Search found 7 matches

by Barbouze
28 May 2018, 22:24
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Roland RE-201 Space Echo - analysis
Replies: 15
Views: 4745

Re: Roland RE-201 Space Echo - analysis

Back at it, I managed to get a better grasp of what is going on and broken down the power supply for each key component/bloc. I also found out that BC550C and BC560C are the recommended replacement transistors for the original 2SC-1000 GR and 2SA493 GR. I needed only minor tweaking in the test signa...
by Barbouze
22 May 2018, 12:17
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Roland RE-201 Space Echo - analysis
Replies: 15
Views: 4745

Re: Roland RE-201 Space Echo - analysis

The NFB was frequency-independent using R33, after having replaced by C59 it is frequency-independent now. The total gain must be high now for the audio frequency range, the NFB attenuate higher frequencies above, thus C28 can omitted. Probably a typo but I suppose you mean that C59 makes the circu...
by Barbouze
22 May 2018, 01:32
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Roland RE-201 Space Echo - analysis
Replies: 15
Views: 4745

Re: Roland RE-201 Space Echo - analysis

I spent some more time figuring how each part is doing its job and understood in the process that the numbers in dashed boxes were RMS values of the 1kHz -50dBm test signal. This also confirms your statement: A rough calculation gives a gain of about 50 for the stages with Q1 and Q2. Correct! from t...
by Barbouze
18 May 2018, 15:43
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Roland RE-201 Space Echo - analysis
Replies: 15
Views: 4745

Re: Please help me decipher/analyse this schematic

There are a lot of informations in your two posts that I'll have to perfectly understand but this has helped me a lot! :thumbsup
Manfred wrote:The capacitors C24 and C26 avoid oscillations.
Are these oscillations related to the Miller effect?
by Barbouze
11 May 2018, 23:39
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Roland RE-201 Space Echo - analysis
Replies: 15
Views: 4745

Re: Please help me decipher/analyse this schematic

C29, and C23, are power supply decoupling capacitors. They filter out power supply noise. So in a simulation they are not needed :D C27 bypasses R29 (effectively shorts it out to AC) so the preamp will behave differently to AC than it does to DC. I suppose this means that basses are treated differe...
by Barbouze
10 May 2018, 23:16
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Roland RE-201 Space Echo - analysis
Replies: 15
Views: 4745

Re: Please help me decipher/analyse this schematic

Thanks! For the now I've been simulating the circuit attached in this post, replacing the transistors with two 2N5089 and one 2N5087 instead of the original ones. You're right about tolerances, this can lead to dramatical changes and given that this is an official manual, I'll stick to the given vol...
by Barbouze
10 May 2018, 11:52
Forum: Vintage Stompbox Corner ( ... - 1975)
Topic: Roland RE-201 Space Echo - analysis
Replies: 15
Views: 4745

Roland RE-201 Space Echo - analysis

Hi! First post here so I'm introducing myself :D . I'm not a guitarist (booo!) but I'm interested in guitar FXs, sound design and audio DSP. Lately I've been using a modeling tool to generate audio plugins from schematics (like a simplified spice simulation in real time) and after successfully creat...