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Review & Measurements of Talema Relay Pre-amp

amirm

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This is a review and detailed measurements of the Talema power Volume Remote Control Relay 128 Steps Constant input impedance 4 CH passive pre-amplifier. It is on kind loan from a member. You can find it on various online sites. An ebay listing shows it costing US $130. Given the four channel input and remote control, it seems like very good value.

The box won't win any design awards but is solid metal as is the remote:

Talema power Volume Remote Control Audio review.jpg

The knob on the left selects input and the one on the right changes volume. Max volume level is 128 by the way, not 100.

The remote is ugly but is made out of heavy metal. It has nice little green LED that comes on when you press any buttons.

The back panel is as you would expect:

Talema power Volume Remote Control Back Panel Audio review.jpg


The inclusion of power supply inside the box makes things tidy but of course, there is NO regulatory certification. The picture on ebay listing does NOT show proper grounding of the safety terminal:

s-l1600.jpg


Audio Measurements
Let's start with our dashboard with 2 volt input and volume set to max (128):

Talema power Volume Remote Control Full Volume Audio Measurements.png


Channel matching is excellent. THD+N and hence SINAD is dominated by the mains noise and harmonics created by the power supply. As it is, it would degrade the performance of any audio device with SINAD better than 97 dB or so. Then again those low frequency spikes are likely not audible due to high threshold of hearing in that region.

You won't be using this device at full volume often so I reduced the volume until the display showed 100:

Talema power Volume Remote Control Full Volume 100 Audio Measurements.png


Relative amplitude of mains noise increases of course and once again sets the limit for SINAD. There is also a bunch of extra junk to the right, some of which are mains harmonics but others are likely noise from the display, microprocessor and such.

Frequency response shows ruler flat so no issues there:
Talema power Volume Remote Control Full Volume Frequence Response Audio Measurements.png


Crosstalk is also quite nice:

Talema power Volume Remote Control Full Volume Crosstalk Audio Measurements.png


Intermodulation distortion at maximum volume is almost the same as what the analyzer produces plus some noise:
Talema power Volume Remote Control Full Volume IMD Audio Measurements.png


Let's reduce the volume to "100" again and see what happens:
Talema power Volume Remote Control 100 Volume IMD Audio Measurements.png


Ouch. The baseline noise is really hurting its performance. Digging deeper, here is the spectrum with 20 millivolt input:

Talema power Volume Remote Control 100 Volume IMD Spectrum Audio Measurements.png


The spurious tones are taking over relative to our main tones resulting in poor IMD. Looking at the scope display, a sequence of dancing spikes show up:

Talema power Volume Remote Control 100 Volume IMD Scope Audio Measurements.png


Conclusions
I must say, I went into this review expecting a very broken device but did not find such. There is a ton of functionality here for just $130 and performance is really good. Yes, more attention needed to be there to guard against unexpected noise from the rest of the unit bleeding into audio path. But that is to be expected at this price range.

I can't recommend the unit based on measured performance. But with respect to functionality and value, it is a worthwhile option.

FYI, I am boxing the unit right away to ship to the owner who sent me the Schiit headphone amps. All have been here for 3 months and I need to get them back to him. So no more measurement requests please. :)

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As always, questions, comments, recommendations, etc. are welcome.

Came back from our nice road trip to western Canada. Expectly, I depleted some of my pocket money so appreciate you all help replenish the bank account by donating using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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amirm

amirm

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It was worth it though, I bet you look fabulous in this..,
You should have seen the horse I bought to go with that to blend into the mounted police!
 

restorer-john

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Consider there are tens of millions of high performance vintage amplifiers and receivers in the world that are not remote controlled. This device (and others like it) give remote volume functionality and four source selection to that gear, all with easy integration into the tape loop.

It is an excellent device for that purpose.
 

AndrewDavis

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FYI, I am boxing the unit right away to ship to the owner who sent me the Schiit headphone amps. All have been here for 3 months and I need to get them back to him. So no more measurement requests please. :)

Special thanks to the lender!!
 

Matias

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@amirm typo on the title: measurements.
 

