Built a micro 5150 / 6505+ around an ECC99 parallel single ended output stage

[PeanutNore]

The preamp is an exact clone of a Peavey 6505+ (5150II) lead channel, the power amp is an ECC99 dual triode running both triodes in parallel SE on an Edcor GXSE5-8-5.5K OT - each triode sees an 11K load if you use an 8 ohm speaker or 22K if you use 16 like I'm using now. Plate voltage is 433v. Cathode biased for 3.5w per triode idle dissipation on a 1k cathode resistor - this is max for a 12BH7, but as I understand the ECC99 should be able to take 5w per triode. I'm just not sure if it can do 5w on both triodes at the same time. I'm either going to try biasing it hotter and see if it redplates, or try a 12AU7 in there.

The PT is a replacement part for a Blackstar HT-5 which I bought because it was super cheap and the HT-5 uses the same output tube I'm using here. What I didn't realize is that it doesn't have a traditional heater winding, just a single center tapped low voltage winding that's about 16-0-16. I full wave rectified it for about 21vdc, then used a 12v regulator for all of the heaters (total heater current is 850mA, so it's within spec). I had to mount the regulator to the chassis because it kept going into thermal protection after about 5 minutes of playing.

This is my first venture into super high gain territory after building a couple JCM800 type amps, and I have to say I really nailed the layout on this one. This is my first time placing the circuit board between the sockets and the pots / input jack and all the wire runs are nice and short, and even with the gain maxed the amp is almost dead silent if you turn your guitar volume all the way down - no hum whatsoever, just a small amount of hiss, which I also get from my Peavey 6505+ combo and seems to be unavoidable thermal noise from the high value resistors being amplified by all the gain in the preamp.

Here's a quick demo video - ignore the dog barking in the background. Also in this demo I had yet to finalize the grid stoppers on the output tube, and they are way too large here, combining with the ~95pF Miller capacitance to low pass the signal at less than 2khz. I'll record a non-cell-phone demo of it in its final form soon.
https://drive.google.com/open?id=0B_...k5RS3hmZ1ZZeVU

[Lqhuy2205]

It's a great build,i also planning to build a 6505+ preamp lead channel,I would appreciate it if you could share your project,can you share the schematic and pcb layout(if you have) .i looked up on the google but only find a full schematic(all stages) from Peavey documents,i only need a lead channel preamp stage,i can't find any schematic of only 6505+ preamp lead channel,I'm not very good at tube amp territory ,this may be a second build after i built a JCM800 from a PCB layout,thanks.

Sorry for my bad English.

Can i get your email?
This is my email: lqhuy2205@gmail.com

[Mick Bailey]

Suggest you edit your post to delete your email address, as this an open forum. Send him a PM instead. He hasn't logged in here for 11 months.

[PeanutNore]

It's a great build,i also planning to build a 6505+ preamp lead channel,I would appreciate it if you could share your project,can you share the schematic and pcb layout(if you have) .i looked up on the google but only find a full schematic(all stages) from Peavey documents,i only need a lead channel preamp stage,i can't find any schematic of only 6505+ preamp lead channel,I'm not very good at tube amp territory ,this may be a second build after i built a JCM800 from a PCB layout,thanks.

Sorry for my bad English.

Can i get your email?
This is my email: lqhuy2205@gmail.com

I do have a layout for the preamp somewhere that I'll find and post. I actually laid it out in Eagle like I was making a PCB and then used that as a template to build the circuit on perf board. It only includes the preamp circuit, I built the power amp on terminal strips but you can pair it with whatever power amp you feel like. Also, I built the tone stack on the back of the tone pots so that's not included in the preamp board layout either