Dynaco St-150 (35kOHM input impedance) ok match for PAS 3Z?

I'll be building the Z-mod with regulated PS this week and wonder if I can use the ST-150 with its 35k input impedance. I know it was not a good match with the stock PAS 3, even with the 62k and 510k resistors removed.

In general, is there a guideline (50k, 100k) for what might be a good match for the 3Z loading/capacitance wise? Also, I know the Z is based on the SP6 VTA unit, are the specs for the SP6 still available and will they be the same with the Z-mod?

No.
You need a buffer between them for high-quality sound.

Thanks, is there a documented modification to raise the 35k up to something more universally friendly? I like the amp and would be up for tinkering if it meant I could use it natively with the 3Z.

oldsmobuick wrote:Thanks, is there a documented modification to raise the 35k up to something more universally friendly? I like the amp and would be up for tinkering if it meant I could use it natively with the 3Z.

One example is this :
http://www.ebay.com/itm/NEW-MK4-Indeed-Class-A-Valve-Buffer-Amp-Amplifier-electro-harmonix-6922EH-tube-/290827123772?pt=LH_DefaultDomain_0&hash=item43b6a5bc3c


This will make your PAS3 able to drive any amp without loss of fidelity

Interesting, thanks for that link! Specifically, I'm wondering if the Z-Modded PAS will also need such buffering?

oldsmobuick wrote:Interesting, thanks for that link! Specifically, I'm wondering if the Z-Modded PAS will also need such buffering?

That you will have to ask your vendor ( or examine the schematics which i do not have)

Myself found no suitable buffer, instead i built one : http://n.manet.nu/fm1/fm1.html

.

I have a PAS3. I connect it to a Bozak N-106 electronic crossover between the PAS & ST-70. As I live in the bay area, I asked Joe Curcio his thoughts on a CF. He had built a few and had great success with them. His CF board adds a 2nd transformer for an all new beefier power supply. The tube is a 12AT7 (6201). Since then I've added VTA boards (with a bit of Roy's expert help). I have pretty good pictures if you would be interested in looking at them.

if you have or obtain a Zmod line stage for your PAS preamp you can easily drive the Dynaco ST150 amp.
The Zmod has an output impedance of around 1K and can drive any amp with an input impedance above 10K.
www.tubes4hifi.com/PAS3-CAT.htm

Thanks Roy! Good news! And thanks for the other replies also, this is the info I need as I'm builing the Z-mod.