Newbie SE and preamp question.

[markedwardsims]

Hello all, and thank you in advance for your guidance. I am finishing up my first build, a TW Express clone, and I'm hooked. Rather than another scratch build and the associated costs, I'm interested in using my PicoValve as a donor. I did some small mods to it a while back, but am ready to reimagine it if you will. I'm going to catalog what all it has, but at a glance, the transformers and choke seem legit to do something interesting. Here's my question:

Can I "mix and match" preamp and power amps? For example, could I take the SLO Nakid schematic and layout that Rob Robinette published (https://robrobinette.com/How_the_Saldan ... #SLO-Nakid) which is push pull, use the preamp and then pass the output through a coupling cap to a simple 6V6 power section like you see in a 5F1? I'm trying to stay in bounds with the transformers I have in the PicoValve which limits me to SE. I know there are many things to consider, but is it too simplistic to think that as long as the voltages match what the components want, this could work?

As an alternative, I can explore some of the SE projects, but I would love to bring some of that SLO tone home since my SLO100 is not neighborhood friendly.

School me, friends.

[bal704]

The simple answer is 'yes', you can mix preamps and power sections. There is always the caveat that you may have to tweak either a bit for the best sound, but I do that very thing all the time.

[xtian]

With SE amps, especially high-gain ones, be sure to use an extra first filter stage, called Pi or CLC/CRC filter. This will cut the hum common to SE builds.

[markedwardsims]

With SE amps, especially high-gain ones, be sure to use an extra first filter stage, called Pi or CLC/CRC filter. This will cut the hum common to SE builds.

The Pico has a 10H choke, so I planned on using that. I'll take a look at the caps it is using. I'm hoping to reuse the entire power section with some resistor modifications, but we'll see.

[LOUDthud]

Check that you have an extra couple of Amps of heater current available from the PT.

[markedwardsims]

Sounds good, thank you! I'll take a pass at a proposed schematic, including the transformer and choke specs, and post back.

[markedwardsims]

Ok all, here's the schematic that I cobbled together. I used a combination of the PicoValve schematic for the power section, a VHT Special 6 power amp, and Rob's SLO Nakid preamp. I measured the B+ voltage on the amp, and I'm getting 320v off the single B+ the PicoValve has. That seems low compared to the voltage specs in the SLO preamp schematic. Maybe an adjustment of the dropping resistors could help here? Any advice on this design is really appreciated.

SlimLO Schematic V1.png

[bepone]

there is no feedback, due to the nature of the beast, and SE, sound will be too harsh and in triode mode maybe too dull

[bepone]

here will be perfect to deploy output transformer with cathode feedback winding, but this is so rare ofcourse to get.
i'm winding them but i can help you only if you are in EU

[markedwardsims]

I appreciate this, and I am in the US or I would talk more about your proposition. Sounds like I would need to upgrade to a real high-voltage power supply. The irony is that this project idea started because the amp sounds pretty harsh when you lean on it and lacks the distortion that I like.

Assuming I upgrade the PT, are there other glaring issues that I need to be aware of?

[bepone]

PT is ok, if you dont have OPT with cathode winding, you can create one
put WHOLE secondary winding in cathode of output tube, in series with cathode resistor and connect speaker there !

[bepone]

on V3a, 22k-82k divider, put 22k lower resistor, 82k upper