VelvetGeorge wrote:
Lets gather info in this thread and see if we can nail this down. On my stock kit I have Mallory 150 signal caps. Anyone using these and experiencing the squeal? Or might they be unique to Sozo?
Anyone having this issue with VA KT66's from 6 months ago or longer? Maybe a new run of these tubes is less stable.
Is your bias grounded on the pot buss?
Are your dual 32 and dual 16uf can grounded on the same lug, near the PT?
Anyone have this issue with the F&T 16uf cap on the board? The Sprague Atom 16uf?
Do your OT primary wires run parallel to the orange and green grid wires?
Thanks,
george
I just finished a "customer" Metro 45 and encountered the squeal. Only happens with the new VA '66's supplied with the amp. I tried some 5 and 6 year old VA '66's and some NOS GEC's... no squeal. The grid wires go directly to pin 5 on each output socket, no resistors.
To answer your "data gathering questions" George:
1. The bias IS grounded on the pot buss, the buss is soldered to the backs of the supplied Alpha pots, the pots were well sanded by me on the backs before soldering.
2. The dual 32 and 16uf F&T's are grounded to the same lug near the PT.
3. The 16uf preamp cap on the board is a TAD, as supplied with the kit and it's fine.
4. The OT primaries run at a bit of an angle to the grid wires under the board... both are twisted well but not bound to each other.
I'm going to put a couple of 5.6k's on pin 5 of each output tube and see if that's the fix. I think my wiring/grounding's good, I think the tubes are a bit suspect as the older VA's and the Genelex's don't squeal.
The amp, by the way, sounds like records... amazing tone!