Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on November 19, 2025, 10:39:34 am
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Few days ago there was an active thread about the Wangs Mini 5 Amp
A lot of people had interest on that small amp and the feedback that you can find on the web is of enthusiast peoples
https://el34world.com/Forum/index.php?topic=33104.0 (https://el34world.com/Forum/index.php?topic=33104.0)
(https://el34world.com/Forum/index.php?action=dlattach;topic=33104.0;attach=122930;image)
Looking to the schematic I liked it too but ... no 12BH7 tubes .... but I've other that can adapt to the project
I went to see what components I have available
12AX7 I've but I've also 6N2P tubes and many people consider it good for Blues and similar (more good than the original 12AX7)
12BH7 I don't have but have 6N6P, it is a bit strongher so a bit of more power if wanted
6Z4 - I've 6X4 and also EZ81, so my choiche was for the EZ81 (more current available .. with the 6N6P)
About the OT the original Wangs use a 10K aa, this will be a compromise for the 6N6P but I've a 10K aa OT (also if it may be I'll swap for an OT with different Z)
About the TA on the schematic I post there is a 0-190V PT (that I've) but I think I'll change with one with other spec because I want to preserve the Y and X nodes at the level of the original project to preserve the tone of the amp (note that on the Clone schematic is indicated a 300v-0-300v PT but measuring B+ it was estimated it will be a 240V-0-240V AC one)
the 12BH7 has a bit lower µ than the 6N6P and gm is way lower in the 12BH7 than in the 6N6P that has around a x3 gm respect the 12BH7
So, what to do to compensate and preserve the original project pre + PI ?
I’m thinking about adding a PPIMV, rather than a regular master volume, so that the signal from the preamp and phase inverter remains untouched and PI can still overdrive if pushed
As PPIMV my choiche was a Frondelli (a kind of PPIMV that is appreciated also by Robinette), but also if this circuit has less impact on tone, searcing for the PPIMV to choice I've find that when the shaft is turned to reduce the signal the load for the PI increases and it will arrive near the max it can afford
What to do ? accept this situation or ..... I did some days of search and found ..... near nothing
Thinking how to eliminate the interaction between the PI and the PPIMV I've think that a buffer may be the solution, so a pair of SF (Source Follower) will be used, this will act as an impedance adaptor between the PI and the PPIMV and solve the problem (I think, read I Hope)
I put toghether this Modded Version of the Wangs Mini 5
(https://i.imgur.com/F3YeWwt.jpeg)
What do you think ?
Do you think the SF add will perform as hoped ?
Many Thanks
Franco
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Well I don't know if your plan will work, but I like it and hope you'll build it!