Tatteredmidnight

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It's surprisingly difficult to find a device with this functionality for a reasonable price. It's even more difficult to know what you're getting. Sometimes this site really delivers exactly what you need.
 

direstraitsfan98

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I'm using the Akitika PR-101 preamp. It's got a ton of features.
 

cjfrbw

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On the DIY audio site, some people are attempting to put a Pass B1 Korg NuTube card directly into the chassis of these things to have a remote controlled B1 Korg NuTube preamp. I haven't heard yet if they have been successful. They would use a wall wart power supply to the Korg board, which is pretty small and needs 24V DC. Probably requires punching a few holes in the chassis.
 

Bamboszek

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It makes my wonder why ebay sellers decided to name it Talema Pre-amp. Talema is just manufacturer of toroidal transformers. Even naming it NEC makes more sense as relays are more important that power transformer in that type of product :rolleyes:
Mains harmonics issue could be probably resloved with better wiring and maybe some shielding.
 

sychan

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Mains harmonics issue could be probably resloved with better wiring and maybe some shielding.

I'm sorry if this is an obvious question, but I know little to nothing about EE stuff. Would properly grounding the entire enclosure to the safety terminal on the power input (similar to the article on reducing hum/buzz on the Jotenheim headphone amp) take care of most of the mains harmonics? Does that big flappy ribbon cable next to the transformer pick up a lot of mains noise as well? Is there an easy way to shield it, or can a shielded cable be used instead?

Thanks!
Steve
 

wynpalmer

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I'm sorry if this is an obvious question, but I know little to nothing about EE stuff. Would properly grounding the entire enclosure to the safety terminal on the power input (similar to the article on reducing hum/buzz on the Jotenheim headphone amp) take care of most of the mains harmonics? Does that big flappy ribbon cable next to the transformer pick up a lot of mains noise as well? Is there an easy way to shield it, or can a shielded cable be used instead?

Thanks!
Steve
passive.jpg


Just some grounded copper adhesive backed foil plus a wire connecting the case/gnd connection on the supply/display board to the case/gnd connection on the relay boards.
The measurements below were made using an RME ADI-2 PRO FS and REW. The source is the RME DAC, the measurement is using the RME ADC and the signal path includes the passive preamp and a unity gain buffer consisting of an OPA1641 which drives the RME ADC input.
The first is at 2v RMS output, the second at c.16dB of attenuation- more or less equivalent to the 100 setting in the review.
The ADC FS was set at +13dBu (+10.8dBv) so -4.8dBFS =+6dBv or 2vRMS. The second plot was at -10dBv.

passivepreampRMEADC2vRMS outzero attenuation.JPG


passive pre rmeadc 16dB of attenuation.JPG

As you can see just these simple changes make a tremendous difference.
Without these changes the results were essentially identical to the review measurements.
 
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Neddy

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Interesting device - missed this earlier...but, can't resist:
a)Indoor finfoil hats?
b) or, (keeping it musical) instead of Mountie; RCAF, like Col. Loreena McKennitt?
loreena-mckennitt-new - Copy.jpg

;)
 

sychan

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@wynpalmer Thanks for the followup!

Interesting device - missed this earlier...but, can't resist:
a)Indoor finfoil hats?

Semi-seriously: that copper foil shield around the board - would a copper "foil hat" on the transformer have achieved the same effect? Basically just wrap the transformer in copper foil. Or is that a bad idea?
 

wynpalmer

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@wynpalmer Thanks for the followup!



Semi-seriously: that copper foil shield around the board - would a copper "foil hat" on the transformer have achieved the same effect? Basically just wrap the transformer in copper foil. Or is that a bad idea?
Alas, the transformer is but a part of the problem. I don't want to go into too much detail but all flow of current in conductors creates electromagnetic fields that radiate out from those conductors and those fields can cause current flow in other conductors that they reach. It's not just the harmonics of the mains frequency (mostly odd) but all of the digital signals that need to be attenuated, and there are several best practices involved here all of which are violated by the wiring in this box.
The copper shield reduces the fields reaching the sensitive circuitry enough to make it part of a viable solution without ripping the whole thing apart and implementing those best practices.
 

Lerrev

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Hi! I long read this forum, but only now decided to write. Sorry my English is not native. I own it, too. Very high level of interference. Look at the pictures of the Board. You too?
 

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