stay at home type 69 project

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Whoops

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Rocinante said:
Whoops to the rescue. PM me your address Whoops, so when I get PCB's done I can send you one

Thank you so much for the offer, I would love to try one of your boards out.
Thank you so much

pm sent
 

Whoops

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Raindirk (Cyril Jones) has the Lutraphone Clones in their website, you can order directly from them,
here are the details:

http://www.raindirk.com/lustraphoneTransformersRaindirkAudio.php
 

Rocinante

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Okay guys, so how are you doing the vtb9043 and other inductors in Eagle?  Are you building them as a part?  I also suck at relays in schematics. On a pcb i am fine but via schematic i get turned around.  I like to use the Omron g5v's. A little help?
 

dogears

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I have a layout with just the first gain stage (preamp) using a pot for testing. It's a brand new CP pot, but it's got some scratchiness when adjusting. Is that just a consequence of the way the NFB is applied with this design? Any tricks to address that?
 

ruffrecords

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dogears said:
I have a layout with just the first gain stage (preamp) using a pot for testing. It's a brand new CP pot, but it's got some scratchiness when adjusting. Is that just a consequence of the way the NFB is applied with this design? Any tricks to address that?
Possibly place a large value resistor (1 Meg) across the pot to ensure the electrolytic always has a dc path to 0V even if the wiper lifts a little. And/Or make sure you select a very low leakage electrolytic.

Cheers

Ian
 

letterbeacon

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Thanks for this project - it looks great!

I don't really need another pre-amp, but I would love the EQ! Seeing as I have some old BBC 600:600 transformers, I was thinking of using one of those as an input TX and then feed that straight into the EQ part of the circuit and the line amp. I might use another 600:600 as the output TX or maybe just leave it unbalanced.

Where would be a good place to 'inject' the output of the input TX? At the junction of Q4 pin3 and C10?
 

dogears

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Couple of options. You could pad the input, or you could use a very large resistor for the first stage gain (~220k gives you only 1.6 dB gain) and increase the gain resistor in the second stage slightly, to around 10k.  This would bring it back to unity gain through, with a minimal loss of headroom.

Actually you could also try it without a gain resistor at all, which should turn the preamp stage into basically a unity gain buffer.
 

letterbeacon

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dogears said:
Couple of options. You could pad the input, or you could use a very large resistor for the first stage gain (~220k gives you only 1.6 dB gain) and increase the gain resistor in the second stage slightly, to around 10k.  This would bring it back to unity gain through, with a minimal loss of headroom.

Actually you could also try it without a gain resistor at all, which should turn the preamp stage into basically a unity gain buffer.

Thanks for the suggestions. Do you think I even need the pre amp section? Could I not go from the input TX straight into the EQ circuit?

EDIT - what I say input TX, I mean the 600:600 one that I'll be using for a line level source rather than the TX specified in your schematic.
 

Whoops

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letterbeacon said:
Thanks for the suggestions. Do you think I even need the pre amp section? Could I not go from the input TX straight into the EQ circuit?

Ian  (ruffrecords) has a project that is a 3 band Helios EQ, just the EQ section, it seems that project suits you better. Ian made that project open source.

http://www.customtubeconsoles.com/ruff-records-pcb-empporium

http://www.customtubeconsoles.com/diy
 

letterbeacon

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Whoops said:
Ian  (ruffrecords) has a project that is a 3 band Helios EQ, just the EQ section, it seems that project suits you better. Ian made that project open source.

http://www.customtubeconsoles.com/ruff-records-pcb-empporium

http://www.customtubeconsoles.com/diy

I've had a closer look at Ian's circuit and compared it to the one that dogears has made and the EQ sections seem identical after the 240r resistor between the preamp and EQ section (apart from a 100k to ground on Ian's input), so I might go with this PCB and inject the signal in there and not populate the preamp circuit. I can't see a reason why that wouldn't work if that's how Ian's is, but then I'm no expert!

The reason I'm persisting with this PCB, after nearly going with Ian's, is because dogears' PCB has the 2128 card on the PCB. If I went with Ian's I'd have to design my own one.
 

Squeaky

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Rocinante said:
Whoops to the rescue. PM me your address Whoops, so when I get PCB's done I can send you one, albeit it'll be awhile. Slightly off topic but what do we know about the 22117? I saw a dual 22113 card on one of the helios sites and I'm also trying to figure out where that went.

Hi Rocinante. I couldn't see if your question about the 22117 was answered anywhere. One of the schematics that Whoops recently, and so kindly, posted, refers to the 22117/22118. It is the control room monitor schematic.
 

Whoops

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Yes the 22117  it's the control room monitor amp circuit for the Musicland console

index.php


 

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