a soBer Newt
Well-known member
A hopefully quick hijacking, I have been curious as to the cap (C10) in-between the two 16K in the feed back path and what its trying compensate.
I have even found another 1539 in my stash haha, maybe they made a baby when I played that Marvin Gaye record the other night ...I think it need more than just passing a signal.
I am inclined to believe what Lundahl says but since you have the 1539 already there is no harm trying out.
The original transformer is not that expensive, I am wondering if Carnhill would sell directly or it's a proprietary design.
If they don't you should just buy a spare one from the link above and reverse engineer it, I know several toroidal transformer makers that could make a small batch if we can organise a group buy.
I've got the complete, giant arse freaking binder of em! Quick pics below of the input stage of the preamp modules and output stage of the group/master outs. You can see in both cases, it's just strapped as if it were a single winding per side, with the two windings in series. I would imagine that given Lundahl's hype around how low distortion their datasheet circuit is, that the result of using it as it is here would be slightly higher distortion levels.Now you make me want to have a look at the BC3 output schematics haha ! Thanks for sharing the info !
I totally respect Lundahl's high standards, and never meant to discuss their posture or even say they are wrong, by the way.
But I happen to have three LL1539 on my hands and I'd like to put them to use
I'll see if there's interested for a 1:1 circuit and a Carnhill Pumpkin repro, or if I readjust my idea and try to get inspiration from the BC3's use of the 1539.
Edit : I found 22 pages of schematics but it is missing the output stage, so if you have that document somewhere @amplexus I am interested. Apparently the same british console genius designed the circuit discussed here, and the Amek BC3 ? I see 5534 are on the signal path ... It seems the designs are somewhat related / in a similar spirit![]()
2503 has 4 identical windings that are flat out to Mhz range, wire it up as 1:2:1 (with two windings in series for output) as per the original pumpkin and it should work very similarly. As I said before 1539 (which has four 1:1 windings) may also work well, Lundahl won’t sanction it because they probably haven’t tested it in this configuration and they have high quality standards, but it may well work great. You’d just have to try and see.Well, the pumpkin is intersting for sure, but it is hard to find ... the website on the previous page does not have them in stock.
2503 does not seem to be a direct drop in replacement ? It is missing a tap on the output ?
@krabbencutter is having trouble with his AT8 rendition so maybe it's a safer bet to stick to the OG design topology.
I guess I'll have unused LL1539 maybe I can sell them to buy something elese
I hate having different options haha
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