the HI boost section. In this section, the signal goes first into the first stage.. So, there is -at least- one tube in the "linear" path.

Watch it and you will certainly notice....

I hope this gives you the last explanations.

Best regards

Daniel

Hi guys:

I'd really appreciate it if someone could tell me (measure) the values of the HV and bias voltages in the UE100's power supply (after the LC filters).
Thanks in advance.

(Sorry for being slightly off topic.)

Regards,
Milan

Sorry for today, but that can take a long time...

Next week maybe....

[quote author="igloo701"]following the schematics, the scheme is an F - E - D - C- B- A path.

IE (in my very pooor english) : the signal goes first to the Hi Cut Filter, then Lo Cut, then Hi Mid section, Lo Mid section, Hi boost section and finally Lo Boost section.

Many wires are linking the modules, just because some of them are splitted in two blocks. All the audio links are via RCA connectors, both the signal chains and the links between parts of the blocks. But it appears to be a totally serial path.

l[/quote]

I took another look and you are correct. It does look serial. I'm still not sure why it passed signal when half of two sections were physically disconnected. I'll try again to figure it out.

When I originally said a block diagram would be useful I was reffering to the amplifier sections. I don't understand how it works. Where the RC network is in the signal path. I know its all there but there are an awful lot of lines and switches. A block diagram would make it easier for an idiot like me to understand the circuit.

Do you think it would be possible to avoid using the input/output section or avoiding the transformers? I fear that if I can't get it to sound more transparent when set 'flat' I won't be able to use it. If I want to use the high shelf but when I switch it in it sounds like there is more low end then I can't use them in my mastering console.

[quote author="igloo701"]"2. When I switch to "In" I lose a dB across the audio band. This is with all the other amplifiers in Linea r(out). The only thing that has changed is that the signal is going through some cable. "

Not true...

[/quote]

I know it doesn't make any sense but I have four of them here and they all do it. Do you have one that doesn't lose a dB when all amplifier sections are bypassed (lin)? That was one of the reasons I thought there might be summing resistors. The loss is not frequency dependent.

You have a trimmer for 0dB in bypass - the P01 at "Baustein O+S"..

Jakob E.

Paul,

when I say "not true", I mean that it's not a hardwire bypass. It is thus possible that you have a loss in a full "linear" mode. Most of the sections blocks (Baustein) put a load on the input, and some pass the signal through a first amplification stage before going to the "Linear" switch. This can also explain why you have distortion in any case (on mine, the THD+N remains constant with or without "Linear" switches engaged). The gain structure is thus variable and you have, as Jakob says P01 on Baustein O, and also a "O, +5 dB" switch on the same block, to adapt this structure.

We all know that this diagram is not that easy to read, but it corresponds well to the building structure; which helps when troubleshooting.

Moamps - it really needs time to measure, cause I need a tuchel - tuchel cable to make the unit work when it's open...

Regards

Daniel

[quote author="igloo701"]Stutenschatter is stufenschalter and means "selector"...

I'm analysing the diagrams and I come back...[/quote]


Actually it literally means a "stepped switch".

T