175b i/o transformer help
« on: December 24, 2018, 10:55:17 AM »
re: 175b vari-mu compressor builds...

Hey all, been a long time since I've had time to DIY and I'm just now getting to some projects that I started many years ago. One of them is the Drip 175b version 1 pcb's. I'm nearing the finish line but when I look at the transformers I bought for this they don't match the build docs. Since the drip forum has been closed for years I'm trying to figure out if I bought the wrong stuff or I bought a set that is supposed to "work better" or something like that. I vaguely remember there being a few builds that changed things up for better performance and I suspect I was going to do those but I really can't remember for sure. I'm hoping some of you more experienced folks have better memories or can point me in the right direction...

What I've got:
input: Cinemag CMLI 15/15b
output: Sowter 9185s (these are actually what Sowter says to use for the Gates Sta Level)
interstage: Sowter 1133e

What the build docs say:
input: Sowter 1009e, or UTC ha-100x
output: Sowter 8650 or 9900
interstage: Sowter 1133e

Thanks in advance for any help!


Re: 175b i/o transformer help
« Reply #1 on: January 08, 2019, 01:35:35 AM »
Should be fine  ....  it's not all that particular, generally speaking. Some of the recommendations for the v1 of drip 175 can be a little daft. Like the psu traffo specified back then  ...  big enough to power a battle ship, not a little 100mA limiter.  Also good for welding.

Using something 'scaled' a little more appropriately, can have good results in terms of 'radiated noise' into signal traffos - the main bugbear imho of all these 'amp head' type builds.

I ended up using my Hammond 373 (from memory) to instead power a parallel 6550 SE amp head. And I still don't use anywhere near it's capacity. It's a monster.

I bought a smaller (though still impressively sized) Edcor for the psu traffo.

Those signal traffos you mention are top shelf. I used the same interstage traffo from Sowter .. very good performance  (but do check the orientation and wire code ....  as I recall there was a 'reverse' in the drip build guide.

The other thing is to try a few of the gain reduction cell tube  ....  it's quite important to get a decent match from the two triode stages in the envelope. 

If I was to do mine again, I'd 'adjust' it for some proper 6386 remote cutoff dual-triode tubes - I used the 6bc8, and I think they can be a little 'light-weight'  ...  and they can vary about the place quite a bit.  It remains my only '6BC8' limiter of this type.

If I had access to a 'conversion pcb' for the gain reduction tube, I'd use something good yet inexpensive  ..  like a pair of properly selected remote  cutoff 'frame grid' pentode-in-triode-mode tubes. But that requires the 'duo 9 pin pentode to 6BC8' pcb  :)

Good luck with it - it's hard to get sounding bad the drip v1 175b  limiter  ..  generally speaking.

« Last Edit: January 08, 2019, 01:49:30 AM by alexc »
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