1

TS500 Tape Simulator / Re: Heavy Overtones/Intermodulation

« on: April 17, 2021, 06:13:05 PM »

Hm, dropping images here doesn't work today :-/

To describe what happens: On TP3, the level of overtones jump up, especially the uneven ones (3kHz, 5kHz, 7...).

2

TS500 Tape Simulator / Re: Heavy Overtones/Intermodulation

« on: April 17, 2021, 05:57:10 PM »

Hi,
thanks for the advide! I measured the spectrum on all testpoints, and there seem to happen something bad between TP2 and TP3. I'll attach some screenshots.
Could you tell me what components I should have a closer look at?
Thanks
J.

3

TS500 Tape Simulator / Re: Heavy Overtones/Intermodulation

« on: April 13, 2021, 09:10:05 PM »

Hello,
I still don‘t have a clou, how to get my problem solved. Could you help me? As I told, the problem comes up with the unit switched on.
Thanks and greetings
J.

4

TS500 Tape Simulator / Re: Heavy Overtones/Intermodulation

« on: April 07, 2021, 07:29:20 PM »

Ok, that looks quite similar to my device in bypass, about 60dB difference between 1st and 3rd harmonic. But what happens when switched on? Could you tell me some hints/testpoints to measure the signal path, so that I can find the issue here? 

5

TS500 Tape Simulator / Re: Heavy Overtones/Intermodulation

« on: April 05, 2021, 07:09:22 PM »

Any idea, how to go on here?
Thanks ;-)

6

TS500 Tape Simulator / Re: Heavy Overtones/Intermodulation

« on: March 30, 2021, 09:58:18 PM »

7

TS500 Tape Simulator / Re: Heavy Overtones/Intermodulation

« on: March 30, 2021, 09:57:20 PM »

I probed TP7 with a scope, there was no DC.

I checked my audio interface (RME FF400) again, +4dBu output, pad on line in, to make sure that there is no distortion caused by the interface (maybe that was the case last time). Then, I levelled a 1kHz signal to 1Vrms (about -1,5V...1,5V) at TP7 in "Off" mode. Finally, with TS500's output to max, I set the "drive" to get the same level at TP7 in "On" mode (1Vrms). Tape speed: 15, saturation: middle pos, bias: right pos (flat).

I'll attach some spectrum screenshots: 1= 1kHz, TS500 off; 2= 1kHz, TS500 on; 3= 1kHz+1.5kHz, TS500 off; 4= 1kHz+1.5kHz, TS500 on. The distortion seems to be low or moderate when switched off, but is very present when on, even with low input signals.

I also measured U12a: (2), (3) are around 0,5Vrms input with no DC offset, but (1) is 2Vrms with DC offset of 1V. U12b seems to be unused (?), there are no signals at all.

Finally, I measured U13 (below the output trafo). I don't understand it's purpose, but was wondering if it's ok: (1): -15.5V, (2): -14V, (3): 1kHz, 1Vrms

I hope that this info helps somehow :-)

8

TS500 Tape Simulator / Heavy Overtones/Intermodulation

« on: March 28, 2021, 06:38:49 PM »

Hi there,
first of all: Thanks to JPK and the team for the great quality of your modules and the build guides! Unfortunately, some problems came up while building the TS500, and I don‘t know how to solve it. I measured high distortion in the output signal, even with unit switched off! Input signal was sine, 1kHz, 1Vrms. I checked the audio interface and the cables, there was no problem. Sending in a mixed signal (2 sines or more complex material like e.g. an 808 drumloop) causes a lot of sidebands and interference.
I already did all the basic checks (proper components and polarization), resoldered everything, even tested all opamps (one was faulty, I‘m afraid I killed it while testing, but temporarily replaced it by a 072), but the problem persists.
Any hints?
Thanks J.