The original Dynaco ST35 reuires a matched quad of EL84 tubes.
One NOS vendor has a set 1600, 1650, 1650, & 1700. Is this matched close enough? What does that mean?
Another NOS tube vendor is matching a similar tube set with different gear, his at 48mAdc, individual ratings are:
7.0 VDC 11400 uMohs rX3
7.3 VDC 11200 uMohs rX3
6.4 VDC 11200 uMohs rX3
6.7 VDC. 11200 uMohs. rX1
Are those .matched, what do those numbers mean?
One NOS vendor has a set 1600, 1650, 1650, & 1700. Is this matched close enough? What does that mean?
Another NOS tube vendor is matching a similar tube set with different gear, his at 48mAdc, individual ratings are:
7.0 VDC 11400 uMohs rX3
7.3 VDC 11200 uMohs rX3
6.4 VDC 11200 uMohs rX3
6.7 VDC. 11200 uMohs. rX1
Are those .matched, what do those numbers mean?
Talk to Jim McShane and get a set of tubes that are closely matched, under the conditions found in the amp, at a fair price. 😉
11200, etc., are transconductance (gm) measurements. The "modern" ways of stating gm are mA./V and mS. (milli-siemens). 1 siemens = 1 A./V.
rX3 and rX1 are version numbers. In short, that is NOT a matched quad. Not only should all 4 tubes be the same version, but they should come from the same production run. With all 4 EL84s sharing a single bias network, both gm and cathode current should be tightly matched. Contact Jim McShane!
11200, etc., are transconductance (gm) measurements. The "modern" ways of stating gm are mA./V and mS. (milli-siemens). 1 siemens = 1 A./V.
rX3 and rX1 are version numbers. In short, that is NOT a matched quad. Not only should all 4 tubes be the same version, but they should come from the same production run. With all 4 EL84s sharing a single bias network, both gm and cathode current should be tightly matched. Contact Jim McShane!
Well worth adding is Dave Gillespie's EFB mod. You can add individual bias pots for each tube also. Anyway you get longer tube life and the ability to run all new production tubes which normally would get eaten up by an ST/SCA-35. Also noticeably helps the sonics and gives an extra 2-3W/CH.
Dave's Lab
Also read up more on the diytube site under the ST-35.
Dave's Lab
Also read up more on the diytube site under the ST-35.
The one I bought has Dave's new EFB board mounted on top. This has one pot, didn't know that I could fit it for a pot for each tube.
I contacted Jim McShane today. He has some good suggestions. I'll go with him intead of ebay. Thanks for the guidance everybody!
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